11-04 :: April/May 2011


nanotimes News in Brief


202). These sensors can be integrated into the car seat, for example, where they detect not only if the seat is occupied but the position of the occupant as well. Is the person leaning over or sitting back in the seat? Is it a child or an adult?


“The sensor films can measure stretch, as well as pressure,” says Dr. Holger Böse, Scientific and Technical Manager of the ISC’s Center Smart Materials. “They are made of a highly stretchable elastomeric film, coated on both sides with flexi- ble electrodes. Whenever the sensor is stretched by changes in the shape of the seat, the sensor’s thickness and, as a result, its electrical capacitance also change, which we can measure.” In contrast to


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conventional, rather inelastic strain gauge strips, the new dielectric elastomeric sensors can stretch by up to 100 percent in extreme cases – in other words, they can be drawn out to twice their size.


Depending on the field in which the smart materials are applied, it might be necessary to coat the ela- stomer film with multiple electrode pairs. This is the case, for example, when measuring the distribution of body pressure to determine a person’s posture in a seat. Each pair of electrodes serves, in effect, as an independent sensor, measuring the local strain. “This is how we can say precisely where and to what degree the pressure has changed,” explains Böse.


Dielectric elasto- mer sensors can be customized and applied in a variety of ways. © Fraunhofer ISC


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