Natalia Sanchez-Tamayo, Zachary Yoder, Philipp Rothemund, Giulia Ballardini, Christoph Keplinger and Katherine J. Kuchenbecker, Science Advances, 2023 []

Human skin can sense diverse mechanical stimuli, including new contacts, variable pressure, and broad-bandwidth vibrations. However, most wearable haptic devices provide only vibrotactile feedback, under-utilizing the perceptual capabilities of the skin. Further, prolonged vibrations have often been reported as unpleasant, uncomfortable, and causing lasting tingling sensations, thus motivating the creation of haptic devices that can deliver a wider range of cutaneous sensations for richer communication and more pleasant haptic feedback. Such devices have been developed in a relatively compact form for use on high-sensitivity glabrous skin, such as the fingertips. However, over 90% of the body is covered by the hairy skin, which has lower sensitivity than the glabrous skin and therefore requires higher forces and displacements to sense haptic cues. For this reason, it is challenging to create compact devices that deliver a wide range of salient sensations to the hairy skin.

In this project, we showcase cutaneous electrohydraulic (CUTE) wearable devices, which are powered by soft, electrically driven actuators that output expressive haptic feedback on hairy skin in a compact form factor.

Our CUTE wearable device overcomes these challenges by using a multi-layer stack of expanding hydraulically amplified self-healing electrostatic (HASEL) actuators. The custom materials design of these actuators enables high stroke (2.44 mm) and high force (exceeding 2 N) in a small footprint (14 mm × 14 mm). Further, it doubly electrically insulates the high-voltage components of the actuators, rendering them safe to operate in close contact with the skin. Our CUTE wearable device harness electrohydraulic actuation to deliver rich and pleasant haptic sensations to the hairy skin.