Soft robotics for infrastructure protection

Electrically Driven, Bioluminescent Compliant Devices for Soft Robotics

Soft robotics, a research field wherein robots are fabricated from compliant materials, has sparked widespread research interest because of its potential applications in a variety of scenarios. In soft robots, luminescence is an important functionality for communication and information transmission, and it is typically achieved through electroluminescence, which relies on synthetic substances activated by external electric sources, such as batteries. This paper focuses on the use of luciferase, a biologically derived luminescent enzyme, as a luminescent material. Bioluminescence, which is triggered by the luciferin-luciferase reaction, is highly energy-efficient, nontoxic, and eco-friendly. In this regard, a mammalian cell-derived secreted luciferase bioluminescent liquid was developed. This bioluminescent liquid is strongly bright, stable, freezable, and scalable for use as a soft robotic material. To investigate the applicability of this bioluminescent liquid to soft robotics, it was incorporated as an electrode in electrically driven soft actuators, sensors, and robots. Specifically, dielectric elastomer sensors (DESs) and dielectric elastomer actuators (DEAs) were fabricated and characterized using established fabrication processes. The resistivity of the bioluminescent liquid was found to be 448.1 Ω·cm. When the DES was subjected to uniaxial strain, it exhibited a linear response and large deformation of up to 200% strain, with a simultaneous luminance change of 27%. The DEA displayed an areal strain of 46.0% and a luminance change of 31% at an applied voltage of 3.4 kV. The waterproof bending DEA generated a tip angle of 21.8° at 10 kV and was applied to a jellyfish robot that could swim in water at a speed of 2.1 mm/s. The experimental results demonstrated the successful operation of these devices, validating the concept of energy-efficient, safe, and environmentally friendly bioluminescent soft robots.

Magnetically Actuated Trigger Transient Soft Actuators Comprising On-Demand Photo-Initiated and Thermo-Degradable Polypropylene Carbonate-Photo-Acid Generator

Lifetime-reconfigurable soft robots have emerged as a new class of robots, emphasizing the unmet needs of futuristic sustainability and security. Trigger-transient materials that can both actuate and degrade on-demand are crucial for achieving life-reconfigurable soft robots. Here, we propose the use of transient and magnetically actuating materials that can decompose under ultraviolet light and heat, achieved by adding photo-acid generator (PAG) and magnetic particles (Sr-ferrite) to poly(propylene carbonate) (PPC). Chemical and thermal analyses reveal that the mechanism of PPC-PAG decomposition occurs through PPC backbone cleavage by the photo-induced acid. The self-assembled monolayer (SAM) encapsulation of Sr-ferrite preventing the interaction with the PAG allowed the transience of magnetic soft actuators. We demonstrate remotely controllable and degradable magnetic soft kirigami actuators using blocks with various magnetized directions. This study proposes novel approaches for fabricating lifetime-configurable magnetic soft actuators applicable to diverse environments and applications, such as enclosed/sealed spaces and security/military devices.