Dynamic Temperature Control System for the Optimized Production of Liquid Metal Nanoparticles

Abstract

Nanoparticles (NPs) of gallium-based liquid metal (LM) alloys have potential applications in flexible electronics, drug delivery, and molecular imaging. They can be readily produced using top-down methods such as sonication. However, the sonication process generates heat that can cause dealloying of NPs through hydrolysis and oxidation of gallium. This limits the sonication power and period that can be applied for disrupting LM into smaller particles with high concentrations. Also, it remains challenging to achieve long-term colloidal stability of NPs in biological buffers. Here, we develop a dynamic temperature control system for improving the production performance of LM NPs. The enhanced performance is reflected by the significantly increased particle concentration, the decreased overall particle size, the prevention of the formation of oxide nanorods, and the versatility of producing NPs of different types of alloys. In addition, we design a brushed polyethylene glycol polymer with multiple phosphonic acid groups for effectively anchoring the NPs. More importantly, we discover that phosphate can effectively passivate the surface of NPs to further improve their stability. Using these strategies, the produced NPs remain stable in biological buffers for at least six months. Thus, the proposed methods can unleash the vast potential of LM NPs for biomedical applications.

Nano‐Biomedicine based on Liquid Metal Particles and Allied Materials

“…To realize the applications in flexible electronics and biomedicine, nanoparticles with improved performances in yields, stability, small sizes, uniform distribution, and high purity are favored. Many solutions are proposed, including development of dynamic temperature control system, [ 95 ] screening of novel macromolecules, or ligands, such as brushed polyethylene glycol (bPEG), [ 96 ] aliphatic carboxylates with different chain lengths, [ 97 ] phosphonic acids, [ 98 ] alkoxysilane ligands, [ 99 ] and comb‐like polymers. [ 100 ]…”

Biomedical Applications of Liquid Metal Nanoparticles: A Critical Review

“…Lowering the temperature of the suspension using an ice bath can prevent the formation of adverse side products. Alternatively, using a dynamic temperature control system incorporating Peltier cooler pads and a feedback control module can improve the production performance of LMNPs [29]. Maintaining a constant temperature results in a significant increase in particle concentration and a decrease in overall size.…”

“…The grafting process alters the surface properties of LMNPs to mediate aggregation, ligand exchange, release of Ga ions, and further oxidation of LMNPs in biological buffers, thereby increasing their colloidal stability. Previous efforts have attempted to use a range of macromolecules with different anchoring groups, such as thiol [24,27,35], catechol [36], phosphonic acid [29,37], trithiocarbonate [38], carboxylic acid [39,40], silane [41], and amine [7,28,42] to graft the NPs (Figure 3), but achieving long-term stability of LMNPs in biological buffers is an ongoing challenge.…”

“…Phosphonic acid, as an anchoring group, has been shown to facilitate the stability of EGaIn NPs colloids at room temperature [29,37]. In contrast to thiolation, where reversible physisorption is the dominant process, phosphonic acids undergo a series of condensation reactions to form covalent bonds.…”

A Simple and Cost-Effective Method for Producing Stable Surfactant-Coated EGaIn Liquid Metal Nanodroplets

“…However, the efficient and large-scale preparation of LM nanodroplets (NDs) remains a huge challenge [ 22 , 23 , 24 ]. Traditional methods for preparing LM NDs include sonication, high-speed shearing, microfluidic, and grinding [ 25 , 26 , 27 , 28 , 29 , 30 ].…”