Electronic Skin Fully Powered by Sweat can Monitor Health

One of the ways we experience the world around us is through our skin. From sensing temperature and pressure to pleasure or pain, the many nerve endings in our skin tell us a great deal.

Our skin can also tell the outside world a great deal about us as well. Moms press their hands against our foreheads to see if we have a fever. A date might see a blush rising on our cheeks during an intimate conversation. People at the gym might infer you are having a good workout from the beads of sweat on you.

But Caltech's Wei Gao, assistant professor in the Andrew and Peggy Cherng department of Medical Engineering wants to learn even more about you from your skin, and to that end, he has developed an electronic skin, or e-skin, that is applied directly on top of your real skin. The e-skin, made from soft, flexible rubber, can be embedded with sensors that monitor information like heart rate, body temperature, levels of blood sugar and metabolic byproducts that are indicators of health, and even the nerve signals that control our muscles. It does so without the need for a battery, as it runs solely on biofuel cells powered by one of the body's own waste products.

"One of the major challenges with these kinds of wearable devices is on the power side," says Gao. "Many people are using batteries, but that's not very sustainable. Some people have tried using solar cells or harvesting the power of human motion, but we wanted to know, 'Can we get sufficient energy from sweat to power the wearables?' and the answer is yes."

Gao explains that human sweat contains very high levels of the chemical lactate, a compound generated as a by-product of normal metabolic processes, especially by muscles during exercise. The fuel cells built into the e-skin absorb that lactate and combine it with oxygen from the atmosphere, generating water and pyruvate, another by-product of metabolism. As they operate, the biofuel cells generate enough electricity to power sensors and a Bluetooth device similar to the one that connects your phone to your car stereo, allowing the e-skin to transmit readings from its sensors wirelessly.

"While near-field communication is a common approach for many battery-free e-skin systems, it could be only used for power transfer and data readout over a very short distance," Gao says. "Bluetooth communication consumes higher power but is a more attractive approach with extended connectivity for practical medical and robotic applications."

Devising a power source that could run on sweat was not the only challenge in creating the e-skin, Gao says; it also needed to last a long time with high power intensity with minimal degradation. The biofuel cells are made from carbon nanotubes impregnated with a platinum/cobalt catalyst and composite mesh holding an enzyme that breaks down lactate. They can generate continuous, stable power output (as high as several milliwatts per square centimeter) over multiple days in human sweat.

Gao says the plan is to develop a variety of sensors that can be embedded in the e-skin so it can be used for multiple purposes.

"We want this system to be a platform," he says. "In addition to being a wearable biosensor, this can be a human-machine interface. The vital signs and molecular information collected using this platform could be used to design and optimize next-generation prosthetics."

You Yu, Joanna Nassar, Changhao Xu, Jihong Min, Yiran Yang, Adam Dai, Rohan Doshi, Adrian Huang, Yu Song, Rachel Gehlhar, Aaron D Ames, Wei Gao.
Biofuel-powered soft electronic skin with multiplexed and wireless sensing for human-machine interfaces.
Science Robotics, 2020. doi: 10.1126/scirobotics.aaz7946

Most Popular Now

Early Warning System for Intensive Care …

Life-threatening situations occur time and again in an intensive care unit. To make sure that doctors can intervene in time, a team at the German Heart Center Berlin (DHZB) has...

Virtual Reality could Help to Reduce Pai…

We all feel physical pain in different ways, but people with nerve injuries often have a dysfunctional pain suppression system, making them particularly prone to discomfort. Now researchers have uncovered that...

Philips Partners with Orbita to Develop …

Royal Philips (NYSE: PHG, AEX: PHIA), a global leader in health technology, and Orbita Inc., an innovative provider of conversational artificial intelligence (AI) solutions for healthcare, announced a partnership agreement...

CliniSys Group Creates Single Brand for …

CliniSys Group has created a single brand for its businesses in the UK and Europe, with a refreshed logo and a new website. The move creates a unified identity for CliniSys...

East Lancashire Signs Deal for Early War…

Thousands of NHS professionals across five hospitals in East Lancashire are to benefit from early warning technology that will help them detect and swiftly respond to deteriorating patients in need...

FDA Grants Oxehealth Vital Signs De Novo…

Oxehealth has announced another world first after the US Food and Drug Administration granted a De Novo clearance for its Oxehealth Vital Signs product, which is incorporated into Oxevision, the...

Telemedicine Improves Access to High-Qua…

The American Academy of Sleep Medicine recently published an update on the use of telemedicine for the diagnosis and treatment of sleep disorders to reflect lessons learned from the transition...

DMEA 2021: Digital Health. 100 % Virtual…

7 - 11 June 2021, Berlin, Germany. An entire week dominated by digital healthcare! With that in mind, early in June DMEA 2021 will be kicking off with a wide range...

Philips and NHS Implement the First Regi…

Royal Philips (NYSE: PHG, AEX: PHIA), announced it has supported the NHS' Cheshire and Merseyside consortium [1] to become the first regional hub supplying the United Kingdom's National COVID-19 Chest...

Child Brain Tumours can be Classified by…

Diffusion weighted imaging and machine learning can successfully classify the diagnosis and characteristics of common types of paediatric brain tumours a UK-based multi-centre study, including WMG at the University of...

AI could Crack the Language of Cancer an…

Powerful algorithms used by Netflix, Amazon and Facebook can 'predict' the biological language of cancer and neurodegenerative diseases like Alzheimer's, scientists have found.