Abstract
Linear displacement is used for positioning and scanning, e.g., in robotics at different scales or in scientific instrumentation. Most linear motors are either powered by rotary drives or are driven directly by pressure, electromagnetic forces or a shape change in a medium, such as piezoelectrics or shape-memory materials. Here, we present a centimeter-scale light-powered linear inchworm motor, driven by two liquid crystal elastomer (LCE) accordion-like actuators. The rubbing overwriting technique was used to fabricate the LCE actuators, made of elastomer film with patterned alignment. In the linear motor, a scanned green laser beam induces a sequence of travelling deformations in a pair of actuators that move a gripper, which couples to a shaft via friction moving it with an average speed in the order of millimeters per second. The prototype linear motor demonstrates how LCE light-driven actuators with a limited stroke can be used to drive more complex mechanisms, where large displacements can be achieved, defined only by the technical constrains (the shaft length in our case), and not by the limited strain of the material. Inchworm motors driven by LCE actuators may be scaled down to sub-millimeter size and can be used in applications where remote control and power supply with light, either delivered in free space beams or via fibers, is an advantage.
Highlights
To fabricate light-responsive actuators made of liquid crystal elastomer (LCE) films with patterned molecular alignment, we introduced the technique of mechanical rubbing overwriting
We demonstrated how rubbing with masks that leave only some fragments of the surface exposed could be used to prepare LCE films with patterned orientations
In the first few steps in Video S3, the warm-up phase is visible, when the average temperature of the LCE actuators gradually increased with each laser scan, until it reached a steady-state operation
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Nature does not seem to use rotary motion often. We are aware of only three examples of rotary motion used in the animal kingdom: bacterial flagella are powered by a rotating motor built into the cell envelope, driven by the flow of protons or sodium ions; dung beetles use rolling to transport loads; and some caterpillars from the Crambidae family roll away when in danger. On the contrary, relies on rotary motion for energy conversion, transport and manufacturing. Linear motion is vital for many applications, e.g., in handling, positioning and metrology. There are a number of solutions for realizing linear displacement with rotary motors: via rack and pinion, wheel and belt or lead screw
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