Introducing Controlled Microporosity in Melt Electrowriting

Melt electrowriting (MEW) enables the electric field-assisted digital fabrication of precisely defined scaffold architectures of micron-sized fibers. However, charge accumulation and consequent disruption of the precoded pattern by fiber bridging prevents controlled printing at small interfiber distances. This, together with the periodical layer stacking characteristic for additive manufacturing, typically results in scaffolds with channel-like macroporosity, which need to be combined with other biofabrication techniques to achieve the desired microporosity for cellular infiltration. Therefore, a design strategy is devised to introduce controlled interconnected microporosity directly in MEW scaffolds by an algorithm that creates arrays of bridging-free parallel fibers, angularly shifted from layer to layer and starting at a random point to avoid periodical fiber stacking, and hence channel-like pores while defining micropores. This work hypothesizes that pore size can be controlled, decoupled from fiber diameter, and the mechanical properties, including anisotropy ratio, can be tuned. The authors demonstrate this while leveraging the platform for both flat and seamless tubular scaffolds and characterize them via micro-computed tomography and tensile loading. Lastly, successful cell ingrowth into the micropores and extracellular matrix formation are shown. This platform enables microporous scaffolds entirely via MEW that can be tailored to the architectural and mechanical requirements of the target tissues.