In this paper a polymer sensorised microgripping tool for micromanipulation is presented. The gripper structure is made by moulding of polyurethane in silicon moulds by the technique of Shape Deposition Manufacturing (SDM), in which the force sensing elements and part of the actuator (in this case, microstrain gauges and SMA (Shape Memory Alloy) wire, respectively) are embedded into the microgripper in one process step. The actuation principle for the microgripper is an SMA wire. The advantages of the fabrication process are low cost and manufacture cycle time. This paper details the technique for fabrication of the microgripper to produce prototypes. These prototypes were then tested and characterised in terms of force output, hysteresis and repeatability. A further miniaturised unsensorised microgripper based on the same actuation principle and fabrication process (but less than half the size) was fabricated to demonstrate the possibility of further downscaling.
This paper reports a miniaturized triaxial force sensorized cutting tool for minimally invasive robotic surgery. This device exploits a silicon-based microelectromechanical system triaxial force sensor that acts as the core component of the system. The outer diameter of the proposed device is less than 3mm, thus enabling the insertion through a 9 French catheter guide. Characterization tests are performed for both normal and tangential loadings. A linear transformation relating the sensor output to the external applied force is introduced in order to have a triaxial force output in real time. Normal force resolution is 8.2bits over a force range between 0N and 30N, while tangential resolution is 7 bits over a range of 5N. Force signals with frequencies up to 250Hz can successfully be detected, enabling haptic feedback and tissue mechanical properties investigation. Preliminary ex vivo muscular tissue cutting experiments are introduced and discussed in order to evaluate the device overall performances.
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