Droplet scientists push the boundary between living and non-living matter

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Hello, and welcome to the Physics World weekly

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podcast.

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In this episode, you'll hear my colleague, Margaret

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Harris,

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in conversation

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with three

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soft matter scientists

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with an interest in the squishy,

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messy,

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and exciting physics of animate droplets.

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This episode is sponsored by EPL,

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a journal that publishes original

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high quality letters

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in all areas of physics.

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EPL operates under the scientific

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policy and control

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of the European Physical Society

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and is published by EDP

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Sciences,

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the Italian Physical Society,

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and IOP Publishing,

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which also publishes

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Physics World.

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Now over to Margaret.

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My guests in today's podcasts are a trio

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of soft matter scientists who have a particular

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interest in the physics of droplets.

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They are Giorgio Volpe, a professor of soft

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matter at University College London,

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Rob Malinovsky, a research fellow in soft matter

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physics who's also at UCL,

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and Joe Forth, who's a lecturer at University

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of Liverpool, but was at UCL a few

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years ago when this collaboration began.

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Georgio, Rob, and Joe, hello, and welcome to

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the podcast.

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Hello. Thank you for having us here. I'm

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gonna start with the softest possible question and

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maybe the biggest. What is soft matter, and

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why is it so fascinating and important?

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So soft matter is very generally the the

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science of of squishy stuff.

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A lot of it is very everyday stuff.

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You can think of it as the the

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the science of of shampoo, and a lot

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of the fundamental findings were made by

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large companies trying to figure out how do

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we make better soaps, better shampoos.

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It very often consists of

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materials that are a large fraction of liquid.

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You have lots of small particles, lots of

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surface area.

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Surface tension tends to dominate a lot of

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the behavior.

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You have lots and lots of weak multivalent

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forces. So the system can be moved around

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and broken up by thermal motion or or

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just by poking it or shaking it and

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all of these things.

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Physics wise, it's it's interesting because it can

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it can change shape. You can incorporate mechanisms

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for energy conversion, and that in turn means

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that soft matter can can deform itself. It

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can move.

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You have a whole

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diverse range of mechanisms for for elasticity.

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If you if you compare it with, say,

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typical solids, crystalline solids, they're just they're just

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rigid because they consist of repeating patterns. Whereas,

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you know, in soft matter, you have all

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sorts of mechanisms for different types of elasticity,

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viscosity, and viscoelasticity.

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With that comes complex deformation and complex flow.

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With these

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energy conversion mechanisms, you get a whole bunch

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of interesting

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non equilibrium behavior.

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And at that point, the palette of behavior

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you can see in in soft matter systems

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grows massively. It it still feels like a

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field where you can mix a bunch of

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stuff together, stick it under a microscope, and

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you'll you'll see

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something new.

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Beyond physics, just sort of scientifically,

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it's inherently very interdisciplinary.

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You

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have the chance to incorporate interesting

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chemistry.

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The material property sort of underpinning soft matter

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are very similar to the material and physical

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properties underpinning

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biological systems and biological

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tissues.

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And there's with the sort of study of

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non equilibrium systems comes this translational relevance to

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active matter, which we'll sort of get to.

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I guess it's a matter of debate whether

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or not, soft matter,

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how what the overlap is between active matter

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and and soft matter, but there's certainly a

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big big overlap on the the Venn diagram

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of those two circles.

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As for why I I find it interesting,

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my my answer to this has has changed

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over the years. When I first learned about

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it as an undergrad, the the selling point

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for me was that it didn't feel like

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the usual physics. It didn't feel like particles

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and Maxwell's equations and whatever. It felt every

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day,

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this idea that of studying the the physics

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of gunky liquids or the physics of shampoo.

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For me, it was exciting. But, to me,

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it was like, wow. You can you can

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study this stuff and people will pay you

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to do it. That was what excited me.

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So I'm getting the impression here that soft

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matte is everything that's really messy in physics,

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and that's what you love about it.

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Yeah. I I so certainly for me, and

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it's certainly I think it's something that the

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the purists it's sort of on the borderline

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of whether one considers it

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physics. I I because of this inherent interdisciplinarity,

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I I think a lot of it is

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certainly not unusual for the the particle physicist

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think of it as belonging to something more

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like engineering or chemistry, but that interdisciplinarity

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is is a big part of the appeal

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for me.

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Georgio, your work in particular is all on

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animate matter. Do you want to touch on

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them what the difference is if there are

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any differences between soft matter

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and animate matter. Because the word animate

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to a layperson usually means living, but I

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understand that's not necessarily the case with animate

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matter.

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No. It is not the case. And, actually,

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when we talk about animate matter, we're really

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thinking about purely synthetic systems, so

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artificial. In a nutshell, animate matter is lifelike,

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but it doesn't mean that it's alive.

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And if you think, for example,

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about the droplet, since we're going to talk

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about droplets,

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you can think that the droplet can move

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on its own. It can respond to the

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environment.

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It can perform task almost

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if it was following a purpose. Right? It

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looks like it's alive, but it's not.

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And,

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ultimately, it's just responding to physical and chemical

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rules.

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So animate,

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whether we're talking about soft matter or we're

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talking about larger or smaller systems,

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it really is about the behavior.

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It's a system that is fully synthetic and

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it can resemble in terms of properties, in

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terms of behavior,

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those of living systems.

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The way in which we can describe

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animal matter is usually through

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categorizing

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according to three principles. These are called the

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three aids of animacies.

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And the three aids of animacies are three

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principles that tend to describe act this animate

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matter based on whether they are active,

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adaptive,

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or autonomous.

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Animate matter, then there is a third field,

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which is active matter. And there is definitely

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overlap between the freeze of matter, animate matter,

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and active matter, but the each one each

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one of them has their own characteristics. So

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there is overlap, but they're not exactly the

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same field.

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Okay. I want to dig into these three

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a's you say, because you've recently written a

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paper for the journal EPL that focuses on

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animate droplets. And you've said what animate means.

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It comes with these three principles.

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Let's start with active. What does active mean

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in this context?

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So active is the simplest of those three

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principles.

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When you say a droplet is active, it

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simply means that it can take energy from

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its environment and convert it from one form

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into another.

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So a really nice kind of simple example

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is there are these oil droplets. If you

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take a specific kind of oil and you

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put it into into water,

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if you impose a chemical gradient

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onto this droplet,

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various physical forces, they could be surface tension

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driven, could be something else, But it will

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drive up that chemical gradient or down that

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chemical gradient.

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And what droplet is doing there is converting

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kind of this chemical potential into a kinetic

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energy, and, you know, that's the motion.

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And these are really nice because you can

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think of it as a rudimentary form of

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sensing. There's there's no kind of, you know,

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thinking or internal processing. It's all physical based,

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but it's in its really simplest sense, the

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droplet is is sensing this chemical and reacting

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to it. But like I said, not like

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biological something. There's no thinking. There's no internal

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processing. It's just pure physics, and they can

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make really neat, neat little swimmers.

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What do you mean by a swimmer?

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It's just a droplet that can propel itself

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pretty much through, through this bulk medium. So

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it's not gonna be it's not gonna have

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arms. It doesn't have a propeller or anything.

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It's usually a quite common example is through

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surface tension. So you end up with these

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surface tension driven flows. And when you have

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a flow, you can

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impart a force onto the surrounding medium, and

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that causes this this driving, this this causes

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this motion. It's swimming.

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And then the second a was adaptive.

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Do one of you want to tell us

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what adaptive is? Sure.

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Adaptive material or or or material that's exhibiting

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adaptation is the it's the ability of a

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of an object, be that a a bacterium,

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a bird, or a or in this case,

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a droplet, to sense its external environment or

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to sense another object and respond to that

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change.

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As we've sort of seen from from Rob,

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a lot of these examples

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are are biological.

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And going back to what Georgio has said

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previously, a lot of the field of animate

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matter is really about recapitulating a recapitulating a

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lot of phenomena that we see and grasp

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intuitively from from biology and and recapitulating them

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in a in a synthetic system. And that

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and that synthetic system can have biological parts

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in it, but our idea here is to

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to to produce something synthetic

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and maybe from a physicist's perspective, produce something

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reductively.

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In terms of adaptation,

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that change can be both to a change

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in its surrounding environment, be that a change

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in surfactant concentration or a change of in

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pH or whatever, or to the presence of

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another,

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for instance, bacterium.

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So so, you know, a a bacterium might

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adjust its its metabolism based on food or

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reagent concentrations or might change its swimming direction

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in response to the presence of other bacteria.

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We need to be a little bit careful

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here because bacteria have a a fairly

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complex set of stimuli and responses that they

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can exhibit. And so these guys, as I

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guess, Georgio would tell us, definitely count as

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autonomous, which is this third day of animacy.

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And so I think arguably what makes something

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00:10:14,304 --> 00:10:16,545
adaptive is that it can respond to stimuli,

273
00:10:16,545 --> 00:10:18,065
but it can only do so to a

274
00:10:18,065 --> 00:10:18,884
fairly limited

275
00:10:19,264 --> 00:10:19,764
palette

276
00:10:20,144 --> 00:10:22,304
of stimuli and and you respond to only

277
00:10:22,304 --> 00:10:23,024
a fairly limited

278
00:10:23,745 --> 00:10:25,125
respond in a fairly limited,

279
00:10:26,065 --> 00:10:27,205
number of ways.

280
00:10:28,059 --> 00:10:30,540
That adaptation, that that change that your system

281
00:10:30,540 --> 00:10:31,279
can exhibit,

282
00:10:31,899 --> 00:10:34,080
it can be individual or it can be

283
00:10:34,220 --> 00:10:37,259
collective, and that collective response generally emerges from

284
00:10:37,259 --> 00:10:38,399
an individual one.

285
00:10:38,779 --> 00:10:39,440
For instance,

286
00:10:39,899 --> 00:10:42,300
flocking behavior that, again, you'd see in birds,

287
00:10:42,300 --> 00:10:45,035
bacteria, but you might recapitulate in an element

288
00:10:45,035 --> 00:10:46,554
system in a in a in a set

289
00:10:46,554 --> 00:10:47,774
of colloidal particles,

290
00:10:48,235 --> 00:10:50,014
is generally a response to,

291
00:10:50,554 --> 00:10:51,455
local concentration

292
00:10:52,154 --> 00:10:53,695
or some exchange

293
00:10:54,075 --> 00:10:54,975
of information.

294
00:10:55,670 --> 00:10:57,350
In the case of, you know, nature, that

295
00:10:57,350 --> 00:10:59,910
would be bird sensing how far apart they

296
00:10:59,910 --> 00:11:02,389
are from each other. That results in in

297
00:11:02,389 --> 00:11:05,029
flocking. It might be the the bacteria sensing

298
00:11:05,029 --> 00:11:06,170
a local concentration

299
00:11:06,950 --> 00:11:09,690
of a specific compounds, or it might be

300
00:11:09,985 --> 00:11:12,865
colloidal particles being disturbed by the swimming motion

301
00:11:12,865 --> 00:11:14,245
of another colloidal particle.

302
00:11:15,904 --> 00:11:18,544
Most interesting for me in these adaptive systems

303
00:11:18,544 --> 00:11:21,745
is is not the the change between two

304
00:11:21,745 --> 00:11:24,565
equilibrium states, but it's the change between two

305
00:11:24,705 --> 00:11:25,205
dynamical

306
00:11:25,959 --> 00:11:28,279
states. That is states that require the system

307
00:11:28,279 --> 00:11:30,919
to be converting energy to to maintain them.

308
00:11:30,919 --> 00:11:32,759
So rather than simply having a system that

309
00:11:32,759 --> 00:11:35,559
you prepare away from equilibrium and watch it

310
00:11:35,559 --> 00:11:37,959
relax, you have it switching between these two

311
00:11:37,959 --> 00:11:39,345
energy converting states.

312
00:11:39,904 --> 00:11:42,625
There's not necessarily entire agreement in the field

313
00:11:42,625 --> 00:11:43,125
there.

314
00:11:44,064 --> 00:11:45,824
So some, you know, some people would say,

315
00:11:45,824 --> 00:11:46,324
well,

316
00:11:46,784 --> 00:11:47,284
materials

317
00:11:48,064 --> 00:11:51,264
fold themselves in response to illumination from light

318
00:11:51,264 --> 00:11:52,404
count as adaptive.

319
00:11:52,784 --> 00:11:55,259
So we don't wanna rule that out rigidly,

320
00:11:55,879 --> 00:11:58,199
but certainly for me, these this chain it's

321
00:11:58,199 --> 00:12:00,940
this switching between dynamical states that's most interesting.

322
00:12:02,279 --> 00:12:03,959
And what might that look like for a

323
00:12:03,959 --> 00:12:05,959
droplet? Can you give me an example similar

324
00:12:05,959 --> 00:12:07,819
to the Robert's about the chemical,

325
00:12:08,360 --> 00:12:08,860
behavior?

326
00:12:10,695 --> 00:12:13,735
Yeah. So in terms of droplets, a really

327
00:12:13,735 --> 00:12:16,615
simple or a simple ish example is, say,

328
00:12:16,615 --> 00:12:18,855
you have so droplet, you have two liquids.

329
00:12:18,855 --> 00:12:20,774
Right? You have oil and a water. Say

330
00:12:20,774 --> 00:12:23,095
you have some degree of chirality in one

331
00:12:23,095 --> 00:12:23,754
of those

332
00:12:24,134 --> 00:12:26,470
liquids. Could be a liquid crystal. Right?

333
00:12:27,169 --> 00:12:29,750
Under the right circumstances, you can then generate

334
00:12:29,809 --> 00:12:32,690
motion in that system that is inherently somewhat

335
00:12:32,690 --> 00:12:35,190
chiral. It has a handedness. It might spiral

336
00:12:35,250 --> 00:12:36,470
clockwise or anticlockwise.

337
00:12:37,485 --> 00:12:40,045
If you shine a light on the the

338
00:12:40,045 --> 00:12:41,985
chiral phase and it switches handedness,

339
00:12:42,524 --> 00:12:44,764
correspondingly, you can engineer a change in the

340
00:12:44,764 --> 00:12:45,985
handedness of the

341
00:12:46,285 --> 00:12:47,504
the swimming too.

342
00:12:48,125 --> 00:12:50,705
I see. Okay. And I think the third

343
00:12:51,129 --> 00:12:53,610
a, autonomous, that's actually the most difficult to

344
00:12:53,610 --> 00:12:55,449
achieve in a droplet context. Can you wanna

345
00:12:55,449 --> 00:12:57,449
tell us what autonomous means and why it's

346
00:12:57,449 --> 00:12:58,190
so challenging?

347
00:12:58,730 --> 00:13:00,730
Yeah. I'm happy to answer that one. It

348
00:13:00,730 --> 00:13:02,809
it is the one of the most challenges

349
00:13:02,809 --> 00:13:04,589
property to achieve at the microscale.

350
00:13:05,674 --> 00:13:07,674
Let's start with the definition. What is autonomous?

351
00:13:07,674 --> 00:13:08,174
Autonomous

352
00:13:09,034 --> 00:13:11,134
is any behavior that is initiated

353
00:13:11,914 --> 00:13:13,754
due to an internal change of state. It's

354
00:13:13,754 --> 00:13:14,894
not triggered externally.

355
00:13:15,514 --> 00:13:17,595
It is initiated by the object. In this

356
00:13:17,595 --> 00:13:18,735
case, it could be a droplet

357
00:13:19,409 --> 00:13:21,490
or something else, like a bigger a material

358
00:13:21,490 --> 00:13:22,470
or something bigger.

359
00:13:22,850 --> 00:13:25,649
When I think about these, autonomous behaviors, I

360
00:13:25,649 --> 00:13:27,809
like to think about an analogy with something

361
00:13:27,809 --> 00:13:29,570
that people tend to know a bit better,

362
00:13:29,570 --> 00:13:31,269
especially nowadays, which are robots.

363
00:13:31,995 --> 00:13:34,634
Autonomy is not a black and white sort

364
00:13:34,634 --> 00:13:35,295
of property.

365
00:13:35,754 --> 00:13:37,835
It's a spectrum of gray, and you can

366
00:13:37,835 --> 00:13:40,795
go from a system that have some level

367
00:13:40,795 --> 00:13:43,215
of autonomy to system that's extremely autonomous.

368
00:13:43,610 --> 00:13:45,790
Now if we think about, robots,

369
00:13:46,570 --> 00:13:48,570
you can think about some of the robots

370
00:13:48,570 --> 00:13:51,050
that were first introduced in the industrial process.

371
00:13:51,050 --> 00:13:51,710
They were

372
00:13:52,649 --> 00:13:55,690
introduced to help the manufacturing process, but they

373
00:13:55,690 --> 00:13:58,990
were ultimately remotely controlled by humans.

374
00:13:59,615 --> 00:14:02,575
And with the development of technologies, they became

375
00:14:02,575 --> 00:14:05,375
more and more autonomous. The human factor became

376
00:14:05,375 --> 00:14:06,434
less important

377
00:14:07,054 --> 00:14:08,414
to a point that now is being,

378
00:14:09,214 --> 00:14:11,214
put to the side, for example, by development

379
00:14:11,214 --> 00:14:13,429
in artificial intelligence and so on. So if

380
00:14:13,429 --> 00:14:15,829
you look at this, evolution for robots, you

381
00:14:15,829 --> 00:14:16,809
can really see

382
00:14:17,190 --> 00:14:19,370
how you went from systems that were helpful

383
00:14:19,509 --> 00:14:22,970
for, production, but being very not much autonomous,

384
00:14:23,190 --> 00:14:24,329
just helping

385
00:14:24,629 --> 00:14:25,450
with the workforce,

386
00:14:25,904 --> 00:14:28,704
to systems that are becoming more and more

387
00:14:28,704 --> 00:14:29,204
autonomous.

388
00:14:29,745 --> 00:14:32,245
And we can almost start to pinpoint

389
00:14:33,664 --> 00:14:36,324
properties that you will typically associate to,

390
00:14:37,024 --> 00:14:39,125
human beings, like thinking and

391
00:14:39,629 --> 00:14:41,490
capability of extrapolating

392
00:14:42,190 --> 00:14:45,730
information and so on. Now at the microscale,

393
00:14:45,950 --> 00:14:48,529
we want to achieve something similar with droplets

394
00:14:48,590 --> 00:14:50,590
but also with other somatic systems. We want

395
00:14:50,590 --> 00:14:52,210
to develop synthetic materials

396
00:14:52,695 --> 00:14:55,115
that can perform task purposefully

397
00:14:55,735 --> 00:14:56,795
based on a change

398
00:14:57,415 --> 00:14:59,894
of internal state without having,

399
00:15:00,295 --> 00:15:02,695
a remote operator telling them what to do

400
00:15:02,695 --> 00:15:04,394
and when to do it. It will be

401
00:15:04,535 --> 00:15:05,035
intrinsically

402
00:15:06,089 --> 00:15:08,029
triggered by changing conditions.

403
00:15:09,129 --> 00:15:11,129
So in in this sense, if you think

404
00:15:11,129 --> 00:15:11,629
about

405
00:15:12,329 --> 00:15:13,470
increasing autonomy,

406
00:15:14,089 --> 00:15:16,250
this is where really I think that the

407
00:15:16,250 --> 00:15:17,230
lines between

408
00:15:17,610 --> 00:15:20,509
synthetic and living starts to blur.

409
00:15:21,434 --> 00:15:21,934
But

410
00:15:22,394 --> 00:15:25,434
it's also really challenging to achieve because if

411
00:15:25,434 --> 00:15:26,414
you think about

412
00:15:27,434 --> 00:15:27,934
having

413
00:15:28,315 --> 00:15:28,815
this

414
00:15:29,674 --> 00:15:30,654
level of autonomy

415
00:15:31,355 --> 00:15:33,754
comparable to what robots can do nowadays at

416
00:15:33,754 --> 00:15:35,670
the micro scale, It means

417
00:15:36,690 --> 00:15:40,450
including physical and chemical rules in tiny, tiny

418
00:15:40,450 --> 00:15:40,950
volumes

419
00:15:41,570 --> 00:15:43,429
to allow for a certain level of programmability

420
00:15:43,809 --> 00:15:45,730
to develop, and that's not the easy task

421
00:15:45,730 --> 00:15:47,330
to achieve. You know, you really need to

422
00:15:47,330 --> 00:15:50,815
squish down, miniaturize or components to a point

423
00:15:50,815 --> 00:15:51,795
that you can achieve

424
00:15:52,175 --> 00:15:52,675
very

425
00:15:53,375 --> 00:15:56,735
complex life life behaviors, but in tiny, tiny

426
00:15:56,735 --> 00:15:57,235
volumes.

427
00:15:58,815 --> 00:16:01,215
So what's an example of a droplet that's

428
00:16:01,215 --> 00:16:03,459
autonomous? What's some research that's been done that

429
00:16:03,459 --> 00:16:04,360
have has demonstrated

430
00:16:04,820 --> 00:16:05,959
an autonomous droplet?

431
00:16:06,980 --> 00:16:08,899
So in a sense, there is not much

432
00:16:08,899 --> 00:16:10,519
out there that is fully autonomous.

433
00:16:12,659 --> 00:16:14,475
There there is some level of

434
00:16:14,875 --> 00:16:18,254
initial autonomy behavior that kind of connects to

435
00:16:18,554 --> 00:16:20,475
some of the most active and adaptive system

436
00:16:20,475 --> 00:16:22,315
that we have seen, and maybe then Joe

437
00:16:22,315 --> 00:16:24,714
and Rob have also other examples they can

438
00:16:24,714 --> 00:16:26,414
bring up. There is one that I particularly

439
00:16:26,475 --> 00:16:28,420
like or or although we we tend to

440
00:16:28,420 --> 00:16:30,980
have discussion between Joe, Rob, and myself about

441
00:16:30,980 --> 00:16:33,460
whether you can actually classify this as autonomous

442
00:16:33,460 --> 00:16:34,120
or not.

443
00:16:34,980 --> 00:16:37,080
There are some droplets that are

444
00:16:37,540 --> 00:16:40,019
active in as Rob described, so they can

445
00:16:40,019 --> 00:16:42,440
move by consuming chemical fuel.

446
00:16:42,745 --> 00:16:45,384
And if you put these droplets into a

447
00:16:45,384 --> 00:16:48,045
maze structures, they can actually solve it.

448
00:16:48,504 --> 00:16:51,625
I see the insipid of autonomy in there

449
00:16:51,625 --> 00:16:53,485
because it reminds me what

450
00:16:54,024 --> 00:16:57,804
living system, bacteria, slime mold, ants can do.

451
00:16:58,009 --> 00:17:00,490
You know, they can really follow chemical press

452
00:17:00,490 --> 00:17:01,149
to solve

453
00:17:01,610 --> 00:17:02,110
autonomously.

454
00:17:02,570 --> 00:17:03,389
And may I elaborate?

455
00:17:04,490 --> 00:17:06,910
It is borderline whether this can be considered

456
00:17:07,929 --> 00:17:10,089
autonomous or not at this stage. I like

457
00:17:10,089 --> 00:17:11,929
to think that they are, but, you know,

458
00:17:11,929 --> 00:17:13,549
I think Joe and Robert

459
00:17:13,964 --> 00:17:16,365
have slightly different opinions on this. And I

460
00:17:16,365 --> 00:17:17,724
don't know if you guys want to add

461
00:17:17,724 --> 00:17:19,424
any more examples on this.

462
00:17:20,605 --> 00:17:23,164
Yeah. Like, Georgio says the the droplet solving

463
00:17:23,164 --> 00:17:25,325
amaze is a attempting one. I always have

464
00:17:25,325 --> 00:17:27,089
this thing that really if you if you

465
00:17:27,089 --> 00:17:28,769
stick a chemical source at one end of

466
00:17:28,769 --> 00:17:30,210
a maze and you stick a droplet at

467
00:17:30,210 --> 00:17:30,789
the other,

468
00:17:31,169 --> 00:17:33,089
ultimately, the droplet is just gonna move up

469
00:17:33,089 --> 00:17:35,490
the concentration gradient. And so, really, you're just

470
00:17:35,490 --> 00:17:37,669
you're just swimming at the concentration gradient,

471
00:17:38,130 --> 00:17:40,769
under topographical constraint. But I I also I

472
00:17:40,769 --> 00:17:42,789
I see what Georgio says. You have this

473
00:17:42,825 --> 00:17:44,505
you have this system that looks like it's

474
00:17:44,505 --> 00:17:47,625
sort of processing stimuli and and responding. So

475
00:17:47,625 --> 00:17:49,164
I think there's an argument there.

476
00:17:49,704 --> 00:17:51,625
The sort of low hanging fruit in terms

477
00:17:51,625 --> 00:17:53,944
of making an autonomous droplet is to simply

478
00:17:53,944 --> 00:17:56,039
stick a bunch of living material in there.

479
00:17:56,519 --> 00:17:58,200
So if I stick a bunch of swimming

480
00:17:58,200 --> 00:18:00,680
bacteria into a droplet, that droplet can be

481
00:18:00,680 --> 00:18:02,539
can be made to swim, and it incorporates

482
00:18:02,680 --> 00:18:05,320
the same sort of palette of stimulus response

483
00:18:05,320 --> 00:18:07,340
and collective behavior as the bacteria.

484
00:18:07,880 --> 00:18:09,960
Similarly, if I sort of do a cell

485
00:18:09,960 --> 00:18:11,775
free approach, so I take biological

486
00:18:12,394 --> 00:18:14,954
mechanisms for, say, molecular expression and stick them

487
00:18:14,954 --> 00:18:17,275
in a droplet, that also is gonna exhibit

488
00:18:17,275 --> 00:18:17,775
some

489
00:18:18,154 --> 00:18:19,375
degree of autonomy.

490
00:18:19,755 --> 00:18:22,394
I think maybe we me, Georgio, and Rob

491
00:18:22,394 --> 00:18:24,474
would share a frustration there that that system

492
00:18:24,474 --> 00:18:27,569
is not necessarily reducibly complex. We're not we're

493
00:18:27,569 --> 00:18:29,009
showing that we can do a thing. We're

494
00:18:29,009 --> 00:18:30,849
not showing that we can really understand it

495
00:18:30,849 --> 00:18:32,390
in in any meaningful way.

496
00:18:33,490 --> 00:18:35,429
I think the systems that

497
00:18:35,730 --> 00:18:38,609
always appeal to me are these these chemical

498
00:18:38,609 --> 00:18:39,109
oscillators.

499
00:18:39,410 --> 00:18:41,190
And so you have, say,

500
00:18:41,785 --> 00:18:43,224
I don't know if I I'm stealing your

501
00:18:43,224 --> 00:18:44,825
fire here or if you wanna cheat in

502
00:18:44,825 --> 00:18:45,805
this as an example.

503
00:18:46,265 --> 00:18:48,984
But the the classic example is the this

504
00:18:48,984 --> 00:18:52,265
Belisov Jabotinsky reaction where you have, you know,

505
00:18:52,265 --> 00:18:54,585
chemical a reacts to form chemical b, and

506
00:18:54,585 --> 00:18:57,269
then chemical b reacts to form chemical

507
00:18:57,809 --> 00:19:00,929
a. And in systems that incorporate bromine, that

508
00:19:00,929 --> 00:19:03,490
generally results in some change of color. So,

509
00:19:03,490 --> 00:19:05,890
you know, bromine is red, bromide is blue,

510
00:19:05,890 --> 00:19:08,529
and so as the system composition switches from

511
00:19:08,529 --> 00:19:10,929
bromine based to bromide based, you get a

512
00:19:10,929 --> 00:19:13,265
switch from from red to blue, and and

513
00:19:13,265 --> 00:19:16,164
this switch happens at a a characteristic

514
00:19:16,785 --> 00:19:17,285
frequency.

515
00:19:19,424 --> 00:19:21,285
It gets interesting when you start

516
00:19:21,664 --> 00:19:24,144
dimensionally confining these things. So if you which

517
00:19:24,144 --> 00:19:25,829
is a fancy way of saying if you

518
00:19:25,829 --> 00:19:27,589
do it in a petri dish, you have

519
00:19:27,589 --> 00:19:29,109
a, you know, you have an effectively sort

520
00:19:29,109 --> 00:19:30,549
of quasi two d system, and you end

521
00:19:30,549 --> 00:19:31,849
up seeing these traveling

522
00:19:32,309 --> 00:19:35,130
waves of alternating stripe of reds

523
00:19:35,669 --> 00:19:37,669
and blue that look a lot like the

524
00:19:37,669 --> 00:19:39,669
the patterns that Alan Turing studied when he

525
00:19:39,669 --> 00:19:40,569
was trying to

526
00:19:40,994 --> 00:19:42,214
look at morphogenesis

527
00:19:42,595 --> 00:19:44,454
and patterns of animal spots

528
00:19:44,835 --> 00:19:47,315
and describe reaction diffusion mechanisms, I think it

529
00:19:47,315 --> 00:19:48,674
was. Now I might be wrong about that,

530
00:19:48,674 --> 00:19:49,174
though.

531
00:19:50,115 --> 00:19:53,075
Things again get interesting when the catalyst you're

532
00:19:53,075 --> 00:19:55,234
using to make a turn into b or

533
00:19:55,234 --> 00:19:58,240
b turn into a becomes light responsive.

534
00:19:59,019 --> 00:20:00,079
You end up getting

535
00:20:00,779 --> 00:20:03,019
effects that look a lot like analog image

536
00:20:03,019 --> 00:20:03,519
processing.

537
00:20:04,059 --> 00:20:06,059
So you can, you know, you illuminate your

538
00:20:06,059 --> 00:20:07,819
petri dish with a photo mask, and then

539
00:20:07,819 --> 00:20:09,339
you shine a light on the system and

540
00:20:09,339 --> 00:20:11,134
you, you end up getting things like the

541
00:20:11,134 --> 00:20:13,454
skeletonization of the the initial image that you

542
00:20:13,454 --> 00:20:15,234
shone on the the petri dish.

543
00:20:15,694 --> 00:20:18,035
What happens with droplets then is

544
00:20:19,615 --> 00:20:20,115
you

545
00:20:20,894 --> 00:20:23,474
say your say your reagents have a differing

546
00:20:23,830 --> 00:20:24,330
polarity,

547
00:20:24,789 --> 00:20:26,309
so one of them likes the oil more

548
00:20:26,309 --> 00:20:28,070
than the water. And if I have one

549
00:20:28,070 --> 00:20:30,390
of these b zed reactions happening inside a

550
00:20:30,390 --> 00:20:30,890
droplet

551
00:20:31,190 --> 00:20:34,789
and my nonpolar reagent goes travels to another

552
00:20:34,789 --> 00:20:36,789
droplet that also has a a b zed

553
00:20:36,789 --> 00:20:39,535
reaction happening to it, you have exchange of

554
00:20:39,674 --> 00:20:41,694
chemical reagents that are driving

555
00:20:42,394 --> 00:20:44,795
those chemical reactions. And in effect, you have

556
00:20:44,795 --> 00:20:46,255
exchange of chemical information.

557
00:20:46,875 --> 00:20:49,595
And that system is then gonna evolve in

558
00:20:49,595 --> 00:20:52,710
time and space according to rules that are

559
00:20:53,190 --> 00:20:55,190
determined by the transport of reagents and they're

560
00:20:55,190 --> 00:20:57,369
they're partitioning be between the

561
00:20:57,750 --> 00:20:59,769
the two phases, the oil and the water.

562
00:21:00,149 --> 00:21:01,990
And this is a system that then gives

563
00:21:01,990 --> 00:21:02,490
you,

564
00:21:03,109 --> 00:21:04,950
some degree of what I would consider to

565
00:21:04,950 --> 00:21:05,849
be autonomy.

566
00:21:06,309 --> 00:21:09,734
You have complex stimulus response and and processing

567
00:21:09,795 --> 00:21:10,455
of information.

568
00:21:11,154 --> 00:21:12,674
But I don't think we're at the point

569
00:21:12,674 --> 00:21:14,934
where we could really ever call that autonomous

570
00:21:14,994 --> 00:21:16,134
yet. It's just

571
00:21:16,434 --> 00:21:19,154
more this might be an interesting direction to

572
00:21:19,154 --> 00:21:20,615
to go in with this field.

573
00:21:21,549 --> 00:21:23,710
So, Robert, did Joe steal your thunder there?

574
00:21:23,710 --> 00:21:25,470
Do you steal your favorite example of an

575
00:21:25,470 --> 00:21:26,369
autonomous droplet?

576
00:21:27,470 --> 00:21:28,830
No. I actually came up with a new

577
00:21:28,830 --> 00:21:30,430
favorite. There are a few examples of this,

578
00:21:30,430 --> 00:21:31,630
but one system that I really like are

579
00:21:31,630 --> 00:21:33,570
these I wouldn't call these all autonomous.

580
00:21:34,095 --> 00:21:35,934
I think, again, kinda getting there, but for

581
00:21:35,934 --> 00:21:38,335
me, autonomous needs some sort of internal processing.

582
00:21:38,335 --> 00:21:39,615
I I'd I'd really like to see some

583
00:21:39,615 --> 00:21:41,394
sort of, quote, unquote, decision

584
00:21:41,855 --> 00:21:43,855
being made by the droplet. But one one

585
00:21:43,855 --> 00:21:45,295
example of the system I really like are

586
00:21:45,295 --> 00:21:46,515
predator prey interactions.

587
00:21:47,454 --> 00:21:47,615
So,

588
00:21:48,335 --> 00:21:50,920
several examples of kind of droplet pairs of

589
00:21:50,920 --> 00:21:52,840
oil, where if you put them into a

590
00:21:52,840 --> 00:21:54,360
a bath, they like to float on the

591
00:21:54,360 --> 00:21:56,120
surface rather than in in a three d

592
00:21:56,120 --> 00:21:58,840
space, but they will one droplet will chase

593
00:21:58,840 --> 00:21:59,660
the other one.

594
00:22:00,279 --> 00:22:00,779
It's

595
00:22:01,795 --> 00:22:02,835
again, I don't know if I'd call it

596
00:22:02,835 --> 00:22:04,595
autonomous. It's it's a kind of combination of

597
00:22:04,595 --> 00:22:06,595
different sensing and, you know, one droplet likes

598
00:22:06,595 --> 00:22:07,795
to run away from the other one and

599
00:22:07,795 --> 00:22:09,234
one likes to chase the other one. So

600
00:22:09,234 --> 00:22:12,134
it's more of a relationship between between stimuli.

601
00:22:12,275 --> 00:22:13,650
But they're really nice to look

602
00:22:14,130 --> 00:22:16,529
at. And I think they again, it's it's

603
00:22:16,529 --> 00:22:18,930
finding those comparisons with nature. We we like

604
00:22:18,930 --> 00:22:20,609
to call them predator and prey, but it's

605
00:22:20,609 --> 00:22:22,549
it's just, you know, different types of sensing.

606
00:22:23,089 --> 00:22:24,930
There's a really nice example actually where we

607
00:22:24,930 --> 00:22:26,690
can bring in that the soft matter back

608
00:22:26,690 --> 00:22:29,365
into the into the equation where the droplets

609
00:22:29,365 --> 00:22:31,545
can can deform and grow these tendrils,

610
00:22:32,325 --> 00:22:32,825
and

611
00:22:33,204 --> 00:22:34,884
that's part of the chasing. And, you know,

612
00:22:34,884 --> 00:22:36,565
it makes the droplet more terrifying to the

613
00:22:36,565 --> 00:22:38,884
prey. It kind of deforms and grows these

614
00:22:38,884 --> 00:22:40,804
arms, and they follow them along. It's quite

615
00:22:40,804 --> 00:22:42,484
it's quite a complex system. It's not something

616
00:22:42,484 --> 00:22:43,890
you'd see probably

617
00:22:44,829 --> 00:22:47,470
by accident, but, it's a really nice example.

618
00:22:47,470 --> 00:22:48,609
And it kind of shows

619
00:22:49,309 --> 00:22:51,230
the the power the droplets could have. They

620
00:22:51,470 --> 00:22:53,390
especially with this kind of deformation, the shape

621
00:22:53,390 --> 00:22:53,890
change,

622
00:22:54,509 --> 00:22:56,269
and, yeah, there are some really nice examples

623
00:22:56,269 --> 00:22:58,744
of droplets changing shape to in response to

624
00:22:58,744 --> 00:22:59,484
things. And,

625
00:22:59,865 --> 00:23:02,265
that's one of the benefits that that liquids

626
00:23:02,265 --> 00:23:04,265
have over, say, kind of solid micro particles

627
00:23:04,265 --> 00:23:05,804
in that they are soft.

628
00:23:06,585 --> 00:23:08,284
They can change shape. They can flow.

629
00:23:08,825 --> 00:23:10,910
And, yeah, we just we just need to

630
00:23:10,910 --> 00:23:12,130
build that autonomy

631
00:23:12,750 --> 00:23:14,589
more into them. I I guess, Margaret, it

632
00:23:14,589 --> 00:23:17,069
may be something to first take home messages

633
00:23:17,069 --> 00:23:17,549
that,

634
00:23:17,869 --> 00:23:20,049
while animate matter is kind of a framework

635
00:23:20,190 --> 00:23:21,490
to define behaviors,

636
00:23:22,029 --> 00:23:24,445
there is a lot of scope for, reinventing.

637
00:23:24,585 --> 00:23:26,045
And and as you can see,

638
00:23:26,664 --> 00:23:28,825
the definition are still a bit personal. And

639
00:23:28,825 --> 00:23:30,345
one of the things that we're trying to

640
00:23:30,345 --> 00:23:32,505
put forward with this article or with this

641
00:23:32,505 --> 00:23:33,644
perspective is that

642
00:23:34,265 --> 00:23:35,884
there there need to be a conversation

643
00:23:36,184 --> 00:23:38,880
in across communities and the community to

644
00:23:39,580 --> 00:23:41,440
properly define these terms.

645
00:23:41,900 --> 00:23:42,400
And

646
00:23:43,019 --> 00:23:45,980
when do you stop to define autonomy as

647
00:23:45,980 --> 00:23:47,920
autonomy? When do you where do you start?

648
00:23:48,140 --> 00:23:50,835
This is something that we also wanted to

649
00:23:50,835 --> 00:23:52,535
convey with the with the perspective.

650
00:23:53,714 --> 00:23:55,875
So you mentioned in your paper, this perspective,

651
00:23:55,875 --> 00:23:59,255
that it's possible for droplets behave like tissues

652
00:23:59,394 --> 00:24:00,134
or bacterial

653
00:24:00,434 --> 00:24:00,934
colonies.

654
00:24:01,714 --> 00:24:03,154
What does that mean? And can you give

655
00:24:03,154 --> 00:24:05,174
me some examples of how that happens?

656
00:24:07,230 --> 00:24:09,870
So they're two they're two, I guess, very

657
00:24:09,870 --> 00:24:12,190
evocative words that, again, draw more on this

658
00:24:12,190 --> 00:24:13,650
sort of biological inspiration.

659
00:24:14,590 --> 00:24:16,910
When we talk about colonies and the idea

660
00:24:16,910 --> 00:24:18,690
of colonies of of droplets,

661
00:24:19,164 --> 00:24:20,445
I guess the thing it calls to mind

662
00:24:20,445 --> 00:24:22,704
is social insects, things like ants.

663
00:24:23,565 --> 00:24:24,305
You have

664
00:24:24,845 --> 00:24:27,644
information exchange that is, in this case, exchange

665
00:24:27,644 --> 00:24:29,724
of of chemical reagents. It could be in

666
00:24:29,724 --> 00:24:32,509
between individuals in this, you know? And so

667
00:24:32,509 --> 00:24:34,829
so thinking back to the predator prey system

668
00:24:34,829 --> 00:24:36,990
that that Rob was thinking of, you have

669
00:24:36,990 --> 00:24:38,130
a a sort of asymmetric

670
00:24:38,829 --> 00:24:41,730
exchange of chemical reagents between two different

671
00:24:42,349 --> 00:24:44,829
species of droplets, and that can lead to

672
00:24:44,829 --> 00:24:47,250
interesting emergent behavior like transient

673
00:24:47,674 --> 00:24:49,294
and and dynamical clustering.

674
00:24:49,595 --> 00:24:51,515
That exchange of information doesn't need to be

675
00:24:51,515 --> 00:24:53,855
chemical. It can it can be hydrodynamics

676
00:24:54,234 --> 00:24:55,835
as the way a a droplet sort of

677
00:24:55,835 --> 00:24:56,734
swimming through

678
00:24:57,035 --> 00:24:59,434
liquid. That disturbance it makes in the in

679
00:24:59,434 --> 00:25:01,515
the liquid is swimming through will affect the

680
00:25:01,515 --> 00:25:03,559
the swimming of of neighboring droplets. And that,

681
00:25:03,559 --> 00:25:06,200
again, can lead to exchange of information and

682
00:25:06,200 --> 00:25:08,380
and in effect, so clustering behavior.

683
00:25:09,799 --> 00:25:12,359
In terms of tissues, I sort of think

684
00:25:12,359 --> 00:25:14,359
of that in terms of droplets that are

685
00:25:14,359 --> 00:25:16,615
stuck together. Perhaps to give an example to

686
00:25:16,615 --> 00:25:19,015
make it more concrete, there's this wonderful work

687
00:25:19,015 --> 00:25:22,154
on systems called droplet interface bilayers. So you

688
00:25:22,375 --> 00:25:24,934
you take, an aqueous droplet and you print

689
00:25:24,934 --> 00:25:27,734
it with an inkjet printer into, an oily

690
00:25:27,734 --> 00:25:30,960
solution of lipids. The lipid is surfactant, it

691
00:25:30,960 --> 00:25:33,039
will absorb to the the surface of the

692
00:25:33,039 --> 00:25:35,200
droplets. If you print two of these droplets

693
00:25:35,200 --> 00:25:37,039
next to each other, the lipids really like

694
00:25:37,039 --> 00:25:38,740
each other and they'll zip together.

695
00:25:39,039 --> 00:25:41,279
And so these two droplets are then stuck

696
00:25:41,279 --> 00:25:43,220
together and they have a a lipid bilayer

697
00:25:43,680 --> 00:25:44,579
joining them.

698
00:25:45,315 --> 00:25:47,234
What is then very interesting is if you

699
00:25:47,234 --> 00:25:49,015
take pores that enjoy

700
00:25:49,394 --> 00:25:51,794
sitting in lipid bilayers, and there's there's lots

701
00:25:51,794 --> 00:25:53,174
of those in in nature,

702
00:25:53,875 --> 00:25:56,294
because that's just a useful function to have

703
00:25:57,329 --> 00:25:59,089
if you wanna disrupt a cell membrane, and

704
00:25:59,089 --> 00:26:01,569
that's exactly what alpha hemolysin pores do for

705
00:26:01,569 --> 00:26:04,049
instance. They they sit at the the surface

706
00:26:04,049 --> 00:26:05,730
of a lipid bilayer, and they make a

707
00:26:05,730 --> 00:26:07,809
big hole in a cell, and and that's

708
00:26:07,809 --> 00:26:09,650
one of the mechanisms by by which cells

709
00:26:09,650 --> 00:26:10,785
are are killed in nature.

710
00:26:11,105 --> 00:26:13,345
But in this case, it allows information and

711
00:26:13,345 --> 00:26:16,164
transport of material between the two droplets.

712
00:26:16,785 --> 00:26:19,025
What's neat then about sort of mechanization and

713
00:26:19,025 --> 00:26:21,505
printing is you're not limited to just one

714
00:26:21,505 --> 00:26:23,585
or two or three droplets or however many

715
00:26:23,585 --> 00:26:25,630
you can be bothered to place by hand.

716
00:26:25,630 --> 00:26:29,009
You can program your your printer to place

717
00:26:29,070 --> 00:26:29,570
arbitrarily

718
00:26:29,950 --> 00:26:30,450
many

719
00:26:30,750 --> 00:26:32,769
droplets into arbitrarily arbitrarily

720
00:26:33,070 --> 00:26:35,549
complex patterns, and you can select which of

721
00:26:35,549 --> 00:26:37,950
those droplets contain these pores. And so you

722
00:26:37,950 --> 00:26:38,595
can start

723
00:26:39,075 --> 00:26:39,974
building in

724
00:26:40,275 --> 00:26:42,054
complex transportation pathways

725
00:26:42,434 --> 00:26:45,234
for the the the conduction of reagents, for

726
00:26:45,234 --> 00:26:47,554
instance. And so that's sort of what we're

727
00:26:47,554 --> 00:26:50,515
talking about in terms of these tissue like

728
00:26:50,515 --> 00:26:52,740
materials that are that are held together by

729
00:26:52,819 --> 00:26:56,099
by surface tension and exchange information through quite

730
00:26:56,099 --> 00:26:56,599
static

731
00:26:56,980 --> 00:26:59,539
connections as opposed to colony like droplets that

732
00:26:59,539 --> 00:27:01,619
consist of individual things that are sort of

733
00:27:01,619 --> 00:27:03,559
running around and and maybe they exchange,

734
00:27:04,099 --> 00:27:05,880
a chemical reagent with one another.

735
00:27:07,394 --> 00:27:09,035
What I'm hearing here is is just the

736
00:27:09,154 --> 00:27:10,055
such similarities

737
00:27:10,434 --> 00:27:12,515
with life. You talked about things being a

738
00:27:12,515 --> 00:27:13,015
spectrum.

739
00:27:13,634 --> 00:27:15,795
Does this kind of research sort of challenge

740
00:27:15,795 --> 00:27:17,394
the spectrum, what we think of as living

741
00:27:17,394 --> 00:27:18,994
and what we think of as not living?

742
00:27:18,994 --> 00:27:20,515
Or is there for you a very hard

743
00:27:20,515 --> 00:27:22,809
and fast boundary between, okay, this stuff is

744
00:27:22,809 --> 00:27:24,490
living. This is a bacterium, and this stuff

745
00:27:24,490 --> 00:27:26,170
is not living. It's just a collection of

746
00:27:26,170 --> 00:27:26,670
chemicals

747
00:27:27,130 --> 00:27:29,049
in a sort of self assembled bag moving

748
00:27:29,049 --> 00:27:31,049
around. I I don't know if we want

749
00:27:31,049 --> 00:27:33,369
to challenge that because then we will be

750
00:27:33,369 --> 00:27:36,194
bored into with philosophy. But I think anime

751
00:27:36,194 --> 00:27:38,755
and matter is purely synthetic. So in that

752
00:27:38,755 --> 00:27:40,934
sense, it will, by definition, not believing.

753
00:27:41,554 --> 00:27:42,454
But we

754
00:27:43,075 --> 00:27:45,494
the aim is to try to replicate properties

755
00:27:45,554 --> 00:27:48,115
that are usually attributed to living systems, but

756
00:27:48,115 --> 00:27:50,295
still keeping fully synthetic and

757
00:27:50,880 --> 00:27:52,579
controllable in a sense. And

758
00:27:53,359 --> 00:27:55,200
but we want to learn from nature. We

759
00:27:55,200 --> 00:27:57,359
want to learn from what living systems can

760
00:27:57,359 --> 00:27:59,599
do. They're much better at a lot of

761
00:27:59,599 --> 00:28:00,099
things.

762
00:28:00,480 --> 00:28:01,460
So it's really

763
00:28:01,920 --> 00:28:02,420
about

764
00:28:03,274 --> 00:28:06,154
learning from nature and trying to reproduce some

765
00:28:06,154 --> 00:28:09,914
properties, starting from principles that are purely physical

766
00:28:09,914 --> 00:28:10,575
and chemical

767
00:28:11,515 --> 00:28:12,015
to

768
00:28:12,394 --> 00:28:14,654
add some attributes that are beneficial

769
00:28:14,954 --> 00:28:16,015
for materials

770
00:28:16,390 --> 00:28:18,789
like the one we discussed here, but they're

771
00:28:18,789 --> 00:28:19,450
not leaving.

772
00:28:20,230 --> 00:28:22,309
The lines are a bit blurred, but the

773
00:28:22,309 --> 00:28:23,849
distinction is still clear.

774
00:28:24,950 --> 00:28:26,950
That's why it's really tricky, isn't it? I

775
00:28:26,950 --> 00:28:28,890
think, yeah, I don't think we ever go

776
00:28:29,029 --> 00:28:30,275
it's fair to say it's gonna be alive

777
00:28:30,275 --> 00:28:32,194
because even some biological things, I don't I

778
00:28:32,194 --> 00:28:33,815
don't know if I call a virus alive.

779
00:28:34,674 --> 00:28:35,174
And

780
00:28:36,035 --> 00:28:37,974
I don't know. It's it's tricky. Like, what

781
00:28:38,434 --> 00:28:41,015
what level of self sustaining is is alive

782
00:28:41,075 --> 00:28:42,595
is a key question. And I I have

783
00:28:42,595 --> 00:28:43,954
a feeling a lot of these probably won't

784
00:28:43,954 --> 00:28:45,095
be eons

785
00:28:45,450 --> 00:28:47,069
of self sustaining. But

786
00:28:47,609 --> 00:28:49,549
but whether that's a requirement, I'm not sure.

787
00:28:49,609 --> 00:28:52,190
I think that, observation of Robert actually

788
00:28:53,769 --> 00:28:54,669
feeds into

789
00:28:55,929 --> 00:28:59,210
applications or at least applicate aspirational applications of

790
00:28:59,210 --> 00:29:00,730
the field as well. Because if we're being

791
00:29:00,730 --> 00:29:02,904
honest, we don't we don't have applications yet.

792
00:29:02,904 --> 00:29:03,224
But,

793
00:29:03,704 --> 00:29:05,244
you know, what you're what you're

794
00:29:05,625 --> 00:29:07,565
what you're arguably trying to do is

795
00:29:08,105 --> 00:29:10,264
figure out what are the functionally useful properties

796
00:29:10,264 --> 00:29:12,904
of biological systems. You know? The the idea

797
00:29:12,904 --> 00:29:14,924
to change shape in response to

798
00:29:15,640 --> 00:29:17,640
stimulus or change behavior in response to a

799
00:29:17,640 --> 00:29:18,140
stimulus

800
00:29:19,000 --> 00:29:19,500
without

801
00:29:19,960 --> 00:29:22,119
having to create a system that has to

802
00:29:22,119 --> 00:29:24,599
worry about sustaining itself and and has all

803
00:29:24,599 --> 00:29:25,099
the

804
00:29:26,119 --> 00:29:26,619
inherent,

805
00:29:27,000 --> 00:29:29,960
both chemical and philosophical complexity that comes with

806
00:29:29,960 --> 00:29:30,224
that.

807
00:29:31,424 --> 00:29:33,984
On the subject of applications since Joe's brought

808
00:29:33,984 --> 00:29:36,224
it up, your EPL piece is what's called

809
00:29:36,224 --> 00:29:38,464
the perspectives article explaining the current state of

810
00:29:38,464 --> 00:29:40,384
the field and sort of suggesting how it

811
00:29:40,384 --> 00:29:41,684
might develop in the future.

812
00:29:42,144 --> 00:29:44,000
So So focusing on the future, what are

813
00:29:44,000 --> 00:29:46,079
some things that soft matter scientists such as

814
00:29:46,079 --> 00:29:47,920
yourself would like to be able to do

815
00:29:47,920 --> 00:29:49,940
with animate droplets in the future?

816
00:29:51,359 --> 00:29:53,359
I think one of the things that it

817
00:29:53,359 --> 00:29:55,119
would be nice to be able to do

818
00:29:55,119 --> 00:29:58,044
is to have programmable soft robots that are

819
00:29:58,044 --> 00:29:59,505
made of droplets.

820
00:30:00,285 --> 00:30:02,464
They will allow to make

821
00:30:03,325 --> 00:30:06,304
robotic systems that are closer to the microscale

822
00:30:06,605 --> 00:30:07,105
potentially

823
00:30:07,804 --> 00:30:10,845
that are much more deformable than some of

824
00:30:10,845 --> 00:30:11,345
the

825
00:30:12,119 --> 00:30:14,779
robots that we are typically thinking of.

826
00:30:15,160 --> 00:30:16,700
And they can have

827
00:30:17,160 --> 00:30:19,900
can be useful for for applications that

828
00:30:20,359 --> 00:30:22,700
can range from making materials that are

829
00:30:23,240 --> 00:30:26,375
adapting to changes in stimuli for you know,

830
00:30:26,375 --> 00:30:29,174
can go from construction purposes to drug delivery

831
00:30:29,174 --> 00:30:29,674
purposes.

832
00:30:30,295 --> 00:30:32,055
That that will be one of the things

833
00:30:32,055 --> 00:30:32,555
where

834
00:30:33,494 --> 00:30:35,975
further develop development in the level of nemesis

835
00:30:35,975 --> 00:30:37,914
or droplets can actually lead to

836
00:30:38,549 --> 00:30:40,809
creating some impactful applications

837
00:30:41,190 --> 00:30:42,009
down the line.

838
00:30:43,429 --> 00:30:44,409
Robert and Joe?

839
00:30:45,269 --> 00:30:47,269
One thing that I think I'd really like

840
00:30:47,269 --> 00:30:48,230
to see happen is,

841
00:30:50,389 --> 00:30:51,829
a lot of this, like, soft matter and

842
00:30:51,829 --> 00:30:54,884
droplet physics it arises with with quite simple

843
00:30:54,884 --> 00:30:55,384
chemicals,

844
00:30:55,845 --> 00:30:57,605
and you can get these complex behaviors with

845
00:30:57,605 --> 00:30:59,224
these quite simple chemicals. And

846
00:31:00,484 --> 00:31:02,724
that's quite important, say, if we wanted to

847
00:31:02,724 --> 00:31:04,265
apply these things in the environment.

848
00:31:04,724 --> 00:31:06,480
So, you know, if you think about a

849
00:31:06,480 --> 00:31:09,680
lot of, environmental cleanup, sometimes you dump chemicals

850
00:31:09,680 --> 00:31:11,539
in the environment to remove chemicals,

851
00:31:12,240 --> 00:31:13,840
and you obviously have to make sure those

852
00:31:13,840 --> 00:31:16,080
chemicals you're adding are at least not as

853
00:31:16,080 --> 00:31:17,859
bad as the ones you're taking away.

854
00:31:18,255 --> 00:31:18,755
But

855
00:31:19,055 --> 00:31:21,555
what this field can kind of do is

856
00:31:22,654 --> 00:31:25,375
is use this this physics that can arise

857
00:31:25,375 --> 00:31:27,214
from just physical prop and you're using physics

858
00:31:27,214 --> 00:31:29,474
rather than chemistry almost to to do this.

859
00:31:29,855 --> 00:31:30,434
I think

860
00:31:30,950 --> 00:31:33,109
the scope of finding function in the physics

861
00:31:33,109 --> 00:31:33,849
of some more

862
00:31:34,309 --> 00:31:35,369
innocuous chemicals

863
00:31:36,069 --> 00:31:38,950
than using more advanced chemistry, if that makes

864
00:31:38,950 --> 00:31:41,269
sense. So you might have something like you

865
00:31:41,349 --> 00:31:42,950
you'd pour it on an oil spill, and

866
00:31:42,950 --> 00:31:44,730
it would sort of semi autonomously

867
00:31:45,029 --> 00:31:47,075
and in an adaptive and inactive way seek

868
00:31:47,075 --> 00:31:48,375
out the bits of oil

869
00:31:48,674 --> 00:31:50,434
so you wouldn't have to manually apply this

870
00:31:50,434 --> 00:31:52,275
this chemical, whatever it was, to clean up

871
00:31:52,275 --> 00:31:53,414
the the oil spill.

872
00:31:54,115 --> 00:31:55,715
Yeah. One thing I'd really love is if

873
00:31:55,715 --> 00:31:57,154
you add this, like, little bit of liquid

874
00:31:57,154 --> 00:31:58,914
into your oil spill and just sends out

875
00:31:58,914 --> 00:31:59,654
little swimmers,

876
00:32:00,150 --> 00:32:01,750
drags everything back, and then, you know, brings

877
00:32:01,750 --> 00:32:03,350
it back to you. That'd be, you know,

878
00:32:03,350 --> 00:32:05,029
incredible. But I don't know how close we

879
00:32:05,029 --> 00:32:06,009
are to that yet.

880
00:32:06,309 --> 00:32:08,070
Alright, Joe. Take out take out your crystal

881
00:32:08,070 --> 00:32:09,990
ball and show us what, what you think

882
00:32:09,990 --> 00:32:11,750
animate droplets will do in the future. Yeah.

883
00:32:11,750 --> 00:32:13,609
I guess I have I sort of have

884
00:32:14,674 --> 00:32:17,174
two what I think are reasonably promising directions.

885
00:32:17,315 --> 00:32:19,875
One that doesn't have an immediate use, but

886
00:32:19,875 --> 00:32:21,474
I just think is a promising direction in

887
00:32:21,474 --> 00:32:24,195
terms of making an interesting material is is

888
00:32:24,434 --> 00:32:27,075
so I was I was, waxing lyrical about

889
00:32:27,075 --> 00:32:29,410
these droplet interface by layers that we print

890
00:32:29,410 --> 00:32:30,630
into tissues. Right?

891
00:32:31,250 --> 00:32:32,690
And my a lot of my own research

892
00:32:32,690 --> 00:32:33,190
interests

893
00:32:33,650 --> 00:32:35,910
focus on printing soft materials.

894
00:32:36,369 --> 00:32:38,369
And so a very simple question you could

895
00:32:38,369 --> 00:32:40,545
ask is, what happens if we take these

896
00:32:40,625 --> 00:32:42,965
printed droplet tissues that are now technologically

897
00:32:43,424 --> 00:32:45,505
quite well established even if the techniques to

898
00:32:45,505 --> 00:32:47,505
make them are reasonably niche and and only

899
00:32:47,505 --> 00:32:49,105
a few labs have the capability to do

900
00:32:49,105 --> 00:32:51,445
it? And we start incorporating

901
00:32:52,065 --> 00:32:54,005
the sort of well established

902
00:32:54,329 --> 00:32:57,210
energy conversion mechanisms that that we've been talking

903
00:32:57,210 --> 00:33:00,329
about today. And this feeds into what Rob

904
00:33:00,329 --> 00:33:02,569
was saying. Can we even take those energy

905
00:33:02,569 --> 00:33:05,049
conversion mechanisms to move away from needing to

906
00:33:05,049 --> 00:33:07,049
even print a system in the first place?

907
00:33:07,049 --> 00:33:09,130
Can we can we make a system that

908
00:33:09,130 --> 00:33:09,630
chooses

909
00:33:10,154 --> 00:33:12,815
seven sets of quotation marks there, but chooses,

910
00:33:13,515 --> 00:33:15,835
how to build itself, how to how to

911
00:33:15,835 --> 00:33:17,535
build itself into a complex structure?

912
00:33:18,634 --> 00:33:19,134
More

913
00:33:19,755 --> 00:33:20,255
immediately

914
00:33:20,555 --> 00:33:21,055
relevant,

915
00:33:21,515 --> 00:33:22,174
I think,

916
00:33:22,529 --> 00:33:25,250
is actually a lot of the rules being

917
00:33:25,250 --> 00:33:28,690
developed to describe animate droplets in particular, you

918
00:33:28,690 --> 00:33:32,710
know, exchange of materials in solution, evaporation, volatility.

919
00:33:33,330 --> 00:33:35,410
These are extremely relevant to a huge range

920
00:33:35,410 --> 00:33:36,630
of consumer goods.

921
00:33:37,105 --> 00:33:39,345
If you think of what a deodorant is,

922
00:33:39,345 --> 00:33:42,384
right, that is an evaporating, partially volatile phase

923
00:33:42,384 --> 00:33:45,585
separating system, lots of liquid components evaporated on

924
00:33:45,585 --> 00:33:47,605
a heated surface of complex topography.

925
00:33:48,304 --> 00:33:50,369
The the the sort of effects we're seeing

926
00:33:50,450 --> 00:33:52,789
are almost certainly seen on a daily basis

927
00:33:53,009 --> 00:33:55,029
in their systems. And if you wanna improve

928
00:33:55,170 --> 00:33:55,670
the

929
00:33:56,130 --> 00:33:58,369
the the performance of those products, you you

930
00:33:58,369 --> 00:34:00,450
probably want to be digging into the the

931
00:34:00,450 --> 00:34:00,950
fundamental

932
00:34:01,329 --> 00:34:03,734
mechanisms that describe animal droplets.

933
00:34:05,414 --> 00:34:07,015
So going from cleaning up an oil spill

934
00:34:07,015 --> 00:34:08,934
to having a deodorant that seeks out the

935
00:34:08,934 --> 00:34:11,255
exact areas that are smelly and and prevents

936
00:34:11,255 --> 00:34:13,815
them from from driving people away? Can you

937
00:34:13,815 --> 00:34:15,494
make a deodorant that wants wants to live

938
00:34:15,494 --> 00:34:16,554
in a sweat plant?

939
00:34:17,049 --> 00:34:19,049
Excellent. So what are the barriers to achieving

940
00:34:19,049 --> 00:34:21,529
some of these, you know, exciting soft matter

941
00:34:21,529 --> 00:34:23,130
developments of the future? You know, what are

942
00:34:23,130 --> 00:34:24,409
the challenge? You've talked a little bit about

943
00:34:24,409 --> 00:34:26,909
the equipment you use to to make them.

944
00:34:27,130 --> 00:34:29,230
Are there challenges there? Are they more theoretical?

945
00:34:30,025 --> 00:34:31,405
What are the what are the issues?

946
00:34:32,184 --> 00:34:33,405
There there are different

947
00:34:33,945 --> 00:34:35,244
issues. Some are more

948
00:34:35,704 --> 00:34:37,405
fundamental, some are practical.

949
00:34:37,704 --> 00:34:38,844
I would say fundamental,

950
00:34:39,545 --> 00:34:40,605
we start to

951
00:34:41,304 --> 00:34:44,025
enter a realm of non equilibrium, far from

952
00:34:44,025 --> 00:34:45,085
equilibrium physics.

953
00:34:46,219 --> 00:34:47,679
This is a new frontier.

954
00:34:48,380 --> 00:34:50,699
People have been studying non equilibrium physics for

955
00:34:50,699 --> 00:34:51,839
a long time, but

956
00:34:52,619 --> 00:34:54,539
I think that we need to further our

957
00:34:54,539 --> 00:34:57,019
level of understanding. So often when you play

958
00:34:57,019 --> 00:34:59,494
with the systems in the lab, you find

959
00:34:59,494 --> 00:35:01,114
behaviors that are completely

960
00:35:01,574 --> 00:35:03,734
alien to you, and then it's actually quite

961
00:35:03,734 --> 00:35:05,734
fun to try to reverse engineer and understand

962
00:35:05,734 --> 00:35:06,474
what's happening.

963
00:35:06,855 --> 00:35:07,355
But

964
00:35:07,974 --> 00:35:10,694
sometimes starting from first principles with this non

965
00:35:10,694 --> 00:35:12,554
equilibrium physics is not possible.

966
00:35:13,650 --> 00:35:16,849
Another challenge that I see is we already

967
00:35:16,849 --> 00:35:18,549
mentioned it earlier, it's miniaturization.

968
00:35:19,809 --> 00:35:22,929
We want to achieve behaviors that typically we

969
00:35:22,929 --> 00:35:23,989
associate to

970
00:35:24,690 --> 00:35:25,589
living organism.

971
00:35:26,609 --> 00:35:28,069
We have been successful

972
00:35:29,114 --> 00:35:29,934
to a degree

973
00:35:30,315 --> 00:35:31,934
at the macroscopic scale,

974
00:35:32,954 --> 00:35:35,914
and biology is extremely good at achieving very

975
00:35:35,914 --> 00:35:36,894
complex behaviors,

976
00:35:37,195 --> 00:35:38,574
packing a lot of information,

977
00:35:38,875 --> 00:35:41,369
a lot of complex machinery in tiny cells,

978
00:35:41,610 --> 00:35:43,450
but we're not there yet. We're really, really

979
00:35:43,450 --> 00:35:46,030
far from achieving anything that looks like that.

980
00:35:46,809 --> 00:35:48,190
Biologists, the inspiration

981
00:35:48,490 --> 00:35:50,990
for that, we are still quite far.

982
00:35:52,410 --> 00:35:54,890
Even just working with liquid materials is a

983
00:35:54,890 --> 00:35:56,030
challenge because

984
00:35:56,605 --> 00:35:58,765
if you go to macroscopic scale where surface

985
00:35:58,765 --> 00:36:01,085
tension starts to dominate, you can say that

986
00:36:01,085 --> 00:36:02,545
liquid starts to have a shape,

987
00:36:03,485 --> 00:36:06,864
but, technically, they're still liquid. So even achieving

988
00:36:06,925 --> 00:36:07,985
all this complexity

989
00:36:08,285 --> 00:36:09,505
in terms of adaptation,

990
00:36:10,364 --> 00:36:11,744
responding to the environment,

991
00:36:12,130 --> 00:36:12,949
sensing the

992
00:36:13,329 --> 00:36:16,449
environment, having complex reactions happening in these tiny

993
00:36:16,449 --> 00:36:17,349
liquid compartments.

994
00:36:18,369 --> 00:36:20,530
All of this has to happen to achieve

995
00:36:20,530 --> 00:36:21,030
activity,

996
00:36:21,409 --> 00:36:21,909
adaptiveness,

997
00:36:22,210 --> 00:36:25,269
and autonomy while keeping the droplet stable, and

998
00:36:25,329 --> 00:36:26,469
it might not be

999
00:36:27,734 --> 00:36:28,234
compatible

1000
00:36:28,534 --> 00:36:29,034
and,

1001
00:36:29,974 --> 00:36:32,454
you you know, you want the droplet to

1002
00:36:32,454 --> 00:36:35,335
survive the process rather than be consumed with

1003
00:36:35,335 --> 00:36:35,835
it.

1004
00:36:36,775 --> 00:36:37,755
There is interdisciplinarity.

1005
00:36:38,934 --> 00:36:40,530
As you've seen, all of these

1006
00:36:41,010 --> 00:36:43,730
topics we've been discussing, it's somehow the crossroad

1007
00:36:43,730 --> 00:36:45,750
between physics, chemistry, and biology.

1008
00:36:46,289 --> 00:36:49,329
We're getting better at discussing things among disciplines,

1009
00:36:50,449 --> 00:36:52,949
but there is still a lot of, technical

1010
00:36:53,010 --> 00:36:55,944
language, technical barriers, language barriers that need to

1011
00:36:55,944 --> 00:36:56,684
be overcome

1012
00:36:57,704 --> 00:36:59,644
to be able to work together.

1013
00:37:00,025 --> 00:37:02,105
And that's already complex when we think about

1014
00:37:02,105 --> 00:37:05,304
different soft matter systems. Imagine something that can

1015
00:37:05,304 --> 00:37:08,105
span across different case like this animate matter

1016
00:37:08,105 --> 00:37:08,605
behaviors.

1017
00:37:09,464 --> 00:37:11,244
So there there are a lot of challenges

1018
00:37:11,385 --> 00:37:13,109
that, need to be tackled,

1019
00:37:13,409 --> 00:37:14,449
and I'm sure that,

1020
00:37:14,849 --> 00:37:16,690
both Joe and Rob will have their own

1021
00:37:16,690 --> 00:37:18,710
challenges that can add up to this. But

1022
00:37:18,769 --> 00:37:20,070
as you can see, it's a very

1023
00:37:20,690 --> 00:37:22,849
rounded and complex problem, and that's why it's

1024
00:37:22,849 --> 00:37:25,175
also fun to to study it.

1025
00:37:26,195 --> 00:37:27,255
Robert and Joe?

1026
00:37:28,195 --> 00:37:29,555
I would like to add to what Georgi

1027
00:37:29,555 --> 00:37:31,195
was saying is, I think we do focus

1028
00:37:31,195 --> 00:37:33,094
a lot on equilibrium physics, but

1029
00:37:33,394 --> 00:37:35,894
there's really exciting stuff happening in non equilibrium

1030
00:37:36,114 --> 00:37:37,829
physics. And some of us actually were hiding

1031
00:37:37,829 --> 00:37:39,690
in plain sight. There's a really nice paper

1032
00:37:39,750 --> 00:37:40,569
from Stanford

1033
00:37:41,029 --> 00:37:43,049
where they looked at food coloring.

1034
00:37:43,509 --> 00:37:44,789
And if you put it down on a

1035
00:37:44,789 --> 00:37:46,630
glass slide, they just chase each other and

1036
00:37:46,630 --> 00:37:48,389
sense each other and, like, dance around on

1037
00:37:48,389 --> 00:37:49,049
the slide.

1038
00:37:49,364 --> 00:37:51,784
It's it's stuff that's everywhere. It's just we

1039
00:37:52,324 --> 00:37:53,465
it tends to be overlooked.

1040
00:37:54,485 --> 00:37:56,965
So finding the thing that's in plain sight

1041
00:37:56,965 --> 00:37:58,744
and understanding it for what it is?

1042
00:37:59,445 --> 00:38:01,204
Yeah. In plain sight or maybe just hiding

1043
00:38:01,204 --> 00:38:02,724
a little bit under the surface with some

1044
00:38:02,724 --> 00:38:04,724
really complicated physics behind it for for some

1045
00:38:04,724 --> 00:38:05,099
reason.

1046
00:38:06,539 --> 00:38:08,059
And, Joe, you want to add to that?

1047
00:38:08,059 --> 00:38:09,920
No. I I think from my perspective,

1048
00:38:10,220 --> 00:38:12,619
both Giorgio and Rob have mostly nailed it.

1049
00:38:12,619 --> 00:38:14,400
I think the the challenge

1050
00:38:14,780 --> 00:38:17,820
to design animate materials, animate droplets is is

1051
00:38:17,820 --> 00:38:19,119
a challenge of interdisciplinary

1052
00:38:19,500 --> 00:38:20,000
collaboration.

1053
00:38:20,934 --> 00:38:21,434
Fundamentally,

1054
00:38:21,974 --> 00:38:24,135
the chemist is scared of physics. The physicists

1055
00:38:24,135 --> 00:38:26,474
are scared of chemists. Everyone's scared of biology.

1056
00:38:27,014 --> 00:38:27,674
This is

1057
00:38:28,295 --> 00:38:29,434
a huge overgeneralization.

1058
00:38:29,974 --> 00:38:31,894
There's obviously tons of people doing great work

1059
00:38:31,894 --> 00:38:34,135
across those disciplines, but I I think maybe

1060
00:38:34,135 --> 00:38:34,875
we do.

1061
00:38:36,190 --> 00:38:38,110
We sit too much in our comfort zone

1062
00:38:38,110 --> 00:38:39,710
and maybe we sit too much in what

1063
00:38:39,710 --> 00:38:42,110
we perceive to be prestigious. Like Rob says,

1064
00:38:42,110 --> 00:38:43,890
I think there's a huge value

1065
00:38:44,910 --> 00:38:46,610
in studying and understanding

1066
00:38:46,910 --> 00:38:48,610
the everyday. And I think there's

1067
00:38:48,989 --> 00:38:49,650
a huge

1068
00:38:50,015 --> 00:38:52,195
a huge wealth of really interesting stuff

1069
00:38:52,494 --> 00:38:54,735
just sort of sat there in, to quote

1070
00:38:54,735 --> 00:38:56,434
his example, a bottle of food coloring.

1071
00:38:58,015 --> 00:39:00,175
Hopefully, that inspires some more listeners to go

1072
00:39:00,175 --> 00:39:02,094
out and look for the interesting soft matter

1073
00:39:02,094 --> 00:39:04,730
phenomena in their in their daily lives. Georgiou

1074
00:39:04,730 --> 00:39:06,889
Volpe, Rob Malinovsky, and Joe Fort, thank you

1075
00:39:06,889 --> 00:39:08,489
so much for coming on the podcast to

1076
00:39:08,489 --> 00:39:10,250
talk about this work, which you can read

1077
00:39:10,250 --> 00:39:12,170
in full in the journal EPL. Thank you

1078
00:39:12,170 --> 00:39:13,230
very much, Margaret.

1079
00:39:13,609 --> 00:39:15,469
Thank you very much. Thank you.

1080
00:39:22,704 --> 00:39:26,405
That was Margaret Harris in conversation with Giorgio

1081
00:39:26,625 --> 00:39:27,125
Volpe,

1082
00:39:27,425 --> 00:39:28,644
Rob Malinowski,

1083
00:39:29,344 --> 00:39:30,565
and Joe Forth

1084
00:39:31,105 --> 00:39:33,204
about the mini review article

1085
00:39:33,585 --> 00:39:34,335
or perspective

1086
00:39:34,809 --> 00:39:36,510
that they wrote for EPL

1087
00:39:36,969 --> 00:39:38,670
about animate droplets.

1088
00:39:39,529 --> 00:39:41,789
Their article is entitled Towards

1089
00:39:42,089 --> 00:39:43,150
Animate Droplets,

1090
00:39:43,849 --> 00:39:45,069
Active, Adaptive,

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00:39:45,369 --> 00:39:46,109
and Autonomous.

1092
00:39:46,824 --> 00:39:48,505
And if you'd like to read it, it's

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00:39:48,505 --> 00:39:52,285
available for free on the IOP science website.

1094
00:39:52,905 --> 00:39:55,085
Just search for the journal EPL.

1095
00:39:56,344 --> 00:39:57,804
Our thanks to Giorgio,

1096
00:39:58,344 --> 00:39:59,724
Rob, and Joe,

1097
00:40:00,030 --> 00:40:01,650
and to the journal EPL,

1098
00:40:02,030 --> 00:40:05,390
which sponsored this episode of the Physics World

1099
00:40:05,390 --> 00:40:06,369
weekly podcast.

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00:40:06,989 --> 00:40:09,710
I'm Hamish Johnston, and our producer is Fred

1101
00:40:09,710 --> 00:40:10,210
Iles.

1102
00:40:10,590 --> 00:40:12,989
The theme music for this podcast is called

1103
00:40:12,989 --> 00:40:15,464
one three seven, and it was composed

1104
00:40:15,764 --> 00:40:16,505
and performed

1105
00:40:16,804 --> 00:40:17,704
by the physicist

1106
00:40:18,324 --> 00:40:19,224
Philip Moriarty.

1107
00:40:20,244 --> 00:40:23,464
Join us next week for more fascinating stories

1108
00:40:23,605 --> 00:40:25,385
from the world of physics.