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Chen et al. Soft Sci. 2026, 6, 3 Page 3 of 26

contractions, variable biochemical milieus, and highly heterogeneous tissue-robot interface, this review
discusses organ-specific materials and structural designs of magnetic soft robots [Figure 1]. We
systematically discuss the development and biosafety of magnetic soft materials, focusing on four categories:
magnetic hydrogels, silicone-based magnetic elastomers, ferrofluids, and magnetically responsive active
composites. We analyze the chemical composition, mechanical properties, degradation behavior, and
biocompatibility for in vivo implementations (Section MATERIAL DESIGN AND SAFETY ANALYSIS OF
MAGNETIC SOFT ROBOTS). We also present a detailed assessment of organ-specific applications of
small-scale magnetic soft robots in GI, urogenital, and vascular systems (Section ORGAN-SPECIFIC
MATERIALS AND STRUCTURAL DESIGNS). We conclude the review by discussing the key challenges of
the next-generation magnetic soft materials and robots for clinical translation, including the biofunctional
material design, intelligent closed-loop control strategies, and multifunctional platform integration.

MATERIAL DESIGN AND SAFETY ANALYSIS OF MAGNETIC SOFT ROBOTS
Magnetic soft materials govern the actuation efficiency, biocompatibility, durability, and clinical safety of soft
robots [12,83] . A systematic understanding of material composition and biological responses is essential for safe
and effective interactions in physiological environments. This section reviews four major categories of
magnetic soft materials [Table 1] and discusses material-tissue interactions.

Magnetic soft materials
Magnetic hydrogel
Magnetic hydrogels are composed of cross-linked hydrophilic polymer networks incorporated with
superparamagnetic nanoparticles [84-88] (typically iron oxide). They exhibit high water content and a low
mechanical modulus, which is important for minimizing mechanical irritation at the material–tissue
interface in biomedical applications [89-99] . Owing to these favorable characteristics, robots fabricated from
magnetic hydrogels have been widely employed in biomedical applications, particularly in targeted
delivery [100-103] . For instance, an iron gel composed of Fe O nanoparticles, alginate, and adipic acid
3
4
dihydrazide has been developed as a magnetically active scaffold capable of carrying therapeutic cargo or
cells . Similarly, a magnetic hydrogel composed of neodymium-iron-boron (NdFeB), Fe O nanoparticles,
[84]
4
3
and alginate has been developed as a soft capsule microrobot capable of carrying therapeutic cargos .
[97]
Poly(N-isopropylacrylamide) has also been used to develop thermoresponsive magnetic soft robots with dual
actuation strategies, i.e., photothermally induced deformation for biopsy tissue and magnetically guided
navigation for targeted delivery . However, their inherently low mechanical strength, primarily due to high
[104]
water content, limits their suitability for dynamic and high-strain environments, such as the GI or
cardiovascular systems.

Silicone-based magnetic elastomer
Silicone-based magnetic elastomers, consisting of hard magnetic particles such as NdFeB and soft
elastomeric materials such as polydimethylsiloxane (PDMS) [75,76,105-107] and Ecoflex [106,108-112] , represent a class of
durable, high-performance magnetic soft materials. These elastomers exhibit tunable elastic moduli in the
MPa range, excellent fatigue resistance, and long-term mechanical stability. Moreover, they can be encoded
with predefined permanent magnetization patterns, enabling diverse motion modes such as rolling, jumping,
and walking under low-frequency magnetic fields, as well as carrying and releasing cargo through shape
morphing . These multimodal motions are particularly advantageous for navigating the robots in complex
[57]
geometries of the GI tract, blood vessels, or respiratory pathways.

However, their non-biodegradable nature necessitates post-operative retrieval methods, often via surgical or
endoscopic means, which may limit clinical practicality. The potential cytotoxicity of ferromagnetic particles,
especially under corrosive physiological conditions, further underscores the need for robust encapsulation