Page 68 - Read Online

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

In short, the mechanical method offers a chemical-free and scalable strategy to fabricate MLMs by leveraging
the dynamic oxide chemistry and interfacial mechanics of LMs. However, it is noteworthy that the
mechanical preparation process can induce oxidation of LMs, significantly degrading their key properties
such as fluidity and thermal/electrical conductivity [61,74] .

Chemical method
Compared to mechanical methods, chemical methods for preparing MLMs offer distinct advantages in
precision, tunability, and stability. For example, acid/base treatments can effectively remove surface oxides
for the combination of magnetic particles without hindering the fluidity of LM . In addition, electrochemical
[51]
methods enable real-time tuning of the MLM composition and properties through redox reactions,
offering dynamic tunability . Reactive wetting enhances interfacial adhesion and enables stronger bonds
[75]
between LMs and magnetic particles, improving the stability of the MLMs . Electroplating allows for the
[76]
uniform deposition of magnetic layers with controlled thickness and composition .
[72]
When Galinstan was treated with the HCl solution to remove the oxide skin, Fe powders were automatically
coated on the LM droplet without mechanical intervention [Figure 3A] . Similarly, it is also observed that
[51]
when Fe particles were mixed with EGaIn and flux HCl solution at room temperature, they were rapidly
absorbed and suspended within the LM bulk within seconds of contact . This can be attributed to the HCl
[77]
flux removing the less-conductive oxide layer and enhancing the polarizability of the Fe particles, thereby
promoting wetting through stronger liquid-solid van der Waals interactions compared to liquid-liquid
attraction . In addition, the base solution, such as NaOH, can also remove the oxide skin to facilitate the
[77]
integration of the LM and magnetic particles .
[60]

Moreover, Tang et al. found the phagocytosis phenomenon of EGaIn in aqueous solutions covering a full pH
range [Figure 3B] . In the acidic (HCl) solution, spontaneous phagocytosis occurs as the acid dissolves both
[75]
the oxide layers on the EGaIn and copper particles, enabling direct intermetallic wetting. In a neutral (NaCl)
solution, phagocytosis requires electrical polarization (≥ 2 V), where cathodic reduction removes oxides and
activates reactive wetting. In the alkaline (NaOH) solution, a sacrificial metal of aluminum is needed to
generate a localized electrochemical potential, dissolving only the amphoteric oxides while leaving the copper
oxides intact until reduction occurs. Each method achieves particle internalization but differs in
oxide-removal mechanisms, timescales (fastest with polarization), and byproducts.

Reactive wetting involves chemically driven interfacial interactions that enhance spreading and adhesion by
forming new compounds at the contact interface. Ga-based LMs readily undergo reactive wetting with
metals such as Cu and Ag by forming intermetallic compounds such as CuGa and Ag In at the
y
2
x
interface [54,78] . Coating magnetic particles with appropriate metals to form transition layers facilitates their
easy integration and stabilization in LMs. For instance, the NdFeB microparticles were coated with an Ag
shell (NdFeB@Ag) and were directly mixed with LM in HCl solution by stirring , or the Fe O nanoparticles
[76]
3
4
were coated with an Ag shell to prepare the MLM [Figure 3C] .
[54]
In addition, the magnetic agents can also be electroplated onto the surface of LM droplets . Specifically, two
[72]
parallel NdFeB magnets positioned outside the electroplating bath generated a constant magnetic field
during the process. A cobalt foil served as the anode, while the LM droplet, connected to the cathode via a
stainless-steel needle, was supported on a fluorocarbon-coated polydimethylsiloxane (PDMS) pillar.
Electroplating was conducted under a fixed current density for a set duration, producing a magnetic
CoNiMnP coating on the droplet surface.

In summary, chemical methods for preparing MLMs involve diverse mechanisms, showing a high degree of
diversity and flexibility. The fabricated MLMs typically exhibit better stability than those produced by