Conversion of light into macroscopic helical motion
A key goal of nanotechnology is the development of artificial machines capable of converting molecular movement into macroscopic work. While conversion of light into shape changes has been reported and compared to artificial muscles, real applications require work against an external load. Here, we describe the design, synthesis and operation of spring-like molecular materials capable of converting light energy into mechanical work at the macroscopic scale. These versatile materials consist of molecular switches embedded in helical liquid-crystalline polymer springs. In these springs, molecular movement is converted and amplified into controlled and reversible twisting motion. The springs display a range of helical shapes associated with complex motion including winding, unwinding and helix inversion as dictated by their initial shape. Importantly, they can produce work by moving a macroscopic object and mimicking mechanical movements, such as those used by plant tendrils to help the plant access sunlight. These functional materials have potential applications in micro-mechanical systems, soft robotics and artificial muscles.