Design and Development of Surgical Gripper Using Compliant Mechanism

Khoo, Teng Joon (2020) Design and Development of Surgical Gripper Using Compliant Mechanism. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Minimally Invasive Surgery (MIS) are constantly developed and witnessed great success due to its advantages that it offers compared to conventional open surgeries. MIS will only require to make around 10mm incisions with the aids of surgical instruments. This will then result in fewer complications, significantly reduced scar and faster recovery period from the incision made. The benefits that MIS provides to medical practitioners, particularly to surgeons. This motivates the research in reducing the size of surgical gripper to further reduce the size of incision while being able to complete the surgery. However, for the conventional surgical gripper mechanism, which are rigidly linked, faces the difficulty in scaling down in size as desired. The main objective of this project dissertation was to design a surgical gripper via compliant mechanism. This is achieved by modelling a reference design concept, which is a slider crank mechanism and modelling it into a surgical gripper via Pseudo-Rigid Body Method (PRBM), fulfilling the objective of converting the conventional rigidly linked mechanism of the surgical gripper into a monolithic one via compliant mechanism. Before synthesising the rigid-linked surgical gripper, analysis and selection of different ergonomics and materials were done before proceeding to the dimensional synthesising. The selected materials are polyethylene terephthalate (PET), Polylactide (PLA) and This synthesise method only required the length of one of the linkages, the translational distance of the gripping jaw and the thickness of one of the flexural hinges, where the other dimensions including the angle of deflection and the remaining length of linkages will be calculated via MATLAB with reference to the nondimensional parameters. Next, the Computer Aided Design (CAD) of the compliant surgical gripper is generated based on the dimension synthesised. After that, the stress at each of the flexural hinges alongside with the output force of the gripping jaw will be calculated via PRBM and Finite Element Analysis (FEA) method via non-linear analysis for validation of data obtained. From Pseudo-Rigid Body Method (PRBM) under dimensional synthesis, it is found out that the deflection is greatest at the flexure hinge between the slider and the crank of the compliant surgical gripper. From the non-linear analysis under displacement plot, the output feedback from the input displacement applied does not behave out of logic for all three types of material selected. The output force analysis highest percentage difference between the PRBM and FEA method output force estimation is 30.74%, whereas for stress analysis the highest percentage error is only at 13.64%, hence the data obtained is within acceptable range.