Stimuli‐Responsive Liquid Marbles: Controlling Structure, Shape, Stability, and Motion

Fujii, Syuji; Yusa, Shin‐ichi; Nakamura, Yoshinobu

doi:10.1002/adfm.201603223

Cited by 153 publications

(160 citation statements)

References 154 publications

(219 reference statements)

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“…This is why it is difficult to measure contact angle hysteresis on MOF powders. The advancing contact angle can be measured with reasonable accuracy by increasing the droplet volume, but the removal of liquid to measure the receding contact angle can cause the droplet to pick up powder grains, which strongly influences the measurement and may lead to the formation of a “liquid marble.” Therefore, it is inadvisable to measure contact angle hysteresis on powders; such measurements should ideally only be performed on pressed pellet disks.…”

Section: Synthesis Of Hydrophobic Mof Materialsmentioning

confidence: 99%

Hydrophobic Metal–Organic Frameworks

et al. 2019

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formed from organic ligands and metal cations. [1][2][3][4][5][6][7][8][9][10] They are typically synthesized under mild conditions via coordinationdirected self-assembly processes and are also known as metal-organic coordination networks and porous coordination polymers. [11][12][13][14] Due to their high surface areas, large porosity, tunable pore sizes, and functionalities, MOFs have prospective applications in fields such as gas storage/separation, sensing or recognition, proton conduction, and magnetism. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] However, the advantageous unique structural features of even some of the best-performing MOFs are readily degraded because of their high moisture sensitivity, which may limit their practical applications. [29][30][31][32] Consequently, there is an ongoing search for highly hydrophobic, porous, sorbent materials to be employed in various large-scale applications in industry such as oil spill cleanup, hydrocarbon storage/separation, or water purification. [33][34][35][36][37] Many academics, industrial scientists, and engineers have therefore conducted research on the fabrication of superhydrophobic surfaces, which involves hydrophobic surface modification and creating surface roughness on the micrometer-or nanoscale. Hydrophobic surfaces are defined as substrates with an apparent contact angle greater than 90° with respect to water. On superhydrophobic materials, water droplets have contact angles above 150° and show very low adhesion because the drops partially rest on an air cushion. The surface energy and roughness govern the wettability of hydrophobic surfaces. In general, lower surface energies and higher roughness are associated with larger contact angles, lower contact angle hysteresis, and robust superhydrophobicity. Because of their ultralow surface energies (10-20 mN m −1 ), alkyl-based or fluorinated compounds are commonly used as hydrophobic modifiers to prepare surfaces with high intrinsic contact angles (>90°). [33][34][35][36][37][38][39][40][41][42] Recently, few methods have been developed for synthesizing hydrophobic MOFs including both pristine and composite systems. This review offers a comprehensive overview of the state of the art in hydrophobic MOF synthesis and the field's challenges and opportunities. Various synthetic strategies for preparing hydrophobic MOFs and their composites are introduced. We discuss the basics of wetting and critical challenges in the characterization of these hydrophobic materials. The potential applications of hydrophobic MOFs and related Metal-organic frameworks (MOFs) have diverse potential applications in catalysis, gas storage, separation, and drug delivery because of their nanoscale periodicity, permanent porosity, channel functionalization, and structural diversity. Despite these promising properties, the inherent structural features of even some of the best-performing MOFs make them moisture-sensitive and unstable in aqueous media, limiting their practical usefulness. This problem could be ...

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Section: Synthesis Of Hydrophobic Mof Materialsmentioning

confidence: 99%

Hydrophobic Metal–Organic Frameworks

et al. 2019

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“…[21] The lifetime is related to many aspects, like particles size, surface chemistry, and the external conditions. [21][22][23] The manipulation of single LMs, by the mechanical force, [24,25] magnetic locomotion [26][27][28] and light-driven motivation [29,30] have been developed in the past decade. Benefiting from the single LM manipulation and liquid control, the coalescence of the well-prepared LMs can mix the Coalescence and splitting of liquid marbles (LMs) are critical for the mixture of precise amount precursors and removal of the wastes in the microliter range.…”

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confidence: 99%

On‐Demand Coalescence and Splitting of Liquid Marbles and Their Bioapplications

Wang

Chan

et al. 2019

Advanced Science

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Coalescence and splitting of liquid marbles (LMs) are critical for the mixture of precise amount precursors and removal of the wastes in the microliter range. Here, the coalescence and splitting of LMs are realized by a simple gravity‐driven impact method and the two processes are systematically investigated to obtain the optimal parameters. The formation, coalescence, and splitting of LMs can be realized on‐demand with a designed channel box. By selecting the functional channels on the device, gravity‐based fusion and splitting of LMs are performed to mix medium/drugs and remove spent culture medium in a precise manner, thus ensuring that the microenvironment of the cells is maintained under optimal conditions. The LM‐based 3D stem cell spheroids are demonstrated to possess an approximately threefold of cell viability compared with the conventional spheroid obtained from nonadhesive plates. Delivery of the cell spheroid to a hydrophilic surface results in the in situ respreading of cells and gradual formation of typical 2D cell morphology, which offers the possibility for such spheroid‐based stem cell delivery in regenerative medicine.

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“…Destabilization of the bubbles prepared at pH ~10 could be induced by subsequent pH adjustment to ≤ 3.0, and the stabilization/destabilization cycles were reversible. Recently, it has been confirmed that there are lots of similarities among particle-stabilized bubbles, emulsions and liquid marbles/dry liquids (Fujii et al, 2016). The principles demonstrated in this study should also be applicable to predict the stabilities and microstructures of these particle-stabilized soft dispersed systems.…”

Section: Resultsmentioning

confidence: 98%

pH-Responsive Aqueous Bubbles Stabilized With Polymer Particles Carrying Poly(4-vinylpyridine) Colloidal Stabilizer

et al. 2018

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Free radical dispersion polymerization was conducted to synthesize near-monodispersed, micrometer-sized polystyrene (PS) particles carrying pH-responsive poly(4-vinylpyridine) (P4VP) colloidal stabilizer (P4VP-PS particles). The P4VP-PS particles were extensively characterized in terms of morphology, size, size distribution, chemical composition, surface chemistry, and pH-response using optical and scanning electron microscopies, elemental microanalysis, X-ray photoelectron spectroscopy, laser diffraction particle size analysis, and zeta potential measurement. The P4VP-PS particles can work as a pH-responsive stabilizer of aqueous bubbles by adsorption at the air-water interface. At and above pH 4.0, where the particles have partially protonated/non-protonated P4VP stabilizer with relatively hydrophobic character, particle-stabilized bubbles were formed. Optical and scanning electron microscopy studies confirmed that the P4VP-PS particles were adsorbed at the air-water interface of the bubbles in aqueous media. At and below pH 3.0, where the particles have cationic P4VP stabilizer with water-soluble character, no bubble was formed. Rapid disruption of the bubbles can be induced by decreasing the pH; the addition of acid caused the in situ protonation of pyridine groups in P4VP, which impart water-soluble character to the P4VP stabilizer, and the P4VP-PS particles were desorbed from the air-water interface. The bubble stabilization/destabilization cycles could be repeated at least five times.

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Stimuli‐Responsive Liquid Marbles: Controlling Structure, Shape, Stability, and Motion

Cited by 153 publications

References 154 publications

Hydrophobic Metal–Organic Frameworks

Hydrophobic Metal–Organic Frameworks

On‐Demand Coalescence and Splitting of Liquid Marbles and Their Bioapplications

pH-Responsive Aqueous Bubbles Stabilized With Polymer Particles Carrying Poly(4-vinylpyridine) Colloidal Stabilizer

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