Go Soft on Me

Whether one is exploring a virtual world, or the real world, there are many useful reasons that they might want to modulate their sense of touch to simulate realistic physical effects. In both cases, it is desirable to use physical props because of the realism that they offer, but it is not practical to have a vast collection of props to simulate every possible scenario. That is where efforts to alter perceptions of sensations come into play — a single physical object can feel as if it were any number of different objects.

Naturally, there are many factors that come together to form our sensations of the physical world, but one of the key factors is the perception of softness. A trio of researchers from the University of Chicago have created a device around a surprisingly simple principle that can make hard objects seem much softer by mechanically deforming the fingerpad.

When the fingerpad comes into contact with a rigid object, pressure is exerted on a small area, and the fingerpad tends to be deformed, and move outwards, in response to that pressure. The surface of the rigid object does not conform to the fingerpad. Contrast that with a soft object, where the fingerpad comes into contact with a wider area because the more compliant material conforms mechanically to the shape of the fingerpad. This effect leads to a more even distribution of pressure across this larger area. These factors greatly influence our perceptions of the hardness of materials.

The research team used this insight to create a small, fingertip mounted device that can deform the fingerpad on demand, and thereby alter the way in which they come into contact with surfaces. The device, centered around a Nordic Semiconductor nRF52811 microcontroller, uses a pulley controlled by a small DC motor to pull on a 3D printed frame that gently squeezes the fingerpad and makes it bulgier. This increases the contact area of touched surfaces, and gives the perception that they are softer than they really are.

A small study including five individuals was conducted to validate the device. Participants were asked to touch objects of a variety of hardnesses, which were blocked from their view. One of their hands was instrumented with the device, while the other was not. They were asked to simultaneously touch two objects, each with a finger from separate hands, then to rank which object felt harder. On average, participants did perceive objects as being softer when the device was in use.

This device prototype presents an interesting and inexpensive method of modulating perception of everyday objects. It does have some limitations, however. The effect is limited to small areas of the fingertips, and requires instrumentation to be worn on each finger to achieve that effect. It is also unclear if the act of deforming the fingerpads has any unintentional impacts on otherwise normal sensations, or if there would be any issues with discomfort with long-term use of the device. In any case, this research has the potential to move the ball forward in haptic wearables.