Stretchable, Ultrathin Electronic Skin Holds Potential in Human-Machine Interactions

Sensitive nerve cells present in the human skin have the ability to detect a variety of sensations including temperature and pressure that enable tactile interactions with the environment.

In order to mimic the same abilities in prosthetic devices and robots, researchers are striving to create electronic skins, or e-skins. Now, scientists have described a novel technique in ACS Applied Materials & Interfaces that produces a stretchable, ultrathin e-skin, which can be possibly utilized in various human-machine interactions.

For instance, e-skin could be employed in many different applications, such as virtual reality, robotics, wearable health monitors, and prosthetic devices. However, it is very difficult to transfer ultrathin electrical circuits onto intricate 3D surfaces, and added to this, the electronics have to be sufficiently stretchable and bendable to facilitate movement.

In this regard, some researchers have created flexible “electronic tattoos” specifically for this purpose; however, their production is often costly and time-intensive and also needs clean-room fabrication techniques, for example, photolithography. Carmel Majidi, Mahmoud Tavakoli, and colleagues wanted to create a simple, fast, and low-cost technique for creating thin-film circuits with built-in microelectronics.

In the latest method, the researchers used a circuit template and patterned it onto a sheet of transfer tattoo paper using a standard desktop laser printer. Next, they used a silver paste to coat the template, allowing it to fix only to the printed toner ink. The team then deposited an indium liquid metal alloy on top of the silver paste that helped in increasing the circuit’s flexibility and electrical conductivity, and finally added external electronics, like microchips, using a conductive “glue” composed of vertically aligned magnetic particles integrated in a polyvinyl alcohol gel. The investigators finally transferred the electronic tattoo to many different objects and showed how the latest technique can be used in various ways, for example, integrating proximity sensors into a 3D model of a hand, tracking the activity of human skeletal muscles, and controlling a robot prosthetic arm.

The study was funded by the Foundation of Science and Technology of Portugal, through the Carnegie Mellon University Portugal Program.

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