Medical devices based on haptic feedback are limited to simple vibrations. This means attempts to mimic human skin are limited. This arises because our skin is packed with tiny sensors that detect pressure, vibration, and stretching.
The sense of touch involves different types of mechanoreceptors (or sensors) — each with its own sensitivity and response characteristics — located at varying depths within the skin. When these mechanoreceptors are stimulated, they send signals to the brain, which are translated as touch.
A new device, based on bioelectronics, applies dynamic forces in any direction to simulate a more realistic sense of touch (this is achieved through a variety of sensations, including vibrations, stretching, pressure, sliding and twisting). Northwestern University engineers have unveiled a new technology that creates precise movements to mimic these complex sensations. The small, lightweight device enhances virtual reality. This will particularly help individuals with visual impairments and provide tactile feedback for remote health visits.
Powered by a small rechargeable battery, the device uses Bluetooth to wirelessly connect to virtual reality headsets and smartphones. The technology also is small and efficient, so it could be placed anywhere on the body, combined with other actuators in arrays or integrated into current wearable electronics.
The scientists behind the technology envision their device eventually could enhance virtual experiences, help individuals with visual impairments navigate their surroundings, reproduce the feeling of different textures on flat screens for online shopping, provide tactile feedback for remote health care visits and even enable people with hearing impairments to “feel” music.
“Almost all haptic actuators really just poke at the skin,” Northwestern’s John A. Rogers, who led the device design, explains.
“But skin is receptive to much more sophisticated senses of touch. We wanted to create a device that could apply forces in any direction — not just poking but pushing, twisting and sliding. We built a tiny actuator that can push the skin in any direction and in any combination of directions. With it, we can finely control the complex sensation of touch in a fully programmable way.”
Replicating that sophistication and nuance behind ‘touch’ required precise control over the type, magnitude and timing of stimuli delivered to the skin.
The new device is an advancement because the actuator at the core of the technlogy is not constrained to a single type of movement or limited set of movements. Instead, it can move and apply forces in all directions along the skin. These dynamic forces engage all mechanoreceptors in the skin, both individually and in combination with one another.
Another part of the device is an accelerometer. This enables the device to gauge its orientation in space. With this information, the system can provide haptic feedback based on the user’s context. If the actuator is fixed onto a hand, for example, the accelerometer can detect if the user’s hand is palm up or palm down. The accelerator also can track the actuator’s movement, providing information about its speed, acceleration and rotation.
The platform also can transfer information through the skin. By changing the frequency, intensity and rhythm of haptic feedback, the researchers converted the sound of music into physical touch, for example. They also were able to alter tones just by changing the direction of the vibrations. Feeling these vibrations enabled users to differentiate between various instruments.
The new technology appears in the journal Science, titled “Full freedom-of-motion actuators as advanced haptic interfaces.”
