Brief Overview on Nitinol as Biomaterial

Abdul Wadood

doi:10.1155/2016/4173138

Abstract

Shape memory alloys remember their shape due to thermoelastic martensitic phase transformation. These alloys have advantages in terms of large recoverable strain and these alloys can exert continuous force during use. Equiatomic NiTi, also known as nitinol, has a great potential for use as a biomaterial as compared to other conventional materials due to its shape memory and superelastic properties. In this paper, an overview of recent research and development related to NiTi based shape memory alloys is presented. Applications and uses of NiTi based shape memory alloys as biomaterials are discussed. Biocompatibility issues of nitinol and researchers’ approach to overcome this problem are also briefly discussed.

Highlights

Biomedical applications of nitinol are related to transformation temperatures of nitinol that are close to body temperature (310 K)
In order to improve the biocompatibility of nitinol, the current author of this study has studied the effect of partial substitution of nickel with silver on the biocompatibility and corrosion behavior of nitinol in saliva solution and at 303 K [62]
Mechanisms of shape memory effect and superelasticity are presented in this paper

Summary

Introduction

Upon removal of force, the material becomes in detwinned martensitic state When we heat this material above the austenite finish temperature (Af), reverse transformation occurs from detwinned/deformation-induced martensite to parent phase and the original shape is recovered. This is the mechanism of shape memory effect (SME). Applications of shape memory alloys depend upon their phase transformation temperatures. In near-equiatomic NiTi alloys, shape memory effect and superelasticity are due to thermoelastic martensitic transformation from parent austenite phase with B2 structure to the monoclinic (M) or rhombohedral (R) martensitic phase transformation [23,24,25]. Due to the possibility of large recoverable strain of about 8% without force generation and 700 MPa stress without recoverable strain, there is a high possibility to use NiTi shape memory alloy for the design of components with different strain outputs and different amounts of external work output [3]

Biomedical Applications of Nitinol

Biocompatibility Issues of Nitinol

Nitinol and Stainless Steel as Biomaterial

Findings

Conclusions