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Synthetic Skin Designed with Sense of Touch

Artificial skin

Artificial skin prototype (EPFL)

27 Sept. 2019. Robotics and materials science labs developed a soft, thin, flexible material that senses and responds like an electronic sense of touch. Researchers from Ecole Polytechnique Fédérale de Lausanne, or EPFL in Switzerland describe their synthetic skin in the 23 September issue of the journal Soft Robotics (paid subscription required).

A team from EPFL’s Reconfigurable Robotics Laboratory led by Jamie Paik, and Laboratory for Soft Bioelectronic Interfaces led by Stéphanie Lacour are seeking a way of integrating more tactile or sense of touch functions into robotic or prosthetic devices. In addition, the solution should also be thin and flexible enough for extending the human sense of touch to provide tactile feedback in wearable devices.

The Reconfigurable Robotics Lab studies soft robotics that can safely interact with humans. Paik and colleagues develop actuators or operating devices using pneumatic pressure that also include sensors. The Soft Bioelectronic Interfaces lab investigates artificial stretchable skins with electrodes and circuits simulating a sense of touch. The lab’s research includes work on devices for prosthetics and medical implants.

The team’s synthetic skin is made of flexible silicone that can stretch up to four times its original size. The material has layers of sensors and soft pneumatic actuators filled with air that respond to pressure by vibrating rapidly, up to 100 impulses per second. The sensors use liquid metal electrodes that measure the deformation of the skin. These measurements are then sent to a microcontroller device that adjusts and relays the sensation to the wearer, in response to movements or other factors.

To prove the concept, the researchers developed a prototype skin-like material worn over the fingers. In lab tests, the material is able to maintain its shape and provide tactile feedback under varying mechanical strains. In addition, researchers can predict the inflation behavior of the skin with a statistical model, based on resistance measured by the embedded sensors.

“This is the first time we have developed an entirely soft artificial skin where both sensors and actuators are integrated,” says doctoral student and first author Harshal Sonar in an EPFL statement. “This gives us closed-loop control, which means we can accurately and reliably modulate the vibratory stimulation felt by the user.”

The researchers believe the synthetic skin can be configured for wearable systems and medical devices that measure an individual’s awareness of movement or position. “The next step,” notes Sonar, “will be to develop a fully wearable prototype for applications in rehabilitation and virtual and augmented reality.” He adds that the prototype, “will also be tested in neuroscientific studies, where it can be used to stimulate the human body while researchers study dynamic brain activity in magnetic resonance experiments.”

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