Design and Fabrication of Fibrous Spindle-Like Constructs Using a Melt Electrohydrodynamic Writing Process

Advanced manufacturing of 3D-structured materials enables the production of biomimetic muscle tissues. While models of muscle tissue exist, current approaches possess a limited ability to capture essential elements of the muscle tissue microarchitecture. Therefore, this paper aims to engineer the intrinsically complex muscle spindle-like ellipsoid geometry using a polymer melt-based electrohydrodynamic (EHD) printing system. EHD systems have conventionally reported fiber deposition in a layerwise fashion. However, without mitigation, the observed fiber sagging and residual charge phenomena for the melt electrowriting (MEW) process limit the ability to produce layered fibrous 3D constructs with in-plane fiber alignment. However, in this work, fiber sagging and residual charge phenomena are leveraged as part of the design intent to deposit nonoverlapping suspended fibers between two stationary walls toward spindle-like construct fabrication. Specifically, herein the structural and mechanical properties of the MEW-enabled spindle-like constructs are analyzed as a function of the process and design parameters that govern control over fiber sagging and residual charge. The results indicate that the collector speed and wall-to-wall distance are the key parameters for tuning the spindle morphology. Moreover, cycle number and fiber diameter are identified as effective parameters for tuning the spindle mechanical properties.