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Silvera Batista CA, Wang K, Blake H, Nwosu-Madueke V, Marbach S. Artificial chemotaxis under electrodiffusiophoresis. J Colloid Interface Sci 2024; 677:171-180. [PMID: 39142158 DOI: 10.1016/j.jcis.2024.08.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Revised: 07/30/2024] [Accepted: 08/01/2024] [Indexed: 08/16/2024]
Abstract
HYPOTHESIS Through a large parameter space, electric fields can tune colloidal interactions and forces leading to diverse static and dynamical structures. So far, however, field-driven interactions have been limited to dipole-dipole and hydrodynamic contributions. Nonetheless, in this work, we propose that under the right conditions, electric fields can also induce interactions based on local chemical fields and diffusiophoretic flows. EXPERIMENTS Herein, we present a strategy to generate and measure 3D chemical gradients under electric fields. In this approach, faradaic reactions at electrodes induce global pH gradients that drive long-range transport through electrodiffusiophoresis. Simultaneously, the electric field induces local pH gradients by driving the particle's double layer far from equilibrium. FINDINGS As a result, while global pH gradients lead to 2D focusing away from electrodes, local pH gradients induce aggregation in the third dimension. Evidence points to a mechanism of interaction based on diffusiophoresis. Interparticle interactions display a strong dependence on surface chemistry, zeta potential and diameter of particles. Furthermore, pH gradients can be readily tuned by adjusting the voltage and frequency of the electric field. For large Péclet numbers, we observed a collective chemotactic-like collapse of particles. Remarkably, such collapse occurs without reactions at a particle's surface. By mixing particles with different sizes, we also demonstrate, through experiments and Brownian dynamics simulations, the emergence of non-reciprocal interactions, where small particles are more drawn towards large ones.
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Affiliation(s)
- Carlos A Silvera Batista
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, 37205, United States; Vanderbilt Institute for Nanoscale Science and Engineering, Vanderbilt University, Nashville, 37205, United States.
| | - Kun Wang
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, 37205, United States
| | - Hannah Blake
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, 37205, United States
| | - Vivian Nwosu-Madueke
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, 37205, United States
| | - Sophie Marbach
- CNRS, Sorbonne Université, Physicochimie des Electrolytes et Nanosystèmes Interfaciaux, Paris, F-75005, France.
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2
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Feng K, Shen W, Chen L, Gong J, Palberg T, Qu J, Niu R. Weak Ion-Exchange Based Magnetic Swarm for Targeted Drug Delivery and Chemotherapy. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2306798. [PMID: 38059804 DOI: 10.1002/smll.202306798] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 11/06/2023] [Indexed: 12/08/2023]
Abstract
Swimming microrobots that are actuated by multiple stimuli/fields display various intriguing collective behaviors, ranging from phase separation to clustering and giant number fluctuation; however, it is still chanllenging to achieve multiple responses and functionalities within one colloidal system to emulate high environmental adaptability and improved tasking capability of natural swarms. In this work, a weak ion-exchange based swarm is presented that can self-organize and reconfigure by chemical, light, and magnetic fields, showing living crystal, amorphous glass, liquid, chain, and wheel-like structures. By changing the frequency and strength of the rotating magnetic field, various well-controlled and fast transformations are obtained. Experiments show the high adaptability and functionality of the microrobot swarm in delivering drugs in confined spaces, such as narrow channels with turns or obstacles. The drug-carrying swarm exhibits excellent chemtherapy for Hela and CT26 cells due to the pH-enhanced drug release and locomotion. This reconfigurable microswarm provides a new platform for biomedical and environmental applications.
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Affiliation(s)
- Kai Feng
- Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, Hubei Key Laboratory of Material Chemistry and Service Failure, Hubei Engineering Research Center for Biomaterials and Medical Protective Materials, Semiconductor Chemistry Center, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
| | - Wenqi Shen
- Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, 221002, China
| | - Ling Chen
- Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, Hubei Key Laboratory of Material Chemistry and Service Failure, Hubei Engineering Research Center for Biomaterials and Medical Protective Materials, Semiconductor Chemistry Center, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
| | - Jiang Gong
- Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, Hubei Key Laboratory of Material Chemistry and Service Failure, Hubei Engineering Research Center for Biomaterials and Medical Protective Materials, Semiconductor Chemistry Center, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
| | - Thomas Palberg
- Institut für physics, Johannes Gutenberg-Universtät Mainz, Staudingerweg 7, 55128, Mainz, Germany
| | - Jinping Qu
- Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, Hubei Key Laboratory of Material Chemistry and Service Failure, Hubei Engineering Research Center for Biomaterials and Medical Protective Materials, Semiconductor Chemistry Center, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
- Guangdong Provincial Key Laboratory of Technique and Equipment for Macromolecular Advanced Manufacturing, School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou, 510641, China
| | - Ran Niu
- Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, Hubei Key Laboratory of Material Chemistry and Service Failure, Hubei Engineering Research Center for Biomaterials and Medical Protective Materials, Semiconductor Chemistry Center, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
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3
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Zhou H, Ouyang W, Zou S, Xu S. The Control of the Expansion or Compression of Colloidal Crystals Lattice with Salt Solution. NANOMATERIALS (BASEL, SWITZERLAND) 2024; 14:355. [PMID: 38392728 PMCID: PMC10893356 DOI: 10.3390/nano14040355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Revised: 02/06/2024] [Accepted: 02/10/2024] [Indexed: 02/24/2024]
Abstract
Tuning the lattice spacing or stop bands holds great significance in the design and application of materials with colloidal crystals. Typically, particle surface modifications or the application of external physical fields are needed. In this study, we demonstrated the ability to expand or compress the lattice of colloidal crystals simply by utilizing a salt solution, without the need for any special treatments to the colloidal particles. We found that by only considering the diffusiophoresis effect we cannot explain the reversion of lattice expansion to lattice compression with the increase in the salt concentration and that the diffusioosmotic flow originating from the container wall must be taken into account. Further analysis revealed that variations in the salt concentration altered the relative amplitudes between diffusiophoresis and diffusioosmosis through changing the zeta potentials of the particles and the wall, and the competition between the particle diffusiophoresis and wall diffusioosmosis lay at the center of the underlying mechanism.
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Affiliation(s)
- Hongwei Zhou
- Key Laboratory of Microgravity, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China; (H.Z.); (W.O.); (S.Z.)
| | - Wenze Ouyang
- Key Laboratory of Microgravity, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China; (H.Z.); (W.O.); (S.Z.)
| | - Shuangyang Zou
- Key Laboratory of Microgravity, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China; (H.Z.); (W.O.); (S.Z.)
| | - Shenghua Xu
- Key Laboratory of Microgravity, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China; (H.Z.); (W.O.); (S.Z.)
- School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, China
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4
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Lorenz N, Wittenberg C, Palberg T. Porous crystals in charged sphere suspensions by aggregate-driven phase separation. SOFT MATTER 2023. [PMID: 37367202 DOI: 10.1039/d3sm00660c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/28/2023]
Abstract
The kinetics of phase transition processes often governs the resulting material microstructure. Using optical microscopy, we here investigate the formation and stabilization of a porous crystalline microstructure forming in low-salt suspensions of charged colloidal spheres containing aggregates comprising some 5-10 of these colloids. We observe the transformation of an initially crystalline colloidal solid with homogeneously incorporated aggregates to individual, compositionally refined crystallites of perforated morphology coexisting with an aggregate-enriched fluid phase filling the holes and separating individual crystallites. A preliminary kinetic characterization suggests that the involved processes follow power laws. We show that this route to porous materials is neither restricted to nominally single component systems nor to a particular microstructure to start from. However, it necessitates an early rapid solidification stage during which the aggregates become trapped in the bulk of the host-crystals. The thermodynamic stability of the reconstructed crystalline scaffold against melting under increased salinity was found comparable to that of pure phase crystallites grown very slowly from a melt. Future implications of this novel route to porous colloidal crystals are discussed.
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Affiliation(s)
- Nina Lorenz
- Institute of Physics, Johannes Gutenberg Universität Mainz, Germany.
| | | | - Thomas Palberg
- Institute of Physics, Johannes Gutenberg Universität Mainz, Germany.
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5
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Lorenz N, Gupta I, Palberg T. Microstructural diversity, nucleation paths, and phase behavior in binary mixtures of charged colloidal spheres. J Chem Phys 2023; 158:114902. [PMID: 36948792 DOI: 10.1063/5.0140949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/17/2023] Open
Abstract
We study low-salt, binary aqueous suspensions of charged colloidal spheres of size ratio Γ = 0.57, number densities below the eutectic number density nE, and number fractions of p = 1.00-0.40. The typical phase obtained by solidification from a homogeneous shear-melt is a substitutional alloy with a body centered cubic structure. In strictly gas-tight vials, the polycrystalline solid is stable against melting and further phase transformation for extended times. For comparison, we also prepare the same samples by slow, mechanically undisturbed deionization in commercial slit cells. These cells feature a complex but well reproducible sequence of global and local gradients in salt concentration, number density, and composition as induced by successive deionization, phoretic transport, and differential settling of the components, respectively. Moreover, they provide an extended bottom surface suitable for heterogeneous nucleation of the β-phase. We give a detailed qualitative characterization of the crystallization processes using imaging and optical microscopy. By contrast to the bulk samples, the initial alloy formation is not volume-filling, and we now observe also α- and β-phases with low solubility of the odd component. In addition to the initial homogeneous nucleation route, the interplay of gradients opens various further crystallization and transformation pathways leading to a great diversity of microstructures. Upon a subsequent increase in salt concentration, the crystals melt again. Wall-based, pebble-shaped β-phase crystals and facetted α-crystals melt last. Our observations suggest that the substitutional alloys formed in bulk experiments by homogeneous nucleation and subsequent growth are mechanically stable in the absence of solid-fluid interfaces but thermodynamically metastable.
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Affiliation(s)
- Nina Lorenz
- Institute of Physics, Johannes Gutenberg University, 55122 Mainz, Germany
| | - Ishan Gupta
- Graz University of Technology, Institute of Applied Mechanics, Graz, Austria
| | - Thomas Palberg
- Institute of Physics, Johannes Gutenberg University, 55122 Mainz, Germany
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6
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Tavari T, Meamardoost S, Sepehry N, Akbarzadeh P, Nazari M, Hashemi NN, Nazari M. Effects of 3D electrodes arrangement in a novel AC electroosmotic micropump: Numerical modeling and experimental validation. Electrophoresis 2023; 44:450-461. [PMID: 36448415 DOI: 10.1002/elps.202200215] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 11/07/2022] [Accepted: 11/16/2022] [Indexed: 12/03/2022]
Abstract
To date, a comprehensive systematic optimization framework, capable of accurately predicting an efficient electrode geometry, is not available. Here, different geometries, including 3D step electrodes, have been designed in order to fabricate AC electroosmosis micropumps. It is essential to optimize both geometrical parameters of electrode, such as width and height of steps on each base electrode and their location in one pair, the size of each base electrode (symmetric or asymmetric), the gap of electrode pairs, and nongeometrical parameters such as fluid flow in a channel and electrical characteristics (e.g., frequency and voltage). The governing equations comprising of electric domain and fluid domain have been coupled using finite element method. The developed model was employed to investigate the effect of electrode geometric parameters on electroosmotic slip velocity and its subsequent effect on pressure and flow rate. Numerical simulation indicates that the optimal performance can be achieved using a design with varying step height and displacement, at a given voltage (2.5 V) and frequency (1 kHz). Finally, in order to validate the numerical simulation, the optimal microchip was fabricated using a combination of photolithography, electroplating, and a polydimethylsiloxane microchannel. Our results indicate that our micropump is capable of generating a pressure, velocity, and flow rate of 74.2 Pa, 1.76 mm/s, and 14.8 µl/min, respectively. This result reveals that our proposed geometry outperforms the state-of-the-art micropumps previously reported in the literature by improving the fluid velocity by 32%, with 80% less electrodes per unit length, and whereas the channel length is ∼80% shorter.
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Affiliation(s)
- Tannaz Tavari
- Department of Mechanical and Mechatronics Engineering, Shahrood University of Technology, Shahrood, Iran
| | - Saber Meamardoost
- Department of Chemical and Biological Engineering, University at Buffalo, Buffalo, New York, USA
| | - Naserodin Sepehry
- Department of Mechanical and Mechatronics Engineering, Shahrood University of Technology, Shahrood, Iran
| | - Pooria Akbarzadeh
- Department of Mechanical and Mechatronics Engineering, Shahrood University of Technology, Shahrood, Iran
| | - Mostafa Nazari
- Department of Mechanical and Mechatronics Engineering, Shahrood University of Technology, Shahrood, Iran
| | - Nicole N Hashemi
- Department of Mechanical Engineering, Iowa State University, Ames, Iowa, USA
| | - Mohsen Nazari
- Department of Mechanical and Mechatronics Engineering, Shahrood University of Technology, Shahrood, Iran
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7
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Fang Y, Wereley ST, Moran JL, Warsinger DM. Electric double layer overlap limits flow rate in Janus electrocatalytic self-pumping membranes. Electrochim Acta 2022. [DOI: 10.1016/j.electacta.2022.140762] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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8
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From radial to unidirectional water pumping in zeta-potential modulated Nafion nanostructures. Nat Commun 2022; 13:2812. [PMID: 35589767 PMCID: PMC9120507 DOI: 10.1038/s41467-022-30554-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 04/25/2022] [Indexed: 11/08/2022] Open
Abstract
Chemically propelled micropumps are promising wireless systems to autonomously drive fluid flows for many applications. However, many of these systems are activated by nocuous chemical fuels, cannot operate at high salt concentrations, or have difficulty for controlling flow directionality. In this work we report on a self-driven polymer micropump fueled by salt which can trigger both radial and unidirectional fluid flows. The micropump is based on the cation-exchanger Nafion, which produces chemical gradients and local electric fields capable to trigger interfacial electroosmotic flows. Unidirectional pumping is predicted by simulations and achieved experimentally by nanostructuring Nafion into microarrays with a fine tune modulation of surrounding surface zeta potentials. Nafion micropumps work in a wide range of salt concentrations, are reusable, and can be fueled by different salt cations. We demonstrate that they work with the common water-contaminant cadmium, using the own capture of this ion as fuel to drive fluid pumping. Thus, this system has potential for efficient and fast water purification strategies for environmental remediation. Unidirectional Nafion pumps also hold promise for effective analyte delivery or preconcentration for (bio)sensing assays. Chemically propelled micropumps are wireless fluid flow driving systems with many potential applications. Here, the authors report a self-driven reusable Nafion micropump fueled by different salt cations in a wide range of concentrations that triggers both radial and unidirectional flows, showing efficient water remediation capabilities.
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9
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Liebchen B, Mukhopadhyay AK. Interactions in active colloids. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 34:083002. [PMID: 34788232 DOI: 10.1088/1361-648x/ac3a86] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 11/16/2021] [Indexed: 06/13/2023]
Abstract
The past two decades have seen a remarkable progress in the development of synthetic colloidal agents which are capable of creating directed motion in an unbiased environment at the microscale. These self-propelling particles are often praised for their enormous potential to self-organize into dynamic nonequilibrium structures such as living clusters, synchronized super-rotor structures or self-propelling molecules featuring a complexity which is rarely found outside of the living world. However, the precise mechanisms underlying the formation and dynamics of many of these structures are still barely understood, which is likely to hinge on the gaps in our understanding of how active colloids interact. In particular, besides showing comparatively short-ranged interactions which are well known from passive colloids (Van der Waals, electrostatic etc), active colloids show novel hydrodynamic interactions as well as phoretic and substrate-mediated 'osmotic' cross-interactions which hinge on the action of the phoretic field gradients which are induced by the colloids on other colloids in the system. The present article discusses the complexity and the intriguing properties of these interactions which in general are long-ranged, non-instantaneous, non-pairwise and non-reciprocal and which may serve as key ingredients for the design of future nonequilibrium colloidal materials. Besides providing a brief overview on the state of the art of our understanding of these interactions a key aim of this review is to emphasize open key questions and corresponding open challenges.
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Affiliation(s)
- Benno Liebchen
- Institute for Condensed Matter Physics, Technische Universität Darmstadt, 64289 Darmstadt, Germany
| | - Aritra K Mukhopadhyay
- Institute for Condensed Matter Physics, Technische Universität Darmstadt, 64289 Darmstadt, Germany
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10
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Feuerstein L, Biermann CG, Xiao Z, Holm C, Simmchen J. Highly Efficient Active Colloids Driven by Galvanic Exchange Reactions. J Am Chem Soc 2021; 143:17015-17022. [PMID: 34523911 DOI: 10.1021/jacs.1c06400] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Micromotors are propelled by a variety of chemical reactions, with most of them being of catalytic nature. There are, however, systems based on redox reactions, which show clear benefits for efficiency. Here, we broaden the spectrum of suitable reactions to galvanic exchange processes, or an electrochemical replacement of a solid metal layer with dissolved ionic species of a more noble metal. We study the details of motility and the influence of different reaction parameters to conclude that these galvanophoretic processes circumvent several steps that lose efficiency in catalytic micromotors. Furthermore, we investigate the chemical process, the charge, and flow conditions that lead to this highly efficient new type of active motility. Toward a better understanding of the underlying processes, we propose an electrokinetic model that we numerically solve via finite elements.
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Affiliation(s)
- Linda Feuerstein
- Physical Chemistry, TU Dresden, Zellescher Weg 19, 01069 Dresden, Germany
| | - Carl Georg Biermann
- Institute for Computational Physics (ICP), Allmandring 3, 70569 Stuttgart, Germany
| | - Zuyao Xiao
- Physical Chemistry, TU Dresden, Zellescher Weg 19, 01069 Dresden, Germany
| | - Christian Holm
- Institute for Computational Physics (ICP), Allmandring 3, 70569 Stuttgart, Germany
| | - Juliane Simmchen
- Physical Chemistry, TU Dresden, Zellescher Weg 19, 01069 Dresden, Germany
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11
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Natu A, Ghosh U. Electrokinetics of polymeric fluids in narrow rectangular confinements. SOFT MATTER 2021; 17:8712-8729. [PMID: 34522922 DOI: 10.1039/d1sm00537e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The flow of polymeric liquids in narrow confinements with a rectangular cross section, in the presence of electrical double layers is analyzed here. Our analysis is motivated by the fact that many of the previous studies on the flow of complex fluids tend to focus on highly idealized parallel plate channels, which are markedly different from the rectangular ducts, used in many experiments and devices. We consider the combined electroosmotic and pressure driven flows as well as the streaming potential resulting from a mechanically driven flow. We use two distinct constitutive relations to model the polymeric liquids, namely the simplified exponential Phan-Thien-Tanner (sePTT) model and the Giesekus model, both of which are non-linear viscoelastic models, capable of capturing the shear thinning behavior. We establish that the applied electric field may have a strong influence on the overall flow rate, which rapidly increases with the field strength as well as the extent of viscoelasticity of the fluid. Viscoelasticity and shear thinning behavior also enhance the streaming potential by several fold as compared to a Newtonian medium. We demonstrate that the aspect ratio of a channel has a bigger influence on the net throughput and the streaming potential, when the extent of viscoelasticity is relatively large. We illustrate that for sePTT fluids, the flow is strictly unidirectional, while for Giesekus fluids, secondary flows are inevitably present on account of their non-zero second normal stress coefficient. Although the electric field does not change the overall patterns of these secondary flows, their magnitude does depend on the imposed field strength for combined flows.
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Affiliation(s)
- Aditya Natu
- Discipline of Mechanical Engineering, Indian Institute of Technology Gandhinagar, Gujarat-382355, India.
| | - Uddipta Ghosh
- Discipline of Mechanical Engineering, Indian Institute of Technology Gandhinagar, Gujarat-382355, India.
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12
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Mercado-Uribe H, Guevara-Pantoja FJ, García-Muñoz W, García-Maldonado JS, Méndez-Alcaraz JM, Ruiz-Suárez JC. On the evolution of the exclusion zone produced by hydrophilic surfaces: A contracted description. J Chem Phys 2021; 154:194902. [PMID: 34240904 DOI: 10.1063/5.0043084] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
After exciting scientific debates about its nature, the development of the exclusion zone, a region near hydrophilic surfaces from which charged colloidal particles are strongly expelled, has been finally traced back to the diffusiophoresis produced by unbalanced ion gradients. This was done by numerically solving the coupled Poisson equation for electrostatics, the two stationary Stokes equations for low Reynolds numbers in incompressible fluids, and the Nernst-Planck equation for mass transport. Recently, it has also been claimed that the leading mechanism behind the diffusiophoretic phenomenon is electrophoresis [Esplandiu et al., Soft Matter 16, 3717 (2020)]. In this paper, we analyze the evolution of the exclusion zone based on a one-component interaction model at the Langevin equation level, which leads to simple analytical expressions instead of the complex numerical scheme of previous works, yet being consistent with it. We manage to reproduce the evolution of the exclusion zone width and the mean-square displacements of colloidal particles we measure near Nafion, a perfluorinated polymer membrane material, along with all characteristic time regimes, in a unified way. Our findings are also strongly supported by complementary experiments using two parallel planar conductors kept at a fixed voltage, mimicking the hydrophilic surfaces, and some computer simulations.
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Affiliation(s)
- H Mercado-Uribe
- CINVESTAV-Monterrey, PIIT, 66600 Apodaca, Nuevo León, Mexico
| | | | - W García-Muñoz
- CINVESTAV-Monterrey, PIIT, 66600 Apodaca, Nuevo León, Mexico
| | - J S García-Maldonado
- Departamento de Física, CINVESTAV, Av. IPN 2508, Col. San Pedro Zacatenco, 07360 Ciudad de México, Mexico
| | - J M Méndez-Alcaraz
- Departamento de Física, CINVESTAV, Av. IPN 2508, Col. San Pedro Zacatenco, 07360 Ciudad de México, Mexico
| | - J C Ruiz-Suárez
- CINVESTAV-Monterrey, PIIT, 66600 Apodaca, Nuevo León, Mexico
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13
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Katuri J, Uspal WE, Popescu MN, Sánchez S. Inferring non-equilibrium interactions from tracer response near confined active Janus particles. SCIENCE ADVANCES 2021; 7:7/18/eabd0719. [PMID: 33931441 PMCID: PMC8087409 DOI: 10.1126/sciadv.abd0719] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Accepted: 03/12/2021] [Indexed: 05/02/2023]
Abstract
Chemically active Janus particles sustain non-equilibrium spatial variations in the chemical composition of the suspending solution; these induce hydrodynamic flow and (self-)motility of the particles. Direct mapping of these fields has so far proven to be too challenging. Therefore, indirect methods are needed, e.g., deconvolving the response of "tracer" particles to the activity-induced fields. Here, we study experimentally the response of silica particles, sedimented at a wall, to active Pt/silica Janus particles. The latter are either immobilized at the wall, with the symmetry axis perpendicular or parallel to the wall, or motile. The experiments reveal complex effective interactions that are dependent on the configuration and on the state of motion of the active particle. Within the framework of a coarse-grained model, the behavior of tracers near an immobilized Janus particle can be captured qualitatively once activity-induced osmotic flows on the wall are considered.
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Affiliation(s)
- Jaideep Katuri
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology (BIST), Baldiri Reixac 10-12, 08028 Barcelona Spain.
| | - William E Uspal
- Department of Mechanical Engineering, University of Hawaii at Manoa, 2540 Dole Street, Holmes Hall 302, Honolulu, HI 96822, USA.
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, D-70569 Stuttgart, Germany
| | - Mihail N Popescu
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, D-70569 Stuttgart, Germany.
| | - Samuel Sánchez
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology (BIST), Baldiri Reixac 10-12, 08028 Barcelona Spain.
- Institució Catalana de Recerca i Estudis Avancats (ICREA), Pg. Lluís Companys 23, 08010 Bacelona, Spain
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14
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Möller N, Liebchen B, Palberg T. Shaping the gradients driving phoretic micro-swimmers: influence of swimming speed, budget of carbonic acid and environment. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2021; 44:41. [PMID: 33759011 PMCID: PMC7987694 DOI: 10.1140/epje/s10189-021-00026-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Accepted: 01/22/2021] [Indexed: 05/07/2023]
Abstract
pH gradient-driven modular micro-swimmers are investigated as a model for a large variety of quasi-two-dimensional chemi-phoretic self-propelled entities. Using three-channel micro-photometry, we obtain a precise large field mapping of pH at a spatial resolution of a few microns and a pH resolution of [Formula: see text] units for swimmers of different velocities propelling on two differently charged substrates. We model our results in terms of solutions of the three-dimensional advection-diffusion equation for a 1:1 electrolyte, i.e. carbonic acid, which is produced by ion exchange and consumed by equilibration with dissolved [Formula: see text]. We demonstrate the dependence of gradient shape and steepness on swimmer speed, diffusivity of chemicals, as well as the fuel budget. Moreover, we experimentally observe a subtle, but significant feedback of the swimmer's immediate environment in terms of a substrate charge-mediated solvent convection. We discuss our findings in view of different recent results from other micro-fluidic or active matter investigations. We anticipate that they are relevant for quantitative modelling and targeted applications of diffusio-phoretic flows in general and artificial micro-swimmers in particular.
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Affiliation(s)
- Nadir Möller
- Institute of Condensed Matter Physics, Johannes Gutenberg Universität, Staudinger Weg 7, 55128, Mainz, Germany.
- Max Planck Graduade Center, Institute of Physics, Johannes Gutenberg Universität, Staudinger Weg 7, 55128, Mainz, Germany.
| | - Benno Liebchen
- Institute for Condensed Matter Physics, Technische Universität Darmstadt, Hochschulstr. 8, 64289, Darmstadt, Germany
| | - Thomas Palberg
- Institute of Condensed Matter Physics, Johannes Gutenberg Universität, Staudinger Weg 7, 55128, Mainz, Germany
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15
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Seo M, Park S, Lee D, Lee H, Kim SJ. Continuous and spontaneous nanoparticle separation by diffusiophoresis. LAB ON A CHIP 2020; 20:4118-4127. [PMID: 32909576 DOI: 10.1039/d0lc00593b] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The separation of nanoparticles has drawn critical attention in various microfluidic applications including chemical analysis, diagnostics and environmental monitoring. Thus, a number of nanoparticle separation methods have been extensively proposed. However, most of the conventional methods require complicated structured devices, expensive manufacturing processes, and external power sources. While a spontaneous diffusiophoretic separation device based on an ion exchange mechanism could overcome such drawbacks, the recovery of separated particles and the inevitable development of an acidic environment due to the release of H+ from the cation exchange membrane limit its practical applicability. Therefore, in this work, we present a simple but robust nanoparticle separation method based on spontaneously induced diffusiophoresis, which is operated in a continuous manner to overcome the limitations of conventional methods. First, we confirmed that the particle exclusion distance followed the previously developed scaling law of diffusiophoresis. Consequently, we demonstrated the separation of nanoparticles of 40 nm, 200 nm and 2 μm diameter by utilizing the fact that the exclusion distances of various particles were proportional to their diffusiophoretic mobility. Furthermore, the use of Tris buffer increased the diffusiophoretic migration of nanoparticles due to the enhanced concentration gradient, and enabled the produced solution to be compatible with pH-sensitive bio-samples. Therefore, we expect this continuous and spontaneous diffusiophoretic separation platform to be useful in practical applications for analyzing various nano-meter scale bio-particles.
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Affiliation(s)
- Myungjin Seo
- Department of Electrical and Computer Engineering, Seoul National University, Seoul 08826, Republic of Korea.
| | - Sungmin Park
- Department of Electrical and Computer Engineering, Seoul National University, Seoul 08826, Republic of Korea.
| | - Dokeun Lee
- Department of Electrical and Computer Engineering, Seoul National University, Seoul 08826, Republic of Korea.
| | - Hyomin Lee
- Department of Chemical and Biological Engineering, Jeju National University, Jeju 63243, Republic of Korea.
| | - Sung Jae Kim
- Department of Electrical and Computer Engineering, Seoul National University, Seoul 08826, Republic of Korea. and Nano Systems Institute, Seoul National University, Seoul 08826, Republic of Korea and Inter-university Semiconductor Research Center, Seoul National University, Seoul 08826, Republic of Korea
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16
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Munteanu RE, Popescu MN, Gáspár S. The impact of geometrical confinement in a slab on the behavior of tracer particles near active glucose oxidase micropump. Colloid Polym Sci 2020. [DOI: 10.1007/s00396-020-04744-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
AbstractPatches of surface-immobilized and catalytically active enzyme, immersed into a solution with the corresponding substrate, induce flow in the solution. Such systems are currently investigated as a promising direction in the development of self-powered micropumps that could operate autonomously within microfluidic devices. Here, we investigate the influence of confinement, within a slab of height H, on the response exhibited by silica tracer particles sedimented near a chemically active glucose oxidase patch which is immersed into a glucose solution of very low ionic strength. Irrespective of the value H, within the range explored in this study, a region depleted of tracers forms around the patch. When H is not much larger than the radius of the patch, the rate of growth of the depletion zone depends on H; somewhat surprisingly, this dependence is influenced by the glucose concentration. The results are discussed within the context of a simple model for a chemically active patch.
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17
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Cardoso RM, dos Santos RO, Munoz RAA, Garcia CD, Blanes L. A Multi-Pump Magnetohydrodynamics Lab-On-A-Chip Device for Automated Flow Control and Analyte Delivery. SENSORS 2020; 20:s20174909. [PMID: 32877999 PMCID: PMC7506898 DOI: 10.3390/s20174909] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 08/15/2020] [Accepted: 08/24/2020] [Indexed: 11/16/2022]
Abstract
This article shows the development of a computer-controlled lab-on-a-chip device with three magnetohydrodynamic (MHD) pumps and a pneumatic valve. The chip was made of a stack of layers of polymethylmethacrylate (PMMA), cut using a laser engraver and thermally bonded. The MHD pumps were built using permanent magnets (neodymium) and platinum electrodes, all of them controlled by an Arduino board and a set of relays. The implemented pumps were able to drive solutions in the open channels with a flow rate that increased proportionally with the channel width and applied voltage. To address the characteristic low pressures generated by this kind of pump, all channels were interconnected. Because the electrodes were immersed in the electrolyte, causing electrolysis and pH variations, the composition and ionic strength of the electrolyte solution were controlled. Additionally, side structures for releasing bubbles were integrated. With this multi-pump and valve solution, the device was used to demonstrate the possibility of performing an injection sequence in a system that resembles a traditional flow injection analysis system. Ultimately, the results demonstrate the possibility of performing injection sequences using an array of MHD pumps that can perform fluid handling in the 0-5 µL s-1 range.
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Affiliation(s)
- Rafael M. Cardoso
- Institute of Chemistry, Federal University of Uberlândia, Uberlândia 38400-000, Brazil; (R.M.C.); (R.A.A.M.)
| | - Robson O. dos Santos
- Laboratory for Applied Science and Technology in Health, Carlos Chagas Institute, Oswaldo Cruz Foundation (Fiocruz), Curitiba 81350-010, Brazil;
| | - Rodrigo A. A. Munoz
- Institute of Chemistry, Federal University of Uberlândia, Uberlândia 38400-000, Brazil; (R.M.C.); (R.A.A.M.)
| | - Carlos D. Garcia
- Department of Chemistry, Clemson University, Clemson, SC 29634, USA
- Correspondence: (C.D.G); (L.B.)
| | - Lucas Blanes
- Laboratory for Applied Science and Technology in Health, Carlos Chagas Institute, Oswaldo Cruz Foundation (Fiocruz), Curitiba 81350-010, Brazil;
- Correspondence: (C.D.G); (L.B.)
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18
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Botin D, Carrique F, Ruiz-Reina E, Palberg T. Non-monotonic concentration dependence of the electro-phoretic mobility of charged spheres in realistic salt free suspensions. J Chem Phys 2020; 152:244902. [PMID: 32610949 DOI: 10.1063/5.0010692] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Using super-heterodyne Doppler velocimetry with multiple scattering correction, we extend the optically accessible range of concentrations in experiments on colloidal electro-kinetics. Here, we measured the electro-phoretic mobility and the DC conductivity of aqueous charged sphere suspensions covering about three orders of magnitude in particle concentrations and transmissions as low as 40%. The extended concentration range for the first time allows the demonstration of a non-monotonic concentration dependence of the mobility for a single particle species. Our observations reconcile previous experimental observations made on other species over restricted concentration ranges. We compare our results to the state-of-the-art theoretical calculations using a constant particle charge and the carefully determined experimental boundary conditions as input. In particular, we consider the so-called realistic salt free conditions, i.e., we respect the release of counterions by the particles, the solvent hydrolysis, and the formation of carbonic acid from dissolved neutral CO2. We also compare our results to previous results obtained under similarly well-defined conditions. This allows identification of three distinct regions of differing density dependence. There is an ascent during the build-up of double layer overlap, which is not expected by theory, an extended plateau region in quantitative agreement with theoretical expectation based on a constant effective charge and a sudden decrease, which occurs way before the expected gradual decrease. Our observations suggest a relation of the non-monotonic behavior to a decrease in particle charge, and we tentatively discuss possibly underlying mechanisms.
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Affiliation(s)
- Denis Botin
- Institute of Physics, Johannes Gutenberg University, 55128 Mainz, Germany
| | - Felix Carrique
- Institute Carlos I for Theoretical and Computational Physics (iC1), Departamento de Física Aplicada I, Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos, 29071 Málaga, Spain
| | - Emilio Ruiz-Reina
- Institute Carlos I for Theoretical and Computational Physics (iC1), Departamento de Física Aplicada II, Escuela de Ingenierías Industriales, Universidad de Málaga, Campus de Teatinos, 29071 Málaga, Spain
| | - Thomas Palberg
- Institute of Physics, Johannes Gutenberg University, 55128 Mainz, Germany
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19
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Xu L, Wang A, Li X, Oh KW. Passive micropumping in microfluidics for point-of-care testing. BIOMICROFLUIDICS 2020; 14:031503. [PMID: 32509049 PMCID: PMC7263483 DOI: 10.1063/5.0002169] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 05/14/2020] [Indexed: 05/11/2023]
Abstract
Suitable micropumping methods for flow control represent a major technical hurdle in the development of microfluidic systems for point-of-care testing (POCT). Passive micropumping for point-of-care microfluidic systems provides a promising solution to such challenges, in particular, passive micropumping based on capillary force and air transfer based on the air solubility and air permeability of specific materials. There have been numerous developments and applications of micropumping techniques that are relevant to the use in POCT. Compared with active pumping methods such as syringe pumps or pressure pumps, where the flow rate can be well-tuned independent of the design of the microfluidic devices or the property of the liquids, most passive micropumping methods still suffer flow-control problems. For example, the flow rate may be set once the device has been made, and the properties of liquids may affect the flow rate. However, the advantages of passive micropumping, which include simplicity, ease of use, and low cost, make it the best choice for POCT. Here, we present a systematic review of different types of passive micropumping that are suitable for POCT, alongside existing applications based on passive micropumping. Future trends in passive micropumping are also discussed.
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Affiliation(s)
- Linfeng Xu
- Department of Bioengineering and Therapeutic
Sciences, Schools of Medicine and Pharmacy, University of California San
Francisco, 1700 4th Street, Byers Hall 304, San Francisco, California
94158, USA
| | - Anyang Wang
- SMALL (Sensors and MicroActuators Learning Lab),
Department of Electrical Engineering, University at Buffalo, The State University of New
York, Buffalo, New York 14260, USA
| | - Xiangpeng Li
- Department of Bioengineering and Therapeutic
Sciences, Schools of Medicine and Pharmacy, University of California San
Francisco, 1700 4th Street, Byers Hall 304, San Francisco, California
94158, USA
| | - Kwang W. Oh
- SMALL (Sensors and MicroActuators Learning Lab),
Department of Electrical Engineering, University at Buffalo, The State University of New
York, Buffalo, New York 14260, USA
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20
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Esplandiu MJ, Reguera D, Fraxedas J. Electrophoretic origin of long-range repulsion of colloids near water/Nafion interfaces. SOFT MATTER 2020; 16:3717-3726. [PMID: 32232286 DOI: 10.1039/d0sm00170h] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
One of the most striking properties of Nafion is the formation of a long-range solute exclusion zone (EZ) in contact with water. The mechanism of formation of this EZ has been the subject of a controversial and long-standing debate. Previous studies by Schurr et al. and Florea et al. root the explanation of this phenomenon in the ion-exchange properties of Nafion, which generates ion diffusion and ion gradients that drive the repulsion of solutes by diffusiophoresis. Here we have evaluated separately the electrophoretic and chemiphoretic contributions to multi-ionic diffusiophoresis using differently charged colloidal tracers as solutes to identify better their contribution in the EZ formation. Our experimental results, which are also supported by numerical simulations, show that the electric field, built up due to the unequal diffusion coefficients of the exchanged ions, is the dominant parameter behind such interfacial phenomenon in the presence of alkali metal chlorides. The EZ formation depends on the interplay of the electric field with the zeta potential of the solute and can be additionally modulated by changing ion diffusion coefficients or adding salts. As a consequence, we show that not all solutes can be expelled from the Nafion interface and hence the EZ is not always formed. This study thus provides a more detailed description of the origin and dynamics of this phenomenon and opens the door to the rational use of this active interface for many potential applications.
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Affiliation(s)
- Maria J Esplandiu
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain.
| | - David Reguera
- Departament de Física de la Matèria Condensada, Universitat de Barcelona, C/Martí i Franquès 1, 08028 Barcelona, Spain and Universitat de Barcelona, Institute of Complex Systems (UBICS), C/Martí i Franquès 1, 08028 Barcelona, Spain
| | - Jordi Fraxedas
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain.
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21
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Du S, Wang H, Zhou C, Wang W, Zhang Z. Motor and Rotor in One: Light-Active ZnO/Au Twinned Rods of Tunable Motion Modes. J Am Chem Soc 2020; 142:2213-2217. [PMID: 31957432 DOI: 10.1021/jacs.9b13093] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Precise control of the motion of micromachines is the key to achieving their functions for practical applications. The main challenge is that a given micromachine can typically exhibit only one motion mode, i.e., translation or rotation, while having multiple modes of motion resulting from a simple actuation is still rare. Here we designed and synthesized photochemically powered zinc oxide/gold (ZnO/Au) rods that exhibit multiple motion modes. Under homogeneous UV irradiation, these ZnO/Au rods undergo a transition from ballistic motion to persistent rotational motion upon increasing the fuel concentration or the light intensity. In addition, the rods can switch modes from a circular motion to a helical motion and then a straight-line motion by tuning the angle of incident light. We envision that such attractive colloidal micromachines with controllable motions hold considerable promise for diverse practical applications.
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Affiliation(s)
- Sinan Du
- Center for Soft Condensed Matter Physics and Interdisciplinary Research , Soochow University , Suzhou 215006 , China.,College of Chemistry, Chemical Engineering and Materials Science , Soochow University , Suzhou 215123 , China
| | - Huaguang Wang
- College of Chemistry, Chemical Engineering and Materials Science , Soochow University , Suzhou 215123 , China
| | - Chao Zhou
- School of Materials Science and Engineering , Harbin Institute of Technology (Shenzhen) , Shenzhen 518055 , China
| | - Wei Wang
- School of Materials Science and Engineering , Harbin Institute of Technology (Shenzhen) , Shenzhen 518055 , China
| | - Zexin Zhang
- Center for Soft Condensed Matter Physics and Interdisciplinary Research , Soochow University , Suzhou 215006 , China.,College of Chemistry, Chemical Engineering and Materials Science , Soochow University , Suzhou 215123 , China
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22
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Numerical Study of Electro-Osmotic Fluid Flow and Vortex Formation. MICROMACHINES 2019; 10:mi10120796. [PMID: 31757052 PMCID: PMC6953093 DOI: 10.3390/mi10120796] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 11/13/2019] [Accepted: 11/15/2019] [Indexed: 01/28/2023]
Abstract
The phenomenon of electro-osmosis was studied by performing numerical simulations on the flow between parallel walls and at the nozzle microchannels. In this work, we propose a numerical approximation to perform simulations of vortex formation which occur after the passage of the fluid through an abrupt contraction at the microchannel. The motion of the charges in the solution is described by the Poisson-Nernst-Planck equations and used the generalized finite differences to solve the numerical problem. First, solutions for electro-osmotic flow were obtained for the Phan-Thien/Thanner model in a parallel walls channel. Later simulations for electro-osmotic flow were performed in a nozzle. The formation of vortices near the contraction within the nozzle was verified by taking into account a flow perturbation model.
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23
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Glucose Oxidase Micropumps: Multi-Faceted Effects of Chemical Activity on Tracer Particles Near the Solid–Liquid Interface. CONDENSED MATTER 2019. [DOI: 10.3390/condmat4030073] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
We report the development of glucose oxidase pumps characterized by small lateral dimensions (≈200 μ m). We studied the effects of the activity of the enzyme pump on silica particles (“tracers”) sedimented around the enzyme pump/patch. Once the activity of the pump was turned on (i.e., the glucose substrate was added to the solution), in-plane motion of the tracers away from the enzyme patch, as well as the emergence of an in-plane region around the patch which was depleted by tracers, was observed. The lateral extent of this depletion zone increased in time at a rate dependent both on the glucose concentration and on the areal density of the enzyme in the patch. We argue that, when the tracers were very near the wall, their motion and the emergence of the depletion zone were most likely the result of diffusiophoresis and drag by osmotic flows induced at the wall, rather than that of drag by a solutal buoyancy driven convective flow. We infer that, for the glucose oxidase enzymatic pumps, bulk (solutal buoyancy), as previously reported, as well as surface (osmotic) driven flows coexist and have to be explicitly accounted for. It seems plausible to assume that this is the case in general for enzyme pumps, and these complementary effects should be considered in the design of applications, e.g., stirring or sensing inside microfluidic systems, based on such pumps.
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24
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Danis U, Rasooli R, Chen CY, Dur O, Sitti M, Pekkan K. Thrust and Hydrodynamic Efficiency of the Bundled Flagella. MICROMACHINES 2019; 10:mi10070449. [PMID: 31277385 PMCID: PMC6680724 DOI: 10.3390/mi10070449] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 05/23/2019] [Accepted: 05/26/2019] [Indexed: 01/09/2023]
Abstract
The motility mechanism of prokaryotic organisms has inspired many untethered microswimmers that could potentially perform minimally invasive medical procedures in stagnant fluid regions inside the human body. Some of these microswimmers are inspired by bacteria with single or multiple helical flagella to propel efficiently and fast. For multiple flagella configurations, the direct measurement of thrust and hydrodynamic propulsion efficiency has been challenging due to the ambiguous mechanical coupling between the flow field and mechanical power input. To address this challenge and to compare alternative micropropulsion designs, a methodology based on volumetric velocity field acquisition is developed to acquire the key propulsive performance parameters from scaled-up swimmer prototypes. A digital particle image velocimetry (PIV) analysis protocol was implemented and experiments were conducted with the aid of computational fluid dynamics (CFD). First, this methodology was validated using a rotating single-flagellum similitude model. In addition to the standard PIV error assessment, validation studies included 2D vs. 3D PIV, axial vs. lateral PIV and simultaneously acquired direct thrust force measurement comparisons. Compatible with typical micropropulsion flow regimes, experiments were conducted both for very low and higher Reynolds (Re) number regimes (up to a Re number = 0.01) than that are reported in the literature. Finally, multiple flagella bundling configurations at 0°, 90° and 180° helical phase-shift angles were studied using scaled-up multiple concentric flagella thrust elements. Thrust generation was found to be maximal for the in-phase (0°) bundling configuration but with ~50% lower hydrodynamic efficiency than the single flagellum. The proposed measurement protocol and static thrust test-bench can be used for bio-inspired microscale propulsion methods, where direct thrust and efficiency measurement are required.
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Affiliation(s)
- Umit Danis
- Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Reza Rasooli
- Department of Mechanical Engineering, Koc University, Istanbul 34450, Turkey
| | - Chia-Yuan Chen
- Department of Mechanical Engineering, National Cheng Kung University, Tainan 701, Taiwan
| | - Onur Dur
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Metin Sitti
- Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
- Department of Mechanical Engineering, Koc University, Istanbul 34450, Turkey
- Physical Intelligence Department, Max Planck Institute for Intelligent Systems, Stuttgart 70569, Germany
| | - Kerem Pekkan
- Department of Mechanical Engineering, Koc University, Istanbul 34450, Turkey.
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
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25
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Tsai SC, Lee E. Diffusiophoresis of a Highly Charged Porous Particle Induced by Diffusion Potential. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:3143-3155. [PMID: 30714738 DOI: 10.1021/acs.langmuir.8b04146] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Diffusiophoresis, the motion of a colloidal particle in response to the concentration gradient of solutes in the suspending medium, is investigated theoretically on the basis of numerical computations in this study for charged porous particles, especially highly or extremely porous ones, focusing on the electrophoresis component induced by diffusion potential, which is generated spontaneously in a binary electrolyte solution where the diffusivities of the two ionic species are distinct. A benchmark carbonic acid solution of H(aq)+ and HCO3(aq)- is chosen to be the major suspending medium, as its large diffusion potential and remarkable performance in practical applications have been reported recently in the literature. More than 3 orders of magnitude increase in particle diffusiophoretic mobility is predicted under some circumstances, should the permeability of the particle increase 10-fold. Nonlinear effects such as the motion-deterring double-layer polarization effect pertinent to highly charged particles and the counterion condensation or shielding/screening effect pertinent to porous particles are investigated in particular for their impact on the particle motion, among other electrokinetic parameters examined. A visual demonstration of the nonlinear double-layer polarization is provided. Moreover, both the chemiphoresis and the electrophoresis components are explored and analyzed in detail. The results presented here can be applied in biochemical and biomedical fields involving DNAs and proteins, which can be modeled excellently as charged porous particles in their electrokinetic motion.
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Affiliation(s)
- Shan-Chi Tsai
- Department of Chemical Engineering , National Taiwan University , No.1, Sec. 4, Roosevelt Road , Taipei 10617 , Taiwan
| | - Eric Lee
- Department of Chemical Engineering , National Taiwan University , No.1, Sec. 4, Roosevelt Road , Taipei 10617 , Taiwan
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26
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Lee E. Diffusiophoresis of Rigid Particles. THEORY OF ELECTROPHORESIS AND DIFFUSIOPHORESIS OF HIGHLY CHARGED COLLOIDAL PARTICLES 2019. [DOI: 10.1016/b978-0-08-100865-2.00016-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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27
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Kuron M, Kreissl P, Holm C. Toward Understanding of Self-Electrophoretic Propulsion under Realistic Conditions: From Bulk Reactions to Confinement Effects. Acc Chem Res 2018; 51:2998-3005. [PMID: 30417644 DOI: 10.1021/acs.accounts.8b00285] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Active matter concerns itself with the study of particles that convert energy into work, typically motion of the particle itself. This field saw a surge of interest over the past decade, after the first micrometer-sized, man-made chemical motors were created. These particles served as a simple model system for studying in a well-controlled manner complex motion and cooperative behavior as known from biology. In addition, they have stimulated new efforts in understanding out-of-equilibrium statistical physics and started a revolution in microtechnology and robotics. Concentrated effort has gone into realizing these ambitions, and yet much remains unknown about the chemical motors themselves. The original designs for self-propelled particles relied on the conversion of the chemical energy of hydrogen peroxide into motion via catalytic decomposition taking place heterogeneously over the surface of the motor. This sets up gradients of chemical fields around the particle, which allow it to autophorese. That is, the interaction between the motor and the heterogeneously distributed solute species can drive fluid flow and the motor itself. There are two basic designs: the first relies on redox reactions taking place between the two sides of a bimetal, for example, a gold-platinum Janus sphere or nanorod. The second uses a catalytic layer of platinum inhomogeneously vapor-deposited onto a nonreactive particle. For convenience's sake, these can be referred to as redox motors and monometallic half-coated motors, respectively. To date, most researchers continue to rely on variations of these simple, yet elegant designs for their experiments. However, there is ongoing debate on the exact way chemical energy is transduced into motion in these motors. Many of the experimental observations on redox motors were successfully modeled via self-electrophoresis, while for half-coated motors there has been a strong focus on self-diffusiophoresis. Currently, there is mounting evidence that self-electrophoresis provides the dominant contribution to the observed speeds of half-coated motors, even if the vast majority of the reaction products are electroneutral. In this Account, we will summarize the most common electrophoretic propulsion model and discuss its strengths and weaknesses in relation to recent experiments. We will comment on the possible need to go beyond surface reactions and consider the entire medium as an "active fluid" that can create and annihilate charged species. This, together with confinement and collective effects, makes it difficult to gain a detailed understanding of these swimmers. The potentially dominant effect of confinement is highlighted on the basis of a recent study of an electro-osmotic pump that drives fluid along a substrate. Detailed analysis of this system allows for identification of the electro-osmotic driving mechanism, which is powered by micromolar salt concentrations. We will discuss how our latest numerical solver developments, based on the lattice Boltzmann method, should enable us to study collective behavior in systems comprised of these and other electrochemical motors in realistic environments. We conclude with an outlook on the future of modeling chemical motors that may facilitate the community's microtechnological ambitions.
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Affiliation(s)
- Michael Kuron
- Institute for Computational Physics (ICP), University of Stuttgart, Allmandring 3, 70569 Stuttgart, Germany
| | - Patrick Kreissl
- Institute for Computational Physics (ICP), University of Stuttgart, Allmandring 3, 70569 Stuttgart, Germany
| | - Christian Holm
- Institute for Computational Physics (ICP), University of Stuttgart, Allmandring 3, 70569 Stuttgart, Germany
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28
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Popescu MN, Uspal WE, Domínguez A, Dietrich S. Effective Interactions between Chemically Active Colloids and Interfaces. Acc Chem Res 2018; 51:2991-2997. [PMID: 30403132 DOI: 10.1021/acs.accounts.8b00237] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Chemically active colloids can achieve force- and torque-free motility ("self-propulsion") via the promotion, on their surface, of catalytic chemical reactions involving the surrounding solution. Such systems are valuable both from a theoretical perspective, serving as paradigms for nonequilibrium processes, as well as from an application viewpoint, according to which active colloids are envisioned to play the role of carriers ("engines") in novel lab-on-a-chip devices. The motion of such colloids is intrinsically connected with a "chemical field", i.e., the distribution near the colloid of the number densities of the various chemical species present in the solution, and with the hydrodynamic flow of the solution around the particle. In most of the envisioned applications, and in virtually all reported experimental studies, the active colloids operate under spatial confinement (e.g., within a microfluidic channel, a drop, a free-standing liquid film, etc.). In such cases, the chemical field and the hydrodynamic flow associated with an active colloid are influenced by any nearby confining surfaces, and these disturbances couple back to the particle. Thus, an effective interaction with the spatial confinement arises. Consequently, the particle is endowed with means to perceive and to respond to its environment. Understanding these effective interactions, finding the key parameters which control them, and designing particles with desired, preconfigured responses to given environments, require interdisciplinary approaches which synergistically integrate methods and knowledge from physics, chemistry, engineering, and materials science. Here we review how, via simple models of chemical activity and self-phoretic motion, progress has recently been made in understanding the basic physical principles behind the complex behaviors exhibited by active particles near interfaces. First, we consider the occurrence of "interface-bounded" steady states of chemically active colloids near simple, nonresponsive interfaces. Examples include particles "sliding" along, or "hovering" above, a hard planar wall while inducing hydrodynamic flow of the solution. These states lay the foundations for concepts like the guidance of particles by the topography of the wall. We continue to discuss responsive interfaces: a suitable chemical patterning of a planar wall allows one to bring the particles into states of motion which are spatially localized (e.g., within chemical stripes or along chemical steps). These occur due to the wall responding to the activity-induced chemical gradients by generating osmotic flows, which encode the surface-chemistry of the wall. Finally, we discuss how, via activity-induced Marangoni stresses, long-ranged effective interactions emerge from the strong hydrodynamic response of fluid interfaces. These examples highlight how in this context a desired behavior can be potentially selected by tuning suitable parameters (e.g., the phoretic mobility of the particle, or the strength of the Marangoni stress at an interface). This can be accomplished via a judicious design of the surface chemistry of the particle and of the boundary, or by the choice of the chemical reaction in solution.
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Affiliation(s)
- Mihail N. Popescu
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, D-70569 Stuttgart, Germany
- IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, D-70569 Stuttgart, Germany
| | - William E. Uspal
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, D-70569 Stuttgart, Germany
- IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, D-70569 Stuttgart, Germany
| | - Alvaro Domínguez
- Física Teórica, Universidad de Sevilla, Apdo. 1065, 41080 Sevilla, Spain
| | - Siegfried Dietrich
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, D-70569 Stuttgart, Germany
- IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, D-70569 Stuttgart, Germany
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Niu R, Fischer A, Palberg T, Speck T. Dynamics of Binary Active Clusters Driven by Ion-Exchange Particles. ACS NANO 2018; 12:10932-10938. [PMID: 30346687 DOI: 10.1021/acsnano.8b04221] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We present a framework to quantitatively predict the linear and rotational directed motion of synthetic modular microswimmers. To this end, we study binary dimers and characterize their approach motion as effective interactions within a minimal model. We apply this framework to the assembly of small aggregates composed of a cationic ion-exchange particle with up to five passive particles or anionic ion-exchange particles at dilute conditions. Particles sediment and move close to a substrate, above which the ion-exchange particles generate flow. This flow mediates long-range attractions leading to a slow collapse during which long-lived clusters of a few particles assemble. The effective interactions between unlike particles break Newton's third law. Depending on their symmetry, assemblies thus can become linear or circle swimmers, or remain inert (no directed motion).
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Affiliation(s)
- Ran Niu
- Institut für Physik , Johannes Gutenberg Universität Mainz , Staudingerweg 7-9 , 55128 Mainz , Germany
| | - Andreas Fischer
- Institut für Physik , Johannes Gutenberg Universität Mainz , Staudingerweg 7-9 , 55128 Mainz , Germany
| | - Thomas Palberg
- Institut für Physik , Johannes Gutenberg Universität Mainz , Staudingerweg 7-9 , 55128 Mainz , Germany
| | - Thomas Speck
- Institut für Physik , Johannes Gutenberg Universität Mainz , Staudingerweg 7-9 , 55128 Mainz , Germany
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30
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Botin D, Wenzl J, Niu R, Palberg T. Colloidal electro-phoresis in the presence of symmetric and asymmetric electro-osmotic flow. SOFT MATTER 2018; 14:8191-8204. [PMID: 30259053 DOI: 10.1039/c8sm00934a] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We characterize the electro-phoretic motion of charged sphere suspensions in the presence of substantial electro-osmotic flow using a recently introduced small angle super-heterodyne dynamic light scattering instrument (ISASH-LDV). Operation in integral mode gives access to the particle velocity distribution over the complete cell cross-section. Obtained Doppler spectra are evaluated for electro-phoretic mobility, wall electro-osmotic mobility and particle diffusion coefficient. Simultaneous measurements of differing electro-osmotic mobilities leading to asymmetric solvent flow are demonstrated in a custom made electro-kinetic cell fitting standard microscopy slides as exchangeable sidewalls. The scope and range of our approach are discussed demonstrating the possibility of an internal calibration standard and using the simultaneously measured electro-kinetic mobilities in the interpretation of a microfluidic pumping experiment involving an inhomogeneous electric field and a complex solvent flow pattern.
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Affiliation(s)
- Denis Botin
- Institute of Physics, Johannes Gutenberg University, D-55099 Mainz, Germany.
| | - Jennifer Wenzl
- Institute of Physics, Johannes Gutenberg University, D-55099 Mainz, Germany.
| | - Ran Niu
- Institute of Physics, Johannes Gutenberg University, D-55099 Mainz, Germany.
| | - Thomas Palberg
- Institute of Physics, Johannes Gutenberg University, D-55099 Mainz, Germany.
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31
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Abstract
The field of active matter in general and microswimming in particular has experienced a rapid and ongoing expansion over the last decade. A particular interesting aspect is provided by artificial autonomous microswimmers constructed from individual active and inactive functional components into self-propelling complexes. Such modular microswimmers may exhibit directed motion not seen for each individual component. In this review, we focus on the establishment and recent developments in the modular approach to microswimming. We introduce the bound and dynamic prototypes, show mechanisms and types of modular swimming and discuss approaches to control the direction and speed of modular microswimmers. We conclude by highlighting some challenges faced by researchers as well as promising directions for future research in the realm of modular swimming.
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Affiliation(s)
- Ran Niu
- Institut für Physik, Johannes Gutenberg-Universtät Mainz, Staudingerweg 7, 55128 Mainz, Germany.
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32
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Niu R, Palberg T. Correction: Seedless assembly of colloidal crystals by inverted micro-fluidic pumping. SOFT MATTER 2018; 14:7542. [PMID: 30167615 DOI: 10.1039/c8sm90158a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Correction for 'Seedless assembly of colloidal crystals by inverted micro-fluidic pumping' by Ran Niu et al., Soft Matter, 2018, 14, 3435-3442.
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Affiliation(s)
- Ran Niu
- Institut für Physik, Johannes-Gutenberg Universität, Staudingerweg 7, 55128, Mainz, Germany.
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33
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Lee H, Kim J, Yang J, Seo SW, Kim SJ. Diffusiophoretic exclusion of colloidal particles for continuous water purification. LAB ON A CHIP 2018; 18:1713-1724. [PMID: 29796478 DOI: 10.1039/c8lc00132d] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
It has been observed that colloidal particles are anomalously repelled from the interface of nanoporous materials and water by up to hundreds of micrometers even if there is no additional external field present. Recently, the physical origin of this anomalous repulsion has turned out to be diffusiophoretic migration triggered by an ion exchange process through the interface. Since the repulsive force is induced by a salt gradient only, the phenomenon can be applied to a microscale water purification platform without the need for any external power sources. In this work, we suggest a micro/nanofluidic device for continuous water purification utilizing long-range diffusiophoretic migration around ion exchangeable surfaces. An ion concentration boundary layer was characterized by the Sherwood number (Sh) which is a key dimensionless number to describe the purification process. Depending on Sh, we have theoretically and experimentally demonstrated that long-range diffusiophoretic exclusion can be used for continuous water purification. Finally, our platform can be used as a highly energy-efficient and portable water treatment option for operations such as purification, disinfection, water softening, etc.
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Affiliation(s)
- Hyomin Lee
- Department of Electrical and Computer Engineering, Seoul National University, Seoul 08826, Republic of Korea. (H. Lee) (S. J. Kim)
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34
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Niu R, Palberg T. Seedless assembly of colloidal crystals by inverted micro-fluidic pumping. SOFT MATTER 2018; 14:3435-3442. [PMID: 29589860 DOI: 10.1039/c8sm00256h] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We propose a simple seedless approach to assemble millimeter sized monolayer single colloidal crystals with desired orientations at predetermined locations on an unstructured charged substrate. This approach utilizes the millimeter-ranged fluid flow on the bottom glass substrate induced by an ion exchange resin (IEX) fixed on top of the closed sample cell. The fluid flow increases with decreasing height of the sample cell and increasing radius R of the IEX. For a single inverted pump, millimeter sized monolayer single crystals of hexagonal close packing can be obtained. For two closely spaced (D ∼ 4R) pumps, the formed crystals have a predefined orientation along the line connecting the two IEX. By patterning IEX into different structures, colloidal crystals of different complex patterns form. The present method paves a convenient way for fabricating high quality monolayer colloidal crystals for a variety of applications.
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Affiliation(s)
- Ran Niu
- Institut für Physik, Johannes-Gutenberg Universität, Staudingerweg 7, 55128, Mainz, Germany.
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35
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Shum H, Balazs AC. Flow-Driven Assembly of Microcapsules into Three-Dimensional Towers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:2890-2899. [PMID: 29377705 DOI: 10.1021/acs.langmuir.7b04051] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
By harnessing biochemical signaling and chemotaxis, unicellular slime molds can aggregate on a surface to form a long, vertical stalk. Few synthetic systems can self-organize into analogous structures that emerge out of the plane. Through computational modeling, we devise a mechanism for assembling tower-like structures using microcapsules in solution as building blocks. In the simulations, chemicals diffusing from a central patch on a surface produce a concentration gradient, which generates a radially directed diffusioosmotic flow along the surface toward the center. This toroidal roll of a fluid pulls the microcapsules along the surface and lifts them above the patch. As more capsules are drawn toward the patch, some units are pushed off the surface but remain attached to the central microcapsule cluster. The upward-directed flow then draws out the cluster into a tower-like shape. The final three-dimensional (3D) structure depends on the flow field, the attractive capsule-capsule and capsule-surface interaction strengths, and the sedimentation force on the capsules. By tuning these factors, we can change the height of the structures that are produced. Moreover, by patterning the areas of the wall that are attractive to the capsules, we can form multiple vertical strands instead of a single tower. Our approach for flow-directed assembly can permit the growth of reconfigurable, 3D structures from simple subunits.
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Affiliation(s)
- Henry Shum
- Department of Applied Mathematics, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada
| | - Anna C Balazs
- Department of Chemical & Petroleum Engineering, University of Pittsburgh , Pittsburgh, Pennsylvania 15261, United States
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36
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Niu R, Palberg T, Speck T. Self-Assembly of Colloidal Molecules due to Self-Generated Flow. PHYSICAL REVIEW LETTERS 2017; 119:028001. [PMID: 28753375 DOI: 10.1103/physrevlett.119.028001] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Indexed: 06/07/2023]
Abstract
The emergence of structure through aggregation is a fascinating topic and of both fundamental and practical interest. Here we demonstrate that self-generated solvent flow can be used to generate long-range attractions on the colloidal scale, with subpiconewton forces extending into the millimeter range. We observe a rich dynamic behavior with the formation and fusion of small clusters resembling molecules. The dynamics of this assembly is governed by an effective conservative energy that for large separations r decays as 1/r. Breaking the flow symmetry, these clusters can be made active.
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Affiliation(s)
- Ran Niu
- Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 7-9, 55128 Mainz, Germany
| | - Thomas Palberg
- Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 7-9, 55128 Mainz, Germany
| | - Thomas Speck
- Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 7-9, 55128 Mainz, Germany
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37
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Niu R, Botin D, Weber J, Reinmüller A, Palberg T. Assembly and Speed in Ion-Exchange-Based Modular Phoretic Microswimmers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:3450-3457. [PMID: 28346787 DOI: 10.1021/acs.langmuir.7b00288] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We report an experimental study on ion-exchange-based modular microswimmers in low-salt water. Cationic ion-exchange particles and passive cargo particles assemble into self-propelling complexes, showing self-propulsion at speeds of several micrometers per second over extended distances and times. We quantify the assembly and speed of the complexes for different combinations of ion-exchange particles and cargo particles, substrate types, salt types and concentrations, and cell geometries. Irrespective of the experimental boundary conditions, we observe a regular development of the assembly shape with increasing number of cargo. Moreover, the swimming speed increases stepwise upon increasing the number of cargo and then saturates at a maximum speed, indicating the active role of cargo in modular swimming. We propose a geometric model of self-assembly to describe the experimental observations in a qualitative way. Our study also provides some constraints for future theoretical modeling and simulation.
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Affiliation(s)
- Ran Niu
- Institut für Physik, Johannes Gutenberg-Universtät Mainz , Staudingerweg 7, 55128 Mainz, Germany
| | - Denis Botin
- Institut für Physik, Johannes Gutenberg-Universtät Mainz , Staudingerweg 7, 55128 Mainz, Germany
| | - Julian Weber
- Institut für Physik, Johannes Gutenberg-Universtät Mainz , Staudingerweg 7, 55128 Mainz, Germany
| | - Alexander Reinmüller
- Institut für Physik, Johannes Gutenberg-Universtät Mainz , Staudingerweg 7, 55128 Mainz, Germany
| | - Thomas Palberg
- Institut für Physik, Johannes Gutenberg-Universtät Mainz , Staudingerweg 7, 55128 Mainz, Germany
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