Strain gauges based on NBR substrates for the integration into elastic materials

• Preparation of NBR thin films as a hyperelastic substrate for micro sensors.
• Fabrication of strain gauges built on a hyperelastic material for the integration into an elastic host material.
• Evaluation of an embedded sensor inside a silicone gasket during compression.
• The sensor signal of the NBR based strain gauges is directly related to the compression force applied on the gasket.

The fabrication of a thin film hyperelastic nitrile butadiene rubber (NBR) substrate, for micro-structured strain gauges, has been developed. These NBR sensors are integrated into silicone and rubber materials for the purpose of monitoring a change in material properties, such as stress-strain behavior. As an example, they were integrated into silicone gaskets. The signal of the embedded sensors was measured while compressing the gaskets. The change of resistance depends on the applied compression force and is directly correlated with the stress-strain properties of the host material. By using a hyperelastic substrate with similar physical properties as the host material, the distortion on the sensor signal, regarding the properties of the host material, can be minimized. Uniaxial tensile tests were performed on test specimens containing the NBR sensors. It was discovered that the integrity of the host material is slightly less influenced by the embedded NBR sensors compared with commonly used polyimide substrates. However, the test also revealed that the sensor size highly influences the stability of the host material.