Chiral Microwrinkles: Controlled Fabrication of 3D Chiral Microwrinkles via Asymmetrical and Biaxial Bucklings (Adv. Funct. Mater. 29/2019)

Hwang, Myonghoo; Kim, Changho; Kim, Jin-Woo; Son, Jeong Gon; Yeom, Bongjun

doi:10.1002/adfm.201970197

Cited by 4 publications

(10 citation statements)

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“…First, the 3D chiral PDMS micropattern templates were prepared via the two‐step buckling processes with asymmetric and biaxial stretching. [ 22 ] To prepare the chiral microwrinkled pattern templates (Figure 1a), the control axis (the red arrow) was rotated with respect to the base axis (the blue arrow) with a tilt angle of α (denoted as the stretching angle in Figure S1a, Supporting Information) set as 60° and 120° for the LH and RH samples, respectively. Biaxially stretched samples were first UV–ozone treated for 30 min to induce the formation of a hard oxide layer followed by releasing of the strain along the base axis.…”

Section: Resultsmentioning

confidence: 99%

“…[ 20 ] In particular, twisted or asymmetric buckling of the rotating direction can be introduced to prepare chiral‐shaped wrinkled micropatterns with the aid of deformable substrates. [ 21,22 ] However, only a few approaches using mechanical instability‐based self‐assembly processes for the fabrication of chiral metamaterials have so far been reported.…”

Section: Introductionmentioning

confidence: 99%

“…The two‐step buckling process with asymmetric biaxial strains, which does not require biomaterials or lithography, was adapted from our previous research. [ 20–22 ] Structural chirality was controllable via the macroscale manipulation of the tilt angle between the biaxial strain regions. The manufactured chiral metamaterials showed terahertz CD (TCD) signals with maximum CD values of 14° in the range of 0.2–2.5 THz, which were simulated via finite‐difference time‐domain (FDTD) computational simulation.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Lithography‐Free Fabrication of Terahertz Chiral Metamaterials and Their Chirality Enhancement for Enantiomer Sensing

Hwang

Baek

et al. 2023

Advanced Optical Materials

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Chiral metamaterials comprise a promising platform for advanced optoelectronic and biomedical applications. However, conventional fabrication via lithography is limited by its complexity and high cost. Herein, the lithography-free fabrication of terahertz chiral metamaterials and their enhancement for sensing the chirality of biocrystal enantiomers is presented. Chiral Au microstrip patterns (CHAMs) in a saw-tooth shape are fabricated by combining two-step buckling processes and glancing-angle deposition. Non-superimposable geometric chirality is achieved by controlling the tilt angle between the asymmetric and biaxial strain axes and the selective area deposition of the Au layers by using the shadow effect. The manufactured chiral metamaterials show mirror-shaped terahertz circular dichroism (TCD) signals in the range of 0.2-2.5 THz. Coupling of the induced electric and magnetic dipoles to the chiral-shaped Au surfaces results in effective optical chirality enhancement. Finite-difference time-domain computational simulations reveal the homogeneous distribution of optical chirality with an absolute maximum of 2.24 in the near field. Summing the TCD signals for enantiomeric cystine biocrystals onto the chiral metamaterials shows an ≈7-fold amplification in magnitude. This enhancement can be attributed to the synergistic effects of superchiral field enhancement and the electromagnetic resonance between the CHAMs and biocrystals.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Lithography‐Free Fabrication of Terahertz Chiral Metamaterials and Their Chirality Enhancement for Enantiomer Sensing

Hwang

Baek

et al. 2023

Advanced Optical Materials

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“…The aforementioned methods have also been conducted on a pre‐strained substrate, enabling the formation of ordered 1D or 2D structures. [ 21–24 ] However, the surface topology of these materials is irreversible, limiting the dynamic control of such structures. Hydrogel films with cross‐linking gradients have therefore been proposed for the production of dynamic and stimuli‐responsive surface topologies.…”

Section: Figurementioning

confidence: 99%

Stepwise Evolution of Crease Patterns on Stimuli‐Responsive Hydrogels for the Production of Long‐Range Ordered Structures

Kim

Choi

Kim

et al. 2020

Adv Materials Inter

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From cell membrane to epidermis, growth-induced wrinkles and creases that originate in mechanical forces operating on multilayered structures are frequently observed in living organisms. [11] The biomimetic reproduction of similar structures has been achieved by driving the surface instability of polymeric materials, realizing the development of smart surfaces for use in dry adhesion, [12] sensors, [13,14] smart windows, [15] the patterning of biomaterials, [4,16] and cell cultures. [17,18] Although many studies have elucidated the mechanism of surface instability and thereby the formation of creases and wrinkles on elastomeric materials, [11,19] the precise engineering of surface instabilities remains an important challenge. Wrinkling and creasing can be engineered to control the surface topology of a polymer. The use of layered films consisting of soft substrate and rigid thin film has been widely studied with the aim of triggering modulus mismatch within a material. For example, metal deposition [19] or plasma treatment [20] can lead to the elastic substrate-derived spontaneous formation of random surface topology as a result of the mechanical stress caused by the thermal expansion of the materials. By controlling the thickness, the modulus of the materials, and post-processing conditions, the wavelength of wrinkle and crease structures can be controlled. The aforementioned methods have also been conducted on a prestrained substrate, enabling the formation of ordered 1D or 2D structures. [21-24] However, the surface topology of these materials is irreversible, limiting the dynamic control of such structures. Hydrogel films with cross-linking gradients have therefore been proposed for the production of dynamic and stimuli-responsive surface topologies. Recently, the osmotic pressure-driven surface instability of hydrogels was analyzed and used for the formation of long-range ordered surface topologies. [11,25] This strategy was further developed in an attempt to control the characteristic size and shape of the surface topology in order to form pre-defined surface patterns combined with a lithographically patterned structure. [26] However, highly uniform surface patterns were not generated because osmotic pressure-driven swelling was found to occur simultaneously over the entire area. In addition, the omnidirectional propagation of the surface patterns inevitably led to disorder in the surface patterns. The creases and wrinkles that form on soft matter have been comprehensively analyzed and engineered to utilize their topological advantages in various research fields. Although the principle for the formation of such structures is found to be the inhomogeneous distribution of mechanical stress, simultaneous and omnidirectional propagation of surface patterns makes it difficult to engineer these structures. A design strategy for the reversible formation of highly uniform crease patterns on hydrogel films is proposed by driving the stepwise evolution of creases. A hydrogel film with a smooth-and submicron-scale sur...

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“…[ 1–3 ] Recently, an integration of nanoparticles with chirality (an asymmetric property by which an object is non‐superposable on its mirror image) enables the formation of chiral nanoparticles (or CNPs) that have optical activity, denoting differential interactions with left‐ and right‐handed (or LH and RH) circularly polarized light (CPL). [ 4 ] Producing CNPs unavoidably requires chiral stimulation from, e.g., chiral ligands, [ 5–8 ] chiral templates, [ 9–11 ] CPL, [ 12,13 ] helical magnetic fields, [ 14 ] orbital angular momentum, [ 15 ] macroscopic asymmetric gradients of biaxial strain fields, [ 16,17 ] and macroscopic shear forces. [ 18,19 ] An addition of chirality provides CNPs with various promising functions, such as ultrasensitive molecular detection and bioanalysis, [ 20–22 ] enhanced enantiodifferentiation, [ 23–26 ] active nanorheology, [ 27 ] polarization‐dependent display, [ 14,28 ] enantioselective photocatalysis [ 29 ] and synthesis, [ 30–32 ] and enantiospecific bioapplications.…”

Section: Introductionmentioning

confidence: 99%

Chiral Nanoparticles with Enhanced Thermal Stability of Chiral Structures through Alloying

Lin

Cai

et al. 2022

Small

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Metallic chiral nanoparticles (CNPs) promisingly function as asymmetric catalysts but lack an important study in thermal stability of optical activity that stems from metastable chiral lattices. In this work, annealing is applied to silver (Ag) CNPs, fabricated by glancing angle deposition (GLAD), and causes elimination of optical activity at 200 °C, mainly ascribed to chiral‐to‐achiral lattice transformation. The Ag CNPs are remarkedly enhanced in thermal stability through an alloying with aluminum (Al) via layer‐by‐layer GLAD to generate binary Ag0.5Al0.5 CNPs composed of solid‐state liquids, whose optical activity vanishes at 700 °C. Ease in the diffusion of Al atoms in the host Ag CNPs and thermal insulation from the Al2O3 layers partially covering the binary CNPs effectively prohibit structural relaxation of the metastable chiral lattices, accounting for the significant enhancement in thermal stability of chiral lattices. This is a pioneering work to investigate the fundamental principles determining the thermal stability of metallic CNPs in terms of chiral structures and optical activity. It paves the way toward applying metallic CNPs to asymmetric catalysis at high temperature to accelerate an asymmetric synthesis of enantiomers with designable chirality, which is one of the most important topics in modern chemistry.

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Chiral Microwrinkles: Controlled Fabrication of 3D Chiral Microwrinkles via Asymmetrical and Biaxial Bucklings (Adv. Funct. Mater. 29/2019)

Cited by 4 publications

References 0 publications

Lithography‐Free Fabrication of Terahertz Chiral Metamaterials and Their Chirality Enhancement for Enantiomer Sensing

Lithography‐Free Fabrication of Terahertz Chiral Metamaterials and Their Chirality Enhancement for Enantiomer Sensing

Stepwise Evolution of Crease Patterns on Stimuli‐Responsive Hydrogels for the Production of Long‐Range Ordered Structures

Chiral Nanoparticles with Enhanced Thermal Stability of Chiral Structures through Alloying

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