Chinese Calligraphy Inspired Design of Humidity/Light Dual Responsive Magic Paper

Abstract

Paper flowers are frequently, for example as indoor decorations and in wedding bouquets. But these traditional paper flowers can only maintain static conditions, greatly affecting their sensory effects, vividness, and appreciation. The design of novel paper flowers with dynamic shape deformation could effectively broaden the application of paper flowers. Here, inspired by Chinese calligraphy, a novel polyvinyl butyral (PVB)/carbon/cellulose composite (PCC) magic paper with a sandwiched structure is prepared. The hygroscopicity difference between hydrophobic PVB and hydrophilic cellulose layer endows the PCC paper with humidity responsiveness, and the maximum bending angle is up to 91.4° upon exposure to humidity environment. Carbon in the interlayer with strong light–heat conversion capacity could further accelerate water desorption and deformation speed, resulting in highly sensitive light responsiveness. The recovery time of PCC paper from maximum bending to the original flat state is shorter than 1 s. The PCC paper has good flexibility and processability, which can be cut and assembled into flowers with different shapes, and these unique magic flowers could freely bloom and furl upon external stimulus. All these results indicate that PCC paper has great potential in the production of magic props, artworks, and intelligent household decorations fields.

Robust and Highly Sensitive Cellulose Nanofiber-Based Humidity Actuators

“…A new generation of smart responsive actuators that are capable of converting various environmental energies such as light, heat, temperature, electricity, magnetism, and humidity into reversible shape transformation has been greatly developed for cutting-edge applications in soft robotics, wearables electronics, bionics systems, smart switches, and so on. − Among them, actuators driven by humidity have captured substantial research interest owing to the environmental eco-friendliness and ubiquity of water in nature. , Design principles of the humidity actuation are usually established on the asymmetric deformation induced by differential swelling/de-swelling of materials with different hydrophilic capacities responding to humidity change or the same material responding to gradient humidity stimuli. Currently, the humidity-responsive actuators commonly are constructed by combining the active material layer that is sensitive to humidity with a passive material layer that is inert to humidity into the bilayer/multilayer structure. − However, there remain usually some limitations such as the small bending amplitude, low sensitivity, the poor interfacial adhesion between layers, weak mechanical stability, and a complicated fabrication process, thus impeding their application scopes. − …”

Chemical Gradients in Polymer-Modified Paper Sheets—Towards Single-Layer Biomimetic Soft Robots

“…These first demonstrations show that it is possible to create humidity-responsive actuators out of a single sheet of paper, without the need to incorporate multiple layers of different materials that were necessary for stimuli-responsive actuation in previous studies [ 13 , 52 ]. We see clear advantages in such one-sheet functional bi- or even multi-“layers”: (1) The risk of delamination, which is otherwise a threat for layered actuators during deformation cycles (cf.…”

Cellulose‐Based Soft Actuators

“…Numerous studies have been performed toward combining different mechanisms, pursuing advanced active materials, and constructing multistimuli-responsive actuators with superior actuation performance. [61,71,81,83,84,110] For instance, Wang and coworkers designed a new class of self-healing actuators based on light thermal and magnetic actuation by embedding 3D interconnected Fe 3 O 4 @CNC nanohybrids into metal-ligand coordination-crosslinked supramolecular elastomers (Figure 9a). [110] The obtained actuator exhibited superhigh NIR light and magnetic sensitivity (near-infrared light of 0.44 s and magnetic field of 0.36 s).…”

“…[53] A smart cellulose derived actuator effectively generates forces or motions in dependence of an external stimulus. Depending on the stimulation and application scenarios for actuation, the development of cellulose derived actuators can be divided into two main categories: 1) Influence of an external nonuniform stimuli source such as moisture, [32,54,55] electric, [24,[56][57][58][59] or magnetic field [28,29,60] on isotropic structures; 2) fabrication of internal anisotropic structures reacting to an external uniform stimuli source (bilayer structure, [61][62][63][64][65][66][67] Janus structures, [68] gradient structures, [69] patterned structures, [70,71] oriented structures [72][73][74] ), other anisotropic structures [75,76] ) (Figure 1).…”