Biosensing Detection - Bioinspired Approaches for Human-Centric Technologies - page 103

Fig. 3.11 Electrical
behavior of the two coated
sensors in a continuous
water flow. The dashed
lines are intended as a guide
for the eye. The different
coating material
characteristics give a
different curve shape,
tuning from a sublinear to a
super-linear trend. A
common signal saturation
region is shown
Making a biological parallel, the increase of flexural stiffness changes the
behavior of the artificial hair cell from strain-hardening to strain-softening (Rizzi
et al. 2013 ). This behavior is analogous to the hair cell mechanosensors in nature
and suggests that material-based strategies in the design of artificial mechano-
receptors can be further developed to optimization bioinspired sensors.
A linear array of these bioinspired flow sensors has been realized to reproduce
the peculiar lateral flow sensing system of fishes. This system allows fishes to
identify preys or predators without vision and schooling in ordered patterns.
Phylogenetists claim the cochlear systems took its evolutionary origin from the
lateral line in underwater ancestors (Manley and Koppl 1998 ). It has been proposed
that fish lateral line afferents respond only to flow fluctuations (AC) and not to the
steady (DC) component of the flow (Chagnaud et al. 2008 ). Therefore, it should be
possible for a fish to obtain flow information using multiple afferents that respond
only to flow fluctuations variations, retrieving useful information from noisy signals
(Venturelli et al. 2012 ). A flow sensor array has been set up inside a pipeline in
which airflow pulses were injected for testing the flow orientation and velocity
measurements. An algorithm for cross-correlation between signals from conse-
cutive flow sensors allowed to extract information from flow velocity fluctuations
instead of a single velocity read-out, providing a more robust measurement system
that is also capable of measuring events in turbulent flows. This system will be
tested on underwater autonomous systems in order to mimic the natural way fishes
orient underwater without vision.