The Principle And Application Of Electrohydrodynamic Printing Of Fabric Surface Circuit

The electrohydrodynamic(EHD)printing has shown broad application prospects in the field of high-performance flexible electronics,such as smart packaging,medical care,fire protection,military,etc.Compared with inkjet printing and screen printing,the EHD printing is a printing reproduction technology without contact,pressure and plate and can realize the direct digital-writing pattern on the flexible substrate.Among various flexible substrates,textiles are perfectly suitable to the development needs of wearable flexible electronic devices due to their excellent flexibility,breathability and durability.At present,the development of fabric-based the EHD printing flexible circuits is rising rapidly.When the fabric is used as aflexible substrate material,its inherent porous structure and texture characteristics will greatly affect the forming quality of EHD printing circuits.However,the current studies mostly focus on the influence of conductive ink and process parameters,and less attention has been paid to the influence of fabric substrates.Therefore,there is a lack of relevant research on the mechanism of the influence of fabric substrates on the formation and performance of the EHD printing circuits.Based on this,this work prints flexible circuits on the surface of fabrics with different densities by the EHD printing technology.To explore the influence mechanism of the formation and performance of the conductive circuits,this work analyzes the differences in wire morphology and performance,discusses their relationship with fabric characteristics,and investigates the mechanisms affecting the formability and performance of circuits on fabric surfaces.The specific research content and conclusions are as follows:(1)Forming feasibility evaluation of the EHD printing circuits on structurally differentiated fabric surfaceFirstly,the spreading behavior of conductive inks on the surface of three densities of fabrics was explored,and then the circuits were printed on the substrates of three densities under the same process conditions by the EHD printing technology.The morphology and width of the circuits was observed and measured by an optical microscope.The spreading of ink on the surface of fabrics with different structures and its effect on the circuits morphology.The results show that with the decrease of the fabric density and the increase of the roughness,the wettability of the ink on the surface of the fabric substrate increases,causing the spreading of ink faster and broader.This spreading behavior of the ink makes the line width of the EHD printed circuits on the fabric surface increase as the density of the fabric substrate decreases.Secondly,the morphologies of the single printed circuits are affected by the initial position of ink on the surface of fabric.The shape of circuits where the initial position of ink drop is located on a single yarn is better than the shape where the position is located between the gap of two yarns.In addition,compared with inkjet printing and screen printing,the accuracy of the circuit printed by EHD printing is higher.To further explore the effect of fabric substrate on printing accuracy and to meet the demand of flexible circuits for a certain width of conductive wires,further implementation of a certain width of wire printing is required.(2)Width regulation and forming evaluation of the EHD printing circuits on structurally differentiated fabric surfaceAccording to the above-mentioned rules of the spreading of ink on the fabric surface and the diffusion of ink lines,the EHD printing circuits with a certain width are realized on three kinds of commonly used cloth printing substrates with different densities by splicing multiple single lines and regulating single line spacing.Optical microscope and scanning electron microscope were used to observe the circuit morphology,including circuit width,edge uniformity and circuit thickness.The influence of fabric structure differences on its formability have been discussed.The results show that in order to obtain a circuit with a flat and uniform surface morphology,the line spacing of the fixed circuit width needs to meet the two conditions.One is without change of the width of a single line during splicing,and the other is not generating cracks.,There are two boundary value,the maximum and the minimum line spacing.As the contact angle of the fabric surface is larger and the roughness is smaller,the range of the boundary value is smaller.Besides,the printing accuracy of the obtained fixed line width circuit can be controlled by the contact angle of the ink on the fabric surface.Specifically,when the contact angle ? of the ink is in the range of 0