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 to 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 for many industry branches. Switches and pressure sensors
based on 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 more suitable for
soft surfaces, piezoelectric sensors can be utilized more easily with hard
materials such as steel. DES represented a new category of mechanical sensors
that can be used to measure strain, forces, and pressure. It can be integrated
into structures that are subject to significant deformation and strain. An example
would be seat occupancy sensors that provide additional information on load
distribution. CeSMa researchers succeeded in developing innovative sensor mats
that react very sensitively to pressure. Car seats equipped with these
intelligent DES sensor mats can sense the position of the passenger and help to
reduce the risk of injury during an accident. Other potential applications
could be in the field of geriatric care.
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 (HMIs). The sensor concepts developed by the
CeSMa also make it possible to monitor safety relevant components, enabling
continuous or periodic monitoring. Another technique developed by the CeSMa is
suited to detecting structural damage in glass, carbon fibre, or steel
structures. The Würzburg scientists developed ultrasound transducers based on
piezoelectric materials that transform mechanical strain into electric signals
or electric control voltages into movement. This principle can also be applied
to carrier materials with high operating temperatures. Towards this end, the
Würzburg researchers developed high-temperature signal transducers based on
novel monocrystal materials that can be used for permanent structural
monitoring in high-temperature environments. An application example for these
transducers is monitoring hot pipelines operating at temperatures of up to
600°C in chemical and power plants.
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