Study by the Institute of Bioenergy and Bioprocess Technology of the Chinese Academy of Sciences discover new method in stabilising liquid metal nano-capsules for future applications.
Potential of liquid metals are promising and ranges from electronics to biomimetic functional composites. Metals in this state usually undergo nano-meterization and surface modification to improve substrate affinity and processing properties. Nano-droplets of liquid metals are created in capsules in ultra-thin and fragile shells made of oxides or amphiphile monolayers.
The outer layer of the capsule may be disrupted when incorporated homogeneously into various composites through traditional processing methods. Producing stable and processable liquid metal nano-droplets still remain a challenge.
Based on a previous study by Professor Li Chaoxu and his team, they demonstrated that liquid metal is able to initiate free-radical polymerization of vinyl monomer under ultrasonication.
Further to this study, the same team then discovered that the ring-opening polymerization was initiated by sonicating liquid metal in fluidic lactones and proposed multifunctional liquid metal nano-capsules. "By this in-situ polymerization, LM nanodroplets were encapsulated into polylactone shells with tunable thickness, which could further be dried into solid powder," said Professor Li.
On top of achieving high chemical stability and dispersibility in organic solvents, the liquid metal powder capsules had a combination of exceptional properties from the nano-droplets and polylactone shells. These properties allowed them to be introduced into thermoplastic composites through liquid casting and thermal- or photo-moulding for notch-insensitive tearing, sintering-induced electric conductivity and photo-thermal effect.
This demonstrated that the liquid metal initiator of ring-opening polymerization may trigger a pathway able to produce stable and thermal- or photo-mouldable powder of liquid metal capsules. These have the potential for future applications as multi-functional composites in biomedicines, soft electronics, and smart robots.
The study was published in Advanced Materials in September 2020 and was supported by the National Natural Science Foundation of China, QIBEBT & Dalian National Laboratory for Clean Energy (DNL), CAS and Shandong Collaborative Innovation Center.