Soft Robotics Technologies to Address Shortcomings in Today's Minimally Invasive Surgery: The STIFF-FLOP Approach

Most devices for single-site or natural orifice transluminal surgery are very application specific and, hence, capable of effectively carrying out specific surgical tasks only. However, most of these instruments are rigid, lack a sufficient number of degrees of freedom (DOFs), and/or are incapable of modifying their mechanical properties based on the tasks to be performed. The current philosophy in commercial instrument design is mainly focused on creating minimally invasive surgical systems using rigid tools equipped with dexterous tips. Only few research efforts are aimed at developing flexible surgical systems, with many DOFs or even continuum kinematics. The authors propose a radical change in surgical instrument design: away from rigid tools toward a new concept of soft and stiffness-controllable instruments. Inspired by biology, we envision creating such soft and stiffness-controllable medical devices using the octopus as a model. The octopus presents all the capabilities requested and can be viewed as a precious source of inspiration. Several soft technologies are suitable for meeting the aforementioned capabilities, and in this article a brief review of the most promising ones is presented. Then we illustrate how specific technologies can be applied in the design of a novel manipulator for flexible surgery by discussing its potential and by presenting feasibility tests of a prototype responding to this new design philosophy. Our aim is to investigate the feasibility of applying these technologies in the field of minimally invasive surgery and at the same time to stimulate the creativeness of others who could take the proposed concepts further to achieve novel solutions and generate specific application scenarios for the devised technologies.