A Fundamental Study of Charge Effects on Melt Electrowritten Polymer Fibers. (15th September 2019)

• Record Type: Journal Article
• Authors: Ding, Houzhu; Cao, Kai; Zhang, Fucheng; Boettcher, William; Chang, Robert C.
• Is Part Of: Materials & design. Volume 178(2019)
• Publication Date: 2019-09-15
• Subjects: Melt electrowriting -- Residual charge -- Substrate conductivity; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2019.107857
• Languages: English
• ISSNs: 0264-1275

Abstract

Abstract: 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 S f ) and measured S f . Both repulsion (measured S f > set S f ) and attraction (measured S f < set S f ) 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. Graphical abstract: Unlabelled Image Highlights: Based on an oscillating toolpath in a layering experiment, two distinct fiber alignment patterns have been identified, specifically precise fiber overlap on a conductive substrate, and divergent non-overlapping fibers on a non-conductive substrate. The role of charge in regulating inter-fiber distance has been determined by measuring and analyzing the relationship between the electric forces and the repulsive-attractive phenomenon. A charge distribution model has been advanced to describe the repulsion and attraction interaction, as well as the fiber overlap phenomenon.