Design of Self-Folding Origami Architectures for Biomedical Implants: A Finite Element Simulation Framework

Abstract

Minimally invasive brain implants require compact deployment geometries and controlled shape transformation for delivery through confined vessels. Origami-inspired structures enable large shape changes from compact to tailored deployed configurations, but implementation at microscale dimensions remains challenging, as conventional designs rely on predefined mountain and valley folds that become increasingly difficult to fabricate and assemble as unit-cell size is reduced to meet clinical requirements. To address this, we propose a self-folding methodology based on thermally induced stresses in thin-film bimetallic composites. Pairing the shape memory alloy Nitinol (NiTi) with molybdenum or stainless steel (SS316L) exploits their differing thermal expansion coefficients to generate localized hinge bending, enabling deterministic, autonomous folding into prescribed mountain and valley configurations. Using finite element simulations, we systematically optimize hinge length, layer thickness, width, and shape, identifying a hinge geometry achieving a ~50% reduction in unit-cell dimensions relative to previously reported designs. Integration into a complete waterbomb origami unit cell confirms that the strip-level folding mechanism scales to produce coordinated, self-folding deformation across the tessellated structure. These results demonstrate the feasibility of stress-induced, self-folding thin-film origami architectures built from clinically established biomaterials, providing a scalable design framework for next-generation, active neurovascular implants with integrated sensing and monitoring functionality.

arXiv comment20 pages, 7 figures