Coupled transport/hyperelastic model for nastic materials

Abstract

Nastic materials are high energy density active materials that mimic processes used in the plant kingdom to produce large deformations through the conversion of chemical energy. These materials utilize the controlled transport of charge and fluid across a selectively-permeable membrane to achieve bulk deformation in a process referred to in the plant kingdom as nastic movements. The nastic material being developed consists of synthetic membranes containing biological ion pumps, ion channels, and ion exchangers surrounding fluid-filled cavities embedded within a polymer matrix. In this paper the formulation of a biological transport model and its coupling with a hyperelastic finite element model of the polymer matrix is discussed. The transport model includes contributions from ion pumps, ion exchangers, and solvent flux. This work will form the basis for a feedback loop in material synthesis efforts. The goal of these studies is to determine the relative importance of the various parameters associated with both the polymer matrix and the biological transport components.

Two-Scale Model for Mechanical Analysis of Nastic Materials and Structures

“…Generally, the system of nastic materials may consist of a BLM containing ion pumps, ion exchangers, ion cotransporters, and ion channels, as depicted in Figure 2. Homison and Weiland (2006) proposed a general model which can be used to predict the system response through the simultaneous solution of the governing equations for these transporters. In practical application, the explicit expression of the model needs the support of experimental data.…”

“…The fundamental model used in the current research can be found in the work given by Homison and Weiland (2006). (Sundaresan and Leo, 2006a).…”

“…The ion transport model is composed of a set of ordinary differential equations (ODEs) to describe the sucrose concentration, the H þ concentration, the solvent flux, and the membrane potential (Homison and Weiland, 2006;Sundaresan et al, 2007a). It is both highly coupled and highly non-linear, resulting in a stiff system.…”

“…Figure2. A BLM that contains ion pumps, ion exchangers, ion cotransporters and ion channels(Homison and Weiland, 2006).…”

Applications of Biologically Inspired Membranes

“…The need to understand the basic mechanisms of nastic actuation has previously been recognized (Homison and Weiland 2005). The modeling construct employed utilized the equations 2-7 through 2-20 from the previous discussion.…”