Figure 4.

The tele-operated needle threading task. (a) Schematic illustration of experimental set-up. The suture needle is fixed in the acrylic support plate with the pinhole aligned with the sensor hole, and the robotic gripper holds the suture to complete the task. (b) Enlarged view of the structure of the sensor, and the possible relative position with the suture in the experiment. The blue part is the sensing area, and the hole is the area where the suture passes through. (c) Positions of thread, needle and acrylic support, and photo of successful needle threading. The diameter of this needle is 0.9 mm. (d) Real-time response of the MBM-based sensor during three threading attempts. When the suture is not inserted into the pinhole and touches the sensing area of the sensor, the sensor immediately shows obvious response. When threading starts, a low response from the sensor indicates the beginning of threading. The photo in the figure shows three positions of the suture and sensor. (e) The integration of the sensor array onto a robotic gripper. The upper pictures of (i) and (ii) show that the needle is placed on the sensor array and the needle is 1 cm away from the sensor array, respectively. The lower pictures show the pressure mapping of the needle weight (left) and the 3D shape mapping of the needle corresponding to the top picture (right).