Research On Silver Nanowire Alignment And Patterning Method Based On Direct Writing

As an important electrode component in flexible electronic devices,silver nanowire(Ag NW)transparent conductive films need to have excellent photoelectric properties and personalized circuit patterns.At present,the alignment of Ag NWs has been proved to be an effective means to improve the photoelectric properties of the films.However,the difficulty of combining Ag NW alignment technology with film patterning methods also limits the improvement of film manufacturing efficiency.In this paper,a method that can simultaneously realize Ag NW alignment and film patterning is proposed based on direct writing.The method utilizes the parabolic velocity profile of the Ag NW dispersion flowing in a fine needle to pre-align the Ag NWs in the needle under the action of shear force.Then,through the extrusion of the dispersion and the movement of the needle,the Ag NWs are twisted and aligned by the needle drag force,the substrate friction force,the solvent shear force and the hydrodynamic force during the deposition process,thereby achieving the preparation of aligned and patterned Ag NW films.The method can be used for the manufacture of transparent electrodes in electronic devices,and can also provide a certain reference for the alignment and film patterning of other high aspect ratio nanomaterials.The specific research content of this paper mainly includes the following parts:(1)Based on a self-assembled direct writing platform,a preparation method of patterned Ag NW films is proposed.This part introduces the working principle and process characteristics of the direct writing method,carries out the preparation experiment of patterned Ag NW films,shows the direct writing situation of the patterned films,analyzes the process conditions affecting the direct writing effect of films,and explores the manufacturability of three-dimensional curved films.The research results show that the linewidths of the films prepared by the direct writing method on paper,glass and inkjet water transfer film are 0.8 mm,1.8 mm and 2.0 mm,respectively.This method can also be used for the manufacture of three-dimensional curved films by utilizing the water separation characteristics of inkjet water transfer paper.(2)Based on the above patterning method,a one-step Ag NW alignment and film patterning method is proposed.This part expounds the working principle of Ag NW alignment,prepares patterned Ag NW films with unidirectional alignment and criss-cross alignment,explores several order analysis methods,analyzes the order of the aligned Ag NW films,studies the effects of process conditions such as needle-tip to substrate distance and direct writing speed on the ordering of Ag NWs in direct writing,and obtains the optimal experimental scheme.The research results show that the conditions such as the needle-tip to substrate distance of 20 μm,the direct writing speed of about 8mm/s,the flat needles with the long axis perpendicular to the direct writing direction,the repeated direct writing with low extrusion rate,and ethanol as the solvent of Ag NWs are most favorable for the alignment of Ag NWs.(3)The performance characterization of the aligned and patterned Ag NW films prepared by the optimized experimental scheme is introduced.The research results show that the full width at halfmaximum of the unidirectionally aligned Ag NW film is as low as 6.87°,and the number of Ag NWs deviating from the twice direct writing directions within ±30° accounted for 79.04% in the crossaligned Ag NW film.Using several flat needles with outer widths of 0.75 ～ 2.20 mm for direct writing,the film linewidths can be effectively controlled in the range of 1.5 ～ 3.0 mm.The unidirectionally aligned Ag NW films have anisotropic conductivity,polarization reflection characteristics,and improved photoelectric properties(sheet resistance of 22.5 Ω/□ at 87.6% of transmittance)compared with random Ag NW films.