Rapid-manufacturable hair sensor array for legged millirobots

We present a rapid-manufacturable, hair-actuated contact sensor array designed for use on legged millirobots. The sensor is an array of sensitive contact switches. Each switch is activated by loading a hair mounted at the switch tip. The hair sensor array is sufficiently sensitive to detect the small contact forces experienced by a lightweight robot, with an average normal sensitivity of 0.8 grams/hair. The compliant polymer hairs detect both normal and shear contact, allowing the array to detect a variety of contact forces. By virtue of its design, the hair sensor array can be fabricated using a roll-to-roll layered process. We demonstrate a straightforward application of the sensor technology on a hexapedal millirobot, using the array to both estimate average ground speed and detect high-centering when running over obstacles. This application is of particular interest for milliscale robots operating in rough terrain, where the risk of entrapment is high. Our results indicate that the hair sensor array can estimate ground speed and detect high-centering when running over simple geometric obstacles.