Our skin is the largest organ in the body. We mostly interact with the environment and communicate with each other using the sense of touch.

All the fascinating things we can do with our body using this sense inspired an infamous assistant professor at the Andrew and Peggy Cherng Department of Medical Engineering from Caltech, Wei Gao.

Together with Sam Emaminejad and Hnin Yin Yin Nyein in The Javey Research Group, Gao wanted to discover more of our skin and characteristics. This mindset had then led him to develop an electronic skin, better known as e-skin, to apply safely and directly on your real skin.

Human Body Sweats as Biofuels of the Electronic Skin

On April 22, 2020, the Science Robotics issue released a paper, “Biofuel-powered soft electronic skin for multiplexed and wireless sensing“, which fundamentally describes the e-skin.

The E-skin is a material made from soft and flexible rubber embedded with sensors that monitors information about health indicators such as:

  • blood sugar levels
  • body temperature
  • metabolic by-products
  • heart rate
  • nerve signals that control our muscles

Instead of using a battery, what’s interesting about this is that it operates using biofuel cells supplied by one of our body’s waste products, which is sweat.

Challenges Faced by the Wearable Electronic Skin

The initial challenge faced by Gao and his team was obtaining a power source. Rather than using human motion or solar cells to harvest power, they ought to achieve enough energy from sweat to power the device.

According to Gao, our sweat possesses high compound lactate levels produced by standard metabolic procedures, mostly when we train or exercise our bodies, especially our muscles.

The built-in fuel cells from the e-skin absorb this lactate then combines it with oxygen in the atmosphere. This situation, in turn, generates water and another metabolism by-product, which is pyruvate.

Wearable Electronic Skin Pyruvate - THESIS.PH

Furthermore, the biofuel cells used for the skin comprises of:

  • platinum/cobalt catalyst-infused carbon nanotubes
  • compound mesh holding a lactate-disintegrating enzyme

These components allow biofuel cells to produce enough electricity to power sensors and Bluetooth that enables the e-skin to transmit readings from the sensors wirelessly. This form of communication results in another challenge.

Gao said that Bluetooth is a more attractive approach given its extended connectivity for practical robotic and medical applications, though it consumes higher power.

He added the need to have a long-lasting power source with high power intensity and with minimal indignity. Concerning this, the biofuel cells generate a stable and continuous power output over several days from human sweat.

Future Plans and Further Improvements for the E-Skin’s System

Gao plans to develop different sensors to embed in the e-skin to use it for many purposes. He expressed their team’s intentions to convert the system as a platform, where it can grow to be a human-machine interface other than as a wearable biosensor,

They plan to use the molecular information and vital signs collected from the e-skin to outline and hone next-generation prosthetics. Who knew our sweat could create such a fantastic possibility?

Have you ever thought about employing the e-skin technology in your thesis?


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