1
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Meijer JG, Kant P, Lohse D. Freezing-induced topological transition of double-emulsion. SOFT MATTER 2024; 20:2491-2495. [PMID: 38385589 DOI: 10.1039/d3sm01657a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
Solidification of complex liquids is pertinent to numerous natural and industrial processes. Here, we examine the freezing of a W/O/W double-emulsion, i.e., water-in-oil compound droplets dispersed in water. We show that the solidification of such hierarchical emulsions can trigger a topological transition; for example, in our case, we observe the transition from the stable W/O/W state to a (frozen) O/W single-emulsion configuration. Strikingly, this transition is characterised by sudden expulsion of the inner water drop from the encapsulating oil droplet. We propose that this topological transition is triggered by the freezing of the encapsulating oil droplet from the outside in, putting tension on the inner water drop thus, destabilizing the W/O/W configuration. Using high-speed imaging we characterize the destabilization process. Interestingly, we find that below a critical size of the inner drop, Rin,crit ≈ 19 μm, the topological transition does not occur any more and the double-emulsion remains stable, in line with our interpretation.
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Affiliation(s)
- Jochem G Meijer
- Physics of Fluids group, Max Planck Center Twente for Complex Fluid Dynamics, Department of Science and Technology, Mesa+ Institute and J. M. Burgers Center for Fluid Dynamics, University of Twente, P.O. Box 217, Enschede 7500 AE, The Netherlands.
| | - Pallav Kant
- School of Engineering, University of Manchester, M13 9PL, UK
| | - Detlef Lohse
- Physics of Fluids group, Max Planck Center Twente for Complex Fluid Dynamics, Department of Science and Technology, Mesa+ Institute and J. M. Burgers Center for Fluid Dynamics, University of Twente, P.O. Box 217, Enschede 7500 AE, The Netherlands.
- Max Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, Göttingen 37077, Germany.
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2
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Tang J, Chen Z, Cai Y, Gao Y, He J, Xiao Y, Mao J, Zhao J, Gao X, Li T, Luo Y. Composite elastomers with on-demand convertible phase separations achieve large and healable electro-actuation. MATERIALS HORIZONS 2023; 10:4501-4509. [PMID: 37551443 DOI: 10.1039/d3mh00781b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/09/2023]
Abstract
Phase separation has been widely exploited for fabricating structured functional materials. Generally, after being fabricated, the phase structure in a hybrid material system has been set at a specific length scale and remains unchanged during the lifespan of the material. Herein, we report a strategy to construct on-demand and reversible phase switches among homogenous, nano- and macro-phase separation states in a composite elastomer during its lifespan. We trigger the nanophase separation by super-saturating an elastomer matrix with a carefully selected small-molecule organic compound (SMOC). The nanoparticles of SMOC that precipitate out upon quenching will stretch the elastomer network, yet remain stably arrested in the elastomer matrix at low temperatures for a long time. However, at elevated temperatures, the nano-phase separation will transform into the macro-one. The elastic recovery will drive the SMOC onto the elastomer surface. The phase-separated structures can be reconfigured through the homogeneous solution state at a further elevated temperature. Taking advantage of the reversible phase switches leads to a novel strategy for designing high-performance dielectric elastomers. The in situ formed nanoparticles can boost the electro-actuation performance by eliminating electro-mechanical instability and lead to a very large actuation strain (∼146%). Once the actuator broke down, SMOC could on-demand be driven to the breakdown holes and heal the actuator.
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Affiliation(s)
- Jiali Tang
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310058, China.
| | - Zheqi Chen
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310058, China.
| | - Yiting Cai
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310058, China.
| | - Yang Gao
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310058, China.
| | - Jin He
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310058, China.
| | - Youhua Xiao
- School of Chemistry and Materials Engineering, Zhejiang A&F University, Hangzhou, 311300, China
| | - Jie Mao
- State Key Laboratory of High-Efficiency Utilization of Coal and Green Chemical Engineering School of Chemistry and Chemical Engineering, Ningxia University, Yinchuan, 750021, China
| | - Junjie Zhao
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310058, China.
| | - Xiang Gao
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310058, China.
| | - Tiefeng Li
- Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Zhejiang University, Hangzhou 310027, China
- Center for X-Mechanics, Department of Engineering Mechanics, Zhejiang University, Hangzhou, 310027, China
| | - Yingwu Luo
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310058, China.
- Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Zhejiang University, Hangzhou 310027, China
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3
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Abbasi N, Nunes JK, Pan Z, Dethe T, Shum HC, Košmrlj A, Stone HA. Flows of a nonequilibrated aqueous two-phase system in a microchannel. SOFT MATTER 2023; 19:3551-3561. [PMID: 37144458 DOI: 10.1039/d3sm00233k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Liquid-liquid phase separation is a rich and dynamic process, which recently has gained new interest, especially in biology and for material synthesis. In this work, we experimentally show that co-flow of a nonequilibrated aqueous two-phase system within a planar flow-focusing microfluidic device results in a three-dimensional flow, as the two nonequilibrated solutions move downstream along the length of the microchannel. After the system reaches steady-state, invasion fronts from the outer stream are formed along the top and bottom walls of the microfluidic device. The invasion fronts advance towards the center of the channel, until they merge. We first show by tuning the concentration of polymer species within the system that the formation of these fronts is due to liquid-liquid phase separation. Moreover, the rate of invasion from the outer stream increases with increasing polymer concentrations in the streams. We hypothesize the invasion front formation and growth is driven by Marangoni flow induced by the polymer concentration gradient along the width of the channel, as the system is undergoing phase separation. In addition, we show how at various downstream positions the system reaches its steady-state configuration once the two fluid streams flow side-by-side in the channel.
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Affiliation(s)
- Niki Abbasi
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, USA.
| | - Janine K Nunes
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, USA.
| | - Zehao Pan
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, USA.
| | - Tejas Dethe
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, USA.
| | - Ho Cheung Shum
- Department of Mechanical Engineering, University of Hong Kong, Hong Kong, China
| | - Andrej Košmrlj
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, USA.
- Princeton Materials Institute, Princeton University, Princeton, NJ, USA
| | - Howard A Stone
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, USA.
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4
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Fernández-Rico C, Sai T, Sicher A, Style RW, Dufresne ER. Putting the Squeeze on Phase Separation. JACS AU 2022; 2:66-73. [PMID: 35098222 PMCID: PMC8790737 DOI: 10.1021/jacsau.1c00443] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Indexed: 05/06/2023]
Abstract
Phase separation is a ubiquitous process and finds applications in a variety of biological, organic, and inorganic systems. Nature has evolved the ability to control phase separation to both regulate cellular processes and make composite materials with outstanding mechanical and optical properties. Striking examples of the latter are the vibrant blue and green feathers of many bird species, which are thought to result from an exquisite control of the size and spatial correlations of their phase-separated microstructures. By contrast, it is much harder for material scientists to arrest and control phase separation in synthetic materials with such a high level of precision at these length scales. In this Perspective, we briefly review some established methods to control liquid-liquid phase separation processes and then highlight the emergence of a promising arrest method based on phase separation in an elastic polymer network. Finally, we discuss upcoming challenges and opportunities for fabricating microstructured materials via mechanically controlled phase separation.
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5
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Genda T, Knight K, Dai ZR, Balboni E, Goldblum BL, Hosemann P. Iron-rich microstructure records of high temperature multi-component silicate melt behavior in nuclear fallout. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2021; 237:106700. [PMID: 34293717 DOI: 10.1016/j.jenvrad.2021.106700] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 07/06/2021] [Accepted: 07/08/2021] [Indexed: 06/13/2023]
Abstract
Above-ground nuclear explosions that interact with the surface of the earth entrain materials from the surrounding environment, influencing the resulting physical and chemical evolution of the fireball, which can affect the final chemical phase and mobility of hazardous radionuclides that are dispersed in the environment as fallout particles. The interaction of iron with a nuclear explosion is of specific interest due to the potential for iron to act as a redox buffer and because of the likelihood of significant masses of metals to be present in urban environments. We investigated fallout from a historic surface interacting nuclear explosion conducted on a steel tower and report the discovery of widespread and diverse iron-rich micro-structures preserved within the samples, including crystalline dendrites and micron-scale iron-rich spheres with liquid immiscibility textures. We assert these micro-structures reflect local redox conditions and cooling rates and can inform interpretation of high temperature events, enabling new insights into fireball condensation physics and chemistry when metals from the local environment (i.e. structural steel) are vaporized or entrained. These observations also significantly expand the availability of silicate immiscibility datasets applicable to rapidly quenched systems such as meteorite impact melt glass.
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Affiliation(s)
- Tim Genda
- Department of Nuclear Engineering, University of California, Berkeley, USA.
| | - Kim Knight
- Lawrence Livermore National Laboratory, Livermore, USA
| | - Zurong R Dai
- Lawrence Livermore National Laboratory, Livermore, USA
| | | | - Bethany L Goldblum
- Department of Nuclear Engineering, University of California, Berkeley, USA; Lawrence Berkeley National Laboratory, Berkeley, USA
| | - Peter Hosemann
- Department of Nuclear Engineering, University of California, Berkeley, USA
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6
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Li YI, Cates ME. Hierarchical microphase separation in non-conserved active mixtures. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2021; 44:119. [PMID: 34580768 PMCID: PMC8476393 DOI: 10.1140/epje/s10189-021-00113-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 08/18/2021] [Indexed: 05/09/2023]
Abstract
Non-equilibrium phase separating systems with reactions, such as biomolecular condensates and bacteria colonies, can break time-reversal symmetry (TRS) in two distinct ways. Firstly, the conservative and non-conservative sectors of the dynamics can be governed by incompatible free energies; when both sectors are present, this is the leading-order TRS violation, captured in its simplest form by 'Model AB'. Second, the diffusive dynamics can break TRS in its own right. This happens only at higher order in the gradient expansion (but is the leading behaviour without reactions present) and is captured by 'Active Model B+' (AMB+). Each of the two mechanisms can lead to microphase separation, by quite different routes. Here we introduce Model AB+, for which both mechanisms are simultaneously present, and show that for slow reaction rates the system can undergo a new type of hierarchical microphase separation, which we call 'bubbly microphase separation'. In this state, small droplets of one fluid are continuously created and absorbed into large droplets, whose length-scales are controlled by the competing reactive and diffusive dynamics.
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Affiliation(s)
- Yuting I Li
- DAMTP, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Rd, Cambridge, CB3 0WA, UK.
| | - Michael E Cates
- DAMTP, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Rd, Cambridge, CB3 0WA, UK
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7
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Lopez de la Cruz R, Schilder N, Zhang X, Lohse D. Phase Separation of an Evaporating Ternary Solution in a Hele-Shaw Cell. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:10450-10460. [PMID: 34424709 PMCID: PMC8427745 DOI: 10.1021/acs.langmuir.1c01274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 08/10/2021] [Indexed: 06/13/2023]
Abstract
In the present work, we investigate the dynamic phenomena induced by solvent evaporation from ternary solutions confined in a Hele-Shaw cell. The model solutions consist of ethanol, water, and oil, and with the decrease in ethanol concentration by selective evaporation, they may undergo microdroplet formation via the ouzo effect or macroscopic liquid-liquid phase separation. We varied the initial concentration of the three components of the solutions. For all ternary solutions, evaporation of the good solvent ethanol from the gas-liquid interface, aligned with one side of the cell, leads to a Marangoni instability at the early stage of the evaporation process. The presence of the Marangoni instability is in agreement with our recent predictions based on linear stability analysis of binary systems. However, the location and onset of subsequent microdroplet formation and phase separation are the result of the interplay between the Marangoni instability and the initial composition of the ternary mixtures. We classified the ternary solutions into different groups according to the initial concentration of oil. For each group, based on the ternary diagram of the mixture, we offer a rationale for the way phase separation takes place and discuss how the instability influences droplet nucleation. Our work helps us to understand under what conditions and where droplet nucleation can take place when advection is present during phase separation inside a microfluidic device.
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Affiliation(s)
- Ricardo
Arturo Lopez de la Cruz
- Physics
of Fluids Group, Max-Planck-Center Twente for Complex Fluid Dynamics,
Mesa+ Institute, and J. M. Burgers Centre for Fluid Dynamics, Faculty
of Science and Technology, University of
Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Noor Schilder
- Physics
of Fluids Group, Max-Planck-Center Twente for Complex Fluid Dynamics,
Mesa+ Institute, and J. M. Burgers Centre for Fluid Dynamics, Faculty
of Science and Technology, University of
Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Xuehua Zhang
- Physics
of Fluids Group, Max-Planck-Center Twente for Complex Fluid Dynamics,
Mesa+ Institute, and J. M. Burgers Centre for Fluid Dynamics, Faculty
of Science and Technology, University of
Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
- Department
of Chemical and Materials Engineering, University
of Alberta, Edmonton, Alberta T6G 1H9, Canada
| | - Detlef Lohse
- Physics
of Fluids Group, Max-Planck-Center Twente for Complex Fluid Dynamics,
Mesa+ Institute, and J. M. Burgers Centre for Fluid Dynamics, Faculty
of Science and Technology, University of
Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
- Max
Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, 37077 Göttingen, Germany
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8
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Guo W, Kinghorn AB, Zhang Y, Li Q, Poonam AD, Tanner JA, Shum HC. Non-associative phase separation in an evaporating droplet as a model for prebiotic compartmentalization. Nat Commun 2021; 12:3194. [PMID: 34045455 PMCID: PMC8160217 DOI: 10.1038/s41467-021-23410-7] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 04/22/2021] [Indexed: 11/13/2022] Open
Abstract
The synthetic pathways of life’s building blocks are envisaged to be through a series of complex prebiotic reactions and processes. However, the strategy to compartmentalize and concentrate biopolymers under prebiotic conditions remains elusive. Liquid-liquid phase separation is a mechanism by which membraneless organelles form inside cells, and has been hypothesized as a potential mechanism for prebiotic compartmentalization. Associative phase separation of oppositely charged species has been shown to partition RNA, but the strongly negative charge exhibited by RNA suggests that RNA-polycation interactions could inhibit RNA folding and its functioning inside the coacervates. Here, we present a prebiotically plausible pathway for non-associative phase separation within an evaporating all-aqueous sessile droplet. We quantitatively investigate the kinetic pathway of phase separation triggered by the non-uniform evaporation rate, together with the Marangoni flow-driven hydrodynamics inside the sessile droplet. With the ability to undergo liquid-liquid phase separation, the drying droplets provide a robust mechanism for formation of prebiotic membraneless compartments, as demonstrated by localization and storage of nucleic acids, in vitro transcription, as well as a three-fold enhancement of ribozyme activity. The compartmentalization mechanism illustrated in this model system is feasible on wet organophilic silica-rich surfaces during early molecular evolution. Prebiotic compartmentalization could prove essential for the evolution of life. Guo et al. show that liquid-liquid separation in an aqueous two-phase system driven by evaporation may already suffice to facilitate chemical processes required for the RNA world hypothesis.
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Affiliation(s)
- Wei Guo
- Department of Mechanical Engineering, Faculty of Engineering, The University of Hong Kong, Hong Kong (SAR), Hong Kong, China
| | - Andrew B Kinghorn
- School of Biomedical Sciences, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong (SAR), Hong Kong, China
| | - Yage Zhang
- Department of Mechanical Engineering, Faculty of Engineering, The University of Hong Kong, Hong Kong (SAR), Hong Kong, China
| | - Qingchuan Li
- Department of Mechanical Engineering, Faculty of Engineering, The University of Hong Kong, Hong Kong (SAR), Hong Kong, China.,School of Chemistry & Chemical Engineering, National Engineering Research Center for Colloidal Materials, Shandong University, Jinan, 250100, China
| | - Aditi Dey Poonam
- Department of Mechanical Engineering, Faculty of Engineering, The University of Hong Kong, Hong Kong (SAR), Hong Kong, China
| | - Julian A Tanner
- School of Biomedical Sciences, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong (SAR), Hong Kong, China. .,Advanced Biomedical Instrumentation Centre, Hong Kong Science Park, Shatin, New Territories, Hong Kong (SAR), Hong Kong, China.
| | - Ho Cheung Shum
- Department of Mechanical Engineering, Faculty of Engineering, The University of Hong Kong, Hong Kong (SAR), Hong Kong, China. .,Advanced Biomedical Instrumentation Centre, Hong Kong Science Park, Shatin, New Territories, Hong Kong (SAR), Hong Kong, China.
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9
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Abstract
The gasification of multicomponent fuel drops is relevant in various energy-related technologies. An interesting phenomenon associated with this process is the self-induced explosion of the drop, producing a multitude of smaller secondary droplets, which promotes overall fuel atomization and, consequently, improves the combustion efficiency and reduces emissions of liquid-fueled engines. Here, we study a unique explosive gasification process of a tricomponent droplet consisting of water, ethanol, and oil ("ouzo"), by high-speed monitoring of the entire gasification event taking place in the well-controlled, levitated Leidenfrost state over a superheated plate. It is observed that the preferential evaporation of the most volatile component, ethanol, triggers nucleation of the oil microdroplets/nanodroplets in the remaining drop, which, consequently, becomes an opaque oil-in-water microemulsion. The tiny oil droplets subsequently coalesce into a large one, which, in turn, wraps around the remnant water. Because of the encapsulating oil layer, the droplet can no longer produce enough vapor for its levitation, and, thus, falls and contacts the superheated surface. The direct thermal contact leads to vapor bubble formation inside the drop and consequently drop explosion in the final stage.
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10
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Balaj RV, Zarzar LD. Reconfigurable complex emulsions: Design, properties, and applications. ACTA ACUST UNITED AC 2020. [DOI: 10.1063/5.0028606] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Rebecca V. Balaj
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Lauren D. Zarzar
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
- Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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11
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Mao S, Chakraverti-Wuerthwein MS, Gaudio H, Košmrlj A. Designing the Morphology of Separated Phases in Multicomponent Liquid Mixtures. PHYSICAL REVIEW LETTERS 2020; 125:218003. [PMID: 33275007 DOI: 10.1103/physrevlett.125.218003] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 10/06/2020] [Indexed: 05/03/2023]
Abstract
Phase separation of multicomponent liquid mixtures plays an integral part in many processes ranging from industry to cellular biology. In many cases the morphology of coexisting phases is crucially linked to the function of the separated mixture, yet it is unclear what determines the morphology when multiple phases are present. We developed a graph theory approach to predict the topology of coexisting phases from a given set of surface energies, enumerate all topologically distinct morphologies, and reverse engineer conditions for surface energies that produce the target morphology.
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Affiliation(s)
- Sheng Mao
- Department of Mechanics and Engineering Science, BIC-ESAT, College of Engineering, Peking University, Beijing 100871, People's Republic of China
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | | | - Hunter Gaudio
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA
- Department of Mechanical Engineering, Villanova University, Villanova, Pennsylvania 19085, USA
| | - Andrej Košmrlj
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA
- Princeton Institute for the Science and Technology of Materials (PRISM), Princeton University, Princeton, New Jersey 08544, USA
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12
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Park S, Lee SS, Kim SH. Photonic Multishells Composed of Cholesteric Liquid Crystals Designed by Controlled Phase Separation in Emulsion Drops. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e2002166. [PMID: 32519408 DOI: 10.1002/adma.202002166] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2020] [Revised: 04/23/2020] [Indexed: 06/11/2023]
Abstract
Cholesteric liquid crystals (CLCs), also known as chiral nematic LCs, show a photonic stopband, which is promising for various optical applications. In particular, CLCs confined in microcompartments are useful for sensing, lasing, and optical barcoding at the microscale. The integration of distinct CLCs into single microstructures can provide advanced functionality. In this work, CLC multishells with multiple stopbands are created by liquid-liquid phase separation (LLPS) in a simple yet highly controlled manner. A homogeneous ternary mixture of LC, hydrophilic liquid, and co-solvent is microfluidically emulsified to form uniform oil-in-water drops, which undergo LLPS to form onion-like drops composed of alternating CLC-rich and CLC-depleted layers. The multiplicity is controlled from one to five by adjusting the initial composition of the ternary mixture, which dictates the number of consecutive steps of LLPS. Interestingly, the concentration of the chiral dopant becomes reduced from the outermost to the innermost CLC drop due to uneven partitioning during LLPS, which results in multiple stopbands. Therefore, the photonic multishells show multiple structural colors. In addition, dye-doped multishells provide band-edge lasing at two different wavelengths. This new class of photonic multishells will provide new opportunities for advanced optical applications.
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Affiliation(s)
- Sihun Park
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, South Korea
| | - Sang Seok Lee
- Functional Composite Materials Research Center, Institute of Advanced Composite Materials, KIST, Wanju-gun, Jeollabuk-do, 55324, South Korea
| | - Shin-Hyun Kim
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, South Korea
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13
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Chao Y, Mak SY, Rahman S, Zhu S, Shum HC. Generation of High-Order All-Aqueous Emulsion Drops by Osmosis-Driven Phase Separation. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2018; 14:e1802107. [PMID: 30118584 DOI: 10.1002/smll.201802107] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2018] [Revised: 07/28/2018] [Indexed: 05/14/2023]
Abstract
Droplets containing ternary mixtures can spontaneously phase-separate into high-order structures upon a change in composition, which provides an alternative strategy to form multiphase droplets. However, existing strategies always involve nonaqueous solvents that limit the potential applications of the resulting multiple droplets, such as encapsulation of biomolecules. Here, a robust approach to achieve high-order emulsion drops with an all-aqueous nature from two aqueous phases by osmosis-induced phase separation on a microfluidic platform is presented. This technique is enabled by the existence of an interface of the two aqueous phases and phase separation caused by an osmolality difference between the two phases. The complexity of emulsion drops induced by phase separation could be controlled by varying the initial concentration of solutes and is systematically illustrated in a state diagram. In particular, this technique is utilized to successfully achieve high-order all-aqueous droplets in a different aqueous two-phase system. The proposed method is simple since it only requires two initial aqueous solutions for generating multilayered, organic-solvent-free all-aqueous emulsion drops, and thus these multiphase emulsion drops can be further tailored to serve as highly biocompatible material templates.
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Affiliation(s)
- Youchuang Chao
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China
- HKU-Shenzhen Institute of Research and Innovation (HKU-SIRI), Shenzhen, Guangdong, 518000, China
| | - Sze Yi Mak
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China
- HKU-Shenzhen Institute of Research and Innovation (HKU-SIRI), Shenzhen, Guangdong, 518000, China
| | - Shakurur Rahman
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Shipei Zhu
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Ho Cheung Shum
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China
- HKU-Shenzhen Institute of Research and Innovation (HKU-SIRI), Shenzhen, Guangdong, 518000, China
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