Programmable 3D Self‐Folding Structures with Strain Engineering

Abstract

Morphogenesis, commonly found in leaves, [1-3] flowers, [4,5] cones, [6] seed pods [7,8] and other biological systems, is typically driven by differential growth, swelling, or shrinkage [6,9,10] that occurs within multilayered components of species. For example, the opening and closing of pine cones are attributed to the tissue's self-bending, which undergoes three states of humidity-driven deformation. [6] As these morphological changes in nature result from the variation of the surrounding environment, it is desirable to mimic these natural examples to fabricate multilayered structures that can spontaneously respond to various external stimuli, such as temperature, pH, biochemical enzymes, magnetic fields, and solvent composition, [11-14] which can find a variety of applications, such as semiconductor nanotubes, [15-18] soft robotics, [19-22] snapping surface, [23] and micro/ nanoelectromechanical systems. [24-26] For a multilayer structure, the misfit strain across layers can lead to some interesting phenomena such as multistability, where more than one stable state exists with the same boundary conditions or control parameters of the system. One specific case is called neutral stability, in which the system can stay stable at each point in a continuous path of shape change. In such a case, the system is said to have zero stiffness because the potential energy of the system keeps unchanged during the shape change and theoretically no external force is needed. Various cases that incorporate neutrally stable (zero stiffness) systems have been studied. Guest et al. [27,28] discovered neutral stability of a heated copper beryllium strip, the shape of which depended on the residual stresses. The strip has zero stiffness for finite deformation along

Etching-Free Ultrafast Fabrication of Self-Rolled Metallic Nanosheets with Controllable Twisting

“…Now the question is why does the same nanosheet sometimes rolls into a scroll while sometimes into a twisted helix? This phenomenon is intriguing and worthy of a quantitative investigation, which, however, has not been fully understood yet according to ref . As illustrated in Figure a and also shown in Figure b (or Movie S1), the nanosheet of width S (equal to the channel crack spacing) and length L peels off from its long edge from the hydrogel surface after immersion in water and rolls very rapidly into a long scroll afterward.…”

Materials Chemistry of Neural Interface Technologies and Recent Advances in Three-Dimensional Systems

“…Three-dimensional assembly induced by thin-film residual stresses uses mismatches in mechanical strains of stacked thin films (e.g., Si x N y , ZnO, TiO 2 , Al 2 O 3 , GaAs, Cr, vanadium dioxide (VO 2 ), germanium (Ge)). ,, Such multilayers can be prepared on substrates with sacrificial layers that, upon their removal, lead to self-rolling to form tubular, scroll-like, or polyhedral geometries. This process can transform microfabricated 2D electronic structures into 3D geometries for various applications (e.g., energy, , optoelectronics, , electronics, ,− biological studies − ).…”

Patterned Aluminum/Polydimethylsiloxane-Laminated Film for a Solvent-Driven Soft Actuator with Programmable and Multistable Shape Morphing

“…Intelligent actuators with bistable/multistable structures have been widely investigated because they can be used in daily production and life, such as configuration-deformable robots, − flexible electronics, functional medical devices, − and so forth. Under external stimulations, the actuators with bistable/multistable structures only need to overcome the critical state without continuous energy input to realize the mutual conversion between different steady-state configurations. ,− An emerging strategy for intelligent actuators to imitate natural motions is using a well-designed structure combined with active materials that can be driven by humidity, , light, electricity, , solvent, and so forth. For example, Wu et al combined the intelligent deformation of hydrogels with the art of kirigami to achieve multistable and controllable three-dimensional (3D) deformation.…”