Smart sensors offer haptic feedback

July 13, 2014 // By Christoph Hammerschmidt
Fraunhofer ISC's Centre for Smart Materials (CeSMa) has demonstrated smart materials that can be used to create intelligent sensors with haptic feedback.  

Intelligent and adaptive materials possess properties that react on external factors such as magnetic or electrostatic fields. For instance, consistency, flow properties, expansion behaviour or pressure sensibility can change under influence of these external factors. These properties can be used to make these materials act as sensors or actuators. The CeSMa, an entity of the Fraunhofer Institute for Silicate Research (ISR) in Würzburg (Germany), uses such materials to develop prototypes of many industry branches.

Switches and pressure sensors on the basis of highly sensitive piezoelectric layers or dielectric elastomer sensors (DES) - which are extremely stretchy - can adapt to a variety of haptic requirements and mechanical sensor functions. While DES are suitable more for soft surfaces, piezoelectric sensors can be utilised more easily with hard materials such as steel. DES represent a new category of mechanical sensors that can be used to measure strain, forces and pressure. Featuring extreme ductility of up to 100%, DES can be integrated into structures that are subject to significant deformation and strain. An application example in such an environment would be seat occupancy sensors that provide additional information on load distribution. CeSMa researchers succeeded in developing innovative sensor mats that react very sensitively on pressure. Car seats equipped with these intelligent DES sensor mats can sense the position of the respective passenger can help to reduce the risk of injury during an accident. Other potential applications could be in the field of geriatric care: Integrated into a mattress, the mat can support the prophylaxis of pressure sores.

Thin piezoelectric layers on steel foil carriers offer great design freedom with respect to size, shape and curvature. In addition, this technology can be used to implement "invisible" switches and sensors in car interiors, for instance on the instrument panel. Insensitive to dust and dirt, they enable implementing functional surfaces even in rough environments. In addition, electrostatic fields can be integrated into the foils which can serve as proximity sensors. Thus, the control panels generate a proximity signal and at the same time provide a haptic feedback when activated. The combination of proximity and pressure sensor with haptic feedback offers new options in the design of Human-Machine Interfaces (HMI).