Design and evaluation of shape memory alloy-actuated active needle using finite element analysis and deflection tracking control in soft tissues

BackgroundConventional needles lack active mechanisms for large tip deflection to bypass obstacles or guide through a desired trajectory in needle-based procedures, compromising accuracy and effectiveness. MethodsAn active needle with a shape memory alloy (SMA) actuator was designed and evaluated by demonstrating deflections in tissue-mimicking gels. Finite element simulation and real-time needle tip deflection tracking in tissue-mimicking gels were performed. ResultsThe active needle deflected 50 and 39 mm at 150 mm insertion depth in the liver and prostate mimicking gels, respectively. Reasonable simulation errors of 16.42% and 12.62% in needle deflections and small root mean squared errors of 1.42 and 1.47 mm in deflection tracking were obtained. ConclusionsThe proposed needle produced desirable large tip deflections capable of bypassing obstacles in the insertion path and tracked a preplanned trajectory with minor errors. The finite element study would help optimise needle designs and predict deflections in soft tissues.