Liquid metals are of great importance in developing wearable devices and soft robotics owing to its high conductivity and flexibility. However, the high density of such metals turned out to be big concern for many practical situations. With generalized purpose, a new conceptual material as lightweight liquid metal entity, which can be as light as water, is proposed here.
For illustration, an unconventionally ultralight material composed of eutectic galliumindium alloys (eGaIn) and glass bubbles is demonstrated, whose density can be reduced below 2.010 even 0.448 g cm‐3 , even lighter than water, but still maintains excellent conformability, electric conductivity, and stiffness variety under temperature regulation. Such material is further adopted to build various complicated structures through origami or force regulation, representing various application scenarios and can be reused for eight times without evident loss in function. Based on these tests, buoyancy component for water‐r elated devices is designed, which offers the functions of a switch and loading element. The lightweight liquid metal entities are promising for making diverse advanced soft robotics and underwater devices in the near future.
Liquid metal at room temperature, like, Gallium-based alloy, has excellent fluidity, high thermal and electrical conductivity. There are various fields where they can be used such as soft robotics, exoskeleton systems, biomedical practices, wearable devices, and flexible electronics. But components made by liquid metal may be heavier than components made by non-metal. Than non-mental materials like wood, plastics, and polymer, the density of metal is larger.
A concept termed as “lightweight liquid metal entity” was proposed by a joint research team from Tsinghua University and the Chinese Academy of Sciences. From the Technical Institute of Physics and Chemistry (TIPC), Prof. LIU Jing led the research team. A group of lightweight liquid metal materials was invented by this research team. In the journal Advanced Functional Materials, their work was published.
A representative composite material GB-eGaIn was fabricated based on a hollow glass bubble and eGaIn, in their work. GB-eGaIn has stiffness variability, high ductility, and low density.
Due to its high adhesion, GB-eGaIn is able to be molded into thin sheets, according to their study. The sheet can be rolled or easily folded and transformed into the 3D structure through assembling processing, cutting or folding.
In a phase transition also, the GB-eGaIn sheet performs well. The sheet can easily shift between rigid metal objects and completely soft state objects by controlling the temperature regulation. For constructing temperature-tuned functional components, the capability of GB-eGaIn was shown in the results.
GB-eGaIn can realize floating and sinking behavior by adding water when combined with water-proof package materials. Researchers from Prof. LIU's team proved that GB-eGaIn has only slight change even after reuse for 8 times according to the recorded resistance variation of the same component both in water and after drying.
Lightweight Liquid Metal Materials
By combining GB-eGaIn with a magnet, they demonstrated that there can be controlled moving, suspending and sinking under the regulation of external magnetic field and package materials, in the study. In developing advanced smart underwater devices, it offered a potential application.