Comparing the efficacy of fiber reinforced actuators to replicate inhalation vs. exhalation

Abstract

Fluid Powered Elastomeric Actuators are a class of soft robotic actuators of particular interest for biomimetic designs because researchers can replicate certain motions by tailoring the mechanical properties of the actuator through the use of different fibers and materials. [1] Hu et al. showed that pre-curved fiber-reinforced actuators could be used to mimic more complex geometries and motions. [2] Optimization techniques for determining optimal fabrication parameters for such actuators were developed by Hu et al. from a modified version of Connolly et al.'s technique to generate fiber reinforced actuators optimized to follow a given input trajectory. [2, 1] This modified optimization technique was adapted for the specific application of creating biomimetic actuators to follow the motion of the human diaphragm. [2] The technology relies on extracting motion trajectories from clinical imaging data.

This work analyzes and optimizes Hu et al.'s assumptions in visually choosing a planar location for the diaphragm anchoring point into the ribs based off of pixel locations within a Magnetic Resonance Imaging (MRI) scan in order to choose actuators to fabricate for further testing. We conducted a sensitivity analysis on the effect of varying this assumed anchoring point over a span of 3.1cm. We found no statistically significant differences in the mean error of the fabrication datasets corresponding to three selected anchoring location values. We determined that an assumed offset of 130 pixels (28.9 cm from the top of the image) provided an optimal compromise for minimizing error while still being a biologically realistic assumption. This fabrication dataset was thus selected for further development. Computer-aided design (CAD) models of the actuators were developed and used in creating molds. The actuators were then manufactured using the developed molds.

Due to the complex nature of studying generated forces on a curved actuator, a modular test fixture compatible with minor modifications to the molds was developed for an Instron test setup. The test fixture was developed and prepared for testing. The future results of this testing will provide further insights into the feasibility of developing a soft robotic biomimetic diaphragm.