At room temperature, eutectic gallium indium (EGaIn) is a liquid metal alloy. Because of its good thermal conductivity, high dielectric constant, infinite deformability, and metal conductivity, EGaIn is widely used in the research of flexible electronics and software robots, and is an important part of flexible composite materials. Mechanical mixing is usually used to introduce EGaIn droplets into polymer elastomers to produce stretchable and high-strength flexible multifunctional composite materials with high thermal stability and electrical conductivity. However, the current mechanical blending methods can cause anisotropic distribution of irregularly shaped micro-droplets and metal droplets, which greatly affects the performance of this type of composite material.
Therefore, how to obtain stable and uniform micron or smaller EGaIn droplets has drawn great attention from the material science community. Earlier reported methods include the use of surfactants and thiol coordination with metals to stabilize metal droplets. Recently, the research group of Professor Krzysztof Matyjaszewski of the Department of Chemistry of Carnegie Mellon University reported a droplet of EGaIn coated with a polymer coat. They used the surface-initiated ATRP method (SI-ATRP) and grafted poly (methyl methacrylate) (PMMA), poly (n-butyl acrylate) (PBMA), and poly ( 2-dimethylamino) ethyl methacrylate) (PDMAEMA) and poly (n-butyl acrylate-b-tert-butyl methacrylate) (PBA-b-PMMA) can be adjusted by adjusting the grafted polymer chain To adjust the morphology of the dispersed phase of the nanodroplets.
These nanodroplets can be stable in organic solvents and water at a concentration of 50% by weight. PMMA-grafted nanoparticles are stable for one week at a metal content of 1.5mM, while samples treated with a surfactant with a metal content of less than 0.17mM A precipitate appeared after 24 hours. In addition, due to the presence of the polymer, an organic-inorganic hybrid one-component flexible material having a clear microstructure can be formed by a direct solution drip coating method. The prepared hybrid material is almost transparent in the visible light range, and the mechanical properties of the material can be adjusted by selecting different polymers. At the same time, they also found that the surface grafting method significantly reduced the EGaIn crystallization and melting temperature (from 15 ° C to -80 ° C), which is beneficial to the preparation of composites with glass transition temperature lower or higher than room temperature.
Prof. Anna Carlmark from the Swedish RISE Institute commented: The research progress in stabilizing EGaIn droplets is highly recognized. In addition, she is more concerned about the electrical properties of such mixed single-component materials, and hopes to further determine their potential applications in software robots, stretchable sensors and biomedical devices.
(A) The molecular structure of BiBADA; (b) BiBADA modification and SI-ATRP polymerization on the surface of nanoparticles; (c) Stepwise or in-situ functionalization of EGaIn using the SI-ATRP method; (d) Photograph of EGaIn; (E) Photo of BiBADA-functionalized EGaIn droplets dispersed in tetrahydrofuran; (d) Settled EGaIn-PMMA polymer fibers; (f) EGaIn-PMMA uniformly dispersed phase redispersed in tetrahydrofuran; (h) in Separation of EGaIn droplets after adding three drops of 36% HCl solution; (i) TEM image of EGaIn-PMMA; (j) i. TEM of EGaIn-PMMA film; ii. Film containing 10wt% EGaIn-PMMA60mm; iii. 10wt % Content of mechanically mixed EGaIn / PDMS binary composite membrane.
(A) TEM image of the supernatant of EGaIn-PBMA dispersion in tetrahydrofuran; (b) Microscopic TEM image of EGaIn-PBMA spline; (c) Tensile experiment of EGaIn-PBMA spline; (d) EGaIn- PBMA splines; (e) EGaIn-PBMA-Sylgard splines; (f) stress-strain curves of EGaIn-PBMA splines; (g) stress-strain curves of EGaIn-PBMA-Sylgard splines.
(A) Diagram of PMMA-b-PBA grafted EGaIn; (b) Exclusion chromatography of isolated PMMA-bPBA; (c) 1HNMR of isolated PBA-b-PMMA, which can calculate the repeating unit ratio; (d ) Tensile experiment of EGaIn-PBA-b-PMMA spline; (e) Stress-strain curve of EGaIn-PBA-b-PMMA spline; (f) DSC curve of EGaIn-PBA-b-PMMA.
(A) Synthesis method; (b) EGaIn-PDMAEMA vacuum dried sample photo; (c) cationic gel-encapsulated EGaIn photo; (d) EG image of EGaIn-PDMAEMA; (e) TEM image of cationic gel-encapsulated EGaIn; (F) Shear force and viscosity curve of 2.0% by weight cationic gel-dispersed EGaIn in water; (e) DSC curve of cationic gel-encapsulated EGaIn; (h) cationic gel-encapsulated EGaIn dispersed in 1mgml-1 water Intensity-weighted hydrodynamic size distribution in the volume; (i) Zeta potential of EGaIn, EGaIn-PDMAEMA and cationic gel-coated EGaIn in a 1 mgml-1 aqueous dispersion.