Dispensing highly viscous zeptoliter droplets by nanotip infiltration focused electrohydrodynamic jet printing

Manipulation and dispensing of droplets with a wide range of viscosities on the micro/nano scale is a key issue in many fields of technology. However, the simple and high-efficiency dispensing of highly viscous droplets down to the zeptoliter scale is still a major challenge. Herein, we propose a nanotip infiltration focused electrohydrodynamic jet (NIFEJ) printing method. This technique uses a solid nanotip rather than a hollow nozzle, so it can dispense a wide range of high viscosity inks without nozzle clogging problems. The ink viscosity range spans six orders of magnitude, from 6.3 × 10^-4 Pa s to 292.8 Pa s. The NIFEJ printing technique improves the dispensing resolution through geometric focusing and electric field focusing. Nanodroplets with an average diameter of 49.6 nm were obtained. Moreover, the ink volume for dispensing a single nanodot is about 44.6 zL. To the best of our knowledge, this is the smallest droplet volume dispensed by electrohydrodynamic jet printing to date using an ink with a high viscosity of 0.3 Pa s. The results show that NIFEJ printing can dispense high-viscosity droplets at the micro/nano scale and expand printing applications.