Bidirectional biomimetic flow sensing with antiparallel and curved artificial hair sensors

Abstract

Background: Flow stimuli in the natural world are varied and contain a wide variety of directional information. Nature has developed morphological polarity and bidirectional arrangements for flow sensing to filter the incoming stimuli. Inspired by the neuromasts found in the lateral line of fish, we present a novel flow sensor design based on two curved cantilevers with bending orientation antiparallel to each other. Antiparallel cantilever pairs were designed, fabricated and compared to a single cantilever based hair sensor in terms of sensitivity to temperature changes and their response to changes in relative air flow direction. Results: In bidirectional air flow, antiparallel cantilever pairs exhibit an axially symmetrical sensitivity between 40 μV/(m s−1) for the lower air flow velocity range (between ±10–20 m s−1) and 80 μV/(m s−1) for a higher air flow velocity range (between ±20–32 m s−1). The antiparallel cantilever design improves directional sensitivity and provides a sinusoidal response to flow angle. In forward flow, the single sensor reaches its saturation limitation, flattening at 67% of the ideal sinusoidal curve which is earlier than the antiparallel cantilevers at 75%. The antiparallel artificial hair sensor better compensates for temperature changes than the single sensor. Conclusion: This work demonstrated the successive improvement of the bidirectional sensitivity, that is, improved temperature compensation, decreased noise generation and symmetrical response behaviour. In the antiparallel configuration, one of the two cantilevers always extends out into the free stream flow, remaining sensitive to directional flow and preserving a sensitivity to further flow stimuli.

Engineering Stress in Thin Films: An Innovative Pathway Toward 3D Micro and Nanosystems

“…[197,201] Inspired by the concept of AHC, several out-of-plane cantilevers have been fabricated for liquid and air flow measurement. [197,198,201,205,[207][208][209][210]285,286] Figure 11a shows a piezoresistive flow sensor made of SiN/Si bilayer. [201] The SiN/Si cantilever was coated by parylene for waterproof, and can function in both air and water environments.…”

“…The sensor exhibited superior response under various airflow velocity in two opposite directions compared to single cantilever, Figure 11b. [285] In 3D MEMS flow sensors, capacitive [287] and piezoresistive effects [197,201,210] effects are most commonly employed due to the ease of their integration capability and associated readout circuits. Capacitive airflow sensors employ out-of-plane cantilevers as movable electrodes, and the substrate as fixed electrodes.…”

“…Reproduced with permission. [ 285 ] Copyright 2019, Beilstein Institute for the Advancement of Chemical Sciences; c) electronic whisker of SMP. Reproduced with permission.…”

“…The sensor exhibited superior response under various airflow velocity in two opposite directions compared to single cantilever, Figure 11b. [ 285 ]…”

“…Fish image (https://pixabay.com/photos/discus-fish-fish-aquariumfauna-1943755/); b) bidirectional flow sensor. Reproduced with permission [285]. Copyright 2019, Beilstein Institute for the Advancement of Chemical Sciences; c) electronic whisker of SMP.…”