Chapter 6
Cocoon Silk: From Mesoscopic Materials
Design to Engineering Principles
and Applications
Wu Qiu and Xiang-Yang Liu
Abstract In this chapter, we present a comprehensive review on five levels of hierarchical structures of silk fibroin (SF) materials in correlation with macroscopic
properties/performance such as the toughness, strain-stiffening, etc. It follows that
the crystalline binding force turns out to be very crucial in the stabilization of
the mesoscopic hierarchical structures of silk materials. In addition, β-crystallites,
β-crystallite networks (nanofbrils) and the interactions between helical nanofbrils
within nanofibril networks are determined to be the most essential meso structures,
which greatly determine the macroscopic performance of various forms of silk materials. In this context, the characteristic structural factors such as the orientation, size,
and density of β-crystallites are very relevant. It reveals that the formation of these
structural elements is mainly controlled by the continuous intermolecular nucleation
of β-crystallites. Consequently, the rational design and reconstruction of silk materials can be implemented by controlling the molecular nucleation via proper seeding
(i.e., with carbon nanotubes). Moreover, by adding functional seeds, i.e., carbon
nontubes, one can reconstruct the mesoscopic networks of SF materials, which can
endow silk materials with new performance, i.e.,. electrical conductivity. In general,
the knowledge of the correlation between hierarchical structures and performance
provides an understanding of the structural reasons behind the fascinating behaviors
of silk materials. In this chapter, we also provide a summary on the state-of-art technologies in characterization of the structures of various levels of SF materials. The
principles of SF nucleation and the application to reconstruct the meso structures of
SF materials are also presented, together and the methods of investigation.
Keywords Hierarchical structure · Mesoscopic engineering · Functionalization ·
Silk fibroin materials · Nucleation model
W. Qiu
Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542,
Singapore
X.-Y. Liu (B)
Research Institution for Biomimetics and Soft Matter, Xiamen University, Lingfeng Building,
Xiamen 31005, China
e-mail: liuxy@xmu.edu.cn
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
X.-Y. Liu (ed.), Frontiers and Progress of Current Soft Matter Research,
Soft and Biological Matter, https://doi.org/10.1007/978-981-15-9297-3_6
241
Cocoon Silk: From Mesoscopic Materials
Design to Engineering Principles
and Applications
Wu Qiu and Xiang-Yang Liu
Abstract In this chapter, we present a comprehensive review on five levels of hierarchical structures of silk fibroin (SF) materials in correlation with macroscopic
properties/performance such as the toughness, strain-stiffening, etc. It follows that
the crystalline binding force turns out to be very crucial in the stabilization of
the mesoscopic hierarchical structures of silk materials. In addition, β-crystallites,
β-crystallite networks (nanofbrils) and the interactions between helical nanofbrils
within nanofibril networks are determined to be the most essential meso structures,
which greatly determine the macroscopic performance of various forms of silk materials. In this context, the characteristic structural factors such as the orientation, size,
and density of β-crystallites are very relevant. It reveals that the formation of these
structural elements is mainly controlled by the continuous intermolecular nucleation
of β-crystallites. Consequently, the rational design and reconstruction of silk materials can be implemented by controlling the molecular nucleation via proper seeding
(i.e., with carbon nanotubes). Moreover, by adding functional seeds, i.e., carbon
nontubes, one can reconstruct the mesoscopic networks of SF materials, which can
endow silk materials with new performance, i.e.,. electrical conductivity. In general,
the knowledge of the correlation between hierarchical structures and performance
provides an understanding of the structural reasons behind the fascinating behaviors
of silk materials. In this chapter, we also provide a summary on the state-of-art technologies in characterization of the structures of various levels of SF materials. The
principles of SF nucleation and the application to reconstruct the meso structures of
SF materials are also presented, together and the methods of investigation.
Keywords Hierarchical structure · Mesoscopic engineering · Functionalization ·
Silk fibroin materials · Nucleation model
W. Qiu
Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542,
Singapore
X.-Y. Liu (B)
Research Institution for Biomimetics and Soft Matter, Xiamen University, Lingfeng Building,
Xiamen 31005, China
e-mail: liuxy@xmu.edu.cn
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
X.-Y. Liu (ed.), Frontiers and Progress of Current Soft Matter Research,
Soft and Biological Matter, https://doi.org/10.1007/978-981-15-9297-3_6
241