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Session: Poster session II
Session starts: Thursday 24 January, 16:00

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Françoise Bobbert (Department of Biomechanical Engineering, Delft University of Technology)
Shahram Janbaz (Department of Biomechanical Engineering, Delft University of Technology)
Amir Zadpoor (Department of Biomechanical Engineering, Delft University of Technology)

Abstract:
Meta-biomaterials exhibit unprecedented or rare combinations of properties not usually found in nature. Such unconventional mechanical, mass transport, and biological properties could be used to develop novel categories of orthopedic implants fulfilling desired requirements, otherwise known as meta-implants. In this study, we used bi-stable elements working on the basis of snap-through instability to design deployable meta-implants. Deployable meta-implants are compact in their retracted state, which enables the possibility to bring them to the surgical site with minimum invasiveness. Once in place, they could be deployed into their full-size load-bearing shape. By using minimally invasive surgery, the recovery time of the patient and the risk of infection could be reduced. We used an Ultimaker 3D printer to manufacture biocompatible PLA bi-stable elements. Five types of meta-implants were created by arranging these bi-stable elements in such a way to obtain a radially deployable structure, three types of auxetic structures, and an axially deployable structure. The intermediate stable conditions (i.e. multi-stability features), deployment force, and stiffness of the meta-implants were found to be strongly dependent on the geometrical parameters of the bi-stable elements as well as on their arrangement. The high porosity of these deployable structures allows for improved bone ingrowth. Because multi-stable deployable impl¬¬ants have different stable equilibrium states, a major design challenge is to ensure that they provide enough mechanical support in their deployed configuration. Future research should therefore be focused on evaluation of the mechanical performance of meta-implants as well as on designing miniaturized versions that make them more suitable for the application as bone substitutes.