A coupled FEBio–immersed boundary framework for fluid-structure interaction in biological applications

We present a computational framework for simulating fluid-structure interaction (FSI) in complex biological systems by coupling the open-source finite-element software, FEBio (febio.org), with a custom-developed immersed-boundary (IB) fluid solver. This framework integrates FEBio's nonlinear tissue mechanics capabilities with the IB method's flexibility in handling moving, geometrically complex domains. Validation against standard FSI benchmark problems demonstrates good agreement with reference results, confirming the accuracy and robustness of the coupling. We further apply the framework to simulate flow-induced deformation in bioprosthetic heart valves, incorporating nonlinear, hyperelastic, and anisotropic tissue behaviour. Hemodynamic parameters, including transvalvular pressure gradients, valve surface pressure distribution, effective orifice area, and flow patterns, are analysed in physiologically relevant conditions. The modular architecture of the framework enables extension to patient-specific geometries and boundary conditions, supporting its use in personalized cardiovascular modelling and pre-surgical planning. By combining the complementary strengths of FEBio and the immersed-boundary method, this framework provides a flexible and efficient platform for advancing FSI simulations in biological applications involving soft tissues and large deformations and offers strong potential for both fundamental research and translational applications in clinical biomechanics.