Fabrication and Characterization of a Membrane Based Hair Cell Sensor That Features Soft Hydrogel Materials

One of the most common sensory structures in nature is the hair cell. Examples of hair cells include the inner and outer hair cells in the inner ears of vertebrates, external sensory hairs on the legs of spiders, and neuromasts found along the lateral lines of fish. Recent work by Sarles and Leo demonstrated that self-assembly methods could be used to construct a membrane-based hair cell that responds to a physical disturbance of the hair. An artificial cell membrane (or lipid bilayer) formed at the interface of two lipid-encased hydrogel volumes, serves as the transduction element in the device. In this study, a revised sensor embodiment is presented in which the hair is fixed at its base by the encapsulating polymeric substrate. In addition, a highly elastic, photo-polymerizable aqueous gel (PEGDA, 6000g/mole) is used to further increase the resiliency of the hair and to provide a compliant cushion for the bilayer. These changes yield a considerably more durable hair cell sensor. We perform a series of experimental tests to characterize the transduction element (i.e. the bilayer) and the sensing current produced by free vibration of the hair, and we study the directional sensitivity of this hair cell embodiment by perturbing the hair in three directions. These tests demonstrate that the magnitude of the sensing current (30–300pA) is significantly affected by direction of perturbation, where the largest signals result from motion of the hair in a direction perpendicular to the plane of the bilayer.