Russian doll deployable meta-implants: Fusion of kirigami, origami, and multi-stability

F.S.L Bobbert,S Janbaz,T Van Manen,Y Li,A.A Zadpoor

doi:10.1016/j.matdes.2020.108624

Abstract

Deployable meta-implants aim to minimize the invasiveness of orthopaedic surgeries by allowing for changes in their shape and size that are triggered by an external stimulus. Multi-stability enables deployable implants to transform their shape from some compact retracted state to the deployed state where they take their full sizes and are load-bearing. We combined multiple design features to develop a new generation of deployable orthopaedic implants. Kirigami cut patterns were used to create bi-stability in flat sheets which can be folded into deployable implants using origami techniques. Inspired by Russian dolls, we designed multi-layered specimens that allow for adjusting the mechanical properties and the geometrical features of the implants through the number of the layers. Because all layers are folded from a flat state, surface-related functionalities could be applied to our deployable implants. We fabricated specimens from polylactic acid, titanium sheets, and aluminum sheets, and demonstrated that a deployment ratio of up to ≈2 is possible. We performed experiments to characterize the deployment and load-bearing behavior of the specimens and found that the above-mentioned design variables allow for adjustments in the deployment force and the maximum force before failure. Finally, we demonstrate the possibility of decorating the specimens with micropatterns.

Highlights

It is often said that in biological tissues such as bone, “form follows function” [1,2]
The specimens were manufactured from a variety of materials including polylactic acid (PLA), aluminum, and titanium
Since the fabrication of origami-based implants starts from a flat state, it is possible to incorporate precisely-controlled and arbitrarily complex surface micro-/ nanopatterns onto the specimens

Summary

Introduction

It is often said that in biological tissues such as bone, “form follows function” [1,2] It should, come as no surprise that in orthopaedic implants that replace the human bone either temporarily or permanently, ‘function follows form’. Come as no surprise that in orthopaedic implants that replace the human bone either temporarily or permanently, ‘function follows form’ This short statement summarizes the underlying principle of the so-called “meta-biomaterials” [3] and “meta-implants” [4,5], where the geometrical design at various scales is used to develop unprecedented functionalities. Bobbert et al / Materials and Design 191 (2020) 108624 techniques [7], the problem of developing implants with advanced functionalities reduces to the problem of geometrically designing them using the “rational design” principles [3,9]

Methods

Results

Discussion

Conclusion