Bio-inspired “jigsaw”-like interlocking sutures: Modeling, optimization, 3D printing and testing

• Published in: Journal of the mechanics and physics of solids 2017-05, Vol.102, p.224-238
• Main Authors: Malik, I.A., Mirkhalaf, M., Barthelat, F.
• Format: Article
• Language: English
• Subjects: 3D printing; Analytical model; Angles (geometry); Biological materials; Biomimetics; Boundary conditions; Brittle materials; Ceramics; Coefficient of friction; Damping; Deformation; Design optimization; Energy absorption; Finite element simulation; Locking; Mathematical models; Mechanical tests; Optimization; Shells; Suture; Sutures; Teeth; Three dimensional models; Three dimensional printing; Traction
• ISSN: 0022-5096; 1873-4782
• DOI: 10.1016/j.jmps.2017.03.003

•We developed analytical solution to determine the pullout response and maximum stress in the interlocking suture materials using non-Hertzian contact solution problem.•The material response can be tuned with geometrical parameter and friction coefficient.•The resistance to pull-out of the suture interface increases with increasing interlocking angle and friction coefficient.•A “brute-force” optimization scheme showed that to optimize the maximum strength, stiffness and energy absorption, it is preferable to use low friction coefficient with relatively high locking angle.•3D printing and mechanical testing of jigsaw interlocking sutures validated the pullout response from the models. Structural biological materials such as bone, teeth or mollusk shells draw their remarkable performance from a sophisticated interplay of architectures and weak interfaces. Pushed to the extreme, this concept leads to sutured materials, which contain thin lines with complex geometries. Sutured materials are prominent in nature, and have recently served as bioinspiration for toughened ceramics and glasses. Sutures can generate large deformations, toughness and damping in otherwise all brittle systems and materials. In this study we examine the design and optimization of sutures with a jigsaw puzzle-like geometry, focusing on the non-linear traction behavior generated by the frictional pullout of the jigsaw tabs. We present analytical models which accurately predict the entire pullout response. Pullout strength and energy absorption increase with higher interlocking angles and for higher coefficients of friction, but the associated high stresses in the solid may fracture the tabs. Systematic optimization reveals a counter-intuitive result: the best pullout performance is achieved with interfaces with low coefficient of friction and high interlocking angle. We finally use 3D printing and mechanical testing to verify the accuracy of the models and of the optimization. The models and guidelines we present here can be extended to other types of geometries and sutured materials subjected to other loading/boundary conditions. The nonlinear responses of sutures are particularly attractive to augment the properties and functionalities of inherently brittle materials such as ceramics and glasses.