Acoustic resonators, a concept once confined to musical instruments, are now being reimagined as a novel propulsion system for small robots. This innovative approach, as demonstrated by Junsun Hwang and colleagues, leverages the power of Helmholtz resonance to generate thrust and steering capabilities. By stimulating the resonance frequency of a chamber with an external acoustic source, a jet of air is produced at the chamber's neck, offering a unique and efficient means of propulsion.
The research showcases a variety of applications, including a boat equipped with three resonance chambers for both propulsion and steering. Perhaps the most intriguing application, however, is the microflier. When placed above an ultrasonic phased array, the microflier hovers due to the jet of air produced by the resonance chambers. This concept was further refined by integrating angled resonator chambers to drive a propeller, resulting in a thrust of a fraction of a Newton.
The challenge lies in minimizing the weight of these structures, as they must be in the microgram range. High-resolution 3D printing has been instrumental in creating these microfliers, with several iterations to determine the optimal configuration. For the boat, ultrasonic transducers were directly mounted on the resonance chamber, but for the microfliers, external transducers were necessary due to weight constraints.
While the microflier may not be the most practical flying robot, it serves as an excellent demonstrator of acoustic propulsion using Helmholtz resonance. This technology opens up exciting possibilities for small-scale robotics, offering a unique and efficient means of propulsion and steering. As the field of robotics continues to evolve, the integration of unconventional propulsion methods like this one could pave the way for innovative and agile robots that can navigate diverse environments.
