The difficulty of transurethral ureterolithotripsy while operating in a complex and elaborate structure of the urinary system hinders surgeons from using a ureteroscope with a fixed optical fiber to reach the targeted calculus. A continuum-robotic device is proposed to position laser irradiation independently in ureteroscopes actuated by three slackened shape memory alloy (SMA) wires. The deformation of SMA wires is driven by the joule heat generated by electrical current. An adjustable constant current source was fabricated to provide triple power outputs for SMA tendons.

This device is unique because of the tiny diameter of 1.1 mm which can be used inside the ureteroscope through a 1.2 mm inner channel into the kidney for transurethral ureterolithotripsy. Three cameras and a corresponding program for synchronizing cameras were used to observe the device’s motion and shape of the device. The control system consisted of an MCU (Micro Control Unit) and a lever button as the interface between the manipulator and the device. The maximum bending angle in water was over 25° when the current value was 800 mA. The control system could provide stable and fast-reponed PID-controlled currents to SMA tendons with a difference of less than 2%. The device could achieve multidirectional bending with the control system in the direction of pseudo 360°. The whole could simplify the operation and improve the efficiency in transurethral ureterolithotripsy.