Abstract
Liquid metal (LM) droplets show the superiority in coalescing into integral liquid conductors applicable in flexible and deformable electronics. However, the large surface tension, oxide shells and poor compatibility with most other materials may prevent spontaneous coalescence of LM droplets and/or hybridisation into composites, unless external interventions (e.g., shear and laser) are applied. Here, we show that biological nanofibrils (NFs; including cellulose, silk fibroin and amyloid) enable evaporation-induced sintering of LM droplets under ambient conditions into conductive coating on diverse substrates and free-standing films. The resultants possess an insulating NFs-rich layer and a conductive LM-rich layer, offering flexibility, high reflectivity, stretchable conductivity, electromagnetic shielding, degradability and rapid actuating behaviours. Thus this sintering approach not only extends fundamental knowledge about sintering LM droplets, but also starts a new scenario of producing flexible coating and free-standing composites with flexibility, conductivity, sustainability and degradability, and applicable in microcircuits, wearable electronics and soft robotics.
Highlights
Liquid metal (LM) droplets show the superiority in coalescing into integral liquid conductors applicable in flexible and deformable electronics
Biological NFs with the diameter of
With the advantages of low cost and sustainability, these NFs have seen promising applications in biomedicine, catalysis, reinforcing fillers, optoelectronics and energy-harvest[25]. Among these NFs, the synthesised Cellulose NFs (CNFs) typically had plentiful carboxyl groups and hereby negatively charged surfaces (e.g., ζ-potential ~−50 mV at pH 7 shown in Supplementary Fig. 2, 3), being capable of forming a stable aqueous suspension at the nematic liquid-crystalline state
Summary
Liquid metal (LM) droplets show the superiority in coalescing into integral liquid conductors applicable in flexible and deformable electronics. ~20 °C, ordinary pressure of ~0.1 MPa and relative humidity (RH) of ~40%) can sinter colloidal suspensions of EGaIn droplets in the presence of biological nanofibrils (NFs, with the diameter of ~5–10 nm) as low as 0.05 wt% of cellulose, silk fibroin and amyloid, and hereafter produce conductive layers on diverse substrates and free-stranding composites with multiple functionalities, such as optical reflectivity, flexible conductivity (up to 8.9 × 105 S m−1) and rapid responsive actuation.
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