Plasticized Liquid Crystal Networks for the Active Control of Power Transmission in Gear Train*

There is growing interest in the development of small-scale machines and devices across a variety of fields, including sensing, bioengineering, and robotics. As current methods of powering and control have inherent size limitations, there is a demonstrated need for mechanisms that operate at small scales. One approach of interest is untethered control of self-powering systems. This can be achieved using protein motors in conjunction with liquid crystal networks (LCNs). Protein motors provide high efficiency, sustained power without hazardous chemical reactions. LCNs are molecularly anisotropic and demonstrate shape-change programmability when external stimuli, such as light or heat, are applied.  In this work we showcase the use of these materials for the untethered control and powering of a multi-component mechanical device. We design and fabricate a milli-scale gear train with integrated motor and clutch functionalities. The driving gear contains protein motors and uses the Marangoni effect to generate a propulsive force. A clutch gear composed of plasticized LCNs uses photothermal actuation of the gear teeth to disengage from the gear train, halting the chain of motion on demand.