Mobile Touch Screens Could Soon Feel the Pressure

A quantum switch could add pressure sensing to mobile screens.

Forget swiping or pinching--the next generation of portable touch-screen devices will be able to distinguish between a gentle touch and a hard poke.

Peratech, a U.K. company, has signed a $1.4 million deal to license its pressure-sensing touch-screen technology to Japanese screen manufacturer Nissha, which makes displays for companies including LG and Nintendo. Peratech's technology is one of several approaches that can be packed into portable devices. But it uses a novel quantum mechanism to sense pressure, and this promises to be more sensitive and more efficient than the other approaches.

Peratech, which was spun out of a research lab at Durham University in 1996, uses an electrically conductive material dubbed a quantum tunneling composite (QTC). Quantum tunneling occurs when electrons jump between two conductors that are brought close together, but remain separated by an insulating barrier. In Peratech's switches, a polymer acts as the insulating layer. It is embedded with spiky, conductive metallic particles, each about 10 nanometers in size.

"These are polymer materials that change their resistance as force is applied," says Philip Taysom, Peratech's CEO. So as force is applied, these particles are brought closer together. "As they come into proximity, they allow quantum tunneling," he says.

The approach allows Peratech's QTC sensors to be extremely thin: just 75 micrometers thick. The sensors line the perimeter of a display. When pressure is applied and the screen bends very slightly (as little as two micrometers), the switches detect this change. By comparing the readings from the sensors with sensory data from the touch screen, it is possible to tell precisely where, and how hard, the screen is being pressed.

Patrick Olivier, a human-computer interaction and computer graphics expert at Newcastle University, in the U.K., says that pressure sensing has largely been limited to large screens with cameras mounted behind them. An example is Microsoft's tabletop system, called Surface. This approach works by using a technique called frustrated total internal reflection, where the camera detects light from within the screen itself as it is refracted by a finger that makes contact with the screen.

Jeff Han, founder of New York-based Perceptive Pixel, a company that has pioneered the development of large pressure-sensitive, multi-touch interfaces, says that Peratech's approach is one of many that could bring pressure sensing to mobile devices. "There have been many efforts to augment touch screens with strain gauges or force-sensing resistor sensors situated at the mounting points of the screen," he says.

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However, Peratech says that using quantum tunneling means that its material is more sensitive to pressure than competing materials such as carbon composites. It also means that the sensors draw no power unless someone applies pressure. The company says the sensors can be fitted to existing screens relatively easily, and can be manufactured using standard printing methods.

Gadgets that use the technology should hit the market as early as April of this year, says Taysom. These devices could bring with them new interactive functionality. "The harder you press, the faster the screen will scroll or the faster a character will run in a game," says Taysom. This could also make it easier to drag and drop on-screen items, or to perform two tasks at the same time, such as simultaneously dragging and zooming an image, Taysom says.