Multidisciplinary Study of Soft Shape Morphing Systems

Abstract

Nature abounds with examples of shape morphing systems where an entity either gradually grows into a complex 3-D shape pattern or rapidly morphs into a new configuration. Inspired by the shape shifting capabilities of biological systems, in this work we study the response of natural and synthetic morphing systems through a few examples. These include the in vitro adaptive contraction of a cardiac muscle cell inside a constraining hydrogel, inflation of architectured rubber membranes, and a shape morphing soft robot.

Cardiac muscle cells (cardiomyocytes), have an intrinsic mechano-chemo-transduction (MCT) mechanism that enable them to automatically convert mechanical loads into biochemical signals to actively regulate their amplitude and speed of contraction. At the molecular level, this is attributed to the morphing of regulatory and motor proteins (actin and myosin filaments) to facilitate muscle contraction. The underlying MCT mechanisms, however, are unclear and currently under investigation. To help decipher these mechanisms, we develop a mathematical model, as a companion tool for the experimental in vitro Cell-in-Gel system of our collaborators, to analyze the time-dependent, 3-D strains and stresses within a cardiomyocyte contracting in a viscoelastic medium. The model utilizes the exact analytical solution of the viscoelastic Eshelby inclusion boundary value problem as an efficient computational tool to simulate the mechanical fields inside and outside the cardiomyocyte.

In a second study, we investigate the inflation of shape morphing synthetic soft composites with architectured geometry and material properties. Such shape morphing systems could have desirable applications in space deployable systems where there is a growing demand for energy-efficient lightweight and low-cost structures. These structures possess an exceptionally high mechanical packaging efficiency and very small stowage volume, which makes them attractive candidates for space applications including antenna reflectors, solar arrays, inflatable rovers, re-entry equipment, and human habitats. In particular, we explore several feasible 3-D shapes that can be achieved through the inflation of an initially flat rubber membrane with nonuniform geometrical and material properties. Our rubber-based prototypes provide a convenient basis for conceptual scientific and design explorations in shape morphing inflatable structures.

In a third study, we explore the idea of shape shifting in the design and fabrication of synthetic soft robots with active components. Motivated by the swimming mechanisms of jellyfish, we develop a novel concept for a soft biomimetic underwater robot that imitates the shape and kinematics of the typical animal. The robot swims by harnessing the buckling instability of its soft body to quickly morph from an initially flat into a deformed dome-shaped configuration, which generates the required thrust for underwater locomotion. Joule heating of an embedded pre-stretched shape memory alloy spring, serves as an artificial muscle for the robot to make this shape morphing possible. The proposed synthetic shape morphing system introduces a new idea in design of simple, compact, and biomimetic robots with smart artificial muscles.