Feeling Your Way Through

One of the most common ways that we interact with our digital devices is through display screens. This should come as no big surprise considering how versatile and efficient this technology has proven itself to be over the years. However, visually presenting information is not the right choice for every application. Consider the challenges that display-based interfaces pose for the visually impaired, for example. And even in cases where visual information is crucial, as is the case with virtual reality, it does not provide everything that is needed, such as the haptic feedback necessary to create an immersive experience.

Haptic interfaces can fill in these gaps and provide their users with a dynamic sensory experience that stimulates the sense of touch. Unfortunately these technologies are not nearly as advanced as modern, high-definition displays. They suffer from a number of problems that render them impractical for most use cases. They tend to be bulky and cumbersome to use, and since they are frequently powered by some type of actuator, they tend to draw a lot of power, making them unsuitable for mobile applications.

A team led by engineers at Northwestern University has developed a novel type of haptic interface that can stimulate the sense of touch while overcoming several issues associated with present technologies. The device takes the form of a flexible and relatively thin skin patch that is equipped with an array of actuators. It is able to conform to the shape of the body and move along with its wearer for comfortable use. Also notable about the design is that the actuators draw very little power, making them suitable for use on the go.

The physical device is composed of an array of 19 small magnetic actuators in a silicone-mesh material. These actuators have a bistable design that only requires power when a state change is requested. The rest of the time, they are happy to hold their positions without a source of power. Another clever efficiency hack stores energy in the wearer’s skin when the actuator presses against it. During the next state change, this stored energy is released to minimize the amount of battery power that is consumed.

Aside from simply drawing precious little energy, the actuators are also quite useful. They can be coerced into simulating a wide range of sensations including pressure, vibration, and twisting. These sensations can be triggered wirelessly by an external system — like a virtual reality headset, for example — via Bluetooth.

To evaluate the interface, a group of volunteers was blindfolded and given a haptic interface patch to wear. They were then given a series of tasks to perform, like navigating through a room or altering their posture to improve their balance. The actuators stimulated the volunteers in different ways to guide them through these exercises. After just a short period of training, the patch was found to give a big boost to those that were using it. The level of assistance it provided was compared with the way in which a white cane helps those with visual impairments.

While the early results are promising, the actuators are likely not small enough to be accepted by users of a commercial device. Moreover, having to adhere the patch to the skin opens the door to errors and maintenance issues that could sink this device in the eyes of casual users. Perhaps with some future work this system will arrive at a place where it becomes practical for more real-world applications.