Auxetic metamaterials for bone-implanted medical devices: Recent advances and new perspectives

Auxetic metamaterials and structures are characterized by their negative Poisson's ratio meaning that they exhibit lateral expansion under tensile axial loads and densification under compressive loads. The unique properties of the auxetic metamaterials have been generated by designing the micro- and macro-structures with various materials/designs. These types of structures are attracting interest for different reasons such as high energy absorption and improvement in mechanical and biological properties of medical devices. However, some of their interesting characteristics have not been widely explored yet in the field of biomedical engineering. This review aims at highlighting the applications of the auxetic structures in various bone medical devices. Additionally, it investigates different unit cells that were introduced as auxetic designs. The potential of using the auxetic structures in bone tissue engineering is discussed as well.