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Page 18 of 25 Lin et al. Soft Sci 2023;3:14 https://dx.doi.org/10.20517/ss.2023.05

Table 2. Advantages of magnetic nanomaterials in soft electronics and robotics
Advanced or unique Representative Functions Improved performances
properties examples
Magnetoresistance effect GMR Perceive the presence of static or dynamic Expanding the sensing capability of
magnetic field the human skins
AMR Distinguish the direction of magnetic field Providing a better navigation ability
TMR High MR ratios Enabling higher sensitivity
Size-dependent coercivity Nanomagnets Programmable shapes using different dimensions Offering means to achieve tunable
with various coercivity shapes and sensitivities
Iron nanowires Afford high remanence and coercivity to some soft
magnetic materials
Structure-dependent Porous matrix Provide giant magnetoelastic effect Enabling the devices to sense
magnetic field mechanical deformations
Cilia Measure a variety of mechanical stimuli Improving perception in different
directions
Pyramids Offer a magnetically permeable path to yield a Locally enhancing the
more concentrated magnetic flux at the tip magnetization
Programmable Template assisted Allow for sophisticated deformations and Enhancing capabilities in
magnetization1 magnetization locomotion manipulation and deformation
Thermally assisted
magnetization
3D printing assisted
magnetization

AMR: Anisotropic magnetoresistance; GMR: giant magnetoresistance; MR: magnetoresistance; TMR: tunneling magnetoresistance.

The examples shown in this section prove that soft robots based on magnetic composites can adopt a
diverse set of materials, including micro/nanoparticles in NdFeB, Fe, FePt, CrO and other magnetic
2
materials as the filler [172-175] , and silicone elastomers, hydrogels, and polymers as the matrix [167,176-179] , to
achieve programmable deformation and multifunctional integration. Other examples in this area include
programmable and reprocessable elastomer sheets for manufacturing multifunctional soft origami
robots , biotic-abiotic hybrid systems for in vivo targeted therapy , and facile fabrication methods to
[180]
[181]
create microrobots with functional heterogeneous materials, complex 3D geometries, as well as 3D
programmable magnetization profiles .
[182]
CONCLUSION AND PROSPECT
This review provides an overview of recent progress in soft electronics and robotics based on magnetic
nanomaterials by classifying the materials into magnetic nanomembranes/nanostructures and magnetic
composites. Table 2 summarizes the advantages of using magnetic nanomaterials in soft electronics and
robotics. Soft electronics based on these magnetic nanomaterials have shown significant potential in
applications of non-contact electronic skin, wearable compass, highly sensitive tactile or strain sensors, and
integrated medical tools with the capability of wireless in vivo navigation. Meanwhile, soft robots built with
magnetic nanomaterials provide vast application foreground for targeted drug delivery, precise cell
manipulation, and programmable, multimodal locomotion, due to the advantages of magnetic actuation
such as remote controllability, programmability, transparency to biological tissues, and compatibility with
many advanced manufacturing approaches.

One of the future opportunities in this area lies in the development of advanced materials. For soft
electronics, a promising yet challenging goal is to develop materials with properties (e.g., resistance) highly
sensitive to the intensity and/or direction of a magnetic field. The target is to achieve sensitivities beyond
existing TMR materials and replace SQUID and OPM techniques that are tethered to wires or optical fibers.
An envisioned application is the acquisition of magnetocardiography (MCG), magnetoencephalography