Shape Memory Investigation of α-Keratin Fibers as Multi-Coupled Stimuli of Responsive Smart Materials

Abstract

Like the water responsive shape memory (SM) effect of β-keratin bird feathers, α-keratin hairs either existing broadly in nature are found responsive to many types of coupled stimuli in SM behaviors. In this article, α-keratin hairs were investigated for the combined stimuli of thermo-solvent, solvent-solvent, and UV (radiation)-reductant sensitive SM abilities. The related netpoints and switches from the hair molecular networks were identified. The experimental results showed that α-keratin hairs manifested a higher ability of shape fixation under thermal stimulus followed with the stimuli of solvent and UV-radiation. Shape recovery from the hair with a temporarily fixed shape showed a higher recovery ability using solvent than the stimuli of heat and UV-radiation. The effects of coupled stimuli on hair's shape fixation and recovery and on variations of the crystal, disulfide, and hydrogen bonds were studied systematically. A structural network model was thereafter proposed to interpret the multi-coupled stimuli sensitive SM of α-keratin hair. This original study is expected to provide inspiration for exploring other natural fibers to reveal related smart functions and for making more types of remarkable adapted synthetic materials.

Wool Can Be Cool: Water‐Actuating Woolen Knitwear for Both Hot and Cold

“…Recently, researchers investigated the effect of water on the shape memory of animal hairs, such as that of sheep, goats, and camels, and on the variations of the crystal, disulfide, and hydrogen bonds in the macromolecules and reported that the wool fibers exhibit water-responsive SME. [17] Clothing materials generally have a hierarchical structure because of the twisting of fibers into yarns and the knitting or weaving of yarns into fabrics. Besides wool fiber, the water responsiveness of a hydrogel-coated wool yarn was investigated; [18] however, the materials exhibited a poor response time because of slow water diffusion.…”

Controllable Crimpness of Animal Hairs via Water-Stimulated Shape Fixation for Regulation of Thermal Insulation

“…dry) can be converted to each other, judging from their IR characteristic peaks in shifting of wavenumber and variation of peak intensity ratio. This indicates the switch role of hydrogen bond for controlling the hair crimping shape [32].…”

Polyvinyl alcohol/chitosan/carbon nanotubes electroactive shape memory nanocomposite hydrogels

“…38 As shown in Figure 3(b), the intrinsic black color of the CNT would darken the color of the PVA/CNT hydrogel when comparing with the neat PVA matrix in relevant FE-SEM micrographs. 39 The freezing-thawing process cycle is an effective way to build a porous hydrogel structure. 40,41 Theoretically, as the number of freezing-thawing cycles increases, the density of hydrogen bonds increases, due to the formation of the crystalline phase.…”

“…40,41 Theoretically, as the number of freezing-thawing cycles increases, the density of hydrogen bonds increases, due to the formation of the crystalline phase. 39,42 The wall thickness of the pores in hydrogels was measured with Image J analyzer for 10 random points. The average pore wall thickness was obtained 1.012 μm, and the interconnections are established.…”