Exploiting Nonlinear Fiber Patterning to Control Tubular Scaffold Mechanical Behavior

Abstract

Melt electrowriting is an additive manufacturing technique capable of fabricating highly biomimetic polymer scaffolds with high‐resolution microarchitecture for a range of tissue engineering applications. The use of a rotating mandrel to fabricate tubular scaffolds using this technique is increasing in popularity; however, the translation of many novel scaffold designs that have been explored on flat collectors has yet to be realized using mandrels. This study reports novel tools to automatically generate scaffold gcode for several new tubular scaffold designs, investigating a range of auxetic pore geometries and open unit cell designs. Through optimization of printing parameters, the novel scaffold designs are successfully printed and mechanically tested to assess tensile properties. Open unit cells significantly reduce the tensile stiffness of scaffolds manufactured with closed pores. Auxetic scaffolds could also be widely tuned using the novel gcode generator tool to exhibit similar stress–strain profiles to typical crosshatch scaffolds but could be made to expand to desired radial dimensions. Finally, heterogeneous auxetic constructs are also fabricated with regions of various radial compliances. This study presents several, mechanically validated novel scaffold designs that are of interest for future applications in targeted tissue engineering product development as well as in soft robotic actuation.

Volumetric Printing across Melt Electrowritten Scaffolds Fabricates Multi-Material Living Constructs with Tunable Architecture and Mechanics

“…[25, 43] The hexagonal constructs feature a higher stiffness compared to the rhomboid structures in radial deformation as an effect of their geometry, which is likely the main cause for the linear rise of stress in the recorded measurements and is supported by other studies on the influence of MEW geometries on their mechanical behavior. [44] The rhomboid structures illustrated a certain degree of flexibility depending on the winding angle, allowing the construct to behave elastically in the direction of radial tensile deformation before transitioning to plastic deformation. This allows the rhomboid geometry to assume vastly different mechanical properties depending on the chosen winding angle.…”

Melt electrowritten scaffold architectures to mimic vasculature mechanics and control neo-tissue orientation

“…Remarkably, the results here presented showed a match in stress-strain behaviour of native tissue until 10% strain and non-significant differences between native and polymeric grafts for the elastin dominant region, the physiological region, and ultimate tensile strength (UTS). It has been shown that different printing geometries affect stress-strain response of tubular grafts [27], which gives a versatile platform for different engineered tissue. Together, the analysis of the mechanical behaviour here reported show that tuning scaffold geometry the J-shape response and the anisotropy of native vessels were matched.…”

“…Indeed, within the cardiovascular space, MEW has been utilised to recreate the ECM structure of a heart valve [22] and tubular scaffolds have been fabricated to simulate a patient specific aortic root [24] and heart valve complexes [23]. Furthermore, tubular MEW scaffolds have also been fabricated, demonstrating printability up to 300 stacked layers at a winding angle (WA) of 60° [26], while others having printed auxetic tubular scaffolds and examined the mechanical behaviour of these unique architectures [27]. Very few studies have investigated these tubular scaffolds in the context of tissue regeneration.…”

Earthworm‐Inspired Multi‐Material, Adaptive Strain‐Limiting, Hybrid Actuators for Soft Robots

“…Researchers have worked on different types of strain-limiting layers prior to our work. [26][27][28][29][30] However, there are several limitations. One, these strain-limiting layers are fixed and can hardly alter their length and position.…”