Mechanics of tunable helices and geometric frustration in biomimetic seashells

¹ College of Materials Science and Engineering, Fuzhou University - Fujian 350118 China
² Department of Mathematics and Physics, Fujian University of Technology - Fujian 350118 China
³ Department of Biomedical Engineering, Washington University in St. Louis - St. Louis, MO 63130, USA
⁴ College of Materials Science and Engineering, Fujian University of Technology - Fujian 350118 China

^(b) guoqh@fjut.edu.cn
^(c) chen.z@seas.wustl.edu

Received: 17 October 2013
Accepted: 13 March 2014

Abstract

Helical structures are ubiquitous in nature and engineering, ranging from DNA molecules to plant tendrils, from sea snail shells to nanoribbons. While the helical shapes in natural and engineered systems often exhibit nearly uniform radius and pitch, helical shell structures with changing radius and pitch, such as seashells and some plant tendrils, add to the variety of this family of aesthetic beauty. Here we develop a comprehensive theoretical framework for tunable helical morphologies, and report the first biomimetic seashell-like structure resulting from mechanics of geometric frustration. In previous studies, the total potential energy is everywhere minimized when the system achieves equilibrium. In this work, however, the local energy minimization cannot be realized because of the geometric incompatibility, and hence the whole system deforms into a shape with a global energy minimum whereby the energy in each segment may not necessarily be locally optimized. This novel approach can be applied to develop materials and devices of tunable geometries with a range of applications in nano/biotechnology.