Technology: Stretchable sensors for smart textiles

Würzburg, Germany – The Fraunhofer Institute for Silicate Research (ISC) is employing elastomer film technology in a programme to develop expandable strain and pressure sensors for a range of applications.

The institute’s Smart Materials Centre is studying silicone rubber-based sensors for applications in the areas of intelligent textiles, electronic connections, control systems and displays, Fraunhofer ISC said 15 May.

According to the research body, the advanced sensors are based on “extremely elastic dielectric elastomers (DES)” especially for use in textiles.

Developed by Fraunhofer, DES is a new class of mechanical sensors for measuring deformations, forces and pressures.

Due to their high elasticity, softness and flexibility, DES are particularly well suited for integration into woven or knitted fabrics.

DES consist of thin elastomer films with ultra-flexible electrode areas on both sides of the film forming an elastic capacitor, Fraunhofer explained.

Under tensile load or deformation, the surface expands while, at the same time, the thickness of the sensor film decreases, causing a measurable increase in capacitance.

Apart from the design and the geometric dimensions, the elastomer hardness determines the sensitivity of the sensor.

“Silicone rubber offers a broad variability of hardness through chemical cross-linking. As a result, the material can be adapted to specific requirements of the sensor,” the institute pointed out.

The electrodes on the elastomer film consist of electrically conductive particles integrated into a matrix. The measuring signal is passed into a conductive elastic yarn.

The sensors can be integrated into textiles and, therefore, be used for measuring signals from the human body, such as breathing, movement or muscle contraction.

Potential application areas include in medical care, shoes and sports training by measuring posture and weight with appropriately equipped garments or mats.