As robotic technology rapidly advances, scientists look to improve synthetic smart skins that help make robotics more human-like and are essential in giving them touch-sensitivity.
So far, scientists have produced touch and texture-sensitive artificial skin, electronic skin that “feels” in three dimensions, and even “paper skin” made of everyday household objects like foil, Post-It notes, sponges, and tape.
A group of Chinese scientists at the National Key Laboratory of Science and Technology on Micro/Nano Fabrication have reported success in developing a simpler, cheaper, and self-powered transparent smart skin that does not suffer sensitivity loss.
Up to this discovery, previously designed smart skins had a direct correlation between sensitivity increase and energy consumption; higher resolution, or sensitivity, required a more complex system, which meant more electrodes. Furthermore, necessary power sources consisted of wired external batteries, which add bulk, increase cost, and restrict usage time.
Working at Peking University under Professor Haixia Zhang, the researchers created a more practical solution using a combination of planar electrostatic induction and the triboelectric effect. In layman’s terms, that means creating electric charge through friction — or static electricity.
“We use spontaneous triboelectric charges, combined with planar electrostatic induction, to sense the touch applied on the smart skin,” explains Zhang. “Triboelectric charges occur in our daily life everywhere when two surfaces touch each other. And when the charged surface approaches a metal block (or electrode) it will induce the opposite charge, which is the so-called ‘electrostatic induction’ effect.”
The effect is found everywhere, from rubbing a balloon in your hair to smart phone touch screens. The skin’s ability to turn mechanical energy, such as movement of prosthetic fingers, into an electric current essentially eliminates the need for an external power source.
The state-of-the-art smart skin was designed using ultra-thin plastic films and a mere four electrodes created from silver nanowires, a drastic reduction in comparison to other smart skins that can have up to 36 electrodes.
“Compared with the previous works, this smart skin reduces the number of electrodes remarkably,” says Zhang. “This helps a lot to reduce the complexity of the signal processing circuit. Although using less electrodes, our smart skins achieve 1.9 mm resolution, much better than previous results.”
Zhang adds that the analogue smart skin needs further in-depth study, as well as continued development on the skin’s “stretchability” and improvement on the current prototype’s performance. The team will also further explore options to protect the smart skin from environmental interferences, a vital proponent for practical application.