Work and Activation in a Nematic Polymer Network Ribbon

TL;DR

This paper investigates how nematic polymer network ribbons can perform work when activated under mechanical loads, analyzing their deformation, energy capacity, and efficiency through numerical experiments and exploring ways to optimize their performance.

Contribution

It introduces a numerical framework to study work-capacity and efficiency of activated nematic ribbons, and proposes strategies to enhance their activation performance.

Findings

Ribbons can perform work against external loads when activated.

Deformation and work capacity depend on ribbon thickness and nematic texture.

Efficiency of activation can be improved by adjusting load and nematic texture.

Abstract

We study spontaneous deformations of a ribbon made of nematic polymer networks and activated under the action of a mechanical load. We show that when such ribbons are activated appropriately, the deformations produced can pull back and perform work against the externally applied load. We perform two numerical experiments to demonstrate this effect: (1) the \emph{pulling} experiment, where the ribbon is pulled longitudinally by a point force, and (2) the \emph{bending} experiment, where the ribbon is bent out of plane by a terminally applied point force. We quantify the capacity of the ribbon to work against external loads, and compute its dependence on both the ribbon thickness and the imprinted nematic texture (that is, the distribution of the nematic directors across the ribbon's length). Finally, we compute the efficiency of the activation process. Building on the outcomes of our numerical explorations, we formulate two educated conjectures on how the activation efficiency can in general be improved by acting on both the applied load and the imprinted nematic texture.