Tactile Sensing With Scalable Capacitive Sensor Arrays on Flexible Substrates

The development of advanced, human like tactile sensing capabilities is one of the key challenges for next generation robots or prosthetics. Tactile sensors arrays will need to exhibit the desired sensing capabilities, show robustness to external influences as well as good approaches for the integration of large amounts of sensors. We present a tactile sensor array technology, based on the fabrication of a flexible interconnection substrate containing directly integrated tactile sensors. This approach has several advantages: interconnection substrate technology is widely available making upscaling of sensor arrays easy to a large amount of sensors and/or large sensing areas, the direct integration of sensors allows for a simple and very compact approach to densely packed sensor arrays and the structured flexible substrate enables integration into complex, three-dimensional bodies. We present sensors with a size of 600 μm and arrays of up to 12 x 12 individually addressable sensors. The sensors have a wide measurement range; free membrane deformation results in a high sensitivity of 2.6 kPa⁻¹ respectively 2600 N⁻¹ for small applied pressures (0-0.6 kPa) whereas deforming polymer studs extend the measurement range for larger applied pressures (5-25 kPa) with a sensitivity of 0.022 kPa⁻¹ respectively 22 N⁻¹. A statistical study of six sensor arrays from three wafers showed repeatable performance of the fabricated structures and robustness tests proved the stable sensing conditions over 10'000 cycles.