A Charge-Based Mechanistic Study into the Effects of Process Parameters on Fiber Accumulating Geometry for a Melt Electrohydrodynamic Process

et al. 2022

Macro Materials & Eng

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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 r is 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 conductivity 𝝈, printing time t, layer number N), and process parameters (including voltage U, translational stage speed v, and material temperature T m ), on Q r are investigated. An increase of 𝝈 or decrease of N helps to decrease Q 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 (U and T m ) or antagonistic (e.g., v) for different process parameters. Under same conditions, Q r in 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.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Quantitative Investigation into the Design and Process Parametric Effects on the Fiber‐Entrapped Residual Charge for a Polymer Melt Electrohydrodynamic Printing Process

et al. 2022

Macro Materials & Eng

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“…On the other hand, the complex interplay of MEW process parameters (voltage, translational speed of the collector, material temperature etc. ) 7,8 as well as residual charges entrapped in deposited fibers causes imprecise fiber deposition, thereby limiting the applications for the MEW process 9 . Currently, continuous efforts have been made to broaden the application of MEW, including decreasing fiber diameter (0.8 μm), 10 printing large volume scaffolds (thickness greater than 7 mm), 11 producing scaffolds with complex geometries, 12 and fabricating tubular structures 13 …”

Section: Introductionmentioning

confidence: 99%

Design, fabrication, and analysis of spatially heterogeneous scaffold by melt electrospinning writing of poly(ε‐Caprolactone)

J of Applied Polymer Sci

et al. 2022

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Melt electrospinning writing (MEW) that processes molten polymers has emerged as a reliable method to fabricate high-fidelity fibrous tissue scaffolds for investigation of cell biological performance as a function of structural features. However, most of the current investigations have focused on the scaffolds with homogeneous features, which can yield homogeneous cell performance outcomes as expected. In contrast, spatially heterogeneous scaffolds with well-defined, nonuniform pore attributes can serve as biomimetic, multiplexed platforms for biological investigations. In this study, an analytically derived general heterogeneous toolpath design model is introduced. In addition to the traditional orthogonal fiber orientations, fiber placement along diagonal directions is introduced to generate semi-0-θ patterned or 0-θ patterned heterogeneous scaffolds. By specifying model parameters and hence tuning the relative location of the diagonal fibers to orthogonal fibers, the customized heterogeneous scaffolds produced can possess at most three different pore morphologies. The various distributions of different pore morphologies within one scaffold are subsequently mapped by an advanced mathematical matrix method for the first time. Moreover, the proportion of different pore morphologies of semi-0-θ patterned scaffolds can be obtained numerically. Finally, this proposed analytical design model is preliminarily validated by fabrication using a MEW printing process.

“…[ 20 ] Second, residual charges entrapped in scaffolds can affect the deposition behavior of the fiber greatly. [ 21,22 ] Because of the residual charges, the fiber deviation is notably observed during the fabrication of scaffolds with a small inter‐fiber distance, [ 22,23 ] or a large layer number. [ 24 ] The processing parameters and scaffold design parameters can affect the printing accuracy.…”

Section: Introductionmentioning

confidence: 99%

Effects of Printing Sequence on the Printing Accuracy of Melt Electrowriting Scaffolds

et al. 2022

Macro Materials & Eng

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Melt electrowriting (MEW), an emergent additive manufacturing process, shows significant potential in fabricating high‐fidelity fibrous scaffolds for tissue engineering applications. However, fiber deviation can deteriorate the printing accuracy of MEW. To evaluate the printing accuracy, an evaluation protocol along with an index (Ip) is proposed. For the first time, 0–90 patterned and 0–θ patterned scaffolds with varying inter‐fiber distances along different printing directions are fabricated to establish the dependence of Ip on two distinct printing sequences. One sequence is the small–large sequence, which first prints the fibers separated by a small inter‐fiber distance, followed by fibers separated by a large inter‐fiber distance. Alternatively, for the large–small sequence, the fibers separated by a large inter‐fiber distance are printed prior to the fibers separated by a small inter‐fiber distance. The small–large sequence contributes to larger Ip results compared to the large–small sequence. Moreover, the printing sequence has more significant effects on the Ip for the 0–θ pattern compared to the 0–90 pattern. These differences can be attributed to different fiber morphologies at the intersection points, accompanied by resultantly varying charge amounts, which gives an insight into the cause of fiber deviation phenomena.