Sonic Actuation of Small-Scale Robots in a Fluidic Environment

Microrobotics represents an important development in technology that has vast applications, particularly in medical fields. Some challenges with these systems include the method of propulsion, control, and power delivery for the device. Many groups are currently developing magnetically based actuation methods, either to create a pulling drive, oscillatory motion, or a corkscrew motion. These magnetically based systems tend to be inefficient and could potentially lead to undesirable effects on the human body. This project is focusing on an alternative method of actuation in which acoustic waves would excite the robot structure to resonance, thus propelling and steering the robot. Acoustic control provides an interesting alternative to existing magnetic or electrostatic actuation in that acoustic signals produce few harmful effects on the human subject. Furthermore, the use of acoustic signals allows for the possibility to leverage existing medical imaging technology. This project focuses on the development of a doublejointed, flagella-like, flapper designed for non-reciprocal motion. Unlike reciprocal motion, nonreciprocal motion has a time irreversible nature, causing displacement regardless of the surrounding environment. Such motion is essential for microscale propulsion, where surface forces dominate inertial forces. Since the flapper uses a resonance mode, it is also frequency selective; this could allow for future steering capability by using multiple flagella tuned to different frequencies. The flapper mechanism was tested in a high viscosity fluid to reproduce the low Reynolds number environment of microrobotics. The contribution of this project would be the demonstration of a novel form of microscale propulsion using acoustic radiation forces to drive mechanical flappers to resonance, creating non-reciprocal motion. This novel form of actuation would be extendable to future microrobot applications, to include in vivo medical applications such as non-invasive surgery, targeted drug delivery, and telemetry.