Bistable Haptic Patch Sends Touch Sensations to Skin

Author: Northwestern University
Published: 6 Nov 2024 - Updated: 10 Aug 2026
Publication Details: Peer-Reviewed | Product Release, Update

Table of Contents:
Synopsis - Definition - Overview - FAQs - Insights, Updates - Related Content

Synopsis

This research describes a peer-reviewed development from Northwestern University, published in the study Bioelastic state recovery for haptic sensory substitution, in which engineers created a thin, flexible, wireless patch that delivers complex touch sensations - including pressure, vibration, and twisting motion - through a hexagonal array of 19 magnetic actuators encapsulated in a silicone-mesh material. Led by bioelectronics researcher John A. Rogers with co-leads Yonggang Huang, Hanqing Jiang, and Zhaoqian Xie, the team moved well beyond the simple buzzing of earlier haptic devices by using an energy-saving bistable design that stores and reuses elastic energy in the skin itself. The work matters to people who stand to gain from richer tactile feedback, including individuals with vision impairments who could "feel" their surroundings through smartphone LiDAR data, amputees needing more natural prosthetic feedback, and medical trainees who rely on realistic simulation, and blindfolded test subjects were able to navigate around obstacles and adjust their balance after only brief training, which makes the findings both credible and directly relevant to accessibility.*

At a Glance

• 1 - The device connects over Bluetooth through a smartphone to translate surroundings into touch.
• 2 - First author Matthew Flavin, then a postdoctoral researcher at Northwestern, is now an assistant professor at the Georgia Institute of Technology.
• 3 - The patch builds on the team's 2019 Nature work on epidermal VR, which used an array of miniature vibrating actuators with fast wireless control.
• 4 - During obstacle navigation testing, feedback grew more intense and moved toward the center of the device as the wearer approached an object, functioning much like an information-rich white cane.

Topic Definition

Haptic Sensory Substitution

Haptic sensory substitution is the practice of taking information a person would normally gather through one sense, most often vision, and delivering it to the body through touch instead, using patterns of pressure, vibration, or motion applied to the skin. In the Northwestern patch, a wearable array of small actuators receives data about the surrounding environment - such as the distance to nearby objects captured by a smartphone's 3D LiDAR imaging - and converts it into tactile cues that grow stronger and shift position as an object draws closer, letting the wearer sense their surroundings without relying on eyesight. The approach draws on the brain's ability to learn and reinterpret new streams of sensory input, so that a carefully designed touch signal can stand in for sight or another missing sense. Long explored as a route to greater independence for people with vision or hearing loss, sensory substitution is now becoming more practical as thin, flexible, energy-efficient wearables replace bulkier laboratory hardware.

Overview

A Northwestern University-led team of engineers has developed a new type of wearable device that stimulates skin to deliver various complex sensations. The thin, flexible device gently adheres to the skin, providing more realistic and immersive sensory experiences. Although the new device obviously lends itself to gaming and virtual reality (VR), the researchers also envision applications in healthcare. For example, the device could help people with visual impairments "feel" their surroundings or give feedback to people with prosthetic limbs. The title of the study is "Bioelastic state recovery for haptic sensory substitution."

The device is the latest advance in wearable technology from Northwestern bioelectronics pioneer John A. Rogers. The new study builds on work published in 2019 in Nature, in which his team introduced "epidermal VR," a skin-interfaced system that communicates touch through an array of miniature vibrating actuators across large areas of the skin, with fast wireless control.

"Our new miniaturized actuators for the skin are far more capable than the simple 'buzzers' that we used as demonstration vehicles in our original 2019 paper," Rogers said. "Specifically, these tiny devices can deliver controlled forces across a range of frequencies, providing constant force without continuous application of power. An additional version allows the same actuators to provide a gentle twisting motion at the surface of the skin to complement the ability to deliver vertical force, adding realism to the sensations."

Rogers is the Louis A. Simpson and Kimberly Querrey Professor of Materials Science and Engineering, Biomedical Engineering and Neurological Surgery, with appointments in Northwestern's McCormick School of Engineering and Northwestern University Feinberg School of Medicine. He also directs the Querrey Simpson Institute for Bioelectronics.

Rogers co-led the work with Northwestern's Yonggang Huang, the Jan and Marcia Achenbach Professorship in Mechanical Engineering at McCormick; Hanqing Jiang of Westlake University in China; and Zhaoqian Xie of Dalian University of Technology in China. Jiang's team built the small modifying structures needed to enable twisting motions.

Leveraging Skin-stored Energy

The new device comprises a hexagonal array of 19 small magnetic actuators encapsulated within a thin, flexible silicone-mesh material. Each actuator can deliver different sensations, including pressure, vibration and twisting. Using Bluetooth technology in a smartphone, the device receives data about a person's surroundings for translation into tactile feedback - substituting one sensation (like vision) for another (touch).

Although the device is powered by a small battery, it saves energy using a clever "bistable" design. This means it can stay in two stable positions without needing constant energy input. When the actuators press down, it stores energy in the skin and in the device's internal structure. When the actuators push back up, the device uses the small amount of energy to release the stored energy. So, the device only uses energy when the actuators change position. With this energy-efficient design, the device can operate for longer periods of time on a single battery charge.

"Instead of fighting against the skin, the idea was ultimately to actually use the energy that's stored in skin mechanically as elastic energy and recover that during the operation of the device," said Matthew Flavin, the paper's first author. "Just like stretching a rubber band, compressing the elastic skin stores energy. We can then reapply that energy while we're delivering sensory feedback, and that was ultimately the basis for how we create the created this really energy-efficient system."

At the time of the research, Flavin was a postdoctoral researcher in Rogers' lab. Now, he is an assistant professor of electrical and computer engineering at the Georgia Institute of Technology.

Sensory Substitution

To test the device, the researchers blindfolded healthy subjects to test their abilities to avoid objects in their path, change foot placement to avoid injury and alter their posture to improve balance.

One experiment involved a subject navigating a path through obstructing objects. As the subject approached an object, the device delivered feedback in the form of light intensity in its upper right corner. As the person moved nearer to the object, the feedback became more intense, moving closer to the center of the device.

With only a short period of training, subjects using the device were able to change behavior in real time. By substituting visual information with mechanical, the device "would operate very similarly to how a white cane would, but it's integrating more information than someone would be able to get with a more common aid," Flavin said.

"As one of several application examples, we show that this system can support a basic version of 'vision' in the form of haptic patterns delivered to the surface of the skin based on data collected using the 3D imaging function (LiDAR) available on smartphones," Rogers said. "This sort of 'sensory substitution' provides a primitive, but functionally meaningful, sense of one's surroundings without reliance on eyesight - a capability useful for individuals with vision impairments."

Frequently Asked Questions

NOTE: Researched FAQs by Disabled World (DW)

What is a bistable design in a wearable device

A bistable design lets a device rest in either of two stable positions without drawing continuous power, so energy is only needed when the actuators change position, which extends battery life during operation.

How does the haptic patch attach to the body

The patch is thin and flexible and gently adheres to the skin, and it can be worn on areas such as the neck to receive tactile feedback comfortably during normal movement.

Can the patch help people who are deaf or hard of hearing

The research focuses on vision substitution, but the same principle of turning information into skin sensations could in theory support other senses, though the article does not confirm hearing-specific results.

What is the difference between this patch and a standard vibration motor

A standard vibration motor produces a single simple buzz, while this array of 19 actuators can deliver graded pressure, vibration, and a gentle twisting motion for far richer and more realistic touch feedback.

Do users need special training to understand the touch signals

Testing showed that blindfolded subjects adapted after only a short period of training and could change their behavior in real time, suggesting the signals are reasonably intuitive to learn.

Is the haptic patch available to buy yet

The article presents the device as a peer-reviewed research advance rather than a consumer product, so it describes capabilities and applications rather than commercial availability or pricing.

What smartphone feature does the device rely on for spatial data

The system uses the 3D imaging LiDAR function found on some smartphones to gather distance data about surroundings, then translates that information into haptic patterns on the skin.

Insights, Analysis, and Developments

Editorial Note: What sets this work apart is less the array of tiny actuators than the quiet engineering insight behind it - the recognition that skin is not an obstacle to work against but a reservoir of elastic energy to borrow from, compressing like a rubber band and giving that energy back during operation, which is precisely why the patch can run longer on a single charge while still delivering constant force without drawing continuous power; for the disability community the promise is concrete rather than speculative, since a wearable that can render a functional sense of nearby space through touch, refine prosthetic feedback, or support balance and safe foot placement points toward assistive tools that convey far more than the single buzz of today's devices, and the fact that healthy subjects adapted after only brief training suggests the learning curve for real-world users may be gentler than many would expect.*

Attribution/Source(s): This peer reviewed publication was selected for publishing by the editors of Disabled World (DW) due to its relevance to the disability community. Originally authored by Northwestern University and published on 6 Nov 2024, this content may have been edited for style, clarity, or brevity.

* Editorial additions by Ian C. Langtree.