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Chen et al. Soft Sci. 2026, 6, 9 Page 29 of 36

Table 2. Summary of characteristics and applications of magnetically manipulated LM soft robots
Composition and
Type Key characteristics Typical applications
morphology
Composition: High fluidity Microfluidics
low magnetic particle content (< (surface tension, reversible splitting and merging, and (valves and pumps)
10 wt%) deformation) Reconfigurable electronics
Droplet
Morphology:
spherical droplets dominated by Excellent Biomedical engineering
surface tension electrical conductivity (injectable therapy, ECG electrodes)
Composition: Tunable stiffness Soft grippers
high magnetic particle content
(> 10 wt%) Plasticity Printable circuits
Slurry
Good printability Biomedical engineering
Morphology: (adaptive bioelectrodes, bone scaffolds,
viscoelastic paste or semi-solid Spike formation skin patches)
Environmental engineering
Composition: High chemical reactivity and functionalization (microplastic removal, pollutant
surface modification potential
decomposition)
Particle
Photothermal/magnetothermal conversion Biomedical engineering
Morphology: (chemoembolization, neuromodulation,
nano- or micro-scale particles Ability to cross biological barriers antibiosis)
Composition: encapsulated in Leakage-free and structurally stable Soft grippers
soft elastomers High operational dimensionality Mobile robots
Composite
Morphology: Biomedical engineering
solid-state soft structures Integration of sensing and actuation (surgical capsules, wearable sensors)
LM: Liquid metal; ECG: electrocardiogram.

matrix (or their metallic shells) may induce intermetallic diffusion and compound formation, degrading the
magnetic performance . Moreover, the aggregation and sedimentation of inner magnetic particles within
[74]
the LM matrix often happen due to the magnetic attraction and density difference between the magnetic
particles and the LM matrix. The introduction of shell structures (e.g., silica or polymer [132] ) is a promising
strategy that can improve suspension stability, prevent alloying between magnetic particles and LM matrix,
and also reduce magnetic agglomeration.

The most critical factor for using LM platforms in the body is their biocompatibility, which has been a
subject of extensive investigation . Gallium-based LMs, such as EGaIn and Galinstan alloys, are generally
[32]
considered to exhibit favorable biocompatibility profiles. Their low cytotoxicity has been demonstrated in
various in vitro studies, where cells remain viable and continue to proliferate upon exposure to bulk
LM [133,134] . However, extrapolating these findings to the complex physiological environment remains a
significant challenge that has not yet been adequately addressed. Biocompatibility is not absolute and is
highly contingent upon dosage, exposure time, and physical form. A critical unresolved issue is the dynamic
stability of the LM surface oxide layer in vivo [135,136] . Unlike in controlled laboratory settings, physiological
fluids contain high concentrations of electrolytes, proteins, and varying pH levels, which can induce the
dissolution, reconstruction, or passivation of the protective oxide skin.

This surface instability presents two critical risks. Firstly, compromising the oxide barrier accelerates metal
ion leaching. The chronic release of gallium and indium, alongside potentially more cytotoxic ions from the
corrosion of embedded magnetic particles (e.g., Fe, Ni, or Nd), warrants profound scrutiny concerning
long-term bioaccumulation and immune response [33,136] . Secondly, the corrosion of magnetic particles due to
oxide failure could lead to a progressive degradation of magnetic responsiveness over time, compromising
device functionality. Therefore, future research must move beyond acute in vitro cytotoxicity. Rigorous