Multimode Hydraulically Amplified Electrostatic Actuators for Wearable Haptics

• Published in: Advanced materials (Weinheim) Vol. 32; no. 36; pp. e2002564 - n/a
• Main Authors: Leroy, Edouard, Hinchet, Ronan, Shea, Herbert
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.09.2020
• Subjects: actuator arrays; Actuators; Elastomers; electrostatic actuators; Materials science; Response time; Shear forces; soft actuators; soft robotics; Transducers; Virtual reality; wearable haptics; Wearable technology
• ISSN: 0935-9648; 1521-4095; 1521-4095
• DOI: 10.1002/adma.202002564

The sense of touch is underused in today’s virtual reality systems due to lack of wearable, soft, mm‐scale transducers to generate dynamic mechanical stimulus on the skin. Extremely thin actuators combining both high force and large displacement are a long‐standing challenge in soft actuators. Sub‐mm thick flexible hydraulically amplified electrostatic actuators are reported here, capable of both out‐of‐plane and in‐plane motion, providing normal and shear forces to the user’s fingertip, hand, or arm. Each actuator consists of a fluid‐filled cavity whose shell is made of a metalized polyester boundary and a central elastomer region. When a voltage is applied to the annular electrodes, the fluid is rapidly forced into the stretchable region, forming a raised bump. A 6 mm × 6 mm × 0.8 mm actuator weighs 90 mg, and generates forces of over 300 mN, out‐of‐plane displacements of 500 µm (over 60% strain), and lateral motion of 760 µm. Response time is below 5 ms, for a specific power of 100 W kg−1. In user tests, human subjects distinguished normal and different 2‐axis shear forces with over 80% accuracy. A flexible 5 × 5 array is demonstrated, integrated in a haptic sleeve. Hydraulically amplified zipping taxels (HAXELs) are thin, soft fluidically coupled electrostatic actuators, generating both out‐of‐plane and in‐plane motion, delivering rich haptic sensations by locally applying normal and shear forces to the skin. A 90 mg actuator generates 300 mN of force and 500 µm displacement in under 5 ms. Arrays of wearable HAXELs provide a realistic sense of touch.