Functionalization of Colored/Fluorescent Silkworm Silk Fibrous Materials - Soft Fibrillar Materials: Fabrication and Applications - page 222

the rapid production of highly ordered 3D colloidal crystals with face-center cubic
structure. In connection with this technology, the wettability can be adjusted by the
intrinsic roughness of colloidal crystals in combination with the tunable chemical
composition of latex surfaces, while the band gaps can be tuned by changing the
size of the colloidal spheres [103, 111-113].
To create structural colors on fabrics is a challenging task, but remains to be
extremely important in practice. As color fading caused by leaching or oxida-
tion/bleaching is a key problem in fabric care, producing with vivid and durable
structural colors on fabrics by fabricating 3D colloidal crystals onto the surface
of fabrics will revolutionize textile and fashion industries [103]. If the physical
structure of photonic crystals on the fabrics is strong enough, the colors will last
forever. Recently, a combined surface treatment technology allows us to create
opal and/or inverse opal structures on silk fabrics (cf. Figure 7.7). In producing
structural colors on silk fabrics, polystyrene spheres with different diameters were
assembled on the surface of silk fabrics. Silk fibroin was dispersed on the colloidal
crystals as binding materials (Figure 7.7b). Thus, silk fabrics with different reflec-
tion peaks ranging from Ultraviolet to NIR can be obtained. It follows that the
colors (the reflected wave lengths) can be created by tuning the lattice constant of
theinverseopal, a, according to λ = va ( v is a function of the refractive index of the

material).
Moreover, by controlling the band gaps of the photonic crystals, multi-functional
silk fabrics may also be invented. For instance, we can acquire the UV protective
clothing by creating photonic crystals or inverse capable of reflecting UV light.
Similarly, the thermal insulating performance due to a reflection peak in the IR
range will create cooling textiles in a hot summer. On the other hand, it will
preserve to some extent our body heat in a cold winter if the IR reflecting structure
is generated in the inner layer of textiles.

7.5
Summary and Outlook

Silk is a remarkable biomaterial that has been optimized by millions of years of
evolution. It has serviced human for thousands of years. Applying new functions
to nature silk materials now incites the future for modern silk industry. The
functional silk will bridge the biomaterials and the functional materials, such
as optical materials, magnetic materials. It can be foreseen that functional silk
materials can be widely applied in our life. As mentioned early, this paves the new
silk road to the future.

References

1. Vepari, C. and Kaplan, D.L. (2007)
Prog. Polym. Sci. ,

3. Ghosh, S., Parker, S.T., Wang, X.,
Kaplan, D.L., and Lewis, J.A. (2008)
Adv. Funct. Mater. , 18 , 1883.

, 991.
2. Service, R.F. (2008) Science , 322 , 1460.

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