Topology Optimization and 3D printing of Large Deformation Compliant Mechanisms for Straining Biological Tissues

TL;DR

This paper introduces a topology optimization method for designing large deformation compliant mechanisms to induce specific strains in biological tissues, utilizing nonlinear modeling and 3D printing for validation.

Contribution

It presents a novel synthesis approach combining density-based topology optimization with nonlinear modeling and robust design techniques for biological tissue applications.

Findings

Optimized mechanisms successfully induce target strains in tissues.

3D-printed prototypes match simulation predictions.

The method improves design stability under large deformations.

Abstract

This paper presents a synthesis approach in a density-based topology optimization setting to design large deformation compliant mechanisms for inducing desired strains in biological tissues. The modelling is based on geometrical nonlinearity together with a suitably chosen hypereleastic material model, wherein the mechanical equilibrium equations are solved using the total Lagrangian finite element formulation. An objective based on least-square error with respect to target strains is formulated and minimized with the given set of constraints and the appropriate surroundings of the tissues. To circumvent numerical instabilities arising due to large deformation in low stiffness design regions during topology optimization, a strain-energy based interpolation scheme is employed. The approach uses an extended robust formulation i.e. the eroded, intermediate and dilated projections for the design description as well as variation in tissue stiffness. Efficacy of the synthesis approach is demonstrated by designing various compliant mechanisms for providing different target strains in biological tissue constructs. Optimized compliant mechanisms are 3D-printed and their performances are recorded in a simplified experiment and compared with simulation results obtained by a commercial software.