Electrorheological fluid-based robotic fingers with tactile sensing

Prototype fingertips using electrorheological (ER) fluids with elementary tactile sensing were fabricated and tested. The fingertips consist of a layer of ER fluid sandwiched between a grounded elastomer skin and a positively charged electrode. This arrangement forms a capacitor whose value increases as the elastomer is deflected toward the positive electrode. The ER fingertips can be put on a robot gripper or the fingers of a dextrous robot hand. The fluid layer acts as a soft conformal pad when the voltage is turned off. When energized, the fluid changes from a Newtonian fluid to a Bingham plastic with a yield stress of a few kPa. The result is a finger with simple tactile sensing and the ability to generate large lifting forces with small grasp forces, due to interlocking between the deformed skin/solidified fluid and the gripped object. A gripper with ER fingertips was able to grip a raw egg gently using capacitance sensing. The authors examine the improved lifting force available with ER fingertips over passive designs. The design of a multielement fingertip for shape sensing is investigated and recommendations are offered for designing practical ER robotic hands