Smart helical structures inspired by the pellicle of euglenids

TL;DR

This paper introduces a bio-inspired reconfigurable cylindrical structure that changes shape through the sliding of strips, mimicking euglenid cell walls, and analyzes its complex mechanics and controllability.

Contribution

It presents a novel, simple cylindrical structure inspired by euglenids that can reconfigure shape via strip sliding and provides a detailed mechanical analysis.

Findings

The structure can change from a tall cylinder to a shorter, wider one.

Mechanical behavior is complex and tunable by curvature or twist.

External forces required for shape change are characterized.

Abstract

This paper deals with a concept for a reconfigurable structure bio-inspired by the cell wall architecture of euglenids, a family of unicellular protists, and based on the relative sliding of adjacent strips. Uniform sliding turns a cylinder resulting from the assembly of straight and parallel strips into a cylinder of smaller height and larger radius, in which the strips are deformed into a family of parallel helices. We examine the mechanics of this cylindrical assembly, in which the interlocking strips are allowed to slide freely at their junctions, and compute the external forces (axial force and axial torque at the two ends, or pressure on the lateral surface) necessary to drive and control the shape changes of the composite structure. Despite the simplicity of the structure, we find a remarkably complex mechanical behaviour that can be tuned by the spontaneous curvature or twist of the strips.