Abstract
With continuous miniaturization of many technologies, robotics seems to be lagging behind. While the semiconductor technologies operate confidently at the nanometer scale and micro-mechanics of simple structures (MEMS) in micrometers, autonomous devices are struggling to break the centimeter barrier and have hardly colonized smaller scales. One way towards miniaturization of robots involves remotely powered, light-driven soft mechanisms based on photo-responsive materials, such as liquid crystal elastomers (LCEs). While several simple devices have been demonstrated with contracting, bending, twisting, or other, more complex LCE actuators, only their simple behavior in response to light has been studied. Here we characterize the photo-mechanical response of a linear light-driven LCE actuator by measuring its response to laser beams with varying power, pulse duration, pulse energy, and the energy spatial distribution. Light absorption decrease in the actuator over time is also measured. These results are at the foundation of further development of soft, light-driven miniature mechanisms and micro-robots.
Highlights
Scaling down mechanical devices, in particular robots, calls for new approaches to power sources, motors, drivetrains, and actuators
Results and Discussion look into this issue, we performed absorption measurements of the Liquid crystalline elastomers (LCEs) film of the same type as used
When experimenting with pulsed illumination of the light-responsive actuators, an interesting question arises: how does the photo-mechanical response compare for a long laser pulse with low instantaneous power and a short pulse of higher instantaneous power, both delivering the same energy to the light-responsive element? In Figure 3b, we present the measured maximum actuator stroke for pulse durations between 1 s and 100 ms, with the laser power adjusted so that the total energy in each laser pulse was always 0.19 J
Summary
In particular robots, calls for new approaches to power sources, motors, drivetrains, and actuators. Soft actuators, driven with different stimuli, have been demonstrated in small scales [1]. A large class of magnetically driven actuators have been developed, mostly based on soft polymers with suspensions of magnetic particles and different modes of actuation are possible via temporally and/or spatially varying external magnetic fields [6,7]. Small scale actuators can be powered by chemical reactions that induce the material deformation, by e.g., selective modification of chemical bonds in polymers [8]. Pressure driven soft actuators rely on structures with spatially varying stiffness that deform upon expansion of gas- or liquid-filled chambers [9]—they have been realized on a small scale [10], but still need the tubing to deliver the pressurized medium
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