Analysis and modeling non-Newtonian fluid transferring process and dot formation in contact dispensing

Non-Newtonian fluid transferring-which denotes non-Newtonian fluid transfers from needle tip to the substrate-in contact fluid dispensing dot is very complicated and has important influences on dots qualities including dot shape and size, and dots consistency. But there have been no models and little research on non-Newtonian fluid transferring process and dot formation, although there are a few studies focusing on fluid flow in feed channel between syringe and needle exit and control models that slide over influence of fluid transferring. From the view of fluid dynamics, this paper puts forward an idea of phasing study fluid transferring mechanism and dividing the fluid transferring process into four different phases in contact dispensing dot. Also it establishes fluid dynamics models of non-Newtonian fluid transferring process from non-Newtonian fluid extrusion out of needle exit to dot formation such as model for evolvement of fluid drop at needle tip, fluid contact and spread on substrate, fluid separation into two independent part both at the needle tip and on the substrate, and dot formation. These models can study the important influences of some parameters such as dispensing height, surface tension and contact angle of the dispensing fluid material, needle tip configuration and sizes, and needle movement characteristics on dispensing dots qualities. They can also study the dispensing process parameters matching between some parameters such as dispensing height and parameters influencing fluid extrusion