A Feel Good Story About Haptic Interfaces

Nothing breaks the illusion of a virtual reality (VR) experience faster than reaching out for a virtual object and feeling absolutely nothing. For this reason, a lot of effort has gone into building effective haptic interfaces in recent years to simulate the feeling of a variety of objects and textures. But while the display, computing, and sensing technologies that are tightly-packed into a modern VR headset have become quite advanced, haptic interfaces still lag far behind today.

These systems are plagued with a variety of issues, like a lack of resolution and bulky form factors that make them a pain to use, especially for extended periods of time. Engineers have explored a number of solutions to solve the latter issue that involve the use of thin sheets of electrodes that adhere directly to the skin. By providing stimulation via pulses of electricity, the user can be made to believe they are touching complex surfaces. And since these devices are built into thin sheets that stick directly on the skin, they are all but transparent to the user.

However, these interfaces also have some problems. First and foremost, the contact between the device’s electrodes and the skin tends to be imperfect due to a poor conformation to the shape of the body. These gaps not only impede the delivery of stimulation, but they can also cause painful electrical shocks. If feeling nothing breaks the illusion, then how much more will a painful shock ruin the experience?

A group led by researchers at the University of California San Diego set out to design a better thin form factor haptic interface. What they came up with is relatively simple, but by all accounts it works quite well and overcomes the issues with present systems. The device consists of an electrode, in a serpentine pattern for stretchability, that is built into a soft silicone patch. The softness and stretchability of the patch allow it to mold itself to the shape of the body, preventing air gaps and the associated shocks.

The device is composed of a polymer known as PEDOT:PSS to form the electrode, while a stretchier polymer known as PPEGMEA was utilized for the strip that attaches it to the body. Fabrication involves laser-cutting the electrode into its distinctive shape before attaching it to the substrate.

In a small study, the haptic interface was tested on a group of 10 participants. After finding the lowest level of electrical current that was noticeable, they tested out a variety of patterns of stimulation. It was found that the sensations could range from the feeling of vibration to a sense of pressure being applied.

Beyond VR, the team hopes that their technology will find novel applications in medical prosthetics and other wearable devices in the future.