Real-time, non-vision sensory feedback during minimally invasive surgery

Minimally invasive surgery is a favorable choice for many operations. But it suffers from lack of tactile sensing information when grasping and handling of tissues. Sole force information in grasper-tissue interface cannot represent the firmness of the grasping nor is sufficient for guaranteeing safety of tissue while handling it. Measurement of stiffness in the grasper-tissue interface is proposed to be included as a supplementary measure. This paper presents the concept and design of a MEMS tactile sensor which is planned to be integrated into the grasper of a surgical manipulator. The sensor is an array of two group of sensing units which are arranged alternately. Each group of the sensing units is a 3 axial force sensor. But for sensing the stiffness their stiffness is different. The design concept is proposed and a lumped model formulation and FEM analysis was used to explain its performance. It is shown that higher stiffness difference results in higher measurement sensitivity. The sensor array is proposed to be developed out of polyimide polymer. ANSYS is used for detailed design of the sensor. The results showed that linear relationship is present between applied load and sensing elements reading; Tuning of stiffness can be done by diaphragm's span size and its; and Force requirements are satisfied by proposed dimensions and polyimide properties. Future work plan includes sensor development, Calibration of the Sensor and Integration into a laboratory grasper.