Electronic skin has a strong future that extends forward

A material that mimics human skin in strength, elasticity and sensitivity could be used to collect biological data in real time. Electronic skin, or e-skin, can play an important role in next-generation prosthetics, personalized medicine, soft robotics and artificial intelligence.

“The ideal e-skin will mimic the many natural functions of human skin, such as sensing temperature and touch, accurately and in real time,” says Yichen Cai, postdoc at KAUST. However, making adequately flexible electronic components that can perform such delicate tasks and at the same time withstand the bumps and scratches of everyday life is challenging and every material involved must be carefully designed.

Most e-skins are made by layering an active nanomaterial (the sensor) on an elastic surface that sticks to human skin. However, the connection between these layers is often too weak, which reduces the durability and sensitivity of the material; alternatively, if it is too strong, the flexibility becomes limited, making it more likely to break and break the circuit.

“The skin electronics landscape continues to change at a spectacular rate,” says Cai. “The emergence of 2D sensors has accelerated efforts to integrate these atomically thin and mechanically strong materials into functional and durable artificial leathers.”

A team led by Cai and colleague Jie Shen has now created a tough e-skin using a silica nanoparticle-reinforced hydrogel as a strong, elastic substrate and a 2D titanium carbide MXene as a sensitive layer, bonded together with highly conductive nanowires.

“Hydrogels contain more than 70% water, which makes them very compatible with human skin tissues,” explains Shen. By lending the hydrogel in all directions, applying a layer of nanowires, and then carefully controlling its release, the researchers created conductive paths to the sensor layer that remained intact even when the material was stretched to 28 times its original size. .

Their prototype e-skin could detect objects from a distance of 20 centimeters, respond to stimuli in less than a tenth of a second and, when used as a pressure sensor, distinguish the handwriting written on it. It continued to perform well after 5,000 deformations, recovering about a quarter of a second each time. “It is an amazing result for an e-skin to maintain its hardness after repeated use,” says Shen, “which mimics the elasticity and rapid recovery of human skin.”

Such e-skins could monitor a range of biological information, such as changes in blood pressure, which can be detected from vibrations in the arteries to movements of large limbs and joints. This data can then be shared and stored in the cloud via Wi-Fi.

“Another obstacle to the widespread use of electronic skins lies in the expansion of high resolution sensors,” adds group leader Vincent Tung; “however, laser-assisted additive manufacturing offers new promise.”

“We see a future for this technology beyond biology,” adds Cai. “One day, the stretchable sensor tape could monitor the structural health of inanimate objects, such as furniture and airplanes.”

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