Chitosan/Polyvinyl Alcohol-Based Direction-Controlled Photo-Humidity Dual Responsive Membrane

Abstract

Photoresponsive materials based on azobenzene (Azo) and its derivatives have attracted wide attention because the cis-trans isomerization of Azo under illumination often leads to changes in shape, color, size, polarity, and so on; it has great application potential in soft robot, actuator, sensor, and other fields. In this paper, by using evaporation-induced self-assembly method, taking advantage of the hydrogen bonding among chitosan (CS), polyvinyl alcohol (PVA) and Azo, and by polishing and grinding the surface of the adopted silicon film mold in advance to form grooves, the Azo/CS/PVA film with a certain degree of oriented aggregation convex surface was prepared. The film has good deformation characteristics of dual response of light and humidity. Also, it has excellent light response direction controllability under UV light, sunlight, and LED illumination. By studying the structure, morphology, photo-stimulus response behavior, humidity-photo response behavior, and mechanical properties of the films, it is found that when the Azo content reaches 10% wt, the response speed is the fastest and the response deformation is the largest. The result shows that under the irradiation of summer sunlight (sunny day), the film can reach 144°directional bending within 55 s. Moreover, the film has excellent humidity response performance, which can absorb sweat in the fingertips, deform quickly, and recover quickly after leaving fingers. The film with an Azo content of 10% wt has a fast humidity response speed, and the maximum bending angle is 140°.The designed simple sunlight response driver can lift a heavy object five times heavier than itself to a certain height, and realize the effective conversion from light energy to mechanical energy. This work effectively broadens the application range of bio-based environmentally friendly materials and has guiding significance for the development and design of multi-stimulus response intelligent materials. The light response directional control method is simple and practical. It is of great significance for the effective utilization of solar energy.

Fabrication of a sustainable superhydrophobic surface of Ag-NPs@SA on copper alloy for corrosion resistance, photocatalysis, and simulated distribution of Ag atoms

“…14 Surface wettability is influenced by key parameters of surface science, which are surface energy and surface roughness. 15,16 The fabrication of SHSs involves various artificial techniques such as the template method, sol-gel, lithography, electrospinning, vapor deposition, simple etching, layer assembling, and a dip-coating method. Although these methods produce SHSs successfully, numerous problems arise from the messy and tedious procedures of formation, [17][18][19][20][21][22][23] and these issues prevent the adoption of these materials for large-scale applications.…”

Heterogeneity Regulation of Bilayer Polysaccharide Hydrogels for Integrating pH- and Humidity-Responsive Actuators and Sensors

“…Actuators are devices that are able to change the shape reversibly driven by external stimuli, , including light, − heat, − electricity, , humidity, − ions (such as salts , and pH , ), etc., or to release stored energy by mechanical deformation to realize programmed shape shifting or complete asynchronous/synchronous actions via the reconfiguration of geometry-determining skeletons and/or the programming of actuation-controlling units. − With the rapid development of actuators, the concept of ‘smaller, lighter, and softer’ becomes more and more important. As compared to the traditional actuators composed of hard and heavy substrates that are commonly driven by pneumatic, hydraulic, and electromagnetic technologies, soft actuators composed of compliant substrates allow for increased flexibility and adaptability for accomplishing sophisticated tasks with improved safety and device fabricating capability and as a result have attracted increasing interest in recent years.…”

“…Actuators are devices that are able to change the shape reversibly driven by external stimuli, 1,2 including light, 2−4 heat, 5−7 electricity, 8,9 humidity, 4−6 ions (such as salts 4,10 and pH 11,12 ), etc., or to release stored energy by mechanical deformation to realize programmed shape shifting or complete asynchronous/synchronous actions via the reconfiguration of geometry-determining skeletons and/or the programming of actuation-controlling units. 13−15 With the rapid development of actuators, the concept of 'smaller, lighter, and softer' becomes more and more important.…”

Water-Content-Dependent Switching of the Bending Behavior of Photoresponsive Hydrogels Composed of Hydrophilic Acrylamide-Based Main Chains and Hydrophobic Azobenzene

“…In addition to this simple deformation, functional materials can also respond to multiple stimuli, such as light and moisture. In most cases, multiple stimuli independently or synergistically affect deformation behaviors [ 44 , 45 , 46 , 47 , 48 , 49 ]. However, a photoresponsive mechanism involving the switching of behavior in the presence of another stimulus (moisture) has been rarely reported.…”