Artificial cilia for 360° direction-sensitive acoustic sensing through additive micromanufacturing

Directional acoustic sensing is essential in various fields, including industrial machinery, robotics, and health care. It is, however, a challenge to sense both the amplitude and direction of the acoustic waves with a simple sensor design. In this paper, we have prepared a series of artificial cilia using additive micro-manufacturing technologies for direction-sensitive acoustic sensing, including electrospray and three-dimensional (3D) micro-direct ink writing. The response of the artificial cilia at resonance is significantly enhanced, while the resonance frequencies decrease with increasing length. Two resonances were achieved by printing two independent electrode-to-electrode interconnect bridges. Two signal channels produce an ‘8’-shaped loop by varying acoustic excitation angles, showing both amplitude and phase difference are direction dependent. By micro-manufacturing artificial cilia with two orthogonally arranged electrodes, we have achieved direction-sensitive acoustic sensing. Our effort opens an avenue in cochlear and device detection with promising applications, including directional attitude sensing and water flow sensing.