Electrohydraulic Wearable Devices Create Unprecedented Haptic Sensations

Human skin can feel a wide variety of sensations, such as a gentle squeeze, quick taps, or the thud-thud of a heartbeat. In contrast, phones, game controllers, and watches often output only vibrations to get the user’s attention. Unfortunately, this sudden fast shaking feels different from most everyday touch interactions, and it can quickly become annoying. Researchers at MPI-IS in Stuttgart have developed cutaneous electrohydraulic (CUTE) wearable devices to greatly expand the haptic sensations that can be created by future consumer products.
CUTE wearable devices are electrically driven and can produce a remarkable range of tactile sensations, including pressing on the skin, slow and calming touch, and vibrations at a wide variety of frequencies, from low to high. This new approach to wearable haptic feedback thus offers unprecedented control over the tactile sensations that can be presented to users.

CUTE devices are compact and comfortable, and they can deliver rich and pleasant haptic sensations to the skin.

These CUTE wearable devices have been pioneered by an interdisciplinary team of MPI-IS researchers from the Haptic Intelligence Department, led by Katherine J. Kuchenbecker, and the Robotic Materials Department, led by Christoph Keplinger. The team designed novel hydraulically amplified self-healing electrostatic (HASEL) artificial muscles to create wearable devices with a unique ability to communicate with the user's sense of touch. When a voltage is applied, the soft actuator located at the center of the device expands proportionally to the voltage. This expansion allows the device to make and break contact with the skin, like a person reaching out to touch the user’s wrist. Changing the voltage over time allows the haptic feedback to be freely customized to deliver multiple types of touch sensations according to the desired haptic experience. CUTE devices are compact, silent, safe, and energy efficient, and they stay cool throughout operation. These impressive capabilities are further demonstrated by the team in a video.

CUTE devices can deliver highly customizable and expressive tactile sensations.

Future application avenues for CUTE devices include wearable assistive technologies for guidance, creating tactile sensations to enhance augmented or virtual reality, and complementing audio and visual feedback in loud or visually demanding scenarios.

Potential application avenues for the CUTE devices.

The tactile sensations created by the device can communicate diverse sensations ranging from calming to exciting, such as stroking or tickling of the skin, the feeling of a heartbeat, and even an engine turning on and off. Remarkably, users perceive almost all of its tactile cues as pleasant: the only sensation they didn’t find pleasant was a continuous high-frequency vibration like those produced by many of today’s consumer devices. Furthermore, users can identify diverse cutaneous signals with near-perfect accuracy, highlighting another advantage of CUTE devices over commonly used electromagnetic actuators.

“Our CUTE devices demonstrate the feasibility of creating lightweight wearable systems that provide pleasant and expressive tactile communication. Future developments could see this technology applied to larger areas of the body, producing more complex sensations, and even studying human perception of haptic cues that were previously difficult to create”, says Natalia Sanchez, a Ph.D. student at the MPI-IS and first author of the publication.

Reference: Natalia Sanchez‐Tamayo, Zachary Yoder, Philipp Rothemund, Giulia Ballardini, Christoph Keplinger* & Katherine J. Kuchenbecker*. Cutaneous Electrohydraulic (CUTE) Wearable Devices for Pleasant Broad‐Bandwidth Haptic Cues. Advanced Science, 2402461.

https://doi.org/10.1002/advs.202402461
*Co-corresponding author