Shape Memory Effect of Keratin Fibers

Abstract

In the past thousands of years, keratin fibers were only considered as textile fibers for excellent fiber performances, such as high strength, acceptable elasticity, good thermal insulation, etc. Only recently, some indications have been obtained that keratin fiber may be a smart natural material that may subvert people's perception of this matter. The smart attribute displays shape memory effects (SMEs) responsive to many types of stimuli including water, heat, coupled water-heat, redox agents, UV light, etc. These smart functions of keratin fibers are found to be the result of three structural components: crystals, hydrogen bonds (HBs), and disulfide bonds (DBs) among intra-and inter-keratin macromolecules. In this chapter, keratin fibers (such as camel hair) were employed for investigating their SMEs under five types of stimuli, in which the HBs, DBs, and crystals were characterized separately, as well as the fiber shape fixation and recovery ratios, respectively. The whole test results indicated that keratin hair fiber is a type of shape memory polymer and the related SME depends on the contents of the HBs, DBs, and crystalline phase inside the hair.

Bioperspectives for Shape-Memory Polymers as Shape Programmable, Active Materials

“…Interestingly, keratin fibers have been reported to respond to various environmental stimuli, such as water, heat, coupled heat–water, UV radiation, and redox agents. This ability offers a high potential for developing an “all-in-one” SMP with multistimuli responsiveness …”

“…This ability offers a high potential for developing an "all-in-one" SMP with multistimuli responsiveness. 70 A fascinating demonstration of smart polymers in nature is the dragline silk, which shows the most remarkable combination of strength and extensibility, outperforming the best synthetic fibers. 71 Two interesting features related to shape-memory can be highlighted in this material.…”