A wirelessly actuated robotic arm for endoscopy

Endoscopy enables a number of important minimally invasive medical procedures. Current commercial flexible endoscopes with small diameter often have only one bending section near the tip with only one degree of freedom (DoF). This strongly limits the area that can be reached by the endoscope. Researchers have made many efforts to develop multi-DoF miniaturized robotic endoscopes that can be controlled in multiple bending sections and that still possess an overall size small enough to enter the body through a single-port [1]. Robotic endoscopes are normally actuated by tendons [2], pneumatics [3] or the rotation of concentric tubes [4]. In comparison to these tethered approaches, wireless actuation allows for more flexibility and easier miniaturization. Ultrasound is a promising way to transfer power wirelessly in vivo. Recently, we reported an active surface actuator that directly converts ultrasound power into mechanical work via acoustic streaming from an array of micro-bubbles [5]. Here, we apply such wireless actuators to a miniaturized robotic arm, which works as an endoscopic tip (Fig. 1). The active surfaces consisting of arrays of micro-bubbles are attached to the arm and generate streaming of the adjacent fluid under ultrasound excitation. The recoil force actuates the arm. Different bubble sizes are addressed by different ultrasound frequencies, thus multiple DoFs are realized by the arm and require only one tunable ultrasound source