Exploration of electrohydrodynamic printing potentially for in-space fabrication of microscale functional structures: A preliminary study by an anti-gravity configuration

Additive manufacturing (AM) is considered the most promising technique to realize the in-situ fabrication of complex functional structures in space environments owing to its unique capability of full automation and digitalization. However, unlike printing on the earth, the zero/micro-gravity environment in space makes it extremely challenging to achieve precise deposition and stacking of the printed materials for microscale structures. Here, we proposed to use high-voltage electrostatic force in the electrohydrodynamic printing (EHDP) process as the guiding force for the upward or anti-gravity (AG) printing of microscale functional structures, which can be potentially used for in-space environments. The average electrical field strength for stable AG-EHDP is found in the range of 1.70 × 107 V m−1 to 2.45 × 107 V m−1. In comparison with conventional EHDP, AG-EHDP can fabricate microscale 3D lattice structures with a smaller feature size of 3.65 ± 1.31 µm. A finite element analysis approach is established to simulate the AG-EHDP process at different parameters for the prediction of fiber width, which shows great consistency to the experimental results and applies to zero/micro-gravity printing environments. AG-EHDP also realizes the upward printing of silver microscale structures with a resistance of 7.72 ± 0.83 Ω cm−1, which exhibits the excellent electrothermal capability to heat the cold template from 25 °C to 180 °C within 3 min under an applied voltage of 3 V. It is foreseen that EHDP might provide a promising strategy to fabricate microscale functional structures in zero/micro-gravity space environments.