With the rapid development of electronic technologies and increasing of people's living standard, soft electronic devices with properties of flexibility, stretchability and biocompatibility are in urgent demand. Liquid metals (LMs) have shown great potential in soft electronics due to their fluidity, metallic conductivity, chemical stability and superior biocompatibility.
However, the surface tension has to be increased to stabilize the interfaces of liquid metal with other materials. The spontaneous coalescence of LM droplets may be prevented by the oxide shells or chemical stabilizers, unless external interventions are applied, such as mechanical sintering and laser sintering. These methods not only require external energy, but also have limitations in applications.
A research team led by Prof. LI Chaoxu from the Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT) of the Chinese Academy of Sciences (CAS) developed a novel solvent evaporation-induced sintering method with the presence of biological nanofibrils (Figure 1).
The contributions of biological nanofibrils (NFs) are: attaching on the surfaces of EGaIn droplets for lower droplet size and higher colloidal stability; rupturing the encapsulating shells of EGaIn droplets through higher capillary forces and NF contraction among the droplets during evaporation; promoting the adhesion of EGaIn layers on diverse substrates.
These resultant composites exhibit flexibility, high reflectivity, stretchable conductivity, electromagnetic shielding, degradability and rapid actuating behaviors response to voltage and light.
This evaporation-induced approach starts a new scenario of producing flexible coating and free-standing composites applicable in wearable electronics, soft robotics and implantable biomedicine devices.
The study, published in Nature Communications, was supported by the National Natural Science Foundation of China, Shandong Provincial Natural Science Foundation, and "135" Projects Fund of CAS QIBEBT Director Innovation Foundation.
Figure 1: Electronic ink of liquid metals prepared with assistant of biological nanofibrils (A), evaporation-induced sintering mechanism (B) and the corresponding optical images of liquid metals sintered on different substrates (C). (Image by LI Xiankai)
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