  Mechanosensory ciliary bundles in fishes are the inspiration for carefully
engineered artificial flow sensors. We report the development of a new class of
ultrasensitive MEMS flow sensors that mimic the intricate morphology of the
ciliary bundles, including the stereocilia, tip links, and the cupula, and
thereby achieve threshold detection limits that match the biological example.
An artificial ciliary bundle is achieved by fabricating closely-spaced arrays
of polymer micro-pillars with gradiating heights. Tip links that form the
fundamental sensing elements are realized through electrospinning aligned PVDF
piezoelectric nano-fibers that link the distal tips of the polymer cilia. An
optimized synthesis of hyaluronic acid-methacrylic anhydride hydrogel that
results in properties close to the biological cupula, together with
drop-casting method are used to form the artificial cupula that encapsulates
the ciliary bundle. In testing, fluid drag force causes the ciliary bundle to
slide, stretching the flexible nanofibers, thus eliciting charges.
