Modeling bistable behaviors in morphing structures through finite element simulations

Fast nastic motion of plants and bioinspired structures

The capability to sense and respond to external mechanical stimuli at various timescales is essential to many physiological aspects in plants, including self-protection, intake of nutrients and reproduction. Remarkably, some plants have evolved the ability to react to mechanical stimuli within a few seconds despite a lack of muscles and nerves. The fast movements of plants in response to mechanical stimuli have long captured the curiosity of scientists and engineers, but the mechanisms behind these rapid thigmonastic movements are still not understood completely. In this article, we provide an overview of such thigmonastic movements in several representative plants, including Dionaea, Utricularia, Aldrovanda, Drosera and Mimosa. In addition, we review a series of studies that present biomimetic structures inspired by fast-moving plants. We hope that this article will shed light on the current status of research on the fast movements of plants and bioinspired structures and also promote interdisciplinary studies on both the fundamental mechanisms of plants' fast movements and biomimetic structures for engineering applications, such as artificial muscles, multi-stable structures and bioinspired robots.

Geometric nonlinearity and mechanical anisotropy in strained helical nanoribbons

Fabrication and synthesis of helical nanoribbons have received increasing attention because of the broad applications of helical nanostructures in nano-elecromechanical/micro-electromechanical systems (NEMS/MEMS), sensors, active materials, drug delivery, etc. In this paper, I study the mechanical principles used in designing strained helical nanoribbons, and propose the use of a full three-dimensional finite element method to simulate the coexistence of both left- and right-handed segments in the same strained nanoribbon. This work can both help understand the large deformation behaviours of such nanostructures and assist in the design of helical nanostructures for engineering applications.

FINITE ELEMENT SIMULATIONS ON MECHANICAL SELF-ASSEMBLY OF BIOMIMETIC HELICAL STRUCTURES

Helices are ubiquitous building blocks in natural systems, and have since become major sources of inspiration for engineering design of helical devices with a range of applications in sensors, transducers, transistors and micro-robotics devices. In this work, we illustrate the mechanical self-assembly principle in spontaneous helical structures, and perform finite element simulations to model such large deformation of thin structures in three dimensions. Our work can facilitate designs of tunable helical structures at both macroscopic and microscopic scales with desirable geometric parameters for engineering applications such as in nanoelectromechanical systems (NEMS), drug delivery, sensors, acturators, optoelectronics and microbotics.