Finite Element Analysis and Design Optimization of a Pneumatically Actuating Silicone Module for Robotic Surgery Applications

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 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

Design and Analysis of a Soft Pneumatic Actuator with Origami Shell Reinforcement

“…[5][6][7][8] A commonly used actuator in soft robotics is the soft pneumatic actuator (SPA), which is actuated by the use of compressed air. [9][10][11][12][13][14][15][16][17][18] In particular, bending SPAs derive their deflection from a straight to bent configuration due to the air pressure built within their chambers. This bending motion is suitable for a diverse set of applications such as gripping and manipulating fragile objects, 9,17 adaptable locomotion on unstructured terrains and autonomous navigation, 19,20 operating surgical tools, 21 and biomedical rehabilitation.…”

Skins and Sleeves for Soft Robotics: Inspiration from Nature and Architecture

“…However, such braids are rather rough running 8 the risk of causing erythema, tissue tears and bleeding [17] in abdominal robotic surgery. Finite element analysis (FEA) of the one-chamber actuation was carried out for the combined silicone module-crimped braided sleeve using hyperelastic constitutive models [19] for both silicone and crimped braid. that it is relatively soft weave, would not cause any injury to tissues and organs, is biocompatible and well tested for medical applications.…”

“…The shape of the semicircular cross-section was selected as it was concluded from FEA studies [19] that it minimized ballooning upon one-chamber actuation, compared to other shapes of the pneumatic chamber crosssection such as circular cross-section. A mold was used with the appropriate dimensions and inserts for the channels.…”

Rehabilitative Soft Exoskeleton for Rodents

“…Soft actuators are designed to interact with unstructured environments [31], [32], [33]. They are highly compliant and can produce high power-to-weight ratios (over 10 N with a 100 g actuator) [34].…”

“…Polymer-based SPAs with embedded air chambers show innately low passive stiffness (∼ 200 N/m) number, making them advantageous in tasks involving physical interaction with delicate body parts where the impedance of the machine, either passively or actively modulated, is required to be sufficiently low at times. Their high customizability and ease of fabrication [31], [32], [33], [34] is exploited thoroughly to optimize the geometries of the actuators to match the requirements for foot loading capacity, gait pattern and speed of stimulation. This can be achieved by varying the parameters shown in Figure 2a.…”