Finite element analysis and design optimization of a pneumatically actuating silicone module for robotic surgery applications

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 optimization 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 investigation 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.