As the body’s largest organ, skin is responsible for the transduction of a vast amount of information. This conformable, stretchable, self-healable and biodegradable material simultaneously collects signals from external stimuli, which translates into information such as pressure, pain and temperature. The development of electronic materials, inspired by the complexity of this organ, offers a tremendous unrealized materials’ challenge. Fortunately, the advent of organic-based electronic materials may offer a solution to this longstanding problem.
Zhenan Bao, K.K. Lee Professor of Chemical Engineering, Stanford University, is one of the world’s leading researchers working on the design of organic electronic materials that mimic skin functions. SEMI’s Maria Vetrano interviewed professor Bao to preview her February 25 keynote, Skin-Inspired Electronics, at FLEX|MEMS & Sensors Technical Congress (MSTC) 2020, February 24-27, 2020, at the DoubleTree by Hilton in San Jose, California.
Join us at FLEX|MSTC to meet Professor Bao and other industry influencers furthering innovation in flexible hybrid electronics (FHE) and MEMS sensors. Register now to connect with her at FLEX|MSTC or visit her on LinkedIn.
SEMI: Your pioneering work on the use of electronic materials to construct second skin is a major step forward in human-machine interfaces. Could you please describe second skin?
Bao: Second skin is a new electronic-device platform encompassing electronic devices that have skin-like properties such as stretchability, self‐healing ability, biocompatibility and biodegradability. In essence, the second skin is an electronic system of fully integrated multifunctional components operating on the surface of or inside the body to enable smart healthcare for disease prevention and treatment and to enhance the functional capabilities of natural skin.
The second skin could also serve as a module to connect our human body to the Internet, thereby allowing human integration with the Internet of Things (IoT) for next‐generation wireless communications. In this way, we can view the second skin as an artificial body part that can be used to improve our everyday lives.
SEMI: How might second skin operate in the human body?
Bao: It has many potential uses. It could be a prosthesis for people who have lost their sense of touch. It could be used to repair damaged skin as well as to provide enhanced functionality that’s not possible with biological human skin. It could, for example, connect us with our external environment, with other people, even with our cars.
I can also envision second skin as an implantable device for both neurostimulation and for early detection of disease.
Schematic illustration of structure of second skin composed of functional devices: sensor, integrated circuit, display and power supply. Source: Stanford University
SEMI: How did you get started in this research?
Bao: Sixteen years ago when I started at Stanford, I learned of a colleague in mechanical engineering who was working on robotic cockroaches. That’s when I understood the need for sensor functions in robotics.
I considered the large number of people with prosthetics who do not have a sense of touch. With this audience in mind, I started by designing a simple flexible electronic device that could take the shape of skin, even conforming to a robot hand, thereby approximating the natural sense of human touch.
Once we developed the first sensor, and realized that its touch sensitivity could eclipse that of human touch, I asked myself: what can we learn from second skin – in addition to its sensing functionality?
Skin is not just flexible; it is biodegradable and stretchable. So we started to dream. We began by developing electronic materials, either conductors or semiconductors. We added new functionality, such as self-healing properties, biodegradability and stretchability. That opened the way to new materials’ development.
SEMI: What discoveries have you made in new materials?
Bao: Over the past decade, we’ve developed skin-like materials with electronic properties that are on par with the best conducting and semiconducting polymers. Some of our skin-like semiconducting polymers can perform even better than amorphous silicon. That means with suitable processing methods, we can make stretchable ICs, initially with tens of transistors that can perform analog or digital functions, and in a later stage, stretchable displays driven by active matrix arrays.
SEMI: What would it take to put these materials into production?
Bao: We need to develop methods to pattern the skin-like electronic materials into fine features. We have been leveraging similar processes used for flexible circuit boards. Some research groups are developing roll-to-roll fabrication and printing methods.
SEMI: Which technologies/applications are you commercializing?
Bao: C3Nano is a Bao Research Group spin-off startup that is commercializing nanomaterials that are promising for bendable and foldable electronics.
Another spin-off that is licensing our technology, PyrAmes, is developing a continuously non-invasive blood-pressure monitor. It’s not a cuff so the patient doesn’t have to remember to put it on.
In the shorter term, we’re looking at putting artificial skin on prosthetic limbs and robotic hands. Further down the road, we could put skin on wounded regions of the body, forging connections to nerves that would support realistic sensation.
To realize these applications, we’ll need to conduct further R&D on materials and applications. The manufacturing of these devices still needs much more development.
Fortunately, we’re part of a fertile development ecosystem at Stanford. I started the Stanford Wearable Electronics Initiative (eWEAR) to forge collaborations across Stanford campus as well as with industry.
SEMI: What would you like FLEX|MSTC attendees to take away from your presentation?
Bao: I’d like them to realize that the future of electronics is changing. I imagine a future in which the functions of a smartphone will disappear into what we wear, what we attach to our skin and what we implant inside our body. I believe that skin-like electronics will help to facilitate this future, allowing us to connect with each other and our surroundings in ways that feel natural, yet that also enhance our quality of life.
Zhenan Bao is K.K. Lee Professor of Chemical Engineering with courtesy appointments in Chemistry and Material Science and Engineering at Stanford University. She founded the Stanford Wearable Electronics Initiate (eWEAR) and serves as the faculty director. Prior to joining Stanford in 2004, she was a Distinguished Member of Technical Staff at Bell Labs, Lucent Technologies from 1995 to 2004.
Bao has over 500 refereed publications and over 65 U.S. patents with a Google Scholar H-Index >155. In her recent work, she has developed skin-inspired organic electronic materials, which have resulted in unprecedented performance or functions in medical devices, energy storage and environmental applications. She has pioneered several important design concepts for organic electronic materials. Her work has enabled flexible electronic circuits and displays.
For more information on professor Bao’s research, visit Bao Research Group.
FLEX|MSTC is organized MEMS & Sensors Industry Group (MSIG) and FlexTech, SEMI technology communities focused on the growth of MEMS & sensors and the flexible electronics supply chain, respectively.
Maria Vetrano is a public relations consultant at SEMI.