Mechanical study of 3-D-printed insect and arachnid bio-inspired hair acoustic sensor for separate frequency band acquisition

Insects and arachnids have mechanoreceptors and similar sensilla which allow a wide variety of sensing mechanisms, from air flow to olfactory stimuli. These structures, often hair-like, vary in shape and size based on their function. The trichoid sensilla is a hair-like sensing mechanism that reacts to low-frequency near-field sound. This project successfully 3-D-printed structures inspired by both insects and arachnids. Of particular inspiration is the flat hair structure of the adult Buthus occitanus scorpion, which allows for a larger area of air particles to excite the sensor. The multi-material sensor design mimics trichoid sensilla, with the rigid hair transferring excitation energy to the softer basal area responsible for transduction. Using a Laser Doppler Vibrometer (LDV) it has been possible to show a change in frequency response due to a change in hair structure. Essentially showing a different frequency sensitivity based on hair length, thickness, and shape. The 3-D-printing technique used allows the production of an array of sensors in shorter times. It proves therefore useful for printing sensing arrays that would allow separate frequency band acquisition. Early development to convert mechanical displacement into electric signals has begun. [This work is funded by the Defence Science and Technology Laboratory (DSTL), United Kingdom.]