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.

A facile synthetic method for magnetochromatic Fe3O4 nanoparticles (FNPs) with controllable size and optical properties has been fabricated by the combination of an improved solvothermal method and the usage of ultrasonic irradiation in the surface modification step. The improved solvothermal method enables the alteration of the size of nanoparticles (50nm to 180nm) in a competitively convenient way by adjusting the ratio of binary solvents, including diethylene glycol (DEG) and ethylene glycol (EG). In the surface modification step, the short-chain polyacrylic acid (PAA) is added as the surfactant with ultrasound-assisted method. In this research, due to magnetically-driven assembly FNPs forming photonic crystals, the reflection peaks show blue-shift as the magnetic field is increased from 181 to 2479G. In addition, on the basis of the calculation using Bragg’s Law, the thickness of the solvent layer is measured approximately 35nm, which accounts for the magnetochromatic properties as well as excellent dispersion.

Fe3O4@SiO2 particles were prepared on the gram-scale by selecting Na3Cit as the modifier with binary solvent and were assembled into colloidal amorphous arrays with unique and attractive optical properties for EPD.

In rechargeable batteries, overpotential problems may occur especially when the battery is aging. An alarm system to prevent overpotential may be useful. Colloidal nanoparticles of Fe3O4@SiO2 can self-assemble into amorphous photonic crystals (APCs) with tunable interparticle distances as a function of applied voltage. Here, we fabricated a colloidal APC that changes its color from mahogany to dark blue at applied voltages from 1.0 to 4.0 V, respectively. Citrate-modified Fe3O4 was solvothermally synthesized, followed by a SiO2 shell coating by the Stöber method to achieve a stable APC dispersed in polycarbonate solution. The APC is then connected alongside a zinc–air battery to indicate operational events including discharging, charging, and overcharging by color change of the APC. We anticipate that this simple idea provides an intuitive way to monitor the status of rechargeable batteries.

E-textiles, electronics-integrated textiles, require stretchable interconnects with mechanical and electrical reliability over repeated deformation cycles. Whereas elastomers filled with conductive metallic particles have shown promises for e-textiles, conductive inks printed at the top of the textile substrate are prone to suffer brittleness that leads to failure. Here, we report that controlled permeation of silver particle filled fluoroelastomer ink can indeed strengthen nanofibrous textile substrates in terms of ultimate strain and stress, resulting in a reliable electrical conduction over harsh deformation cycles. The permeated ink forms a cladded-layer on the surface of polyurethane nanofiber strands, where the cladded-layer is intrinsically stronger and tougher than the nanofiber substrate. Selecting a solvent that swells the nano-textile substrate can facilitate deep permeation. Pressing treatment changes the internal structure drastically, which results in a further improvement of mechanical properties of the printed nano-textile. As a result, the strain-to-failure of the e-textile increases ∼3 times and the initial conductivity is 3399 S cm −1 . The resistance increases less than the factor of 2.5 over 4000 cycles of 20% uniaxial strain. The high performance of the stretchable interconnects envisions wearable healthcare and internet-of-things applications.