X-ray tomographic imaging of tensile deformation modes of electrospun biodegradable polyester fibers

Electrospinning allows the production of fibrous networks for tissue engineering, drug delivery, and wound healing in health care. It enables the production of constructs with large surface area and a fibrous morphology that closely resembles the extracellular matrix of many tissues. A fibrous structure not only promotes cell attachment and tissue formation but could also lead to very interesting mechanical properties. Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) is a biodegradable polyester that exhibits a large (>400%) elongation before failure. In this study, synchrotron X-ray phase contrast imaging was performed during tensile deformation to failure on a non-woven fiber mat of P(3HB-co-4HB) fibers. Significant reorientation of the fibers in the straining direction was observed, followed by localized necking and eventual failure. From an original average fiber diameter of 4.3 µm, a bimodal distribution of fiber diameter (modal diameters of 1.9 and 3.7 µm) formed after tensile deformation. Extensive localized necking (thinning) of fibers between (thicker) fiber–fiber contacts was found to be the cause for non-uniform thinning of the fibers, a phenomenon that is expected but has not been observed in 3D previously. The data presented here have implications not only in tissue regeneration but for fibrous materials in general

X-ray Tomographic Imaging of Tensile Deformation Modes of Electrospun Biodegradable Polyester Fibers

Electrospinning allows the production of fibrous networks for tissue engineering, drug delivery, and wound healing in health care. It enables the production of constructs with large surface area and a fibrous morphology that closely resembles the extracellular matrix of many tissues. A fibrous structure not only promotes cell attachment and tissue formation but could also lead to very interesting mechanical properties. Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) is a biodegradable polyester that exhibits a large (>400%) elongation before failure. In this study, synchrotron X-ray phase contrast imaging was performed during tensile deformation to failure on a non-woven fiber mat of P(3HB-co-4HB) fibers. Significant reorientation of the fibers in the straining direction was observed, followed by localized necking and eventual failure. From an original average fiber diameter of 4.3 µm, a bimodal distribution of fiber diameter (modal diameters of 1.9 and 3.7 µm) formed after tensile deformation. Extensive localized necking (thinning) of fibers between (thicker) fiber–fiber contacts was found to be the cause for non-uniform thinning of the fibers, a phenomenon that is expected but has not been observed in 3D previously. The data presented here have implications not only in tissue regeneration but for fibrous materials in general

A multi-loading, climate-controlled, stationary ROI device for in-situ X-ray CT hygro-thermo-mechanical testing

\u3cp\u3eIn-situ CT mechanical testing yields a full 3D description of a sample material’s behaviour under specific loads. In the literature various devices are proposed which enable in-situ CT hygro-, thermo- or mechanical testing, each with its own merits and limitations. However none of them is able to perform advanced hygro-thermo-mechanical tests on specimens subjected to multiple loading modes, while accurately controlling and measuring the force, displacement, temperature and relative humidity in real time. Therefore, this work proposes an in-situ CT device which allows such multi-faceted experiments. Improvements to the current state-of-the-art devices include: (1) a compact, lightweight and rotationally symmetric design that enables high-resolution CT scans by minimization of wobble during scanning, in practically all lab-scale CT scanners; (2) a stationary region of interest by loading the sample from both sides, which enables high resolution CT characterization of materials exhibiting a large fracture strain; and (3) improved testing modularity by exchanging clamping methods to allow samples of various sizes (e.g., circular or rectangular) to be inserted in a variety of ways, thereby facilitating complex experiments such as three- or four-point bending tests. Validation experiments demonstrate that stringent requirements on CT resolution, loading and displacement accuracy and climate control are met. Furthermore, the in-situ testing capabilities of the device were validated by CT characterization of the creasing and folding process of multi-layer cardboard under varying (controlled) levels of relative humidity and temperature.\u3c/p\u3