Going beyond Electronic Skin to “Super Skin”

2019-12-16 Research

Marvel’s superhero Spider-Man fights supervillains using spider-sense that the hairs on his body stand up to warn him of impending danger

It will not be long before this cinematic fantasy comes true. Professor Jin Young Oh of the Chemical Engineering Department and his team developed a semiconductor sensor that can heal itself and sense stimuli in the same way that human skin does. The findings were published on November 9th in Science Advances under the title of “Stretchable Self-healable Semiconducting Polymer Film for Active-matrix Strain-sensing Array.” Below is a detailed interview with Professor Oh.

Developing semiconductor sensors that emulate the sensing property of human skin
Q. What has changed since your previous research project (See the article for more: ‘Electronic Skin’ Unveils ‘Innovative Life Style Change’)?
My previous research was about developing stretchable and self-healing semiconductor materials, and now we have developed a semiconducting sensory film device using the material. This new sensory device is stretchable and feels the same way that human skin does. Think of it as being like the motion control sensors on a smartphone screen. When the device detects a physical signal, it responds with an electrical signal. Previously, similar sensory devices used to break down under strain, so the idea was trying to make a device that maintains a consistent level of electrical performance until the point of fracture. But now the key is to make a new device that can positively accommodate stretching.

As we age, our sensory functions decline. The new device is useful for the elderly or for those who have lost their sensory functions due to an accident. It can also be applied to the skin of robots. Inserting this device into the skin of a robot will not only cause it to feel sensations but also possess a self-healing property. The bottom line is that it is a stretchable, self-healing semiconductor detects pressure-induced deformation.

With the conventional sensors in previous studies raising the strain sensitivity 200-300% was a very difficult and highly praised feat, but this new sensory device has a level of sensitivity 10,000 times greater than that of conventional silicon-based sensors. It is even superior to human skin in terms of sensitivity. This is why we call it super skin, not electronic skin. Now, it is not only useful for people with weakened sensory functions but could function like the equipment that superheroes use in the movies.

The goal is to give all the materials the property of self-healing.
Another distinctive attribute of the device is its capacity to self-heal. Existing materials are so hard and rigid that they require a post-processing with heat or solvent vapor to induce the property of self-healing, but this new material achieves healing without post-processing by blending a polymer semiconductor and a self-healable elastomer.

The resulting “self-healed” semiconductor recovers its performance to the same level as its initial performance after the self-healing process. Six to seven layers of semiconductors and electrodes, substrates, and small electrodes that enclose the semiconductors are so thin in the range of nano- or micro-millimeters that we can barely notice them with our human eyes. The device is also passivated to be waterproof. Waterproof performance is desirable for protection from impurities and moisture, such as sweat generated from human skin that may result in malfunction. Although this is an external device at the moment, it could play a role as a band to be used on the human biofield in the future. Small as it is now, I think we will be able to make it bigger, like a roll of fabric for clothing or quilts.

Q. What is your future goal?
Making all the composition materials self-healing is the way to go. Currently, only the core materials, the semiconductors, possess that property. The next step is to increasingly improve its functionality and turn all the materials into self-healing materials.

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