ORIGINAL ARTICLE Finite Element Analysis and Design Optimization of a Pneumatically Actuating Silicone Module for Robotic Surgery Applications Yahya Elsayed, 1 Augusto Vincensi, 1 Constantina Lekakou, 1 Tao Geng, 2 C. M. Saaj, 2 Tommaso Ranzani, 3 Matteo Cianchetti, 3 and Arianna Menciassi 3 Abstract The design of a pneumatically actuated silicone module, resembling soft tissue, with three pneumatic chambers is considered and optimized in this study with the aim of using it in a soft robot arm for robotic surgery applications. Three types of silicone materials, Ecoflex 0030 and 0050 and Dragonskin 0030, have been investigated, and a constitutive model has been derived for each of them. Design optimization of the silicone module was based on finite element analysis (FEA) that was validated against experimental data of one-degree bending under one-channel actuation. This was followed by FEA parametric studies for module design opti- mization to minimize the ballooning effect in one-degree bending as well as reduce the actuation pressure. Modules made from Ecoflex 0030 and Ecoflex 0050 exhibited the same bending shape in FEA, but about three times higher actuation pressure was required for the harder Ecoflex 0050. Design parameters under investi- gation in the parametric FEA studies included the shape of the pneumatic channel cross section, the ratio of channel length to module length, the distance of channel from the module wall, and the ratio of channel to module cross-sectional area. After FEA design optimization yielded least ballooning for pneumatic chambers of semicircular cross section, an internal dragonskin structure was added internally below the module surface to enable and guide the bending under one-channel pneumatic actuation and further contain the ballooning effect: the benefits of this design were successfully verified under both FEA and experimental analysis. Introduction S oft robotics is a new field of robotic engineering 1,2 that furthers the design of flexible robots consisting of an actuating chain of multiple stiff nodes. 3 Soft robots have the potential to be used in surgical applications, 2,4,5 as the fluidlike flexibility and soft materials of these robots offer them the ad- vantage of being able to navigate through narrow passages be- tween organs with minimum harm to the organ soft tissue, covering outer membrane and vascular blood supply. Elasto- mer-based robotics have shown great promise in developing robots that mimic the muscular hydrostatic systems found in nature 6,7 such as the octopus tentacles, 8,9 caterpillars, 10 jelly fish and asteroids, 11 and elephant trunk. 12,13 Elastomers are of particular interest in the field of lapa- roscopic surgery, as they require low actuation stress or pressure for their deformation, are reliable and low-cost materials, and hence can be used in disposable surgical ma- nipulators 14 eliminating the need of maintenance and steril- ization of current laparoscopic tools. Furthermore, the use of silicone in the manufacture of implants already used in vivo in medicine makes silicone a good candidate for the manufacture of soft medical robot arms, as it will reduce the number of required biocompatibility pretests in vivo. Although several elementary designs of soft robotics actuators have been pro- posed, such as the McKibben’s actuator 15 and the triangular configuration of three or a configuration of more such parallel slimline actuators, 16–18 the feasibility of such designs in the robotic field has been studied traditionally in terms of pure geometrical relationships 16 and kinematic algorithms 18,19 with linear dynamics, 20 without taking into account 16 fluid com- pressibility, which has significant consequences in pneumatic Departments of 1 Mechanical Engineering Sciences and 2 Electronic Engineering, University of Surrey, Guildford, United Kingdom. 3 The BioRobotics Institute, Scuola Superiore Sant’Anna, Pontedera, Italy. SOFT ROBOTICS Volume 2, Number 00, 2014 ª Mary Ann Liebert, Inc. DOI: 10.1089/soro.2014.0016 1