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A fabrication process is presented which allows realizing the dense arrays of fully supported flexible SU-8 membranes with integrated electrodes underneath that support cylindrical hair-like structures on the top. Electrodes have been insulated from liquid to prevent short circuit or electrolysis. The process allows a controllable distance between counter electrodes. The excess squeeze film damping is eliminated with a closed membrane configuration with backside openings. A low-power differential capacitive measurement mechanism is employed as a sensor readout. These flow sensors provide a distributed sensing mechanism inspired by the superficial neuromast as found in the lateral line system of fish. This paper focuses on the fabrication of the sensors with preliminary mechanical results demonstrating the functionality of the fabricated devices.

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In this paper we report on the latest developments in biomimetic flow-sensors based on the flow sensitive mechanosensors of crickets. Crickets have one form of acoustic sensing evolved in the form of mechanoreceptive sensory hairs. These filiform hairs are highly perceptive to low-frequency sound with energy sensitivities close to thermal threshold. Arrays of artificial hair sensors have been fabricated using a surface micromachining technology to form suspended silicon nitride membranes and double-layer SU-8 processing to form 1 mm long hairs. Previously, we have shown that these hairs are sensitive to low-frequency sound, using a laser vibrometer setup to detect the movements of the nitride membranes. We have now realized readout electronics to detect the movements capacitively, using electrodes integrated on the membranes.

Biological sensory systems often display great performance which inspires engineers to design artificial counterparts. In this paper we report the fabrication of aquatic hair based flow sensors inspired by fish lateral line. Geometrically optimized flexible membranes of SU-8 with integrated electrodes underneath have been realized in a reliable, high yield process. By separating the liquid medium from readout electrodes we decrease squeeze film damping and eliminate electrolysis. The procedure allows dense membrane array fabrication.