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Abstract Additive manufacturing (AM) enables the tailored production of precision fibrous scaffolds toward various engineered tissue models. Moreover, by functionalizing scaffolds in either a uniform or gradient pattern of biomolecules, different target tissues can be fabricated in vitro to capture key characteristics of in vivo cellular microenvironments. However, current engineered tissue models lack the appropriate cellular cues that are needed to deterministically direct cell behavior. Specifically, tunable and reproducible scaffold‐guided stimuli are identified herein as the missing link between biomaterial structure and cellular behavior. Therefore, the bottleneck of precision control is addressed here over the immobilization of patterned biomolecular stimuli with either uniform or gradient distribution over the AM‐enabled 3D biomaterial model as a function of different growth factors exposure variables, protocols, and various scaffold architectural design parameters. The produced study outcomes herein will improve the directing and guiding of biological cell attachment and growth direction in the context of scaffold‐guided stimuli techniques. Therefore, unprecedented control is presented here over 3D structured biomaterial gradient functionalization and immobilization of biomolecules toward biomimetic tissue architectures. 

Melt electrohydrodynamic processes, in conjunction with a moveable collector, have promising engineered tissue applications. However, the residual charges within the fibers deteriorate its printing fidelity. To clarify the mechanism through which the residual charges play roles and exclude the confounding effects of collector movement, a stationary printing mode is adopted in which fibers deposit on a stationary collector. Effects of process parameters on generalizable printing outcomes are studied herein. The fiber deposit bears a unique shape signature typified by a central cone surrounded by an outer ring and is characterized by a ratio of its height and base diameter Hdep/Ddep. Results indicate Hdep/Ddep increases with collector temperature and decreases slightly with voltage. Moreover, the steady-state dynamic jet deposition process is recorded and analyzed at different collector temperatures. A charge-based polarization mechanism describing the effect of collector temperature on the fiber accumulating shape is apparent in both initial and steady-state phases of fiber deposition. Therefore, a key outcome of this study is the identification and mechanistic understanding of collector temperature as a tunable process variable that can yield predictable structural outcomes. This may have cross-cutting potential for additive manufacturing process applications such as the melt electrowriting of layered scaffolds. 

Abstract The printing accuracy of the melt electrowriting (MEW) process is adversely affected by residual charge entrapped within the printed fibers. To mitigate this effect, the residual charge amount (Q_r) must first be accurately determined. In this study,Q_ris measured by a commercial electrometer at a nanocoulomb scale for MEW‐enabled scaffolds. Based on this enabling measurement, the effects of various design parameters (including substrate surface conductivityσ, printing timet, layer numberN), and process parameters (including voltageU, translational stage speedv, and material temperatureT_m), onQ_rare investigated. An increase ofσor decrease ofNhelps to decreaseQ_r. The effects of different process parameters on the residual charge can be either dependent or independent of fiber morphologies. Moreover, the fiber‐morphology dependent and independent effect can be either synergistic (UandT_m) or antagonistic (e.g.,v) for different process parameters. Under same conditions,Q_rin the interweaving scaffold design is generally smaller than that in the non‐interweaving scaffold design. These results help to furnish necessary insights into the charge dissipation process for a melt‐based electrohydrodynamic printing process while providing a systematic methodology to mitigate the residual charge accumulation. 

Abstract Melt electrowriting (MEW) is an emerging additive process for high‐fidelity, microscale fibrous scaffold fabrication. However, achieving precise multilayered MEW‐enabled scaffolds is limited by the entrapped residual charges owing to charge‐based mechanisms. Specifically, the semi‐conductive nature of processed materials causes retainment of net positive charges and jet–fiber repulsion, while exposure to the electric field yields charge polarization with resultant jet–fiber attraction. These competing effects work in tandem to determine the distinctive features of jet–fiber interaction. To deconstruct various charge‐related phenomena, the collector temperature is manipulated as a key process variable to investigate its effect on printing outcomes in two printing modes. Moreover, energy analysis is introduced to explain how collector temperature affects the polarization extent, along with the jet–fiber interaction and printing outcomes. In single fiber printing mode, sets of two parallel fibers with variable set interfiber distances (sS_f) are printed at different collector temperatures. At a lowsS_fthreshold, significant fiber attraction is observed, but no significant difference is observed among the cases at different collector temperatures. In scaffold printing mode, 200‐layer scaffolds are printed at different collector temperatures, and the wall morphologies are found to vary with location, layer number, and collector temperature.