Transparent and flexible electrodes on cost effective plastic substrates for wearable electronics have attract great attention recently. Due to the conductivity and flexibility in network form, metal nanowire is regarded as one of the most promising candidates for flexible electrode fabrication. Prior to application, low temperature joining of nanowire processes are required to reduce the resistance of electrodes and simultaneously maintain the dimensionality and uniformity of those nanowires. In the present work, we presented an innovative, robust and cost effective method to minimize the heat effect to plastic substrate and silver nanowires which allows silver nanowire electrodes been directly written on polycarbonate substrate and sintered by different electrolyte solutions at room temperature or near. It has been rigorously demonstrated that the resistance of silver nanowire electrodes has been reduced by 90% after chemical sintering at room temperature due to the joining of silver nanowires at junction areas. After ∼1000 bending cycles, the measured resistance of silver nanowire electrode was stable during both up-bending and down-bending states. The changes of silver nanowires after sintering were characterized using x-ray photoelectron spectroscopy and transmission electron microscopy and a sintering mechanism was proposed and validated. This direct-written silver nanowire electrode with good performance has broad applications in flexible electronics fabrication and packaging.

Flexible electrodes have broad applications in microelectronics. In this work, flexible electrodes were fabricated through chemically induced joining of silver nanoparticles at room temperature. After the joining process, the resistance of the silver track decreased by 8 orders of magnitude. The joining parameters were systematically investigated including the concentration of the chemical solution, sintering time, and drying temperature. This chemical method achieved the same effect at room temperature as compared to the methods using thermal sintering. The changes of the microstructure and the surface composition of silver nanoparticles were characterized to better understand the nanojoining process at room temperature.

Flexible electrodes have attracted much attention in consumer electronic applications. In this work, laser direct writing is used to fabricate copper/graphene composite electrodes on a flexible substrate in one step. This direct writing process with a low power laser can reduce copper ions in thin films to form copper nanomaterials and spontaneously interconnect them to gain good conductivity, while the laser also induces the growth of multi-layer graphene that coats on copper to improve the oxidation resistance of electrodes. The electrical performance and chemical composition of flexible electrodes can be tuned by laser power, scanning speed, and defocus distance. A mechanism of in situ reduction and interconnection of copper nanomaterials during laser direct writing has been proposed. This method could largely reduce the oxidation issue by avoiding synthesis and sintering processes of copper nanomaterials. These as-written copper electrodes have good stability and have potential applications in flexible electronics, such as flexible heaters or antennas as demonstrated.

By using the return flux enhancement factor due to repumping, the spin-damping time of mesospheric sodium can be estimated. Because the absolute return photon number does not need to be measured, this method is independent of sodium abundance. An example of how to find the spin-damping time using this method is given. As a result, it is shown that this method is sensitive and has the potential to improve the precision of the spin-damping time estimations of mesospheric sodium. Finally, the impact of the geomagnetic field on this method is analyzed.

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