Rugged conductive and transparent silver fibre mesh for flexible substrates

February 12, 2018 // By Julien Happich
Researchers from Tsinghua University, Beijing, have devised a novel process to create large and highly flexible 90% transparent submicron silver fibre meshes at room temperature. The highly conductive film (sheet resistance of 9 Ω sq−1) is obtained by draw-spinning ultra-fine silver precursor fibres in a criss-cross pattern, then curing the precursor material by UV irradiation.

In a paper titled "Room-temperature processing of silver submicron fiber mesh for flexible electronics" published in npj Flexible Electronics, the researchers note that silver precursor AgNO3 in solution in Polyvinylpyrrolidone (PVP) can be used as a carrier for continuous draw spinning of ultrathin fibres with a diameter of about 200nm and several kilometres long (at a speed of up to 8m/s). Instead of relying on a heat-curing process like they did in previous research, the authors irradiated the interwoven precursor fibres with a strong UV light which leads to the formation and integration of silver nanoparticles. With irradiation times up to 5 hours, they found that more silver particles were reduced and gradually bonded together while the PVP carrier gradually decomposed. The result was a network of silver particles compactly packed together within each fibre, yielding a fully connected mesh, while a residual carbon-based polymer material filled the gaps within the fibres, enhancing their flexibility and toughness.

SEM image of the curved fiber mesh (scale bar is 100μm).

This UV-curing approach is interesting as it allows the silver fibres to be directly intertwined on most flexible substrates such as polyethylene terephthalate (PET) and polyimide (PI), which are generally thermosensitive materials and can't be submitted to typical heat-sintering processes.

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