No abstract

Patterning and alignment of conductive nanowires are essential for good electrical isolation and high conductivity in various applications. Herein a facile bottom-up, additive technique is developed to pattern and align silver nanowires (AgNWs) by manipulating wetting of dispersions in microchannels. By forming hydrophobic/hydrophilic micropatterns down to 8 μm with fluoropolymer (Cytop) and SiO2, the aqueous AgNW dispersions with the optimized surface tension and viscosity self-assemble into microdroplets and then dry to form anisotropic AgNW networks. The alignment degree characterized by the full width at half-maximum (FWHM) can be well-controlled from 39.8° to 84.1° by changing the width of microchannels. A mechanism is proposed and validated by statistical analysis on AgNW alignment, and a static model is proposed to guide the patterning of general NWs. The alignment reduced well the electrical resistivity of AgNW networks by a factor of 5 because of the formation of efficient percolation path for carrier conduction.

We demonstrate herein a facile approach for constructing -C[double bond, length as m-dash]N- linked COFs from acetals. Three new COFs (imine-linked LZU-20, hydrazone-linked LZU-21, and azine-linked LZU-22) were synthesized by the direct condensation of dimethyl acetals and amines. All the synthesized COFs are highly crystalline and exhibit good thermal stability.

We report a facile technique for patterning and transferring silver nanowires (AgNWs) onto various substrates. By employing only UV/O3 and vapor treatment of hexamethyldisilazane (HMDS), we are able to accurately manipulate the surface energy via alternating the terminal groups of a polydimethylsiloxane (PDMS) substrate, so as to assist selective formation and exfoliation of AgNW films. A simple UV/O3 treatment on PDMS enables uniform, well-defined, and highly conductive patterns of AgNWs after spin-coating. A vapor treatment of HMDS lowers the surface energy of the oxidized PDMS so that the patterned AgNWs embedded in an epoxy resin (EPR) are cleanly transferred from the PDMS to the target substrate. It is found that the AgNW-EPR composite on polyethylene glycol terephthalate (PET) exhibits remarkable durability under the bending test, tape test, ultrasonic treatment in water, and immersion of chemical solvents. In addition, we demonstrate that the AgNW-EPR composite work well as conductive patterns on the oxidized PDMS, polyvinyl alcohol (PVA), paper, and curved glass. The facile technique extends the applicability of AgNWs in the field of electronics, and it is potentially applicable to other nanomaterials.