Hydrogel Actuator with a Built‐In Stimulator Using Liquid Metal for Local Control

Abstract

Hydrogel actuators, comprising gels that convert external stimuli into mechanical motion for actuation, are attracting attention for their promising applications, such as in robotics. The driving force is the absorption or release of water or another solvent, which results in swelling and shrinking motions, leading in turn to more complex functionalities. However, practical hydrogel actuators that can be controlled locally, such as ones that allow local actuation around the joints in rigid‐bodied robots, do not exist. Herein, the driving target of a thermo‐responsive hydrogel, poly(N‐isopropyl acrylamide), is integrated with the stimulation module using a liquid metal. The stimulation module provides heat as an external stimulus to the hydrogel actuator. The motion of the actuator is triggered by the heat supplied by an ultrasoft hydrogel coil, with liquid metal surrounding the driving target. The heat generated by current flowing through the liquid metal changes the temperature only around the desired part of the actuator, which enables the electrical control of an individual part of the hydrogel actuator. The concept of integrating the driving target and stimulator is expected to facilitate functional movement of actuators and expand the range of potential applications of hydrogels.

Ultrafast and Highly Deformable Electromagnetic Hydrogel Actuators Assembled from Liquid Metal Gel Fiber

“…Fabrication of Gel Fiber: The fabrication of gel springs with a core-shell structure was based on the microfluidic method according to the procedures established in the literature. [26] Figure 1a shows the method for fabricating the gel fiber. Two types of gel fibers were fabricated: a straight shape (Figure 4a) and a coil shape (Figure 4b).…”

Liquid metal-based nanocomposite materials: fabrication technology and applications

“…20 (c) Patterning: (i) screen printing-image of Ni-Galn applied to Ecoflex using a rolling brush; 21 (ii) direct printing-schematic of 3D direct printing system and composites printed onto soft 3D substrate (scale bar = 100 μm). 22 (d) Applications: (i) flexible sensor with strain angle; 23 (ii) hydrogel spring actuator; 24 (iii) roomtemperature LM battery. 25 break LMs down to nanoparticles in less time (60 min) than shear liquid into complex particle (SLICE) processes, which can take around 120 min.…”

“…When the lead wire is stretched, a resistance changes of only 1/100th of that of the normal LM lead wire is produced, so actuators can be more stably controlled by using them as heaters. 24 LMs have excellent thermal conductivities; thus, their uses for cooling have been considered. With the development of wearable devices and soft robots in recent years, improving the speed of heat conduction has also become an issue.…”

Recent Advances in Deformable Circuit Components with Liquid Metal

“…Matsabura et al. [ 144 ] created an actuator using temperature responsive poly( N ‐isopropyl acrylamide) (PNIPAM) gel‐like rods that were electrically controlled using current passing through galinstan helical microwires wrapped around the straight PNIPAM rods ( Figure ). The microwires have a <2% change in resistance with 100% strain due to helical shape and a low spring constant of 0.71 N m −1 , allowing the device to deform with PNIPAM rod deformation.…”