The design of a friction-based tissue transportation mechanism for Minimally Invasive Surgery

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Abstract

The surgical procedure of tissue extraction from the human body for precautionary or curative measures is common in many medical fields. Currently, aspiration catheters are the golden standard, enabling removal by means of a suction force. By Sakes et al., an alternative mechanism is proposed, transporting tissue based on friction, inspired by the egg-laying structure of wasps. Challenges within these devices comprise clogging and damage prevention, achieving adequate
transportation rates, transportation of tissue with differing elasticity properties and satisfying the dimensional restrictions of Minimally Invasive Surgery (MIS). Due to the vital impact of MIS, a tissue extraction device overcoming the previously mentioned barriers is highly desirable. The goal of this research is stated as follows, ‘design of a continuous tissue transportation mechanism compatible for MIS in which the transportation velocity is independent of tissue elasticity within the young’s modulus range of 1-110 kPa’. The stated elasticity span resembles a large range of tissue that can be encountered during MIS, whilst aspiration catheters are assumed to be suitable for the removal of liquids. Tissue extraction and retrieval are not included within the scope.

To achieve the stated objective, novel ideas are generated from both a dynamic and nature-based perspective and assessed by means of rapid prototyping. Within the final prototype, a cylindrical conveyor belt is created, consisting of a thread wrapped along a tubular body. Due to friction between the thread and tissue, the latter is transported whenever continuously rotating the thread in the direction of removal. Experiments are performed with the proof of principle prototype to investigate the effects of different rotational velocities, instrument orientation, and tissue shape on the transportation velocity of tissue and the corresponding efficiency and reliability. Maximum mean mass transportation rates of 7.75∓0.48, 8.43∓1.50, and 8.90∓0.56 g/min are attained, as a result of transporting tissue phantoms with a young’s modulus of approximately 1-10, 55, and 100-110 kPa respectively. Whether statistically, variance in transportation rates between these categories appears is not determined, as equivalent power supply voltages did not result in identical rotational velocities due to varying thread tension. However, as the transportation velocities match rates of clinically available morcellator and perfect reliability is attained, the potency of the designed mechanism as an alternative for aspiration-based instruments is demonstrated.