A Decade of Melt Electrowriting

Over the past decade, melt electrowriting (MEW) has established the fundamental understanding of processing (and printer) requirements. Iterative work on parametric development and dissemination of this recent additive manufacturing technology has been performed across many systems and polymers (mainly poly-(ε-caprolactone)), showing similarities and trends. However, the software and hardware ecosystems of MEW are not mature. Further, due to its multi-parametric nature, MEW can be challenging for laboratories to master. This review intends to provide a unique perspective on the dynamic relationship between MEW processing parameters. Such parameters can be divided into 1) those that affect the polymer flow rate to or 2) from the nozzle, and 3) environmental conditions. The most influential parameters for high-quality printing are applied voltage, applied pressure, collector speed, polymer temperature, nozzle diameter, and the conditions that lead to charge buildup (e.g., relative humidity). Other factors such as ambient temperature, nozzle size, and protrusion, collector temperature and conductivity, and collector distance can all affect the process. Success for MEW printing means fibers fall onto the collector according to their pre-programmed path with predicted fiber diameter. Here, the authors elucidate how the dynamic relationship between these parameters can converge into ideal printing conditions to produce scaffolds.