Out-of-plane 3D-printed microfibers improve the shear properties of hydrogel composites

M. de Ruijter, A. Hrynevich, J.N. Haigh, G. Hochleitner, M. Castilho, J. Groll, J. Malda, P.D. Dalton

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Abstract

One challenge in biofabrication is to fabricate a matrix that is soft enough to elicit optimal cell behavior while possessing the strength required to withstand the mechanical load that the matrix is subjected to once implanted in the body. Here, melt electrowriting (MEW) is used to direct-write poly(ε-caprolactone) fibers “out-of-plane” by design. These out-of-plane fibers are specifically intended to stabilize an existing structure and subsequently improve the shear modulus of hydrogel–fiber composites. The stabilizing fibers (diameter = 13.3 ± 0.3 µm) are sinusoidally direct-written over an existing MEW wall-like structure (330 µm height). The printed constructs are embedded in different hydrogels (5, 10, and 15 wt% polyacrylamide; 65% poly(2-hydroxyethyl methacrylate) (pHEMA)) and a frequency sweep test (0.05–500 rad s−1, 0.01% strain, n = 5) is performed to measure the complex shear modulus. For the rheological measurements, stabilizing fibers are deposited with a radial-architecture prior to embedding to correspond to the direction of the stabilizing fibers with the loading of the rheometer. Stabilizing fibers increase the complex shear modulus irrespective of the percentage of gel or crosslinking density. The capacity of MEW to produce well-defined out-of-plane fibers and the ability to increase the shear properties of fiber-reinforced hydrogel composites are highlighted.

Original languageEnglish
Article number1702773
Pages (from-to)1-6
JournalSmall : Nano Micro
Volume14
Issue number8
DOIs
Publication statusPublished - 22 Feb 2018

Funding

This work was financially supported by the Dutch Arthritis Foundation (LLP-12); the European Community’s Seventh Framework Programme (FP7/2007-2013) under grant agreement 309962 (HydroZONES). Further, the authors gratefully acknowledge the European Research Council under grant agreements 647426 (3D-JOINT) and 617989 (Design2Heal), as well as the German Research Foundation (DFG) State Major Instrumentation Programme for funding the Zeiss Crossbeam CB 340 scanning electron microscope (INST 105022/58-1 FUGG). The MEW device used for this study was built by G.H., while the support of the Hofvijverkring for P.D.D. is appreciated.

Keywords

  • biofabrication
  • fiber reinforcement
  • hydrogels
  • mechanical properties
  • melt electrowriting

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