Shape Memory Alloy Actuators in an Active Needle—Modeling, Precise Assembly, and Performance Evaluation

Today, several medical diagnosis and therapeutic cancer interventions are performed using needles via percutaneous surgical procedures. The success of these procedures highly depends on accurate placement of the needle tip at target positions. Improving targeting accuracy necessitates improvements in medical imaging and needle steering techniques. The former provides an improved vision on the target (i.e., cancerous tissue) and the needle, while the latter enables an enhanced interventional tool. In spite of considerable advancements in the medical imaging field, structure of the needle itself has remained unchanged. In the past decade, research works have suggested passive or active navigation of the needle inside the tissue to improve targeting accuracy. In addition, to provide actuation and control for needle steering, an active needle has been introduced activated by shape memory alloy (SMA) actuators. However, actuation of SMAs is complex due to their nonlinear and hysteresis behavior that depends on stress, strain, and temperature during operation. This work studies rapid manufacturing (via 3D printing), precise assembly, and performance evaluation of multiple distributed SMA actuators in an active flexible needle. The interactive response of the SMA actuators was investigated using experimental tests, constitutive material model, and kinematics of the active needle. It was shown that with proper installation of SMA actuators on the active needle, an effective manipulation can be realized in three dimensions.