Microfluidic Mass Production of Stabilized and Stealthy Liquid Metal Nanoparticles

Abstract

Functional nanoparticles comprised of liquid metals, such as eutectic gallium indium (EGaIn) and Galinstan, present exciting opportunities in the fields of flexible electronics, sensors, catalysts, and drug delivery systems. Methods used currently for producing liquid metal nanoparticles have significant disadvantages as they rely on both bulky and expensive high-power sonication probe systems, and also generally require the use of small molecules bearing thiol groups to stabilize the nanoparticles. Herein, an innovative microfluidics-enabled platform is described as an inexpensive, easily accessible method for the on-chip mass production of EGaIn nanoparticles with tunable size distributions in an aqueous medium. A novel nanoparticle-stabilization approach is reported using brushed polyethylene glycol chains with trithiocarbonate end-groups negating the requirements for thiol additives while imparting a "stealth" surface layer. Furthermore, a surface modification of the nanoparticles is demonstrated using galvanic replacement and conjugation with antibodies. It is envisioned that the demonstrated microfluidic technique can be used as an economic and versatile platform for the rapid production of liquid metal-based nanoparticles for a range of biomedical applications.

Light‐Induced Shape Morphing of Liquid Metal Nanodroplets Enabled by Polydopamine Coating

“…Stable aqueous suspensions of LM nanodroplets are not only for electronic applications, but also exhibit great potential in medicine and therapy, such as drug delivery, photothermal therapy, and bioimaging . Water‐soluble surfactants, including cetrimonium bromide, poly(4‐vinyl‐1‐methyl‐pyridinium bromide), lysozyme, and trithiocarbonate‐functionalized brushed polyethylene glycol have been used to stabilize LM nanodroplets during and after sonication of bulk LMs in water . In addition, when LM nanodroplets in aqueous solution are placed at room temperature for 16 h or heated up to about 70 °C for 30 min, the spherical nanodroplets will be oxidized and dealloyed, resulting in the formation of rods of gallium oxide monohydroxide (GaOOH) and spherical indium nanoparticles .…”

Sonication-enabled rapid production of stable liquid metal nanoparticles grafted with poly(1-octadecene-alt-maleic anhydride) in aqueous solutions

“…2e) and 300 s (Fig. 2f) sonication time, as well as bPEG (Mn~20 kDa, see details in previous work 17 and Fig. S4 in ESI) grafted EGaIn NPs (Fig.…”

“…While most conventional metallic nanoparticles (NPs) are synthesized through a tedious bottomup approach (i.e., reducing precursor metal salts), the fluidic nature of liquid metals (LMs) enables facile methods to produce LM NPs. Disruptive forces induced by acoustic stimulation [10][11][12][13][14][15] , microfluidic devices 16,17 or shearing 18 have been utilized to break the LMs into nanosized particles.…”

“…Therefore, it is desirable to have a coating that can both stabilizes the LM NPs and prevents the oxidation reaction on the LM NPs surface. With the presence of a hydrophilic polymer coating, such as polymeric grafts made of brushed polyethylene glycol (bPEG) 17 , the LM NPs could remain stable in aqueous environments up to a few days.…”

Microfluidic Generation of Nanomaterials for Biomedical Applications

“…As analyzed by X‐ray diffraction, UV–vis spectroscopy, and transmission electron microscope (TEM), the resultant AgNPs were produced with high‐quality and monodispersity, owing to the rapid and efficient mixing in individual droplets. In another study, Tang et al also reported a droplet‐based microfluidic chip for efficiently producing eutectic gallium indium (EGaIn) NPs . The EGaIn precursor and suspension medium was respectively pumped into the T‐shaped microchannel which was widely used for generating microdroplets.…”