The Design of a Flexible Friction-Based Transport Mechanism

Abstract

Background: During minimally invasive procedures, tissue damage can be limited by using smaller incisions and by using naturally occurring body orifices to reach the intervention site. During these procedures the need can arise to transport tissue. Think of a biopsy or the removal of polyps. This calls for a tool that can transport tissue and is also flexible such that the tool can be introduced via natural occurring body orifices. Currently either suction based techniques or forceps are used for these procedures. However, both show suboptimal behaviour. Friction-based transport, which is based on the egg laying principle of parasitoid wasps, is not prone to these sub-optimal behaviour modes but is not yet used in flexible systems. Methods: A mechanical analysis was conducted to generate an overview of the challenges that arise in flexible friction-based transport. This resulted in a list of requirements based on which possible concept solutions were analysed. Themost promising design for a flexible friction-based transport mechanism has a flexible shaft that consists of a number of wire ropes in combination with ring magnets. This shaft was manufactured and validated by transporting gelatin tissue phantoms with different material properties with the shaft in straight and in a curved position. After validation of the flexible shaft, an ergonomic handle was designed resulting in the final prototype. This final prototype was also tested by transporting gelatin tissue phantoms. Results: From the results can be concluded that the flexible shaft is able to transport tissue phantoms with different material properties while in straight and curved (R=59mm) position. The final prototype is showed that continuous transport was possible from the tip of the flexible shaft to the end of the handle with the shaft in straight and in curved position. The position of the shaft (straight vs. curved) did not result in a significant difference in the transport rate. Discussion and Conclusion: It can be concluded that friction-based transport is possible in a flexible tool. The mean transport rate in straight position ( 2.3 § 0.29 mm/cycle) is comparable to the transport rate of a rigid friction-based transport mechanism with comparable dimensions. This new flexible friction-based transport mechanism shows great potential to be beneficial for a number of medical procedures.