Abstract:

Today, most people do not know Shape Memory Alloys (SMAs) even though they have many use cases in e.g., medical field, aerospace and automotive. This research project aims to investigate the possibility of using miniaturized SMA engines for drilling in medical applications. Specifically, it modifies an existing concept to meet the technical requirements for drilling in medical applications. In this context, an SMA engine is defined as an engine that transforms heat through SMAs into the mechanical rotation of a shaft. To test the hypothesis that miniaturized SMA can be used for drilling in medical applica- tions, an evaluation of already existing engine concepts was made. This evaluation helps to select the most promising engine concept to meet the requirements. Thereafter, a math- ematical model of the engine’s specifications was created. In addition to the mathematical model, experimentation with a prototype was made to figure the engine’s real behaviour out. The results of the calculations refute the hypothesis of a higher efficiency, because they indicate an efficiency decrease of 88% to common electrical micro motors. On the other hand, the results indicate that a miniaturized SMA engine has a huge advantage in high torque compared to electronic micro motors. The research project indicates that the electrical connection and the wire’s force transmission are the main challenges to focus on. These challenges showed that on the one hand the Nitinol wire is pulled out of the electrical clamping connection by reason of the tensile stress to stretch it. On the other hand, it showed that the Nitinol wire must be guided around the shaft because it urges to shift in axial direction. Even though by reason of the occurred challenges a working prototype could not be built in this research project, solutions were selected methodically to overcome the challenges. The results suggest that an SMA engine can be designed for drilling in medical applications, but cannot supersede electronic micro motors. The downsizing of the modified SMA engine is limited because of the mechanical parts that are needed to transmit the wire’s contraction to the rotation of a shaft. Also further downsizing lowers the output power specifications because their dependency on the distance between the wire and the shaft axis. Regardless, this research reveals that by reason of the high torque SMA en- gines provide compared to electric micro motors, future research can investigate their use for torque dependent applications e.g., a grabbing tool.