Hair cell structures are one of the most common forms of sensing elements found in nature. In nearly all
vertebrates hair cells are used for auditory and vestibular sensing. In humans, approximately 16,000
auditory hair cells can be found in the cochlea of the ear. Each hair cell contains a stereocilia, which is the
primary structure for sound transduction. This study looks to develop and characterize an artificial hair
cell that resembles the stereocilia of the human ear. Recently our research group has shown that a single
artificial hair cell can be formed in an open substrate using a single aqueous droplet and a hydrogel. In
this study, air was blown across the hair and analyzed using spectral analysis. The results of this study
provided the foundation for our current work toward an artificial hair cell that uses two aqueous droplets.
In the current study a test fixture was created in order to consistently measure various properties of the
encapsulated hair cell. The response of the hair cell was measured with an impulse input at various
locations on the test fixture. A frequency response function was then created using the impulse input and
the output of the sensor. It was found that the vibration of the hair was only detectable if the test fixture
was struck at the correct location. By changing the physical parameters of the hair sensor, such as hair
length, we were able to alter the response of the sensor. It was also found that the sensitivity of the sensor
was reliant on the size of the lipid bilayer.
Receptors known as hair cells give many animals this ability to sense a wide range of stimuli, such as sound, orientation,
vibration, and flow. Previous researchers have mimicked natural hair cells by building electromechanical sensor systems
that produce an electric response due to the bending of artificial hairs. Inspired by the roles of sensory hairs in fish, this
work builds on previous research by investigating the flow dependent electrical response of a 'skin'-encapsulated
artificial hair cell in an aqueous flow. This study presents the design, fabrication, and characterization of a flow sensor
that will help close the loop between the sensing mechanisms and control strategies that aquatic organisms employ for
functions such as locomotion regulation, prey capture, and particulate capture. The system is fabricated with a durable,
artificial bilayer that forms at the interface between lipid-encased aqueous volumes contained in a flexible encapsulated
polyurethane substrate. Flow experiments are conducted by placing the bio-inspired sensor in a flow chamber and
subjecting it to pulse-like flows. Specifically, through temporal responses of the measured current and power spectral
density (PSD) analysis, our results show that the amplitude and frequency of the current response are related to the flow
over the hair. This preliminary study demonstrates that the encapsulated artificial hair cell flow sensor is capable of
sensing changes in flow through a mechanoelectrical response and that its sensing capabilities may be altered by varying
its surface morphology.
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