Monday, November 20, 2006

Driving a Wheelchair with Your Shirt

Garments printed with flexible sensors could help people with severely limited mobility control assistive devices.

By Emily Singer

A sensor-laden shirt could help seriously paralyzed individuals steer their wheelchairs. In this photo, a paralyzed volunteer wearing the shirt practices navigating a virtual-reality environment. The garment’s sensors, seen in black, detect movements made by the wearer that are used to control a virtual wheelchair. Credit: Alon Fishbach, Northwestern

Adaptive, sensor-laden garments could provide a new way for quadriplegics to control their wheelchairs. The system, which is still in an early stage of development, identifies the ideal set of movements that can be employed as control commands for each individual user. "We think this will benefit the most difficult patients, such as those who can move only their head or shoulders," says Alon Fishbach, a scientist at Northwestern who is among those developing the device.

People with high-level spinal-cord injuries often lose control of their hands, but they may still be able to move their shoulders or chests. More and more such patients survive their injuries, thanks to respiratory devices that help them breathe. But these people have limited options when selecting devices to control their wheelchairs or computers. They might use a sip/puff switch, which converts the user's sip or puff of air into a specific command, or a headswitch, which records head movements via a switch on the back of the wheelchair. "But the disadvantage of these devices is that patients must fit the capacities of the machine, rather than the other way around," says Ferdinando Mussa-Ivaldi, another Northwestern scientist working on the device. "If a patient can move their right side more than their left, an intelligent interface could pick up on this." Mussa-Ivaldi directs the Robotics Laboratory of the Rehabilitation Institute of Chicago, where the research took place.

To overcome this design flaw, the researchers are developing an adaptive device using sensor-laden fabric. The garment is printed with 52 flexible, piezoresistive sensors developed at the University of Pisa. These sensors are made of electroactive polymers that change voltage depending on the angle at which they are stretched. The sensors can detect fine scale movements of the upper body and arms.