260
Y. Yang et al.
triple-periodic gold network (Fig. 10.12e) [80]. The templating approach has major
disadvantages that deposited amorphous materials may crystallize, and that strain
can accumulate.
Coassembly exploits intermolecular force to get an amphiphilic block copolymer
to interact with inorganic materials in solution. This method has been used to fabricate
an isoprene-block-styrene-block-ethylene oxide polymer with sol (black particles in
Fig. 10.12f); the intermolecular forces drive the particles into the hydrophilic PEO
blocks to yield an alternative gyroid structure [81] (Fig. 10.12g). The coassembly
approach has disadvantages that the amorphous assemblies can shrink and crack
during forming and crystallization, but it could be used to construct superlattices for
novel photonic applications.
Fabrication using BCP self-assembly is a solution process and uses inexpensive constituent monomers, so it is less expensive than photolithography. Bottom up
BCP self-assembly has a great advantage to fabricate sub-wavelength highly ordered
nanostructures over large areas of a surface. These abilities are advantages over topdown approaches such as lithography, which have resolution limits. In addition, BCP
self-assembly is much simpler sequences and requires fewer repeating units than
biological molecular assembly that uses DNA or peptides [78]. BCP self-assembled
plasmonic structure has been applied for organic solar cells, optoelectronics, and plasmonic nanoantennas, and can help to fabricate subminiature drug delivery systems
and biosensing devices [82, 83].
10.5 Conclusion
In this chapter, fabrication methods realizing three-dimensional chiral structures were
discussed and categorized by their manufacturing feature sizes since the working
wavelength of enhanced artificial chirality is generally close to the feature sizes
of the chiral structures. Top-down approaches can be used to fabricate micronscale structures with high precision. Direct laser writing, focused ion beam, and
photolithography can be used to realize three-dimensional structures with a large
degree-of-freedom; however, they are time-consuming and expensive. Bottom-up
approaches are more suitablefor realizing nano-scale structures. Solution processing
and block copolymer self-assembly are cost-effective methods, but the achievable
morphologies are limited.
Acknowledgements This work was financially supported by the National Research Foundation (NRF) grant (NRF-2019R1A2C3003129) funded by the Ministry of Science and ICT,
Republic of Korea. Y.Y. and Y.K. acknowledge the fellowships from the Hyundai Motor Chung
Mong-Koo Foundation. S.S., M.K. and I.K. acknowledge the NRF Global Ph.D. fellowships
(NRF-2017H1A2A1043322, NRF-2017H1A2A1043204, NRF-2016H1A2A1906519), respectively, funded by the Ministry of Education, Republic of Korea.
Author Contributions J. R., Y. Y. and Y. K. conceived and initiated the project. Y. Y., Y. K. and
J. M. mainly wrote the manuscript. J. G, S. S., M. K., H. J., I. K. and T. B. are partially involved in
Y. Yang et al.
triple-periodic gold network (Fig. 10.12e) [80]. The templating approach has major
disadvantages that deposited amorphous materials may crystallize, and that strain
can accumulate.
Coassembly exploits intermolecular force to get an amphiphilic block copolymer
to interact with inorganic materials in solution. This method has been used to fabricate
an isoprene-block-styrene-block-ethylene oxide polymer with sol (black particles in
Fig. 10.12f); the intermolecular forces drive the particles into the hydrophilic PEO
blocks to yield an alternative gyroid structure [81] (Fig. 10.12g). The coassembly
approach has disadvantages that the amorphous assemblies can shrink and crack
during forming and crystallization, but it could be used to construct superlattices for
novel photonic applications.
Fabrication using BCP self-assembly is a solution process and uses inexpensive constituent monomers, so it is less expensive than photolithography. Bottom up
BCP self-assembly has a great advantage to fabricate sub-wavelength highly ordered
nanostructures over large areas of a surface. These abilities are advantages over topdown approaches such as lithography, which have resolution limits. In addition, BCP
self-assembly is much simpler sequences and requires fewer repeating units than
biological molecular assembly that uses DNA or peptides [78]. BCP self-assembled
plasmonic structure has been applied for organic solar cells, optoelectronics, and plasmonic nanoantennas, and can help to fabricate subminiature drug delivery systems
and biosensing devices [82, 83].
10.5 Conclusion
In this chapter, fabrication methods realizing three-dimensional chiral structures were
discussed and categorized by their manufacturing feature sizes since the working
wavelength of enhanced artificial chirality is generally close to the feature sizes
of the chiral structures. Top-down approaches can be used to fabricate micronscale structures with high precision. Direct laser writing, focused ion beam, and
photolithography can be used to realize three-dimensional structures with a large
degree-of-freedom; however, they are time-consuming and expensive. Bottom-up
approaches are more suitablefor realizing nano-scale structures. Solution processing
and block copolymer self-assembly are cost-effective methods, but the achievable
morphologies are limited.
Acknowledgements This work was financially supported by the National Research Foundation (NRF) grant (NRF-2019R1A2C3003129) funded by the Ministry of Science and ICT,
Republic of Korea. Y.Y. and Y.K. acknowledge the fellowships from the Hyundai Motor Chung
Mong-Koo Foundation. S.S., M.K. and I.K. acknowledge the NRF Global Ph.D. fellowships
(NRF-2017H1A2A1043322, NRF-2017H1A2A1043204, NRF-2016H1A2A1906519), respectively, funded by the Ministry of Education, Republic of Korea.
Author Contributions J. R., Y. Y. and Y. K. conceived and initiated the project. Y. Y., Y. K. and
J. M. mainly wrote the manuscript. J. G, S. S., M. K., H. J., I. K. and T. B. are partially involved in