Modelling the interphase of 3D printed photo-cured polymers

Noni, Lorenzo De; Zorzetto, Laura; Briatico‐Vangosa, Francesco; Rink, M.; Ruffoni, Davide; Andena, Luca

doi:10.1016/j.compositesb.2022.109737

Cited by 11 publications

(4 citation statements)

References 35 publications

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“…First, the 6 times larger facet size of the DIC recordings as compared to the micro-brick size has likely led to the averaging of strains in the regions where sharp step transitions were present, blurring the measured step feature. Second, partial resin mixing at the interface between the micro-bricks may have resulted in a gradual transition of the elastic properties across the steps, similar to what other studies have suggested [37,43,47,48]. In contrast, none of these effects were present when simplifying the outcome from the FEM estimations into systems of linear springs.…”

Section: Resultssupporting

confidence: 61%

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Rational positioning of 3D printed micro-bricks to realize high-fidelity, multi-functional soft-hard interfaces

Saldívar

Salehi

Veeger

et al. 2023

Preprint

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Living organisms have developed design principles, such as functional gradients (FGs), to interface hard materials with soft ones (e.g., bone and tendon). Mimicking such design principles can address the challenges faced when developing engineered constructs with soft-hard interfaces. To date, implementing these FG design principles has been primarily performed by varying the ratio of the hard phase to that of the soft phase. Such design approaches, however, lead to inaccurate mechanical properties within the transition zone. That is due to the highly nonlinear relationship between the material distribution at the microscale and the macroscale mechanical properties. Here, we 3D print micro-bricks from either a soft or a hard phase and study the nonlinear relationship between their arrangements within the transition zone and the resulting macroscale properties. We carry out experiments at the micro- and macroscales as well as finite element simulations at both scales. Based on the obtained results, we develop a co-continuous power-law model relating the arrangement of the micro-bricks to the local mechanical properties of the micro-brick composites. We then use this model to rationally design FGs at the individual micro-brick level and create two types of biomimetic soft-hard constructs, including a specimen modeling bone-ligament junctions in the knee and another modeling the nucleus pulposus-annulus fibrosus interface in intervertebral discs. We show that the implemented FGs drastically enhance the stiffness, strength, and toughness of both types of specimens as compared to non-graded designs. Furthermore, we hypothesize that our soft-hard FGs regulate the behavior of murine preosteoblasts and primary human bone marrow-derived mesenchymal stromal cells (hBMSCc). We culture those cells to confirm the effects of soft-hard interfaces on cell morphology as well as on regulating the expression of focal adhesion kinase, subcellular localization, and YAP nuclear translocation of hBMSCs. Taken together, our results pave the way for the rational design of soft-hard interfaces at the micro-brick level and (biomedical) applications of such designs.

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Section: Resultssupporting

confidence: 61%

“…Moreover, the relationship between the numbers of hard and soft micro-bricks and the realized macroscale properties is often assumed to be linear, neglecting its highly nonlinear nature. It has already been shown that such assumptions can lead to inaccurate estimations of effective mechanical behavior [35][36][37].…”

Section: Introductionmentioning

confidence: 99%

Rational positioning of 3D printed micro-bricks to realize high-fidelity, multi-functional soft-hard interfaces

Saldívar

Salehi

Veeger

et al. 2023

Preprint

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“…The absence of these peaks was likely caused by the limited DIC resolution (i.e., between 22 × 10 3 and 27 × 10 3 facets per experiment), which was approximately six times lower than the resolution of the 3D-printed specimens (i.e., 147 × 10 3 voxels). Furthermore, blending of the photopolymers prior to curing might have significantly reduced the magnitudes of the strain peaks 42 , 43 . The FEM predictions were, therefore, more discerning when trying to understand the effects of geometrical design on the mechanical performance of soft–hard interfaces.…”

Section: Resultsmentioning

confidence: 99%

“…Moreover, an analysis of the effects of photopolymer blending (Supplementary Note 6 , Supplementary Fig. 12 , and Supplementary Videos 15 – 18 ) showed that even though material mixing can improve the performance of photopolymer composites, the general observations regarding the effects of various geometrical design alternatives on the performance of the interfaces remain unchanged 42 , 43 . Experimental studies of such effects are currently not possible outside multi-material Polyjet printing due to technological limitations.…”

Section: Resultsmentioning

confidence: 99%

Bioinspired rational design of bi-material 3D printed soft-hard interfaces

Saldívar,

Tay,

Isaakidou

et al. 2023

Nat Commun

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Durable interfacing of hard and soft materials is a major design challenge caused by the ensuing stress concentrations. In nature, soft-hard interfaces exhibit remarkable mechanical performance, with failures rarely happening at the interface. Here, we mimic the strategies observed in nature to design efficient soft-hard interfaces. We base our geometrical designs on triply periodic minimal surfaces (i.e., Octo, Diamond, and Gyroid), collagen-like triple helices, and randomly distributed particles. A combination of computational simulations and experimental techniques, including uniaxial tensile and quad-lap shear tests, are used to characterize the mechanical performance of the interfaces. Our analyses suggest that smooth interdigitated connections, compliant gradient transitions, and either decreasing or constraining strain concentrations lead to simultaneously strong and tough interfaces. We generate additional interfaces where the abovementioned toughening mechanisms work synergistically to create soft-hard interfaces with strengths approaching the upper achievable limit and enhancing toughness values by 50%, as compared to the control group.

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