3D Printed Tubular Scaffolds with Massively Tailorable Mechanical Behavior

Melt electrowriting (MEW) is a promising additive manufacturing technique for tissue scaffold biofabrication. Successful application of MEW scaffolds requires strictly controlled mechanical behavior. This requires scaffold geometry be optimized to match native tissue properties while simultaneously supporting cell attachment and proliferation. The objective of this work is to investigate how geometric properties can be exploited to massively tailor the mechanical behavior of tubular crosshatch scaffolds. An experimentally validated finite element (FE) model is developed and 441 scaffold geometries are investigated under tension, compression, bending, and radial loading. A range of pore areas (4–150 mm2) and pore angles (11°–134°) are investigated. It is found that scaffold mechanical behavior is massively tunable through the control of these simple geometric parameters. Across the ranges investigated, scaffold stiffness varies by a factor of 294× for tension, 204× for compression, 231× for bending, and 124× for radial loading. Further, it is discussed how these geometric parameters can be simultaneously tuned for different biomimetic material applications. This work provides critical insights into scaffold design to achieve biomimetic mechanical behavior and provides an important tool in the development of biomimetic tissue engineered constructs

MEW cylindrical scaffolds with massively tailorable mechanical behaviour

INTRODUCTION: Melt electrowriting (MEW) is a cutting-edge 3D printing technology for manufacturing microfibre scaffolds. Ideally, the geometries of these can be tailored to match mechanical and biological needs, however this requires a detailed understanding of how scaffold geometry impacts mechanical behaviour.METHOD: To fill this gap, a fully automated FE modelling tool was developed to predict the mechanics of cylindrical crosshatch scaffolds, for any given geometry (i.e. length, radius, pore area, pore angle). In the model, based upon beam elements, each ‘strut’ of the scaffold was meshed by five BEAM189 elements and mesh convergence was confirmed. The material was assumed linear-elastic with an elastic modulus of 450 MPa. Loading was displacement controlled and solved under large deformation conditions. Tension, compression, bending, and radial loading were investigated. The model was experimentally validated against MEW scaffolds under tension (Figure 1).To explore mechanical tailorability, 441 different scaffold geometries were investigated with pore areas ranging between 20 and 120 deg, and pore areas ranging between 0.2 - 2 mm2 (length of 20 mm, radius of 1.5 mm).RESULTS: A full spectrum of mechanical behaviour under tension, compression, bending, and radial loading will be presented. The scaffolds showed complex deformation behaviours as a function of pore area and pore angle. Under tension, compression and bending, the scaffold stiffness varied by a factor of >1000x, while under radial loading, the stiffness varied by a factor of >100x. The greatest predictors of stiffness were alignment of MEW threads to loading direction and number of MEW threads.SIGNIFICANCE AND IMPACT: This work provides significant insights into the mechanics of MEW crosshatch scaffolds. The results show how scaffolds can be designed to meet competing needs (e.g. radially stiff, while flexible under bending). Future research directions will be presented.<br/

3D Printed Tubular Scaffolds with Massively Tailorable Mechanical Behavior

Melt electrowriting (MEW) is a promising additive manufacturing technique for tissue scaffold biofabrication. Successful application of MEW scaffolds requires strictly controlled mechanical behavior. This requires scaffold geometry be optimized to match native tissue properties while simultaneously supporting cell attachment and proliferation. The objective of this work is to investigate how geometric properties can be exploited to massively tailor the mechanical behavior of tubular crosshatch scaffolds. An experimentally validated finite element (FE) model is developed and 441 scaffold geometries are investigated under tension, compression, bending, and radial loading. A range of pore areas (4–150 mm2) and pore angles (11°–134°) are investigated. It is found that scaffold mechanical behavior is massively tunable through the control of these simple geometric parameters. Across the ranges investigated, scaffold stiffness varies by a factor of 294× for tension, 204× for compression, 231× for bending, and 124× for radial loading. Further, it is discussed how these geometric parameters can be simultaneously tuned for different biomimetic material applications. This work provides critical insights into scaffold design to achieve biomimetic mechanical behavior and provides an important tool in the development of biomimetic tissue engineered constructs.</p

Materials Design Innovations in Optimizing Cellular Behavior on Melt Electrowritten (MEW) Scaffolds

The field of melt electrowriting (MEW) has seen significant progress, bringing innovative advancements to the fabrication of biomaterial scaffolds, and creating new possibilities for applications in tissue engineering and beyond. Multidisciplinary collaboration across materials science, computational modeling, AI, bioprinting, microfluidics, and dynamic culture systems offers promising new opportunities to gain deeper insights into complex biological systems. As the focus shifts towards personalized medicine and reduced reliance on animal models, the multidisciplinary approach becomes indispensable. This review provides a concise overview of current strategies and innovations in controlling and optimizing cellular responses to MEW scaffolds, highlighting the potential of scaffold material, MEW architecture, and computational modeling tools to accelerate the development of efficient biomimetic systems. Innovations in material science and the incorporation of biologics into MEW scaffolds have shown great potential in adding biomimetic complexity to engineered biological systems. These techniques pave the way for exciting possibilities for tissue modeling and regeneration, personalized drug screening, and cell therapies.</p

An automated parametric ear model to improve frugal 3D scanning methods for the advanced manufacturing of high-quality prosthetic ears

Ear prostheses are commonly used for restoring aesthetics to those suffering missing or malformed external ears. Traditional fabrication of these prostheses is labour intensive and requires expert skill from a prosthetist. Advanced manufacturing including 3D scanning, modelling and 3D printing has the potential to improve this process, although more work is required before it is ready for routine clinical use. In this paper, we introduce a parametric modelling technique capable of producing high quality 3D models of the human ear from low-fidelity, frugal, patient scans; significantly reducing time, complexity and cost. Our ear model can be tuned to fit the frugal low-fidelity 3D scan through; (a) manual tuning, or (b) our automated particle filter approach. This potentially enables low-cost smartphone photogrammetry-based 3D scanning for high quality personalised 3D printed ear prosthesis. In comparison to standard photogrammetry, our parametric model improves completeness, from (81 ± 5)% to (87 ± 4)%, with only a modest reduction in accuracy, with root mean square error (RMSE) increasing from (1.0 ± 0.2) mm to (1.5 ± 0.2) mm (relative to metrology rated reference 3D scans, n = 14). Despite this reduction in the RMS accuracy, our parametric model improves the overall quality, realism, and smoothness. Our automated particle filter method differs only modestly compared to manual adjustments. Overall, our parametric ear model can significantly improve quality, smoothness and completeness of 3D models produced from 30-photograph photogrammetry. This enables frugal high-quality 3D ear models to be produced for use in the advanced manufacturing of ear prostheses.</p

Mechanical behaviour of flexible 3D printed gyroid structures as a tuneable replacement for soft padding foam

Various areas of healthcare utilise custom foam cushioning to treat or mitigate conditions like pressure ulcers, or to provide personalised support structures for patients with specific clinical needs. Polyurethane foams are often used; however, such materials require significant time and expertise to combine different foam types into a device that provides sufficient structural support in some areas, with soft pressure distribution in others. In this paper, flexible 3D printed gyroid based metamaterials are investigated as a tuneable replacement for polyurethane foams. The impact of changing key gyroid structural characteristics on the material's mechanical response is examined. Samples with six different unit cell geometries for each of two flexible TPU 3D printing filaments (NinjaFlex and Flexion X60) were produced using fused filament fabrication, tested, and compared to three types of conventional polyurethane rehabilitation foam. Compression tests were conducted focussing on compressive stress-strain response, strain rate effect, print layer effect, and cyclic fatigue behaviour. In all tests it was observed that gyroid samples of both filament types were able to produce compressive responses comparable to the foams. Solid volume fraction was determined as the critical gyroid geometric parameter that influenced compressive response, and solid volume fractions capable of reproducing the specific response of each of the three rehab foams were determined. It is shown that 3D printed gyroid materials are a viable replacement for soft polyurethane foams, and the direct control of material response possible with simple geometric changes means such metamaterials may lead to improved optimisation of rehabilitation cushions.</p