Bringing hard electronics into soft and squishy bodies

Creating squishy electronics

0:00Hey, it's Flora, and you're listening to Science Friday. A lot of things in life are squishy. Your skin, your organs, goo inside of you. But a lot of our high-tech world is rigid and hard. Figuring out how to get those two worlds to work together is something that my next guest has thought a lot about as the inventor of biocompatible electronic devices. He's designed things like flexible probes, a pacemaker smaller than a grain of rice, wireless sensors that stick to you like a temporary tattoo and monitor your body in real time. And that is just to name a few. John A. Rogers is a prolific inventor with more than 100 patents. He's also a professor at Northwestern University. John, welcome to Science Friday.

0:52Yeah, thanks for having me. Thanks for being here. When you started out, what did people think about this idea of squishy electronics?

1:02Well, I guess mixed feelings in a way. We got interested in this area shortly after I started my independent career at Bell Laboratories. So, you know, the place where the transistor was invented, fiber optic communications, information theory, and so on. We were working on flexible electronics, and we were thinking about applications like, you know, paper-like displays or ultra-low-cost product-level electronic tags, things of that sort. When I moved to University of Illinois, there was a lot of interest from DARPA, sort of the military, you know, R&D division in that area, and thinking about these flexible electronic systems as kind of field deployable communication networks and so on.

1:48And we didn't really start getting into this notion of electronics in biocompatible forms, so thinking about not only flexible devices, but ones that were sort of soft and squishy, as you mentioned, until I gave a talk at University of Pennsylvania in electrical engineering. And it just so happened a few of the neurosurgeons saw the title of my talk, got interested, came over, listened to the talk, and asked whether I ever thought about taking those flexible electronic devices and putting them on a brain. A very squishy organ. Yeah, and that was kind of the starting point, you know, for us in thinking about electronics that look a lot more like biology to allow for that kind of intimate level of integration.

Engineering challenges and biology

2:25I mean, biosensors, biocompatible electronics feel so hot right now, but what are the big problems that you need to overcome to make them? Well, a lot of things. I would say there's a set of challenges kind of in an engineering domain, and then there's a corresponding set of challenges kind of in the realm of fundamental science. At the engineering level, the real challenge is how do we convert conventional sort of silicon-integrated circuit technology, currently built on silicon wafers, which are plainer, rigid, brittle?

2:57How do you transform that kind of function into a platform that would allow for, you know, soft, curvilinear integration with the textured surface of the brain? Or how would you develop a class of electronics that would allow you to gently wrap it around the surface of the heart, where you have not only a complex geometry, but also a time-dynamic motion associated with cycles of, you know, the cardiac rhythm and so on? And that's opening up a whole set of topics that turn out to be really interesting from an academic sort of engineering science standpoint.

3:31But then you have to also grapple with what happens when you put a man-made system into contact with a living, healing, dynamic biological environment. Then you have to think about the interface and how do you exchange information at that interface where the lines of communication are fundamentally different. You think about electronics as operating on the basis of electronics and photons, you think about biology. Now you're thinking about flux of ions and biochemical species and just fundamentally different kind of language and how do you do the translation.

4:01So tremendous set of interesting topics for research, but where successful outcomes, we believe, will really transform the way that we think about basic understanding of living systems and also technologies to aid in the way we care for patients. You have this background in physics and chemistry, obviously engineering. Did you also have to like almost go back to medical school to do this work? Well, a little bit, you know, we're extremely collaborative. So if you take a look at the papers that we published, they almost always involve multiple senior investigators and their students.

4:35So I think it creates a tremendously rich learning environment for the students. And that's kind of my main priority as an educator, as a faculty member. We want to do the research, but we also want to train the next generation. And so we try to learn, but we don't strive to become experts outside of our domain. You know, we have things that we do pretty well. We want to focus on those and then leverage that set of expertise against complementary, you know, knowledge and expertise from collaborators. And we've been able to make that work at a very high level.

5:08Do you know when you don't know enough? Usually I don't know enough, I would say. You know, we kind of have like, I would say, a T-shaped kind of expertise profile. We're pretty good at material science, electronic devices, semiconductor physics. That's the, you know, the pointy part of the T. And then the top of the T, I think it allows us to effectively communicate and engage with people who have expertise outside of our domain. And so the top of that T is very broad and the shaft is very narrow, but very deep.

5:44And that's worked pretty well for us. I'm so interested in your process. Do you start with an idea for something you want to build and work towards it? Or do you start with the materials and the chemistry and say, oh, what could I do with all this? Well, I think it's a blend. You know, I'm fortunate to run a fairly large research group. So we have a variety of activities. I would say in one space we, you know, are interested in sort of blue sky kind of undirected research, discovery oriented, where we, you know, think we have kind of an interesting material, want to investigate that, or we want to develop something that we think could have promise in the future, not crystal clear where that's going to go.

6:26So I think it's important that a certain fraction of our programs are kind of in that sort of space. But a lot of our projects come to us from the clinical community, for the neuroscience community, where they are aware of some of the unique capabilities that we have. And they have a challenge in care for their patients, or they have a challenge in the kind of studies that they're doing on a brain organoid, for example, where they think technology might provide a solution. And then they come to us and say, hey, you know, it'd be really great if you could do X, Y, and Z. So pretty much a blend, I would say, across that entire spectrum.

6:59And then a few things kind of in between those two limiting cases. When you start a project, do you get obsessed? Like, are you the kind of person that sleeps in the office? Pretty much. Yeah, I would say. You know, I think there are a lot of smart people out there, for sure. But I think there's a smaller subset of those folks who can become single-minded and, like, persistent, like, at a scary level. And probably I'm kind of in that domain, for better or worse.

7:30And so obsession is a very key part of it. Give me an example of a project that was really difficult, like, maybe unexpectedly difficult. Give me the case study and how you sort of worked around the problems. Well, I would say, like, almost everything we try to do is difficult. Like, if it's easy, then probably, you know, somebody else could take that on or, you know, it's probably going to happen anyway.

Case study of a temporary pacemaker

7:52But I'll give you one example. So we were approached by cardiac surgeons, and they were interested in developing a new kind of temporary pacemaker. And so I didn't know anything about this, but evidently if you go in and you have a structural failure, valve failure in a heart, and that requires, you know, an invasive surgery, there's a critical risk period following that surgery as the patient is recovering. And so as a consequence of that, these surgeons, in many cases, will leave a temporary pacing lead in the patient, interfaced to the heart, passing transcutaneously to an external box of electronics to deliver the stimulating pulses of the heart to pace it as necessary during that recovery period.

8:33That sounds a little clunky. Yeah, yeah. So that was the problem. Two problems. One is it tethers the patient to that box of electronics. And then the other problem is that it ultimately requires extraction. And the problem with pulling it out is by the time that it's ready for removal, in many cases, there's a fibrotic capsule that's developed around that pacing lead. And so when you pull it out, you tear that scar tissue, but that tearing can also lead to damage to the healthy cardiac tissue, leading to an internal bleed, and that could lead to the death of the patient.

9:05So they came to us and they said, hey, we're aware of this class of bioelectronics that you guys have been working on that have this unique defining characteristic that it's water soluble. So they asked, can you take that base of capability and develop it into a wirelessly powered, fully implantable, temporary pacemaker that would just dissolve away after it's no longer needed? We don't have to do the surgical extraction. We don't have to tether to the external electronics as fully implantable. Can you guys go off and do that?

9:37Wait, so like this is, let me just make sure I understand. This is like disappearing ink for a sensor. Like you put it in, it's completely wireless, it does all of this monitoring that you need, and then when you don't want it, it just poof, degrades away? Yeah, yeah, it's sort of crazy, but you can do that. And so we can build radios and sensors and, you know, A to D converters, amplifiers, whatever you want. It seems like spycraft to me, but okay, keep going. Yeah, it's sort of weird. But just to rewind, we actually got our start in that class of technology, again, through funding from DARPA.

10:10They were interested in electronics to be deployed in the field and then disappear to eliminate the risk associated with unwanted recovery of that sensitive electronics by an adversary. Okay, so it literally is spycraft. Yeah, back to your question. Yeah, pretty much. But then we thought, you know, okay, military, that's important. Probably somebody should work on that. But my students were a lot more interested in how this could be leveraged to improve human health, and so that's kind of the centroid of our activity around this technology.

10:41But anyway, we developed this. It worked, and that was fine. But then they came back and said, well, this looks pretty good, but in most cases, we're using this temporary pacing lead for pediatric patients, and that device is too big for an infant. And we're like, geez, that's unfortunate, you know, so we've got to go back to the drawing board and try to create something that is dramatically smaller but offering the same functionality. And so I think in the intro, you mentioned super tiny pacemakers. That's what led to the development of these, you know, millimeter scale.

11:14It was about the size of a sesame seed, actually, so it provides all the same function. It's a different kind of operating principle. And then, just to cap off this story, then the next challenge was, oh, you can do it with infants. Can you do it with a fetus? And so evidently, there are, well, and we actually work with a fetus scopic surgeon. I didn't know anything about this either, but, you know, the medical community is doing all kinds of stuff. The fetus scopic surgeon at Lurie Children's Hospital approaches and say, hey, you have this temporary pacemaker for infants and adults. Can you develop it for use with a fetus?

11:45And then that places even more stringent requirements on how the device operates, how it needs to be implanted, what the sizes are. So we haven't published that yet, but we've figured that out as well. So anyway, there are multiple challenges, but it's a really stimulating, great kind of research, you know, I think for me. And the students get pretty jazzed about it also. We have to take a quick break, but when we come back, I want to ask you about how you pick your problems, you know, how you pick the problems you know you can solve. Are you up for that?

12:16Sure. John, you have a ton of patents, and the thing that's so striking is that many of them are in use commercially right now, so a lot of successes.

Selecting problems and finding success

12:38But I'm guessing that people must come to you with directed problems that you're like, actually, no, I can't do this. How do you know when to pass?

12:49That's a great question. So I think a lot of our collaborations are kind of in, you know, as I mentioned before, that medical domain. So clinicians are really interesting people in the sense that they're similar to engineers because they are oriented around solving problems. And that's what, you know, engineers like myself are interested in doing, but they have a different language. They have a different knowledge base and different set of perspectives. So we get inquiries, and they fall into three buckets. So the first one would be a problem that one could probably solve in one's garage with a saw and a drill, you know, and a hammer, that type of thing.

13:26Those aren't problems for us. Somebody should solve them, and in many cases, those solutions could really, you know, benefit patients, but somebody else can probably take that on. So that's one extreme. The other extreme would be a request for a technology that would require us to break multiple laws of thermodynamics and physics. One law is okay, but multiple is no good. Well, yeah, one or more typically. So anyway, that's kind of in a Star Trek realm, and those conversations sometimes lead to something that's sort of actionable, but I would say, you know, there is, you know, a set that kind of fall in that space.

14:05And we're looking for something in between, something where there's some level of innovation or some level of uniqueness or some degree of alignment with, you know, our particular approaches and material sets and fabrication schemes and so on. And so that's kind of how we think about project selection and prioritization kind of at a rough level. Is it a gut feeling? Is it a matrix you consult? Like, do you feel like you need to develop an intuition for this?

14:38Yeah, I've been doing it for a long time. So I think over the years, you kind of develop a sense of what's likely to work, what's not going to work. But I would say still, you know, there are a lot of failures. I mean, it's just failures. You're swimming in failures most of the time, and you're just, like, scramming around trying to find something that works. So it's not like you ever kind of figure it out. I think if you've figured it out, then the uncertainty goes away, and then, you know, maybe that's not even research anymore. So I would say that, you know, a lot of times, however, we can see a way to sort of modify or adapt or combine several technologies that we're already pretty comfortable with to create something new.

15:17And so those instances, you know, the risk is the lowest, but you're still doing something that's differentiated, you know, and kind of distinct from things that we or others have done in the past. It doesn't feel great to swim in failure, in my experience, anyway. How do you cope? You really have to savor the successes, I guess. I think more than anything, you know, at my stage in my career, I kind of live for the students more than anything, and I want to see them succeed.

15:48So I would say the greatest level of satisfaction for me is seeing a student develop and then go off and develop like a super successful career of their own, and sometimes that's in academics or industrial lab. And that's kind of, you know, what I do it for at this point, you know, if I publish 1,000 papers, do I need 1,001? No, not really, but my students need to publish, so I got to, you know, kind of work with them to make that happen. You know, there can be this cultural divide between, quote, pure science and the applied world.

16:25How do you feel about that? I like both. You know, I think the Bell Labs environment was a fantastic place for me to kind of experience. It was a little bit kind of at the tail end of the golden age of the labs, but nevertheless, incredible level of talent. I was in the physics lab. I was hired by Horst Stormer, who won the Nobel Prize in Physics the next year. And I think it represents the perfect blend of fundamental science, but in the service of technology that could be broadly beneficial to people.

16:57Trying to, you know, do something that can, you know, benefit humanity, I guess maybe it's a lofty goal. But anyway, we want to get things out of the lab. I think that's the point. I think for me, a role model is John Bardeen, who is a theoretical physicist focused on semiconductor charge transport. And working with Bretagne and Shockley, they invented the transistor, won the Nobel Prize, changed the world. You know, if you can aspire to that level of science and technology, I think that's a model that we like to think about.

17:30So put another way, we'd like to generate knowledge for the ages, but technology for today. I mean, we'd like to be able to do both of those things if we can. I think that's the perfect place to leave it. John A. Rogers is a professor at Northwestern University and director of the Query Simpson Institute of Bioelectronics there. Thank you for joining me today. This was a pleasure. Yeah, thank you. Thank you. Thank you. Thank you. Thank you. Thank you. Thank you.

18:00This episode was produced by Charles Berquist. If Science Friday is your source of knowledge for the ages, consider telling the world about it. You can leave us a review on your favorite podcast app of choice, or even just tell your friends to listen. That helps, too. We'll see you next time. Thank you for listening. I'm Flora Lichtman.