| Summary: | Melt electrowriting (MEW) is an electrohydrodynamics (EHD)-based additive manufacturing paradigm for printing microscale fibers. Although models for charge transport during EHD printing have been described, significant challenges arise from the in-process charge dynamics in MEW process, which limits the achievable print resolution. This paper advances a methodology to analyze the effects of charge dynamics on the MEW-printed structure resolution. First, fibers printed with an oscillating toolpath exhibit two distinct alignment patterns with constituent fibers either successively overlapping along the toolpath or diverging into individual fibers without apparent overlap on conductive and non-conductive substrates, respectively, pointing to the existence of inter-fiber charge phenomena. Next, a set of straight fibers are printed on two types of substrates to investigate the relationship between the prescribed inter-fiber distance (set Sf) and measured Sf. Both repulsion (measured Sf > set Sf) and attraction (measured Sf < set Sf) are observed. Moreover, a mathematical model based on line-point charge interactions is advanced to explain the fiber attraction-repulsion phenomenon. Finally, residual charge measurements with a customized Faraday Cup reveal that printed scaffolds on conductive and non-conductive substrates are negatively and positively charged for residual charge, respectively. Keywords: Melt electrowriting, Residual charge, Substrate conductivity
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