Tiny hair-like sensors, or cilia, play a very important role in detection for many biological species, including humans. This research effort takes inspiration from the transduction processes of the inner ear's cochlea and cilia to design acoustic sensors. Specifically, this project proposes to use nanowires of magnetostrictive materials as hair-like sensors of ultrasonic and acoustic signals. The proposed Artificial Cilia Transducers (ACTs) have many advantages over current sensors, as these "magnetic hairs" can be easily fabricated in arrays for enhanced sensitivity and/or spatial resolution as compared to current ultrasonic pressure detectors, and the diameters, lengths and stiffnesses of the hairs can be tailored to a wide range of frequencies. Our unique choice of magnetostrictive materials will enable simultaneous detection of the distinct resonances of multiple cilia using giant magnetoresistive (GMR) sensors. Along with sensor development, several fundamental concepts of science will be investigated as valuable byproducts of this work, including processes for tailoring crystalline texture and grain size at the nanoscale for achieving materials that are more ductile and have larger transduction than their macroscaled counterparts and an understanding of Young's modulus at the nanoscale will be developed through acoustic resonance measurements. Unique contributions to science will be realized as the development of ACTs lead to the ability to discriminate pressure waves with spatial resolutions on the order of the inter-cilia spacing, ~ 40 nm. Other future sensing capabilities (beyond ultrasonic and acoustic signals) could include fluid flow, pressure variations, chemical contamination, and/or magnetic fields. These parameters can be sensed by measuring sonic resonance (as in hydrophone arrays), acoustic resonance chambers (as in the ear's cochlea), hair motion, changes in resonant frequencies due to adsorbed chemicals and hair motion, respectively. Also, future signal processing should enable the detection of frequency, phase, and directionality using nanoarrays. Additionally, the PIs all have strong track records for involving undergraduate students in laboratory research experiences and will continue to do so with this project, including a new collaboration with Morgan State University (an HBCU) that will provide summer internships for Morgan State undergraduate civil Engineering students. The interdisciplinary, inter-institutional nature of this project will be expose undergraduate and graduate students to many unique opportunities.
