Implanted Electronics and Artificial Skin
Kat - We're joined by Stephanie Lacour from the Cambridge Nanoscience Centre where she's working on making flexible electronics that could be worn over your skin or maybe even under your skin. Hello, Stephanie. Thanks for coming on the show. Tell us about your aim. What's the issue that you're trying to address?
Stephanie - What we're trying to do is to interface electronic components with the human body. One of the challenges is that conventional electronics is typically made on very hard and flat surfaces. If you look at our own body we are a 3D object that is moving all around. The challenge is not only electrical but also mechanical because we need to find ways to make electronic things that can conform the body and therefore use materials that are no longer hard and brittle but materials that can be elastic, similar to our own skin, for example.
Kat - A kind of bionic man-type thing?
Stephanie - Yeah, I was thinking about the six million dollar man, basically.
Kat - What are the sort of challenges? What do you need to make electronics do to make them like skin?
Stephanie - There are two challenges. The first one is to find ways to put electronic components onto a substrate that is very soft. The electronic processes that are available today are usually using fairly high temperature deposits using material. The substrate we're using to make skin-like devices are polymers. In particular we're working with materials called elastomers.
Kat - So they're very bendy?
Stephanie - It's like a rubber band material. These materials don't withstand very high temperature. We need to find processes to deposit the device material at very low temperatures, specifically below 150 degrees C. That's one challenge. Once we've found a way to deposit this material directly on the soft material we have to find a good design or overall architecture for the system so that the electronics can withstand the mechanical deformation. It's one thing to actually deposit the materials onto the substrate but we also want to make sure the transistor is still working when there's cooling onto the transistor.
Kat - Because obviously transistors are made of things like silicon and you don't think of that as very flexible. How are you trying to get round this problem?
Stephanie - The approach we're following is to distribute onto the very soft substrate tiny platforms that would be rigid. This tiny platform would host a very fragile material like the silicon for the transistors. Once you have this pig cell structure all across the elastomer we would need to use very elastic interconnects to connect one platform to the other so they can talk together. What we found a few years ago - I found a way to make stretchable metal. By depositing very thin layers of gold directly into an elastomer on a rubber band I found that I can stretch it up to twice its length and it will not fade electrically. From there we've decided to push forward the technology and use these stretchable metals as interconnects for the electronics.
Kat - Basically, you've got an elastic band covered in gold with all these little transistors studded into it. They'll communicate with each other?
Stephanie - Yes, exactly.
Kat - What sort of applications do you see for this kind of technology?
Stephanie - I'm particularly interested in interfacing with the human body. There is a lot of application in biomedical research. One particular project we're looking at is how to make prosthetic skin. The skin of a patient who's lost a limb, for example, they could wear this like a glove. They could wear this on top of the prosthetic limb and the skin would allow them to get some sensory feedback which is not possible today.
Kat - So they'd be able to feel how hard they were touching something or how hot and cold they were?
Stephanie - Exactly. We're trying to implement various sensors directly onto this rubbery substrate like temperature or touch sensors so that we can mimic sensory function that is embedded in our own skin.
Kat - how are things going at the moment? What sort of stage are we at?
Stephanie - We're at the very first stage. At the moment we're really evaluating the technology to make these. We know how to make stretchable metal so we're investigating how we can implement this to make touch sensors. This is where we're pretty much in the sensing at the moment. We're also evaluating how to make the transistors directly onto this rubbery substrate with a platform. We're just starting so this is where we're at.
Kat - Presumably a big issue is trying to make all this electronics talk to the human brain. It is nerves and electrical impulses.
Stephanie - Right. This is the second aspect of the project. In my group we're looking at ways to make these prosthetic skins but there's also this application where we're looking at a way to use these very soft electronic devices to interface everything with the nervous system. Because the human body and particularly the nervous system is made of extremely compliant material we cannot use a silicon chip to interface directly with your nerve for a long time. What we're doing is to use this polymer and elastomer substrate with embedded electrodes in it to connect directly with a peripheral nerve - so a nerve which is in the limb, not in the spinal cord or the brain - really in the limb, from the electrical signal from the neurons. Once we can do that then the idea would be to connect these peripheral implant directly to the prosthetic skin so that we could take the signals that are coming out of the prosthetic skin and convert them into a neuron format and feed that directly into the implant which would then communicate to the nerve and back to the brain.
Kat - It sounds like exciting stuff. Presumably you have a multidisciplinary team so you have to bring a lot of different people together. What sort of range of scientists are working on this kind of technology?
Stephanie - I'm an electrical engineer by training but in the team we have people who are material scientists, biophysicists and neurosurgeons. Particularly for the project onto the peripheral implant I'm working with lots of people in Cambridge and a couple of other universities in the UK - it's extremely important to collaborate between engineers and the medical field. Without good collaboration we could not do that.
Kat - And when do you think we might see the bionic man?
Stephanie - Not tomorrow! It will take quite a long time. Surely along the way we'll have some devices where you'll have for clinical application but for the final project it could be 25 years or so.