| 1. |
- Park, Kwangseok, et al.
(author)
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Avalanche Coalescence of Liquid Metal Particles for Uniform Flexible and Stretchable Electrodes
- 2022
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In: Advanced Materials Interfaces. - : John Wiley & Sons. - 2196-7350. ; 9:35
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Journal article (peer-reviewed)abstract
- Self-sinterable gallium-based liquid metal (LM) ink for a handy drop-casting coating method is developed. The fabricated LM electrode is coffee-ring-free and bilayer-free, which guarantees high electrical conductivity, wettability, flexibility, and stretchability. The ink consists of Galinstan, ethanol-water mixture, hydrochloric acid, and polyvinylpyrrolidone. The binary mixture provides excellent wetting conditions and suppresses a coffee-ring stain from Marangoni mixing. The acid removes an oxide layer on the LM interface. The colloidal interaction forces by self-assembled polyvinylpyrrolidone induce avalanche coalescences of the particles at the end of evaporation, which produces a thin and uniform dried conductive layer. The acid and polymer provide a bilayer-free structure and electrification without any post sintering. The drop-casted self-transformed LM electrode showed excellent electrical resistance of O (0.1-1 omega) on folding and stretching conditions. It is believed that this method can serve as flexible and stretchable electrodes, on various substances for soft robots and wearable devices, without any complicated post-process.
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| 2. |
- Park, Sung-Joon, et al.
(author)
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Autonomous Interfacial Assembly of Polymer Nanofilms via Surfactant-Regulated Marangoni Instability
- 2023
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In: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 23:11, s. 4822-4829
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Journal article (peer-reviewed)abstract
- Interfacialpolymerization (IP) provides a versatile platform forfabricating defect-free functional nanofilms for various applications,including molecular separation, energy, electronics, and biomedicalmaterials. Unfortunately, coupled with complex natural instabilityphenomena, the IP mechanism and key parameters underlying the structuralevolution of nanofilms, especially in the presence of surfactantsas an interface regulator, remain puzzling. Here, we interfaciallyassembled polymer nanofilm membranes at the free water-oilinterface in the presence of differently charged surfactants and comprehensivelycharacterized their structure and properties. Combined with computationalsimulations, an in situ visualization of interfacial film formationdiscovered the critical role of Marangoni instability induced by thesurfactants via various mechanisms in structurally regulating thenanofilms. Despite their different instability-triggering mechanisms,the delicate control of the surfactants enabled the fabrication ofdefect-free, ultra-permselective nanofilm membranes. Our study identifiescritical IP parameters that allow us to rationally design nanofilms,coatings, and membranes for target applications.
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| 3. |
- Xue, Nan, et al.
(author)
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Laboratory layered latte
- 2017
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In: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 8
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Journal article (peer-reviewed)abstract
- Inducing thermal gradients in fluid systems with initial, well-defined density gradients results in the formation of distinct layered patterns, such as those observed in the ocean due to double-diffusive convection. In contrast, layered composite fluids are sometimes observed in confined systems of rather chaotic initial states, for example, lattes formed by pouring espresso into a glass of warm milk. Here, we report controlled experiments injecting a fluid into a miscible phase and show that, above a critical injection velocity, layering emerges over a time scale of minutes. We identify critical conditions to produce the layering, and relate the results quantitatively to double-diffusive convection. Based on this understanding, we show how to employ this single-step process to produce layered structures in soft materials, where the local elastic properties vary step-wise along the length of the material.
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