Magnetically Controlled Soft Robotics Utilizing Elastomers and Gels in Actuation: A Review

Abstract

A magnetic field has unique advantages in controlling soft robotics inside of an enclosed space, such as surgical catheters or untethered drug‐delivering robots operating in the human body. Soft actuators, made of elastomers and gels functionalized with magnetically active materials, are natural choices to drive magnetically controlled motions of soft robots. Recent innovations in soft material technologies, including 3D printing, origami/kirigami, tough hydrogels, mechanical metamaterials, and liquid metal‐injected elastomers, offer technological foundations to develop soft actuators and robots with significantly enhanced performance. Herein, an overview of magnetic soft actuators and robots from a materials engineer's perspective is provided. First, the historical background and recent trends of magnetic soft actuators are discussed. Second, the motions of tethered or untethered magnetic soft robotics are classified into aquatic swimmers, terrestrial locomotors, and grippers. Herein, preprogrammed motion under patterned magnetic stimuli is achieved by controlled magnetization of elastomeric materials containing hard magnetic particles. Finally, the applications of magnetically controlled soft robotics in surgical and therapeutic medical devices are discussed.

Magnetic Soft Millirobots 3D Printed by Circulating Vat Photopolymerization to Manipulate Droplets Containing Hazardous Agents for In Vitro Diagnostics

“…Magnetic Soft Millirobots (MSMRs): All MSMRs were 3D printed with a composite resin that containing 15% w/w SrFe 12 O 19 particles mixed in a flexible resin (XYZ printing resin B1) except for the caterpillar that used 10% w/w. It took 27,18,12,13,12, and 27 min to print the "milligripper," "caterpillar," "rocking horse," "helicobacter," "fish," and "jellyfish," respectively. The support structures were removed after printing.…”

“…DOI: 10.1002/adma.202200061 robots will transform a vast range of biomedical applications. [7][8][9][10][11] Magnetic actuation is one of the most popular method among the available actuation methods to control soft millirobots, [12,13] because of its remote and wireless control, ability to induce rapid response, and ease of implementation. [13,14] The rapid response helps realize a short latency between the stimulation and shape morphing, and it allows millirobots to work in harsh environments with abrupt changes and unknown variations.…”

Magneto-Mechanical Enhancement of Elastic Moduli in Magnetoactive Elastomers with Anisotropic Microstructures

“…Here, unlike (E L ) SC , only a numerical solution is possible for the transverse elastic modulus (E T ) SC . To extract the values of the dimensionless parameter ζ SC , we equate Equations (A7) and (A2) and receive expression (13) in the main text. The longitudinal and transverse elastic moduli of MAEs with SCs in the absence of an external magnetic field as a function of φ p are shown in Figure A1A.…”

“…Magnetizable particles embedded in soft elastomer matrix form a smart rubber composite known as magnetoactive elastomers (MAEs), whose mechanical and rheological properties can be manipulated externally with the magnetic field [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The ability of controlling mechanical properties externally with an applied magnetic field provides a promising technology for soft robotics and biomedical devices [15,16].…”

Amphibious Transport of Fluids and Solids by Soft Magnetic Carpets

“…In contrast, systems driven by external fields generally perform better in terms of durable activity [ 8 , 16 ] and autonomy. [ 17 , 18 , 19 ] This has led to field‐driven soft actuators, especially ones driven by magnetic fields, receiving significant attention recently, [ 20 , 21 , 22 , 23 , 24 ] also in view of the range of forces that can be applied to transportable cargos using such systems. [ 25 ]…”