Soft and Flexible Actuators

Liquid Metal Marbles

Liquid metal marbles are small drops of eutectic Gallium Indium (eGaIn) suspended in a liquid. They can be induced to move via magnetic field, chemical reaction, or and electrically-induced change in surface tension. Typically these interactions are used to move the metal and this has been used to create morphing antennas, among other things. However, we applied this same principle to move an electrolyte solution that surrounds the marble in a microfluidic channel. We demonstrated the ability to generate flow and pressure to actuate a soft `nub’ under a microfluidic chamber. The power density of the unoptimized marble was low (~ 200 mW/kg) but I believe there was lots of room for improvement through better choices in solution and microchannel design.

Flexible Linear Motor

We also investigated the use of a linear stepper motor embedded in a flexible tube to create a bendable linear actuator. The outer stator consisted of several copper coils in series that generated a phased magnetic field, and the inner core consisted of several permanent magnets joined together with flexible joints to create a single, flexible core. We prototyped a design but found it to have very low power density (~ 150 mW/kg), likely due to the friction between the coils and the magnetic core. It would also have been difficult to miniaturize.