Challenges of high-temperature melt electrowriting: A study of EVOH printing

Melt electrowriting (MEW) is an additive manufacturing technique used for creating thermoplastic microfiber scaffolds for tissue engineering with high precision. Most existing research focuses on polycaprolactone (PCL), a material that is commonly studied for its print behavior and is often used to create scaffolds due to its ease of processing. Although PCL is recognized as a bioresorbable polymer, its complete degradation takes multiple years, and its mechanical properties fail to replicate the high stiffness required by certain tissues. While several alternative polymers can be processed using MEW, their printability generally falls short compared to that of PCL. Most polymers have vastly higher processing temperatures, which can lead to swift degradation and rapid jet quenching, negatively impacting print quality. In this study, we explore the use of ethylene vinyl alcohol copolymer (EVOH), which has a melting point of 174 °C, to investigate the principles of printing high-melting-point polymers through MEW. We analyzed the effects of various melt and collector temperature combinations on jet motion, fiber stacking behavior, and the mechanical properties of scaffolds. Our findings indicate that rapid jet quenching leads to jet jumping, whereas a slower quenching printing promotes fiber adhesion, enhancing correct jet landing and improving mechanical properties, including a breaking stress of 0.2 cN/dtex, a modulus of 4 cN/dtex, and an elongation at break of 400 %. Long-term printing indicates that the process can be sustained for at least 15 h, producing fibers with diameters ranging from 8 to 14 μm. This research broadens the range of printable polymers, advancing the application of MEW technology across various fields.