Stretchable sensors aim at improving airbag control

May 20, 2011 // By Christoph Hammerschmidt
There are situations when an airbag does not protect but instead hurts car passengers: For instance, if it ignites in a moment when the seat occupant has bent forward. A sensor technology developed by Fraunhofer Institute for Silicate Research (ISC) can help to optimize the ignition process by providing information as to the passenger's weight and position.

The sensors will be integrated into the seats. They consist of a stretchable elastomer foil which is coated by stretchable electrodes on both sides. In the case the sensor is stretched, for instance by a seat deformation as a consequence of the passenger moving around, the thickness of the foil changes, and thus its capacity. In contrast to conventional resistance strain gauges the elastomer sensors can be stretched by up to 100 percent, said Holger Böse, scientific manager of the ISC Smart Materials Center.

According to the application, it might be reasonable to add several electrode pairs onto the elastomer foil, enabling engineers to measure pressure distribution across a plane. This, for instance, is the case in a car seat. Each electrode pair takes the function of a separate sensor and measures the local pressure. "Thus, we are able to exactly determine where a person sits and how he/she changes his position", Böse said.

The material can be adjusted to the respective application. For higher pressures, it is possible to use a more rigid material; for lower pressures they would use a softer material.

Besides automotive airbag control, the sensors could also be used for a range of different applications, including gas pressure. They also could be integrated into intelligent apparel, Böse said. For instance in sports apparel they could be used to analyze and optimize movements.

The technology will be presented at Fraunhofer's booth at the Sensor + Test trade fair in Nuremberg (June 7 - June 9)