Hairy electronic skin catches the breeze

Designing sensors that mimic those in human skin could lead to more realistic prosthetic limbs, ones that can feel a light touch or the warm sun. But flexible electronic skin so far has not incorporated the small feelers that make mammals unique: hair. Now, by placing microscopic polymer hairs on top of graphene, researchers have made a skin-like sensing device that can feel wind and detect its direction and angle (ACS Appl. Mater. Interfaces 2019, DOI: 10.1021/acsami.9b01427). Changhyun Pang of Sungkyunkwan University and colleagues built an array of sensors by depositing a thin film of graphene nanoflakes on a piece of flexible polyethylene. Applying pressure to the sensors pushes the nanoflakes together, changing the electrical resistance. On top of the array, the researchers placed a poly(dimethylsiloxane) film molded with a forest of microscopic pillars. Airflow bends the pillars and puts pressure on the graphene sensors, changing their output current. To demonstrate the device, the team attached it to a wheeled robot powered by a sail. The sensors detected airflow and adjusted the sail to the wind direction so the robot could move forward.