Page 105 - Read Online

Kim et al. Soft Sci 2023;3:16 https://dx.doi.org/10.20517/ss.2023.07 Page 17 of 30

Figure 8. (A) 3D mechanical framework with five independently addressable piezoelectric microactuators. (Reproduced with permission
[217] ©
from Ref. . Copyright 2018. American Association for the Advancement of Science); (B) photo-driven biomimetic flower capable of
[218] ©
underwater movement. (Reproduced with permission from Ref. . Copyright 2021. Elsevier); (C) directional locomotion of
[219] ©
submillimeter-scale 3D peekytoe crab. (Reproduced with permission from Ref. . Copyright 2022. American Association for the
Advancement of Science); (D) a multistate electrical circuit made of magnetic responsive soft material switch. (Reproduced with
[220] ©
permission from Ref. . Copyright 2020. Springer Nature); (E) 3D printed soft robotic walkers composed of 16 interconnected
[212] ©
pneumatic actuators. (Reproduced with permission from Ref. . Copyright 2019. Springer Nature); (F) micro-origami system capable
[221] ©
of wing flapping under current stimulation. (Reproduced with permission from Ref. . Copyright 2020. WILEY-VCH Verlag GmbH &
Co. KGaA, Weinheim); (G) magnetic responsive 3D origami machines with various shapes and movements. (Reproduced with
[222] ©
permission from Ref. . Copyright 2022. Springer Nature)
Mechanical/optical meta-materials
Metamaterials are made by periodically arranging metals or dielectric materials that are significantly smaller
than the wavelengths of light of electromagnetic waves, or by designing them to have a very sophisticated
geometry. Generally, metamaterials exhibit artificial properties that do not exist in nature through methods,
where a sub-wavelength metal/dielectric structure resonates with the electric and magnetic fields of incident
waves, or by sophisticated design to have excellent mechanical properties. To improve the performance of
metamaterials with unique properties, abundant spatial controllability is required, and 3D configurations
provide an opportunity to compensate for this deficiency. For example, 2D metamaterials typically have
limited controllability of their properties along the z-axis direction, whereas metamaterials composed of 3D
architectures not only have controllability over the z-axis [223,224] but also exhibit more functionality and