Photo credit: www.sciencedaily.com
Haptic feedback has predominantly relied on simple vibrations, but our skin is equipped with a multitude of sensors that can perceive a range of sensations, including pressure, vibration, and stretching.
In a groundbreaking development, engineers from Northwestern University have introduced a new technology that replicates these intricate tactile experiences through precise movements.
This innovative study is set for publication on March 28 in the esteemed journal Science.
Designed to rest on the skin, this compact, lightweight, and wireless device applies forces in various directions, allowing users to experience an array of sensations such as vibrations, stretching, pressure, sliding, and twisting. It can also merge different sensations and modulate speed to create a more refined and realistic sense of touch.
Powered by a rechargeable battery, the device connects wirelessly via Bluetooth to virtual reality headsets and smartphones. Its small and efficient design allows it to be positioned anywhere on the body, used in conjunction with other actuators in an array, or integrated into existing wearable technology.
The researchers foresee multiple applications for their device, including enhancing virtual experiences, assisting visually impaired individuals in navigating their environment, simulating the feel of various textures in online shopping, offering tactile feedback during remote healthcare consultations, and even enabling those with hearing impairments to perceive music through touch.
“Unlike most haptic actuators that simply poke the skin, we aimed to create a device capable of applying forces in multiple directions—beyond just poking,” stated John A. Rogers of Northwestern, who led the device’s design. “This actuator can apply forces that push, twist, or slide, giving us precise control over the complex sensation of touch in a fully programmable manner.”
Rogers is a noted figure in bioelectronics, serving as the Louis A. Simpson and Kimberly Querrey Professor of Materials Science and Engineering, Biomedical Engineering, and Neurological Surgery, with roles associated with both the McCormick School of Engineering and Northwestern University’s Feinberg School of Medicine. His collaborative work with Yonggang Huang, the Jan and Marcia Achenbach Professor in Mechanical Engineering, highlighted the project, alongside co-first authors Kyoung-Ho Ha, Jaeyoung Yoo, and Shupeng Li.
The study builds upon previously established work by Rogers and Huang’s laboratories, where they created a programmable array of miniature vibrating actuators that convey touch sensations.
The Haptic Hang-up
In recent years, advancements in visual and auditory technologies have surged, leading to immersive experiences through high-fidelity surround-sound systems and fully immersive virtual reality setups. Contrarily, haptic technology has seen relatively limited progress, with even sophisticated systems primarily relying on basic vibration patterns.
This stagnation can largely be attributed to the remarkable intricacy of human touch, which involves various mechanoreceptors situated at different skin depths, each responding uniquely. These receptors send signals to the brain that are interpreted as the sensation of touch.
Reproducing this complexity necessitates precise management over the kind, intensity, and timing of stimuli applied to the skin—a daunting challenge that existing technologies have struggled to address.
“The mechanics of skin deformation are complicated, which partly explains the lag in haptic technology compared to video and audio,” noted J. Edward Colgate, a haptics expert and co-author of the study. “Skin can be manipulated in diverse ways: it may be poked, stretched, or rolled, and these actions can occur at varying speeds and in complex patterns over the surface, such as the palm.”
Actuator Unleashed
The Northwestern team developed a groundbreaking actuator featuring full freedom of motion (FOM), allowing for movement and force application in any direction across the skin. This versatility engages all mechanoreceptors, either independently or collectively.
“This advancement marks a significant progression toward managing the intricate nature of touch,” commented Colgate, who holds the Walter P. Murphy Chair of Mechanical Engineering at McCormick. “The FOM actuator is a compact haptic device that can poke or stretch skin, function at varying speeds, and be utilized in arrays, producing an impressive variety of tactile sensations.”
Measuring just a few millimeters, the actuator employs a small magnet and a set of wire coils arranged in a nested configuration. When electricity runs through these coils, it produces a magnetic field that interacts with the magnet, generating sufficient force to move, push, or twist it. By combining these actuators into arrays, the device can replicate sensations such as pinching, stretching, squeezing, and tapping.
“Creating a compact device with high force output is essential,” added Huang, who was responsible for the theoretical underpinnings. “Our models helped us to optimize designs, ensuring each mode maximizes its force while reducing any unwanted effects.”
Bringing the Virtual World to Life
Additionally, the device incorporates an accelerometer, which tracks its orientation in space, enabling it to deliver haptic feedback relevant to the user’s position. For example, when placed on the hand, the accelerometer can discern whether the palm is facing up or down. It also monitors the actuator’s movements, providing data on speed, acceleration, and rotation.
Rogers highlighted the significance of this tracking capability for navigation and texture exploration on flat screens. “When sliding your finger over silk, it glides more easily than over corduroy or burlap,” he said. “This could revolutionize online shopping for clothing and textiles, allowing consumers to feel material textures.”
Beyond replicating common tactile sensations, the device can transmit information through the skin. By modulating the frequency, intensity, and rhythm of haptic feedback, the team successfully converted music into tactile experiences. They were even able to differentiate tones by varying vibration directions. Users could discern the distinct qualities of different instruments solely through the vibrations.
“We were able to translate the characteristics of music into haptic sensations without compromising the nuanced information linked to individual instruments,” explained Rogers. “This is just one illustration of how enhancing the sense of touch can complement other sensory experiences. Our system has the potential to bridge the gap between digital and physical environments, making digital interactions feel more intuitive and immersive.”
The title of the study is “Full freedom-of-motion actuators as advanced haptic interfaces.”
Source
www.sciencedaily.com