Light Robots: Bridging the Gap between Microrobotics and Photomechanics in Soft Materials

Abstract

For decades, roboticists have focused their efforts on rigid systems that enable programmable, automated action, and sophisticated control with maximal movement precision and speed. Meanwhile, material scientists have sought compounds and fabrication strategies to devise polymeric actuators that are small, soft, adaptive, and stimuli-responsive. Merging these two fields has given birth to a new class of devices-soft microrobots that, by combining concepts from microrobotics and stimuli-responsive materials research, provide several advantages in a miniature form: external, remotely controllable power supply, adaptive motion, and human-friendly interaction, with device design and action often inspired by biological systems. Herein, recent progress in soft microrobotics is highlighted based on light-responsive liquid-crystal elastomers and polymer networks, focusing on photomobile devices such as walkers, swimmers, and mechanical oscillators, which may ultimately lead to flying microrobots. Finally, self-regulated actuation is proposed as a new pathway toward fully autonomous, intelligent light robots of the future.

Preparation of liquid crystalline polymer networks containing a cinnamyl group in the main chain with tunable thermal actuation behavior

“…As early as 1975, P. G. de Gennes predicted that liquid crystal elastomers (LCEs) could realize the functions of human muscles. LCEs are soft materials that can produce a large mechanical actuation and reversible shape change when subjected to various external stimuli, and they have potential applications in artificial muscles, soft robots, and dynamic functional architectures . An LCE can be obtained by moderately crosslinking a liquid crystalline copolyester (LCP) and exhibits elasticity in the isotropic or liquid crystal state while having the dual characteristics of an elastomer and a liquid crystal.…”

Kirigami‐Based Light‐Induced Shape‐Morphing and Locomotion

“…In the past decades, stimuli‐responsive soft material systems have attained an increasing amount of interest. The interest stems from novel possibilities to design and fabricate soft devices with miniaturize sizes and ever‐more‐complex functions . Among the wealth of stimuli‐responsive materials, carbon‐based bilayers, liquid crystal elastomers and polymer networks (LCNs), hydrogels, and magnet‐doped rubbers stand out as prominent candidates for soft microrobotics.…”

“…The interest stems from novel possibilities to design and fabricate soft devices with miniaturize sizes and ever-more-complex functions. [4,5] Among the wealth of stimuli-responsive materials, carbon-based bilayers, [6] liquid crystal elastomers and polymer networks (LCNs), [7] hydrogels, [8] and magnet-doped rubbers [9] stand out as prominent candidates for soft microrobotics. The devices composed of these materials adopt novel control strategies, shifting from conventional wire-connections (electrically or via pneumatic tubes) [10,11] to a wireless approach relying on external energy sources such as magnetic fields, [12] light fields, [13] humidity, [14] or chemical reac-…”

Inorganic Stimuli‐Responsive Nanomembranes for Small‐Scale Actuators and Robots

“…Recently, because of the exciting advances in materials science including the development of stimuli-responsive materials and actuation schemes, the field of small-scale robotics is growing rapidly. [5][6][7][8] Stimuli-responsive materials have the ability to respond to external stimuli, such as light, [9] heat, [10] pH, [11] metal ions, [12] electric fields, [13,14] and magnetic fields. [15] By virtue of the fabrication techniques including traditional composite syntheses and printing, these stimuli-responsive materials have been utilized to construct diverse reconfigurable structures, from the nanoscale to the macroscale, that can reversibly switch their shape in response to different stimuli.…”