Droplet-patterning of viscous adhesive assisted with microfluidic technique

Abstract In transfer process of viscous adhesive, the initial geometrical shape of droplet has crucial influence on the filling completeness. Herein a droplet-patterning method assisted with microfluidic technique was presented to control the shape of viscous adhesive, in which three kinds of adhesives were selected as samples, spanning two orders of viscosity magnitude from 83 mPa s to 7792 mPa s. Microfluidic technique was developed to obtain the anti-adhesive boundaries of original polygon patterns. Considering viscous dissipation, a criterion was established to confirm the droplet-volume limitation of overflowing across anti-adhesive boundary. Moreover, the capability of droplet-patterning was evaluated with the ratio of droplet-pattern to original polygon and the dynamics of patterning was analyzed. Under the conditions of low Reynolds and Weber numbers, the smaller area and more edges of polygon, lower viscosity and more non-polar groups of adhesive are helpful to improve the patterning capability.