Electrohydrodynamic direct-writing microfiber patterns under stretching

In this paper, the rheology and deposition behaviors of electrohydrodynamic direct-write (EDW) jet under stretching tension are studied. The EDW jet is stretched into tightened state by the drag force from moving collector, when moving speed of collector is higher than deposition velocity of jet. The drag force from the moving collector provides an extra force to stretch the charged jet, which promotes the stability and decreases the diameter of direct-written fiber. The whipping and bending motion of jet can be overcome by the drag force, and then, straight orderly fibers are direct-written along the trajectory of collector. The falling jet would be also deviated from the extension line of spinneret by the drag force. As the collector velocity increases from 10 to 1000 mm/s, the average line width of direct-written microfiber decreases from 18.89 to 0.89 µm. The thickness of microfiber ranges from 100 nm to 1.5 µm. The moving collector leads to large deviation of charged jet. The tightened charged jet has good resistance against the interference of charge repulsion force, which helps to direct-write orderly nanofiber. During the EDW process, the mechanical stretching force had provided an excellent function to control the morphology and deposition pattern of micro-/nanofiber.