A pioneer in the field of stretchable electronics, Stéphanie Lacour, assistant professor at the Institute of Microengineering at Ecole Polytechnique Fédérale de Lausanne, has developed wearable devices that transmit real-time biological information.
She answered my questions via email. Below are excerpts.
What got you into the field of stretchable electronics?
I was trained as an electrical engineer and have always been interested in developing devices which would have biomedical and health applications. In 2001, I started my postdoc at Princeton University in the group of Sigurd Wagner, who is a leader in flexible electronics and large-area electronics. I started exploring how to produce thin film devices on polymer substrates and quickly focused on a rubber-like substrate, which has become the key substrate for stretchable electronics
Explain the technology behind stretchable electronics. How do they work?
We are using the elastomer substrate as much as possible as a standard microelectronic substrate. In my lab, we are growing or depositing and patterning all device materials directly on the rubbery substrate. The processes we are using are identical to those developed for thin film electronics on glass (used to produced displays) or on plastic foils. We focus on processes that can be conducted at low temperature because of the stability of the elastomer. Once the thin film devices are patterned on the rubbery substrate, their electrical performance is similar to those fabricated on plastic substrates under similar growth conditions.
What was the first stretchable device you developed?
A stretchable metallic conductor. It was prepared by depositing a thin layer of gold on the elastomer. Upon stretching, the conductor retained continuous electrical conductivity even when stretched to twice its length. Stretchable metallization was the enabling element for stretchable circuits.
We now design stretchable circuits where transistor devices are patterned on rigid platforms distributed across the elastomer and are interconnected with the stretchable metallization. By doing so, fragile semiconductor devices are protected from extensive strain while the interconnects accommodate the macroscopic geometrical change due to the applied stretch.
Talk about your work with Nokia.
This project was conducted when I was at the University of Cambridge. We developed a pool of technologies for stretchable user interfaces. In particular, we designed and produced a matrix of touch sensors (made of elastomer materials and stretchable metallisation) which could be worn around the wrist, mounted on a range of objects and stretched. Of course, that would detect touch in any of the these mehcanical configurations.
What applications do you see for this technology in medicine and biology?
Stretchable electronics is an exciting technology to apply to the biomedical field. The human body is 3D and moving. Providing electronic circuits or transducers that can move along with the body, either in the form of a smart band-aid, a e-shirt and ultimately an artificial skin would definitely benefit the biomedical community.
There are also many potential applications in vivo where electronic implants would benefit from mechanical compliance and resemblance to the organs or tissues they are interfacing. The field of neuroprosthetics is of particular interest for me. We have several projects including two new ones sponsored by the Bertarelli Foundation and in collaboration with Harvard Medical School, which will evaluate how useful our stretchable electronics technology can be.
Where do you see the field going in the future?
Similarly to flexible electronics, stretchable electronics will find applications in novel user interfaces and will contribute to have electronics anywhere and not just everywhere. In the biomedical field, neuroprosthetic applications are definitely promising.
What's next for you?
One objective I have is to produce an artificial version of human skin, both on the sensory side and the neural interface side. Such a prosthetic skin would benefit amputees by providing touch back. This is a long term and challenging goal, but extremely motivating.
Photo: Stéphanie Lacour