Ultrafast electrohydrodynamic 3D printing with in situ jet speed monitoring

Highlights: • We demonstrate a new way to determine speed of electrohydrodynamic jets in situ during printing. • Our strategy is based on electrostatic jet deflection. • Our method enables combining submicrometer resolution with high printing speed. Additive manufacturing by near-field electrospinning is based on the continuous deposition of a nanofiber on a substrate. Owing to the small fiber size and the high jet speeds that can be achieved, this method potentially combines submicrometer resolution with high printing speed. Printing with high fidelity depends critically on controlling the jet arrival speed, which must be matched to the printing speed. Unfortunately, current methods to determine the jet speed are cumbersome and cannot be performed in situ as they are based on laborious high-resolution imaging of individual nanofibers. Using inexpensive optical equipment, here we demonstrate a new way to determine the jet speed in situ during printing. Our strategy is based on electrostatic jet deflection, in which the speed is readily computed from the width of a printed object made from a periodically printed motif. Such width can be easily obtained inline by optical inspection, overcoming the need to resolve individual nanofibers. This information can be used to feedback control the printing process. The proposed approach will not only assist in studying the fundamental relation between the jet speed and other printing parameters, but also enable reproducible printing of fibers in a rapidly expanding area of applications.