1 00:00:08,240 --> 00:00:11,439 Hello, and welcome to the Physics World weekly 2 00:00:11,439 --> 00:00:11,939 podcast. 3 00:00:12,535 --> 00:00:15,595 In this episode, you'll hear my colleague, Margaret 4 00:00:15,734 --> 00:00:16,234 Harris, 5 00:00:16,614 --> 00:00:17,355 in conversation 6 00:00:17,975 --> 00:00:18,795 with three 7 00:00:19,175 --> 00:00:20,795 soft matter scientists 8 00:00:21,414 --> 00:00:23,355 with an interest in the squishy, 9 00:00:23,894 --> 00:00:24,394 messy, 10 00:00:24,774 --> 00:00:28,154 and exciting physics of animate droplets. 11 00:00:29,429 --> 00:00:32,170 This episode is sponsored by EPL, 12 00:00:32,950 --> 00:00:35,210 a journal that publishes original 13 00:00:35,909 --> 00:00:37,369 high quality letters 14 00:00:37,750 --> 00:00:39,850 in all areas of physics. 15 00:00:40,984 --> 00:00:43,564 EPL operates under the scientific 16 00:00:43,945 --> 00:00:45,244 policy and control 17 00:00:45,704 --> 00:00:48,045 of the European Physical Society 18 00:00:48,744 --> 00:00:50,684 and is published by EDP 19 00:00:50,984 --> 00:00:51,484 Sciences, 20 00:00:52,024 --> 00:00:54,125 the Italian Physical Society, 21 00:00:54,750 --> 00:00:56,369 and IOP Publishing, 22 00:00:56,989 --> 00:00:58,369 which also publishes 23 00:00:58,909 --> 00:00:59,890 Physics World. 24 00:01:00,509 --> 00:01:02,049 Now over to Margaret. 25 00:01:10,444 --> 00:01:12,604 My guests in today's podcasts are a trio 26 00:01:12,604 --> 00:01:14,604 of soft matter scientists who have a particular 27 00:01:14,604 --> 00:01:16,224 interest in the physics of droplets. 28 00:01:16,685 --> 00:01:19,325 They are Giorgio Volpe, a professor of soft 29 00:01:19,325 --> 00:01:21,504 matter at University College London, 30 00:01:21,965 --> 00:01:24,524 Rob Malinovsky, a research fellow in soft matter 31 00:01:24,524 --> 00:01:25,984 physics who's also at UCL, 32 00:01:26,469 --> 00:01:28,469 and Joe Forth, who's a lecturer at University 33 00:01:28,469 --> 00:01:30,469 of Liverpool, but was at UCL a few 34 00:01:30,469 --> 00:01:32,329 years ago when this collaboration began. 35 00:01:32,950 --> 00:01:35,030 Georgio, Rob, and Joe, hello, and welcome to 36 00:01:35,030 --> 00:01:35,609 the podcast. 37 00:01:36,629 --> 00:01:38,950 Hello. Thank you for having us here. I'm 38 00:01:38,950 --> 00:01:41,509 gonna start with the softest possible question and 39 00:01:41,509 --> 00:01:43,965 maybe the biggest. What is soft matter, and 40 00:01:43,965 --> 00:01:46,225 why is it so fascinating and important? 41 00:01:47,805 --> 00:01:51,165 So soft matter is very generally the the 42 00:01:51,165 --> 00:01:53,025 science of of squishy stuff. 43 00:01:53,405 --> 00:01:55,645 A lot of it is very everyday stuff. 44 00:01:55,645 --> 00:01:57,405 You can think of it as the the 45 00:01:57,405 --> 00:01:59,140 the science of of shampoo, and a lot 46 00:01:59,140 --> 00:02:01,719 of the fundamental findings were made by 47 00:02:02,099 --> 00:02:03,859 large companies trying to figure out how do 48 00:02:03,859 --> 00:02:05,640 we make better soaps, better shampoos. 49 00:02:06,819 --> 00:02:09,479 It very often consists of 50 00:02:09,780 --> 00:02:12,375 materials that are a large fraction of liquid. 51 00:02:12,534 --> 00:02:15,414 You have lots of small particles, lots of 52 00:02:15,414 --> 00:02:16,314 surface area. 53 00:02:16,935 --> 00:02:19,014 Surface tension tends to dominate a lot of 54 00:02:19,014 --> 00:02:19,594 the behavior. 55 00:02:20,134 --> 00:02:22,235 You have lots and lots of weak multivalent 56 00:02:22,534 --> 00:02:24,694 forces. So the system can be moved around 57 00:02:24,694 --> 00:02:26,775 and broken up by thermal motion or or 58 00:02:26,775 --> 00:02:28,550 just by poking it or shaking it and 59 00:02:28,550 --> 00:02:29,449 all of these things. 60 00:02:30,229 --> 00:02:33,189 Physics wise, it's it's interesting because it can 61 00:02:33,189 --> 00:02:35,770 it can change shape. You can incorporate mechanisms 62 00:02:35,830 --> 00:02:38,150 for energy conversion, and that in turn means 63 00:02:38,150 --> 00:02:40,469 that soft matter can can deform itself. It 64 00:02:40,469 --> 00:02:41,209 can move. 65 00:02:41,509 --> 00:02:43,245 You have a whole 66 00:02:44,025 --> 00:02:47,245 diverse range of mechanisms for for elasticity. 67 00:02:47,544 --> 00:02:49,485 If you if you compare it with, say, 68 00:02:49,784 --> 00:02:52,344 typical solids, crystalline solids, they're just they're just 69 00:02:52,344 --> 00:02:54,745 rigid because they consist of repeating patterns. Whereas, 70 00:02:54,745 --> 00:02:57,030 you know, in soft matter, you have all 71 00:02:57,030 --> 00:02:59,770 sorts of mechanisms for different types of elasticity, 72 00:03:00,389 --> 00:03:01,770 viscosity, and viscoelasticity. 73 00:03:02,949 --> 00:03:05,689 With that comes complex deformation and complex flow. 74 00:03:06,789 --> 00:03:07,849 With these 75 00:03:08,594 --> 00:03:11,394 energy conversion mechanisms, you get a whole bunch 76 00:03:11,394 --> 00:03:12,134 of interesting 77 00:03:12,594 --> 00:03:13,974 non equilibrium behavior. 78 00:03:14,435 --> 00:03:16,694 And at that point, the palette of behavior 79 00:03:16,754 --> 00:03:18,854 you can see in in soft matter systems 80 00:03:19,155 --> 00:03:21,314 grows massively. It it still feels like a 81 00:03:21,314 --> 00:03:23,159 field where you can mix a bunch of 82 00:03:23,159 --> 00:03:25,080 stuff together, stick it under a microscope, and 83 00:03:25,080 --> 00:03:26,300 you'll you'll see 84 00:03:26,760 --> 00:03:27,740 something new. 85 00:03:28,280 --> 00:03:30,540 Beyond physics, just sort of scientifically, 86 00:03:31,000 --> 00:03:32,460 it's inherently very interdisciplinary. 87 00:03:33,480 --> 00:03:33,980 You 88 00:03:35,000 --> 00:03:37,099 have the chance to incorporate interesting 89 00:03:37,400 --> 00:03:37,900 chemistry. 90 00:03:38,405 --> 00:03:41,205 The material property sort of underpinning soft matter 91 00:03:41,205 --> 00:03:43,444 are very similar to the material and physical 92 00:03:43,444 --> 00:03:44,504 properties underpinning 93 00:03:45,205 --> 00:03:46,905 biological systems and biological 94 00:03:47,205 --> 00:03:47,705 tissues. 95 00:03:48,724 --> 00:03:50,564 And there's with the sort of study of 96 00:03:50,564 --> 00:03:53,969 non equilibrium systems comes this translational relevance to 97 00:03:53,969 --> 00:03:56,370 active matter, which we'll sort of get to. 98 00:03:56,370 --> 00:03:58,209 I guess it's a matter of debate whether 99 00:03:58,209 --> 00:03:59,750 or not, soft matter, 100 00:04:00,289 --> 00:04:02,609 how what the overlap is between active matter 101 00:04:02,609 --> 00:04:04,689 and and soft matter, but there's certainly a 102 00:04:04,689 --> 00:04:06,849 big big overlap on the the Venn diagram 103 00:04:06,849 --> 00:04:07,989 of those two circles. 104 00:04:08,745 --> 00:04:10,525 As for why I I find it interesting, 105 00:04:10,585 --> 00:04:13,245 my my answer to this has has changed 106 00:04:13,944 --> 00:04:15,784 over the years. When I first learned about 107 00:04:15,784 --> 00:04:17,865 it as an undergrad, the the selling point 108 00:04:17,865 --> 00:04:19,785 for me was that it didn't feel like 109 00:04:19,785 --> 00:04:22,100 the usual physics. It didn't feel like particles 110 00:04:22,100 --> 00:04:25,060 and Maxwell's equations and whatever. It felt every 111 00:04:25,060 --> 00:04:25,560 day, 112 00:04:25,860 --> 00:04:28,740 this idea that of studying the the physics 113 00:04:28,740 --> 00:04:31,240 of gunky liquids or the physics of shampoo. 114 00:04:31,860 --> 00:04:33,644 For me, it was exciting. But, to me, 115 00:04:33,644 --> 00:04:34,925 it was like, wow. You can you can 116 00:04:34,925 --> 00:04:36,524 study this stuff and people will pay you 117 00:04:36,524 --> 00:04:38,784 to do it. That was what excited me. 118 00:04:39,404 --> 00:04:41,084 So I'm getting the impression here that soft 119 00:04:41,084 --> 00:04:43,084 matte is everything that's really messy in physics, 120 00:04:43,084 --> 00:04:44,625 and that's what you love about it. 121 00:04:45,164 --> 00:04:46,925 Yeah. I I so certainly for me, and 122 00:04:46,925 --> 00:04:49,289 it's certainly I think it's something that the 123 00:04:49,289 --> 00:04:51,849 the purists it's sort of on the borderline 124 00:04:51,849 --> 00:04:53,629 of whether one considers it 125 00:04:53,930 --> 00:04:56,509 physics. I I because of this inherent interdisciplinarity, 126 00:04:56,969 --> 00:04:58,169 I I think a lot of it is 127 00:04:58,169 --> 00:05:01,310 certainly not unusual for the the particle physicist 128 00:05:01,365 --> 00:05:03,925 think of it as belonging to something more 129 00:05:03,925 --> 00:05:07,144 like engineering or chemistry, but that interdisciplinarity 130 00:05:07,685 --> 00:05:09,044 is is a big part of the appeal 131 00:05:09,044 --> 00:05:09,704 for me. 132 00:05:10,245 --> 00:05:12,004 Georgio, your work in particular is all on 133 00:05:12,004 --> 00:05:13,285 animate matter. Do you want to touch on 134 00:05:13,285 --> 00:05:14,644 them what the difference is if there are 135 00:05:14,644 --> 00:05:16,800 any differences between soft matter 136 00:05:17,199 --> 00:05:19,300 and animate matter. Because the word animate 137 00:05:19,680 --> 00:05:21,839 to a layperson usually means living, but I 138 00:05:21,839 --> 00:05:24,240 understand that's not necessarily the case with animate 139 00:05:24,240 --> 00:05:24,740 matter. 140 00:05:25,599 --> 00:05:27,939 No. It is not the case. And, actually, 141 00:05:28,079 --> 00:05:30,159 when we talk about animate matter, we're really 142 00:05:30,159 --> 00:05:32,824 thinking about purely synthetic systems, so 143 00:05:34,645 --> 00:05:37,705 artificial. In a nutshell, animate matter is lifelike, 144 00:05:37,925 --> 00:05:39,785 but it doesn't mean that it's alive. 145 00:05:40,245 --> 00:05:42,264 And if you think, for example, 146 00:05:43,045 --> 00:05:45,045 about the droplet, since we're going to talk 147 00:05:45,045 --> 00:05:45,785 about droplets, 148 00:05:46,360 --> 00:05:48,600 you can think that the droplet can move 149 00:05:48,600 --> 00:05:50,680 on its own. It can respond to the 150 00:05:50,680 --> 00:05:51,180 environment. 151 00:05:51,800 --> 00:05:53,979 It can perform task almost 152 00:05:54,919 --> 00:05:57,479 if it was following a purpose. Right? It 153 00:05:57,479 --> 00:05:59,579 looks like it's alive, but it's not. 154 00:06:00,014 --> 00:06:00,514 And, 155 00:06:00,814 --> 00:06:04,115 ultimately, it's just responding to physical and chemical 156 00:06:04,175 --> 00:06:04,675 rules. 157 00:06:05,694 --> 00:06:06,354 So animate, 158 00:06:06,654 --> 00:06:08,574 whether we're talking about soft matter or we're 159 00:06:08,574 --> 00:06:10,754 talking about larger or smaller systems, 160 00:06:11,134 --> 00:06:12,595 it really is about the behavior. 161 00:06:13,169 --> 00:06:15,810 It's a system that is fully synthetic and 162 00:06:15,810 --> 00:06:18,689 it can resemble in terms of properties, in 163 00:06:18,689 --> 00:06:19,589 terms of behavior, 164 00:06:20,370 --> 00:06:21,750 those of living systems. 165 00:06:22,769 --> 00:06:24,229 The way in which we can describe 166 00:06:24,689 --> 00:06:27,485 animal matter is usually through 167 00:06:27,865 --> 00:06:28,365 categorizing 168 00:06:28,745 --> 00:06:30,824 according to three principles. These are called the 169 00:06:30,824 --> 00:06:32,125 three aids of animacies. 170 00:06:33,145 --> 00:06:35,465 And the three aids of animacies are three 171 00:06:35,465 --> 00:06:38,185 principles that tend to describe act this animate 172 00:06:38,185 --> 00:06:40,125 matter based on whether they are active, 173 00:06:40,425 --> 00:06:40,925 adaptive, 174 00:06:41,550 --> 00:06:42,290 or autonomous. 175 00:06:43,550 --> 00:06:45,790 Animate matter, then there is a third field, 176 00:06:45,790 --> 00:06:48,209 which is active matter. And there is definitely 177 00:06:48,269 --> 00:06:50,910 overlap between the freeze of matter, animate matter, 178 00:06:50,910 --> 00:06:53,550 and active matter, but the each one each 179 00:06:53,550 --> 00:06:55,870 one of them has their own characteristics. So 180 00:06:55,870 --> 00:06:57,764 there is overlap, but they're not exactly the 181 00:06:57,764 --> 00:06:58,665 same field. 182 00:06:59,764 --> 00:07:02,324 Okay. I want to dig into these three 183 00:07:02,324 --> 00:07:04,404 a's you say, because you've recently written a 184 00:07:04,404 --> 00:07:06,904 paper for the journal EPL that focuses on 185 00:07:07,045 --> 00:07:09,365 animate droplets. And you've said what animate means. 186 00:07:09,365 --> 00:07:10,985 It comes with these three principles. 187 00:07:11,419 --> 00:07:13,660 Let's start with active. What does active mean 188 00:07:13,660 --> 00:07:14,480 in this context? 189 00:07:15,660 --> 00:07:17,899 So active is the simplest of those three 190 00:07:17,899 --> 00:07:18,399 principles. 191 00:07:18,779 --> 00:07:20,459 When you say a droplet is active, it 192 00:07:20,459 --> 00:07:22,459 simply means that it can take energy from 193 00:07:22,459 --> 00:07:24,459 its environment and convert it from one form 194 00:07:24,459 --> 00:07:25,199 into another. 195 00:07:25,544 --> 00:07:27,964 So a really nice kind of simple example 196 00:07:28,104 --> 00:07:30,024 is there are these oil droplets. If you 197 00:07:30,024 --> 00:07:31,464 take a specific kind of oil and you 198 00:07:31,464 --> 00:07:32,925 put it into into water, 199 00:07:33,305 --> 00:07:35,324 if you impose a chemical gradient 200 00:07:35,625 --> 00:07:36,604 onto this droplet, 201 00:07:37,144 --> 00:07:39,144 various physical forces, they could be surface tension 202 00:07:39,144 --> 00:07:41,240 driven, could be something else, But it will 203 00:07:41,240 --> 00:07:43,279 drive up that chemical gradient or down that 204 00:07:43,279 --> 00:07:44,100 chemical gradient. 205 00:07:44,480 --> 00:07:46,720 And what droplet is doing there is converting 206 00:07:46,720 --> 00:07:49,120 kind of this chemical potential into a kinetic 207 00:07:49,120 --> 00:07:51,139 energy, and, you know, that's the motion. 208 00:07:51,600 --> 00:07:53,779 And these are really nice because you can 209 00:07:53,914 --> 00:07:55,354 think of it as a rudimentary form of 210 00:07:55,354 --> 00:07:57,035 sensing. There's there's no kind of, you know, 211 00:07:57,035 --> 00:07:59,435 thinking or internal processing. It's all physical based, 212 00:07:59,435 --> 00:08:01,435 but it's in its really simplest sense, the 213 00:08:01,435 --> 00:08:03,675 droplet is is sensing this chemical and reacting 214 00:08:03,675 --> 00:08:05,035 to it. But like I said, not like 215 00:08:05,035 --> 00:08:08,074 biological something. There's no thinking. There's no internal 216 00:08:08,074 --> 00:08:10,209 processing. It's just pure physics, and they can 217 00:08:10,209 --> 00:08:12,069 make really neat, neat little swimmers. 218 00:08:12,449 --> 00:08:13,829 What do you mean by a swimmer? 219 00:08:14,370 --> 00:08:16,290 It's just a droplet that can propel itself 220 00:08:16,290 --> 00:08:19,009 pretty much through, through this bulk medium. So 221 00:08:19,009 --> 00:08:20,610 it's not gonna be it's not gonna have 222 00:08:20,610 --> 00:08:22,610 arms. It doesn't have a propeller or anything. 223 00:08:22,610 --> 00:08:24,689 It's usually a quite common example is through 224 00:08:24,689 --> 00:08:26,795 surface tension. So you end up with these 225 00:08:26,795 --> 00:08:28,955 surface tension driven flows. And when you have 226 00:08:28,955 --> 00:08:30,014 a flow, you can 227 00:08:30,555 --> 00:08:32,394 impart a force onto the surrounding medium, and 228 00:08:32,394 --> 00:08:34,955 that causes this this driving, this this causes 229 00:08:34,955 --> 00:08:36,495 this motion. It's swimming. 230 00:08:37,115 --> 00:08:39,695 And then the second a was adaptive. 231 00:08:40,220 --> 00:08:41,420 Do one of you want to tell us 232 00:08:41,420 --> 00:08:43,279 what adaptive is? Sure. 233 00:08:44,139 --> 00:08:47,360 Adaptive material or or or material that's exhibiting 234 00:08:47,580 --> 00:08:49,660 adaptation is the it's the ability of a 235 00:08:49,740 --> 00:08:52,080 of an object, be that a a bacterium, 236 00:08:52,220 --> 00:08:53,660 a bird, or a or in this case, 237 00:08:53,660 --> 00:08:56,524 a droplet, to sense its external environment or 238 00:08:56,524 --> 00:08:58,924 to sense another object and respond to that 239 00:08:58,924 --> 00:08:59,424 change. 240 00:09:00,044 --> 00:09:02,445 As we've sort of seen from from Rob, 241 00:09:02,445 --> 00:09:03,424 a lot of these examples 242 00:09:04,365 --> 00:09:05,105 are are biological. 243 00:09:05,565 --> 00:09:07,485 And going back to what Georgio has said 244 00:09:07,485 --> 00:09:09,325 previously, a lot of the field of animate 245 00:09:09,325 --> 00:09:11,579 matter is really about recapitulating a recapitulating a 246 00:09:11,579 --> 00:09:14,539 lot of phenomena that we see and grasp 247 00:09:14,539 --> 00:09:17,579 intuitively from from biology and and recapitulating them 248 00:09:17,579 --> 00:09:19,579 in a in a synthetic system. And that 249 00:09:19,579 --> 00:09:22,539 and that synthetic system can have biological parts 250 00:09:22,539 --> 00:09:25,214 in it, but our idea here is to 251 00:09:25,214 --> 00:09:27,235 to to produce something synthetic 252 00:09:27,615 --> 00:09:29,934 and maybe from a physicist's perspective, produce something 253 00:09:29,934 --> 00:09:30,434 reductively. 254 00:09:31,695 --> 00:09:32,995 In terms of adaptation, 255 00:09:33,855 --> 00:09:36,019 that change can be both to a change 256 00:09:36,019 --> 00:09:38,259 in its surrounding environment, be that a change 257 00:09:38,259 --> 00:09:40,580 in surfactant concentration or a change of in 258 00:09:40,580 --> 00:09:43,879 pH or whatever, or to the presence of 259 00:09:44,100 --> 00:09:44,600 another, 260 00:09:45,220 --> 00:09:46,360 for instance, bacterium. 261 00:09:46,740 --> 00:09:49,160 So so, you know, a a bacterium might 262 00:09:49,300 --> 00:09:51,855 adjust its its metabolism based on food or 263 00:09:51,855 --> 00:09:55,235 reagent concentrations or might change its swimming direction 264 00:09:55,375 --> 00:09:57,315 in response to the presence of other bacteria. 265 00:09:57,934 --> 00:09:59,215 We need to be a little bit careful 266 00:09:59,215 --> 00:10:01,715 here because bacteria have a a fairly 267 00:10:02,190 --> 00:10:05,230 complex set of stimuli and responses that they 268 00:10:05,230 --> 00:10:07,549 can exhibit. And so these guys, as I 269 00:10:07,549 --> 00:10:09,549 guess, Georgio would tell us, definitely count as 270 00:10:09,549 --> 00:10:11,970 autonomous, which is this third day of animacy. 271 00:10:12,190 --> 00:10:14,129 And so I think arguably what makes something 272 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, 1091 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 1093 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. 1100 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.