Shape Memory Alloys for Biomedical Applications

Abstract

NiTi shape memory alloy (SMA) products appeared to the medical markets in 1980’s, their global market being more than US$ 130 billion in 2002. In most medical applications material must be biocompatible. NiTi offers the bodytemperature activated shape memory effect (SME), superelasticity (SE) and the damping capacity, which all can be applied in medical use. The dental arch wires and stents are benefiting from SE. The NiTi vena cava filters obtain their umbrella shaped mesh when SMEactivated. Generally the NiTi tubes and guidewires are applied in the minimally invasive medical procedures and in the interventional radiology. There are numerous steerable, hingeless, kink resistant, highly flexible clinical instruments that may provide constant force. NiTi is used for the dental implants and the attachments of the partial dentures and for the orthopaedics. In the latter one the main applications are the clamps for connecting bone fractures or parts for e.g. the spinal bentcalibration bar. Miniaturization has enabled small SMAactuators that are applicable in active endoscopes with allround bending and in actuators for kidney or heart pumps. The main risks using NiTi are the insecure fatigue life and possible cytotoxicity.