1
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Dent FJ, Harbottle D, Warren NJ, Khodaparast S. Exploiting breath figure reversibility for in situ pattern modulation and hierarchical design. Soft Matter 2023; 19:2737-2744. [PMID: 36987660 PMCID: PMC10091834 DOI: 10.1039/d2sm01650h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Accepted: 03/12/2023] [Indexed: 06/19/2023]
Abstract
The breath figure (BF) method employs condensation droplets as dynamic templates for patterning polymer films. In the classical approach, dropwise condensation and film solidification are simultaneously induced through solvent evaporation, leading to empirically derived patterns with limited predictability of the final design. Here we use the temporally arrested BF methodology, controlling condensation and polymerisation independently to create diverse BF patterns with varied pore size, arrangement and distribution. External temperature control enables us to further investigate and exploit the inherent reversibility of the phase change process that governs the pattern formation. We modulate the level of subcooling and superheating to achieve subsequent regimes of condensation and evaporation, permitting in situ regulation of the droplet growth and shrinkage kinetics. The full reversibility of the phase change processes joined with active photopolymerisation in the current approach thus allows arresting of predictable BF kinetics at intermediate stages, thereby accessing patterns with varied pore size and spacing for unchanged material properties and environmental conditions. This simultaneous active control over both the kinetics of phase change and polymer solidification offers affordable routes for the fabrication of diverse predictable porous surfaces; manufacture of monolithic hierarchical BF patterns are ultimately facilitated through the advanced control of the BF assembly using the method presented here.
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Affiliation(s)
- Francis J Dent
- School of Mechanical Engineering, University of Leeds, Leeds, LS2 9JT, UK.
| | - David Harbottle
- School of Chemical and Process Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Nicholas J Warren
- School of Chemical and Process Engineering, University of Leeds, Leeds, LS2 9JT, UK
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2
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Dent F, Harbottle D, Warren NJ, Khodaparast S. Temporally Arrested Breath Figure. ACS Appl Mater Interfaces 2022; 14:27435-27443. [PMID: 35658418 PMCID: PMC9204694 DOI: 10.1021/acsami.2c05635] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 05/23/2022] [Indexed: 06/15/2023]
Abstract
Since its original conception as a tool for manufacturing porous materials, the breath figure method (BF) and its variations have been frequently used for the fabrication of numerous micro- and nanopatterned functional surfaces. In classical BF, reliable design of the final pattern has been hindered by the dual role of solvent evaporation to initiate/control the dropwise condensation and induce polymerization, alongside the complex effects of local humidity and temperature influence. Herein, we provide a deterministic method for reliable control of BF pore diameters over a wide range of length scales and environmental conditions. To this end, we employ an adapted methodology that decouples cooling from polymerization by using a combination of initiative cooling and quasi-instantaneous UV curing to deliberately arrest the desired BF patterns in time. Through in situ real-time optical microscopy analysis of the condensation kinetics, we demonstrate that an analytically predictable self-similar regime is the predominant arrangement from early to late times O(10-100 s), when high-density condensation nucleation is initially achieved on the polymer films. In this regime, the temporal growth of condensation droplets follows a unified power law of D ∝ t. Identification and quantitative characterization of the scale-invariant self-similar BF regime allow fabrication of programmed pore size, ranging from hundreds of nanometers to tens of micrometers, at high surface coverage of around 40%. Finally, we show that temporal arresting of BF patterns can be further extended for selective surface patterning and/or pore size modulation by spatially masking the UV curing illumination source. Our findings bridge the gap between fundamental knowledge of dropwise condensation and applied breath figure patterning techniques, thus enabling mechanistic design and fabrication of porous materials and interfaces.
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Affiliation(s)
- Francis
J. Dent
- School
of Mechanical Engineering, University of
Leeds, LS2 9JT Leeds, U.K.
| | - David Harbottle
- School
of Chemical and Process Engineering, University
of Leeds, LS2 9JT Leeds, U.K.
| | - Nicholas J. Warren
- School
of Chemical and Process Engineering, University
of Leeds, LS2 9JT Leeds, U.K.
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3
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Donina L, Rafique A, Khodaparast S, Porcar L, Cabral JT. Lamellar-to-MLV transformation in SDS/octanol/brine examined by microfluidic-SANS and polarised microscopy. Soft Matter 2021; 17:10053-10062. [PMID: 34713873 DOI: 10.1039/d1sm01215k] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The lamellar-to-multilamellar vesicle (MLV) transformation in a model surfactant system, sodium dodecyl sulfate (SDS), octanol and brine, is investigated under continuous and oscillatory microfluidic contraction-expansion flows, employing polarised optical microscopy and small angle neutron scattering (SANS), with sample volume probed down to ≃20 nL. We determine the lamellar-to-MLV transition requirements at varying flow velocity, oscillation amplitude, frequency, and number of oscillatory cycles. The spatio-temporal evolution of the hierarchical fluid structure is elucidated: lamellar sheets initially align with flow direction upon entering a constriction and then perpendicularly upon exiting; the formation of MLVs at the nanoscale is first observed by SANS within a few (<5) oscillatory cycles, followed by the gradual appearance of a regular (albeit not crystalline) MLV arrangement, at the micronscale, by optical microscopy after tens of cycles, under the conditions investigated. Once MLVs form under flow, these remain metastable for several days.
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Affiliation(s)
- Liva Donina
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK.
| | - Aysha Rafique
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK.
| | - Sepideh Khodaparast
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK.
| | - Lionel Porcar
- Institut Laue-Langevin, 71 Avenue des Martyrs, B.P. 156, F-38042 Grenoble CEDEX, France
| | - João T Cabral
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK.
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4
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Abstract
We examine the formation and growth of isolated myelin figures and microscale multilamellar tubules from isotropic micellar solutions of an anionic surfactant. Upon cooling, surfactant micelles transform into multilamellar vesicles (MLVs) whose contact is found to trigger the unidirectional growth of myelins. While the MLV diameter grows as dMLV ∝ t1/2, myelins grow linearly in time as LM ∝ t1, with a fixed diameter. Combining time-resolved small-angle neutron scattering (SANS) and optical microscopy, we demonstrate that the microscopic growth of spherical MLVs and cylindrical myelins stems from the same nanoscale molecular mechanism, namely, the surfactant exchange from micelles into curved lamellar structures at a constant volumetric rate. This mechanism successfully describes the growth rate of (nonequilibrium) myelin figures based on a population balance at thermodynamic equilibrium.
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Affiliation(s)
- Sepideh Khodaparast
- Leeds Institute of Fluid Dynamics (LIFD), School of Mechanical Engineering, University of Leeds, LS2 9JT Leeds, U.K
| | - William N Sharratt
- Department of Chemical Engineering, Imperial College London, SW7 2AZ London, U.K
| | - Robert M Dalgliesh
- ISIS Neutron and Muon Source, Science and Technology Facilities Council, Rutherford Appleton Laboratory, OX11 0QX Didcot, U.K
| | - João T Cabral
- Department of Chemical Engineering, Imperial College London, SW7 2AZ London, U.K
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5
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Tyagi G, Seddon D, Khodaparast S, Sharratt WN, Robles ES, Cabral JT. Tensiometry and FTIR study of the synergy in mixed SDS:DDAO surfactant solutions at varying pH. Colloids Surf A Physicochem Eng Asp 2021. [DOI: 10.1016/j.colsurfa.2021.126414] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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6
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Shim S, Khodaparast S, Lai CY, Yan J, Ault JT, Rallabandi B, Shardt O, Stone HA. CO 2-Driven diffusiophoresis for maintaining a bacteria-free surface. Soft Matter 2021; 17:2568-2576. [PMID: 33514979 DOI: 10.1039/d0sm02023k] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Dissolution and dissociation of CO2 in an aqueous phase induce diffusiophoretic motion of suspended particles with a nonzero surface charge. We report CO2-driven diffusiophoresis of colloidal particles and bacterial cells in a circular Hele-Shaw geometry. Combining experiments and model calculations, we identify the characteristic length and time scales of CO2-driven diffusiophoresis in relation to system dimensions and CO2 diffusivity. The motion of colloidal particles driven by a CO2 gradient is characterized by measuring the average velocities of particles as a function of distance from the CO2 sources. In the same geometrical configurations, we demonstrate that the directional migration of wild-type V. cholerae and a mutant lacking flagella, as well as S. aureus and P. aeruginosa, near a dissolving CO2 source is diffusiophoresis, not chemotaxis. Such a directional response of the cells to CO2 (or an ion) concentration gradient shows that diffusiophoresis of bacteria is achieved independent of cell shape, motility and the Gram stain (cell surface structure). Long-time experiments suggest potential applications for bacterial diffusiophoresis to cleaning systems or anti-biofouling surfaces, by reducing the population of the cells near CO2 sources.
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Affiliation(s)
- Suin Shim
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA.
| | | | - Ching-Yao Lai
- Department of Geosciences, Princeton University, Princeton, NJ 08544, USA
| | - Jing Yan
- Department of Molecular, Cellular and Developmental Biology, Quantitative Biology Institute, Yale University, New Haven, CT 06511, USA
| | - Jesse T Ault
- School of Engineering, Brown University, Providence, Rhode Island 02912, USA
| | - Bhargav Rallabandi
- Department of Mechanical Engineering, University of California, Riverside, California 92521, USA
| | - Orest Shardt
- Bernal Institute and School of Engineering, University of Limerick, Castletroy, Limerick V94 T9PX, Ireland
| | - Howard A Stone
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA.
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7
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Khodaparast S, Sharratt WN, Tyagi G, Dalgliesh RM, Robles ESJ, Cabral JT. Pure and mixed aqueous micellar solutions of Sodium Dodecyl sulfate (SDS) and Dimethyldodecyl Amine Oxide (DDAO): Role of temperature and composition. J Colloid Interface Sci 2021; 582:1116-1127. [PMID: 32942067 DOI: 10.1016/j.jcis.2020.08.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 05/22/2020] [Accepted: 08/02/2020] [Indexed: 11/26/2022]
Abstract
Aqueous mixtures of anionic and nonionic/cationic surfactants can form non-trivial self-assemblies in solution and exhibit macroscopic responses. Here, we investigate the micellar phase of pure and mixed aqueous solutions of Sodium Dodecyl Sulfate (SDS) and Dimethyldodecyl Amine Oxide (DDAO) using a combination of Small Angle Neutron Scattering (SANS), Fourier-Transform Infrared Spectroscopy (FTIR) and rheological measurements. We examine the effect of temperature (0-60 °C), on the 20 wt% SDS micellar solutions with varying DDAO (⩽5 wt%), and seek to correlate micellar structure with zero-shear solution viscosity. SANS establishes the formation of prolate ellipsoidal micelles in aqueous solutions of pure SDS, DDAO and SDS/DDAO mixtures, whose axial ratio is found to increase upon cooling. Elongation of the ellipsoidal micelles of pure SDS is also induced by the introduction of the non-anionic DDAO, which effectively reduces the repulsive interactions between the anionic SDS head-groups. In FTIR measurements, the formation of elongated mixed ellipsoidal micelles is confirmed by the increase of ordering in the hydrocarbon chain tails and interaction between surfactant head-groups. We find that the zero-shear viscosity of the mixed surfactant solutions increases exponentially with decreasing temperature and increasing DDAO content. Significantly, a master curve for solution viscosity can be obtained in terms of micellar aspect ratio, subsuming the effects of both temperature and DDAO composition in the experimental range investigated. The intrinsic viscosity of mixed micellar solutions is significantly larger than the analytical and numerical predictions for Brownian suspensions of ellipsoidal colloids, highlighting the need to consider interactions of soft micelles under shear, especially at high concentrations.
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Affiliation(s)
- Sepideh Khodaparast
- Chemical Engineering Department, Imperial College London, SW7 2AZ London, United Kingdom; School of Mechanical Engineering, University of Leeds, LS2 9JT Leeds, United Kingdom.
| | - William N Sharratt
- Chemical Engineering Department, Imperial College London, SW7 2AZ London, United Kingdom
| | - Gunjan Tyagi
- Chemical Engineering Department, Imperial College London, SW7 2AZ London, United Kingdom
| | - Robert M Dalgliesh
- ISIS Neutron and Muon Source, Science and Technology Facilities Council, Rutherford Appleton Laboratory, OX11 0QX Didcot, United Kingdom
| | - Eric S J Robles
- The Procter & Gamble Company, Newcastle Innovation Centre, NE12 9TS Newcastle-Upon-Tyne, United Kingdom
| | - João T Cabral
- Chemical Engineering Department, Imperial College London, SW7 2AZ London, United Kingdom.
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8
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Khodaparast S, Marcos J, Sharratt WN, Tyagi G, Cabral JT. Surface-Induced Crystallization of Sodium Dodecyl Sulfate (SDS) Micellar Solutions in Confinement. Langmuir 2021; 37:230-239. [PMID: 33347298 DOI: 10.1021/acs.langmuir.0c02821] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We investigate the role of confinement on the onset of crystallization in subcooled micellar solutions of sodium dodecyl sulfate (SDS), examining the impact of sample volume, substrate surface energy, and surface roughness. Using small angle neutron scattering (SANS) and dynamic light scattering (DLS), we measure the crystallization temperature upon cooling and the metastable zone width (MSZW) for bulk 10-30 wt% SDS solutions. We then introduce a microdroplet approach to quantify the impact of surface free energy (18-65 mN/m) and substrate roughness (Rα ≃ 0-60 μm) on the kinetics of surface-induced crystallization through measurements of induction time (ti) under isothermal conditions. While ti is found to decrease exponentially with decreasing temperature (increasing subcooling) for all tested surfaces, increasing the surface energy could cause a significant further reduction of up to ∼40 fold. For substrates with the lowest surface energy and longest ti, microscale surface roughness is found to enhance crystal nucleation, in particular for Rα ≥ 10 μm. Finally, we demonstrate that tuning the surface energy and microscopic roughness can be effective routes to promote or delay nucleation in bulk-like volumes, thus greatly impacting the stability of surfactant solutions at lower temperatures.
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Affiliation(s)
- Sepideh Khodaparast
- School of Mechanical Engineering, University of Leeds, LS2 9JT Leeds, United Kingdom
| | - Julius Marcos
- Department of Chemical Engineering, Imperial College London, SW7 2AZ London, United Kingdom
| | - William N Sharratt
- Department of Chemical Engineering, Imperial College London, SW7 2AZ London, United Kingdom
| | - Gunjan Tyagi
- Department of Chemical Engineering, Imperial College London, SW7 2AZ London, United Kingdom
| | - João T Cabral
- Department of Chemical Engineering, Imperial College London, SW7 2AZ London, United Kingdom
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9
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Kardan-Yamchi J, Hajihasani A, Talebi M, Khodaparast S, Azimi A, Rahbar M, Fallah F, Douraghi M. Intra-hospital dissemination of clinical and environmental isolates of Stenotrophomonas maltophilia from Tehran. Lett Appl Microbiol 2020; 72:325-331. [PMID: 33064916 DOI: 10.1111/lam.13416] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Revised: 10/11/2020] [Accepted: 10/12/2020] [Indexed: 11/29/2022]
Abstract
Stenotrophomonas maltophilia isolates are responsible for various hospital-acquired infections and are particularly increasing in the immunocompromised patients. The aim of this study was to determine the clonal relatedness between S. maltophilia isolates originating from the clinic and environment. A total of 150 S. maltophilia isolates from patients and 1108 environmental samples obtained in three hospitals from Tehran. Following molecular identification targeting 23S rRNA gene, the clonal relatedness of the environmental and clinical isolates was determined using pulsed field gel electrophoresis (PFGE). Of the 150 clinical and 18 environmental isolates identified using phenotypic tests, the speciation of 120 and 15 was confirmed by targeting the 23S rRNA gene. The 24 common pulsotypes (PTs) and 32 single PTs were identified by PFGE. Only a small cluster was shared among the clinic and environment within a hospital; therefore, the intra-hospital dissemination of certain isolates of S. maltophilia among the clinic and environment was demonstrated.
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Affiliation(s)
- J Kardan-Yamchi
- Division of Microbiology, Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - A Hajihasani
- Division of Microbiology, Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - M Talebi
- Department of Microbiology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran
| | - S Khodaparast
- Division of Microbiology, Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - A Azimi
- Division of Microbiology, Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - M Rahbar
- Department of Microbiology, Reference Health Laboratories, Ministry of Health, Tehran, Iran
| | - F Fallah
- Department of Microbiology, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - M Douraghi
- Division of Microbiology, Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.,Food Microbiology Research Center, Tehran University of Medical Sciences, Tehran, Iran
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10
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Rafique AS, Khodaparast S, Poulos AS, Sharratt WN, Robles ESJ, Cabral JT. Micellar structure and transformations in sodium alkylbenzenesulfonate (NaLAS) aqueous solutions: effects of concentration, temperature, and salt. Soft Matter 2020; 16:7835-7844. [PMID: 32756697 DOI: 10.1039/d0sm00982b] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We investigate the shape, dimensions, and transformation pathways of micelles of linear sodium alkylbenzenesulfonate (NaLAS), a common anionic surfactant, in aqueous solution. Employing Small Angle Neutron Scattering (SANS) and surface tensiometry, we quantify the effects of surfactant concentration (0.6-15 wt%), temperature (5-40 °C) and added salt (≤0.35 M Na2SO4). Spherical micelles form at low NaLAS (≤2.6 wt%) concentration in water, and become elongated with increasing concentration and decreasing temperature. Addition of salt reduces the critical micelle concentration (CMC) and thus promotes the formation of micelles. At fixed NaLAS concentration, salt addition causes spherical micelles to grow into cylindrical micelles, and then multilamellar vesicles (MLVs), which we examine by SANS and cryo-TEM. Above a threshold salt concentration, the MLVs reach diameters of 100 s of nm to few μm, eventually causing precipitation. While the salt concentrations associated with the micelle-to-cylinder transformation increase only slightly with temperature, those required for the cylinder-to-MLV transformation exhibit a pronounced, linear temperature dependence, which we examine in detail. Our study establishes a solution structure map for this model anionic surfactant in water, quantifying the combined roles of concentration, temperature and salt, at practically relevant conditions.
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Affiliation(s)
- Aysha S Rafique
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK.
| | - Sepideh Khodaparast
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK.
| | - Andreas S Poulos
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK.
| | - William N Sharratt
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK.
| | - Eric S J Robles
- The Procter & Gamble Company, Newcastle Innovation Centre, Newcastle-Upon-Tyne, NE12 9TS, UK
| | - João T Cabral
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK.
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11
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Wang H, Khodaparast S, Carroll J, Kelly C, Robles ESJ, Cabral JT. A microfluidic-multiwell platform for rapid phase mapping of surfactant solutions. Rev Sci Instrum 2020; 91:045109. [PMID: 32357682 DOI: 10.1063/1.5144770] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 03/30/2020] [Indexed: 06/11/2023]
Abstract
Measurement of the phase behavior and (meta)stability of liquid formulations, including surfactant solutions, is required for the understanding of mixture thermodynamics, as well as their practical utilization. We report a microfluidic platform with a stepped temperature profile, imposed by a dual Peltier module, connected to an automated multiwell plate injector and optical setup, for rapid solution phase mapping. The measurement protocol is defined by the temperature step ΔT ≡ T1 - T2 (≲100 °C), volumetric flow rate Q ≡ ΔV/Δt (≲50 μl/min), which implicitly set the thermal gradient ΔT/Δt (≃0.1-50 °C/min), and measurement time (which must exceed the intrinsic timescale of the relevant phase transformation). Furthermore, U-shaped microchannels can assess the reversibility of such transformations, yielding a facile measurement of the metastable zone width of the phase diagram. By contrast with traditional approaches, the platform precisely controls the cooling and heating rates by tuning the flow rate, and the absolute temperature excursion by the hot and cold thermal profile, which remain stationary during operation, thus allowing the sequential and reproducible screening of large sample arrays. As a model system, we examined the transition from the micellar (L1) to the liquid crystalline lamellar phase (Lα), upon cooling, of aqueous solutions of sodium linear alkylbenzene sulfonate, a biodegradable anionic surfactant extensively employed in industry. Our findings are validated with quiescent optical microscopy and small angle neutron scattering data.
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Affiliation(s)
- Haoyu Wang
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, United Kingdom
| | - Sepideh Khodaparast
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, United Kingdom
| | - John Carroll
- National Formulation Centre, Centre for Process Innovation, Sedgefield DL1 1GL, United Kingdom
| | - Caroline Kelly
- National Formulation Centre, Centre for Process Innovation, Sedgefield DL1 1GL, United Kingdom
| | - Eric S J Robles
- Procter & Gamble, Newcastle Innovation Centre, Newcastle-Upon-Tyne NE12 9TS, United Kingdom
| | - João T Cabral
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, United Kingdom
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12
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Pellegrino L, Khodaparast S, Cabral JT. Orthogonal wave superposition of wrinkled, plasma-oxidised, polydimethylsiloxane surfaces. Soft Matter 2020; 16:595-603. [PMID: 31776531 DOI: 10.1039/c9sm02124h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We report a versatile approach to generate 2D dual-frequency patterns on soft substrates by superposition of 1D single-frequency wrinkles. Wave superposition is achieved by applying sequential orthogonal strains to elastomeric coupons, as opposed to the application of a (simultaneous) biaxial strain field. First, a 1D wrinkling pattern is induced by the well-known mechanical instability of a bilayer formed by oxygen plasma-oxidation of a (pre-strained) polydimethylsiloxane elastomer. The wrinkled surface formed upon strain release is then replicated to obtain a stress-free substrate, and stretched in the direction perpendicular to the first generation. Subsequent plasma exposure and mechanical relaxation (with independent process parameters) yield a prescribed second-generation wrinkling, whose profile and dependence on the first generation we examine in detail. By independently varying plasma oxidation and strain parameters in both directions, we demonstrate the formation of a wide array of topographies, including arrays of symmetric 2D checkerboard patterns with exceptional area coverage with respect to those formed by simultaneous 2D wrinkling. While the resulting topographies cannot be explained in terms of a simple orthogonal wave superposition, we show that, by accounting for the orthogonal prestrain experienced by the first wrinkling generation, the resulting 2D patterns can be readily calculated from 1D wrinkling behaviour.
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Affiliation(s)
- Luca Pellegrino
- Department of Chemical Engineering, Imperial College London, London, SW7 2AZ, UK.
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13
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Khodaparast S, Mohabati Mobarez A, Saberifiroozi M. A Two-Step Approach for Diagnosing Glutamate Dehydrogenase Genes by Conventional Polymerase Chain Reaction from Clostridium difficile Isolates. Middle East J Dig Dis 2019; 11:135-140. [PMID: 31687111 PMCID: PMC6819966 DOI: 10.15171/mejdd.2019.139] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 05/10/2019] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND Clostridium difficile is the major causative agent of nosocomial antibiotic-associated colitis. The gold standard for C. difficile detection is stool culture followed by cytotoxic assay, although it is laborious and time-consuming. We developed a screening test based on a two-step conventional polymerase chain reaction (PCR) approach to detect gluD, the glutamate dehydrogenase (GDH) enzyme gene, which is a marker for screening of C. difficile. Targeting gluD comparing to the conserved stable genetic element of pathogenicity locus (PaLoc), with an accessory gene of Cdd3, was an effective method for the detection of this pathogen from patients with enterocolitis.
METHODS
Fresh fecal samples of the patients who were clinically suspicious for antibiotic-associated colitis were collected. Stool specimens were cultured on the cycloserine-cefoxitin fructose agar (CCFA) in an anaerobic condition, following alcohol shock treatment and enrichment in Clostridium difficile Brucella broth (CDBB). On confirmed colonies, PCR was carried out for detection of PaLoc subsidiary gene, Cdd3, and toxicogenic genes, tcdA and tcdB. The gluD that is GDH gene detection was performed by conventional PCR on the extracted DNA from 578 fresh stool samples.
RESULTS
57 (9.8%) strains of C. difficile were approved by conventional PCR for gluD and Cdd3 genes, in which 37 (6.4%) colonies had tcdA+/tcdB+ genotype, 2 (0.3%) tcdA+/tcdB-, 4 (0.7%) tcdA-/ tcdB+ and the remaining 14 (2.4%) colonies were tcdA and tcdB negative.
CONCLUSION
These results demonstrate that targeting gluD by PCR is quite promising for rapid detection of C. difficile from fresh fecal samples. Furthermore, the multiple-gene analysis for tcdA and tcdB assay proved a reliable approach for diagnosing of toxigenic strains among clinical samples.
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Affiliation(s)
- Sepideh Khodaparast
- Department of Bacteriology, Faculty of Medical Sciences, Tarbiat Modares University. Tehran, Iran
| | - Ashraf Mohabati Mobarez
- Department of Bacteriology, Faculty of Medical Sciences, Tarbiat Modares University. Tehran, Iran
| | - Mehdi Saberifiroozi
- Digestive Disease Research Institute, Tehran University of Medical Sciences, Tehran, Iran
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14
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Ghasemian A, Mohabati Mobarez A, Najar Peerayeh S, Talebi Bezmin Abadi A, Khodaparast S, Mahmood SS. Expression of adhesin genes and biofilm formation among Klebsiella oxytoca clinical isolates from patients with antibiotic-associated haemorrhagic colitis. J Med Microbiol 2019; 68:978-985. [PMID: 31136296 DOI: 10.1099/jmm.0.000965] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
PURPOSE Biofilm formation and resistance to last-line antibiotics have restricted chemotherapy options toward infection eradication. METHODOLOGY Fifty K. oxytoca isolates were collected from patients with antibiotic-associated haemorrhagic colitis (AAHC). Antibiotic susceptibility tests were conducted and phenotypic biofilm formation was assessed using microtitre tissue plate (MTP) assay. PCR was employed to amplify the adhesins, extended-spectrum β-lactamases (ESBLs), carbapenemase and colistin resistance genes. The expression of adhesin genes was evaluated using quantitative real-time PCR (RT-qPCR).Results/Key findings. The previous antibiotic consumption and hospitalization (P<0.05) and older ages (P=0.0033) were significantly associated with AAHC. None of the isolates produced biofilm strongly, but 70% of them produced moderate-level biofilm. The blaCTX-M (12/14), the blaIMP (8/14 MICIMI =4 µg ml-1 ) and blaOXA-48-like (5/14) and mcr-1 (4/14) genes were predominant, three of which harbouring all the genes. The expression of matB (0.023) and mrkA (0.011) was significantly different between multidrug-resistant and susceptible isolates. Furthermore, moderately biofilm producer isolates significantly exhibited higher expression of fimA (P=.0117), pilQ (P=0.002) and mrkA (P=0.020) genes compared to biofilm non-producers. No significant difference regarding gene expression was observed among ESBL alleles. CONCLUSION Bacterial attachment by adhesins and biofilm formation among extensive drug-resistant K. oxytoca isolates hinder the efficient infection eradication. Hence, control and surveillance studies should be performed and other therapeutic auspicious approaches must be taken into account against AAHC, biofilm formation and drug resistance spread. Furthermore, previous antibiotic consumption and long-term hospitalization should be controlled.
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Affiliation(s)
- Abdolmajid Ghasemian
- Department of Bacteriology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Ashraf Mohabati Mobarez
- Department of Bacteriology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Shahin Najar Peerayeh
- Department of Bacteriology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Amin Talebi Bezmin Abadi
- Department of Bacteriology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Sepideh Khodaparast
- Department of Bacteriology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Suhad Saad Mahmood
- Department of Biotechnology, University of Baghdad, AL Mansour City, Baghdad, Iraq
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15
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Khodaparast S, Sharratt W, Wang H, Robles ES, Dalgliesh R, Cabral JT. Spontaneous formation of multilamellar vesicles from aqueous micellar solutions of sodium linear alkylbenzene sulfonate (NaLAS). J Colloid Interface Sci 2019; 546:221-230. [DOI: 10.1016/j.jcis.2019.03.056] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Revised: 03/14/2019] [Accepted: 03/16/2019] [Indexed: 11/25/2022]
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16
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Abstract
The transport of particulate matter to and from dead-end pores is difficult to achieve due to confinement effects. Diffusiophoresis is a phenomenon that results in the controlled motion of colloids along solute concentration gradients. Thus, by establishing an electrolyte concentration gradient within dead-end pores, it is possible to induce the flow of particles into and out of the pores via diffusiophoresis, as has been demonstrated recently. In this paper, we explain the pore-scale mechanism by which individual colloids are entrained in dead-end pores by diffusiophoresis. We flow particles past a series of dead-end pores in the presence of a solute concentration gradient. Our results reveal that particles execute pore-to-pore hops before ultimately being captured. We categorize an event as particle capture when the particle's trajectory terminates within the dead-end pore. Experiments and numerical simulations demonstrate that particle capture only occurs when flowing particles are positioned sufficiently close to the pore entry. Outside this capture region, the particles have insufficient diffusiophoretic velocities to induce capture and their dynamics are largely dominated by their free-stream advective velocities. We observe that the particles move closer to the device wall as they hop, thereby reducing the effect of flow advection and increasing that of diffusiophoresis. These results enhance our understanding of suspension dynamics in a driven system and have implications for the development, design, and optimization of diffusiophoretic platforms for drug delivery, cosmetics, and material recovery.
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Affiliation(s)
- Sarah Battat
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
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17
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Yan J, Moreau A, Khodaparast S, Perazzo A, Feng J, Fei C, Mao S, Mukherjee S, Košmrlj A, Wingreen NS, Bassler BL, Stone HA. Bacterial Biofilm Material Properties Enable Removal and Transfer by Capillary Peeling. Adv Mater 2019; 31:e1807586. [PMID: 30667139 DOI: 10.1002/adma.201807586] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
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18
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Khodaparast S, Boulogne F, Poulard C, Stone HA. Erratum: Water-based Peeling of Thin Hydrophobic Films [Phys. Rev. Lett. 119, 154502 (2017)]. Phys Rev Lett 2018; 121:269901. [PMID: 30636166 DOI: 10.1103/physrevlett.121.269901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Indexed: 06/09/2023]
Abstract
This corrects the article DOI: 10.1103/PhysRevLett.119.154502.
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19
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Yan J, Moreau A, Khodaparast S, Perazzo A, Feng J, Fei C, Mao S, Mukherjee S, Košmrlj A, Wingreen NS, Bassler BL, Stone HA. Bacterial Biofilm Material Properties Enable Removal and Transfer by Capillary Peeling. Adv Mater 2018; 30:e1804153. [PMID: 30368924 PMCID: PMC8865467 DOI: 10.1002/adma.201804153] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 08/30/2018] [Indexed: 05/22/2023]
Abstract
Biofilms, surface-attached communities of bacterial cells, are a concern in health and in industrial operations because of persistent infections, clogging of flows, and surface fouling. Extracellular matrices provide mechanical protection to biofilm-dwelling cells as well as protection from chemical insults, including antibiotics. Understanding how biofilm material properties arise from constituent matrix components and how these properties change in different environments is crucial for designing biofilm removal strategies. Here, using rheological characterization and surface analyses of Vibrio cholerae biofilms, it is discovered how extracellular polysaccharides, proteins, and cells function together to define biofilm mechanical and interfacial properties. Using insight gained from our measurements, a facile capillary peeling technology is developed to remove biofilms from surfaces or to transfer intact biofilms from one surface to another. It is shown that the findings are applicable to other biofilm-forming bacterial species and to multiple surfaces. Thus, the technology and the understanding that have been developed could potentially be employed to characterize and/or treat biofilm-related infections and industrial biofouling problems.
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Affiliation(s)
- Jing Yan
- Department of Mechanical and Aerospace Engineering, Princeton University, D328 E-Quad, Olden St., Princeton, NJ, 08544, USA
| | - Alexis Moreau
- Department of Mechanical and Aerospace Engineering, Princeton University, D328 E-Quad, Olden St., Princeton, NJ, 08544, USA
| | - Sepideh Khodaparast
- Department of Mechanical and Aerospace Engineering, Princeton University, D328 E-Quad, Olden St., Princeton, NJ, 08544, USA
| | - Antonio Perazzo
- Department of Mechanical and Aerospace Engineering, Princeton University, D328 E-Quad, Olden St., Princeton, NJ, 08544, USA
| | - Jie Feng
- Department of Mechanical and Aerospace Engineering, Princeton University, D328 E-Quad, Olden St., Princeton, NJ, 08544, USA
| | - Chenyi Fei
- Department of Molecular Biology, Princeton University, 329 Lewis Thomas Laboratory, Princeton, NJ, 08544, USA
| | - Sheng Mao
- Department of Mechanical and Aerospace Engineering, Princeton University, D328 E-Quad, Olden St., Princeton, NJ, 08544, USA
| | - Sampriti Mukherjee
- Department of Molecular Biology, Princeton University, 329 Lewis Thomas Laboratory, Princeton, NJ, 08544, USA
| | - Andrej Košmrlj
- Department of Mechanical and Aerospace Engineering, Princeton University, D328 E-Quad, Olden St., Princeton, NJ, 08544, USA
| | - Ned S Wingreen
- Department of Molecular Biology, Princeton University, 329 Lewis Thomas Laboratory, Princeton, NJ, 08544, USA
| | - Bonnie L Bassler
- Department of Molecular Biology, Princeton University, 329 Lewis Thomas Laboratory, Princeton, NJ, 08544, USA
- Howard Hughes Medical Institute, Chevy Chase, MD, 20815, USA
| | - Howard A Stone
- Department of Mechanical and Aerospace Engineering, Princeton University, D328 E-Quad, Olden St., Princeton, NJ, 08544, USA
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20
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Salimizand H, Zomorodi AR, Mansury D, Khakshoor M, Azizi O, Khodaparast S, Baseri Z, Karami P, Zamanlou S, Farsiani H, Amini Y, Moradi B, Meshkat Z, Salimizand H, Hasanzadeh S, Sadeghian H. Diversity of aminoglycoside modifying enzymes and 16S rRNA methylases in Acinetobacter baumannii and Acinetobacter nosocomialis species in Iran; wide distribution of aadA1 and armA. Infect Genet Evol 2018; 66:195-199. [PMID: 30292703 DOI: 10.1016/j.meegid.2018.09.028] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Revised: 09/12/2018] [Accepted: 09/30/2018] [Indexed: 10/28/2022]
Abstract
PURPOSE Acinetobacter baumannii-calcoaceticus complex (ABC) make a great burden on health-care systems due to hospital-acquired infections and antibacterial resistance. Aminoglycoside in combination with other antibacterials used as treatment options. However, ABC species overcome this class of antibacterials in different ways. This study provides a comprehensive report on the distribution of aminoglycoside modifying enzymes (AMEs) and 16S rRNA methylase in Acinetobacter baumannii and Acinetobacter nosocomialis isolated from various provinces in Iran. METHODS During six month of study, from eight referral centers in seven provinces across the country, Iran, 178 A. baumannii and 43 A. nosocomialis isolates were collected. The minimum inhibitory concentration of amikacin, gentamicin, netilmicin, kanamycin and tobramycin were measured by microbroth dilution method. AMEs and 16S rRNA methylase variants were sought by PCR. RESULTS High rates of resistance were seen in all centers. MIC50 and MIC90 for all A. baumannii and A. nosocomialis isolates from different centers were > 512 mg/L. The most frequent AME was ant(3″)-Ia (aadA1) in both of A. baumannii (74.1%) and A. nosocomialis (86%). armA was detected in A. baumannii and A. nosocomialis at the frequency of 41.6% and 67.4%, respectively. rmtA, B, C, D, aac(3)-Ia (aacC1) and aac(6')-Im were not detected, neither in A. baumannii nor A. nosocomialis. Moreover, aac(6')-Ih was only found in A. baumannii isolates. The distribution of some of the ARGs was limited to a definite center. CONCLUSION The overall high-level carriage of ARGs in Acinetobacter species may limited usage of this class of antibacterials as a treatment option.
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Affiliation(s)
- Himen Salimizand
- Liver and Digestive Research Center, Kurdistan University of Medical Sciences, Sanandaj, Iran; Department of Microbiology, Faculty of Medicine, Kurdistan University of medical Sciences, Sanandaj, Iran
| | - Abolfazl Raafati Zomorodi
- Department of Pathobiology, Faculty of Veterinary Medicine, Ferdowsi university of Mashhad, Mashhad, Iran
| | - Davood Mansury
- Student Research Committee, Faculty of Medicine, Mashhad, University of Medical Sciences, Mashhad, Iran; Antimicrobial Resistance Research Center, Avicenna Research Institute, Mashhad University of Medical Sciences, Mashhad, Iran; Department of Microbiology and Virology, Medical School, Mashhad University of medical Sciences, Mashhad, Iran
| | - Mostafa Khakshoor
- Microbiology Department, Faculty of science, Islamic Azad University of Tonekabon, Iran
| | - Omid Azizi
- Department of Laboratory Sciences, Torbat Heydariyeh University of Medical Sciences, Torbat Heydariyeh, Iran
| | - Sepideh Khodaparast
- Department of bacteriology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran; Molecular laboratory, Shariati hospital, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Zohre Baseri
- Molecular laboratory, Shariati hospital, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Pezhman Karami
- Department of Microbiology, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran; Brucellosis Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Sajjad Zamanlou
- Department of Microbiology, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Hadi Farsiani
- Antimicrobial Resistance Research Center, Avicenna Research Institute, Mashhad University of Medical Sciences, Mashhad, Iran; Department of Microbiology and Virology, Medical School, Mashhad University of medical Sciences, Mashhad, Iran
| | - Yousef Amini
- Department of Microbiology, Medical school, Zahedan University of medical Sciences, Zahedan, Iran; Infectious Diseases and Tropical Medicine Research Center, Zahedan University of Medical Sciences, Zahedan, Iran
| | - Bagher Moradi
- Esfarayen University of Medical Sciences, Esfarayen, Iran
| | - Zahra Meshkat
- Antimicrobial Resistance Research Center, Avicenna Research Institute, Mashhad University of Medical Sciences, Mashhad, Iran; Department of Microbiology and Virology, Medical School, Mashhad University of medical Sciences, Mashhad, Iran
| | - Hana Salimizand
- Department of Biology, Sanandaj Branch, Islamic Azad University, Sanandaj, Iran
| | - Sepideh Hasanzadeh
- Student Research Committee, Faculty of Medicine, Mashhad, University of Medical Sciences, Mashhad, Iran; Antimicrobial Resistance Research Center, Avicenna Research Institute, Mashhad University of Medical Sciences, Mashhad, Iran; Department of Microbiology and Virology, Medical School, Mashhad University of medical Sciences, Mashhad, Iran
| | - Hamid Sadeghian
- Antimicrobial Resistance Research Center, Avicenna Research Institute, Mashhad University of Medical Sciences, Mashhad, Iran; Department of Laboratory Sciences, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran.
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21
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Khodaparast S, Atasi O, Deblais A, Scheid B, Stone HA. Dewetting of Thin Liquid Films Surrounding Air Bubbles in Microchannels. Langmuir 2018; 34:1363-1370. [PMID: 29239613 DOI: 10.1021/acs.langmuir.7b03839] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
As an air bubble translates in a microchannel, a thin film of liquid is formed on the bounding walls. In a microchannel with a rectangular cross-section, the liquid in the film leaks toward the low-pressure corners of the geometry, which leads to the appearance of local minima in the film thickness in the cross-sectional plane. In such a configuration, theory suggests that the minimum film thickness scales with Ca and Ca4/3 depending on the distance from the nose of the bubble, where Ca = μUb/γ is the flow capillary number based on the bubble velocity Ub, liquid viscosity μ, and surface tension γ, and Ca ≪ 1. We show that the film of a partially wetting liquid dewets on the channel wall at the sites of the local minima in the film thickness as it acquires thicknesses around and below 100 nm. Our experiments show that the distance Lw between the nose of the bubble and the initial dewetting location is a function of Ca and surface wettability. For channels of different wettability, Lw always scales proportional to Caα, where 1.7 < α < 2 for the range of 10-5 < Ca < 10-2. Moreover, Lw increases up to 10 times by enhancing the wettability of the surface at a given Ca. Our present measurements of Lw provide a design constraint on the lengths of bubbles to maintain a liquid wet channel without dry patches on the wall.
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Affiliation(s)
- S Khodaparast
- Department of Mechanical and Aerospace Engineering, Princeton University , Princeton, New Jersey 08544, United States
- Department of Chemical Engineering, Imperial College London , London SW7 2AZ, United Kingdom
| | - O Atasi
- Department of Mechanical and Aerospace Engineering, Princeton University , Princeton, New Jersey 08544, United States
- TIPs (Transfers, Interfaces and Processes), Université Libre de Bruxelles , Brussels 1050, Belgium
| | - A Deblais
- Van der Waals-Zeeman Institute, Institute of Physics, University of Amsterdam , 1098XH Amsterdam, The Netherlands
| | - B Scheid
- TIPs (Transfers, Interfaces and Processes), Université Libre de Bruxelles , Brussels 1050, Belgium
| | - H A Stone
- Department of Mechanical and Aerospace Engineering, Princeton University , Princeton, New Jersey 08544, United States
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22
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Abstract
Inducing thermal gradients in fluid systems with initial, well-defined density gradients results in the formation of distinct layered patterns, such as those observed in the ocean due to double-diffusive convection. In contrast, layered composite fluids are sometimes observed in confined systems of rather chaotic initial states, for example, lattes formed by pouring espresso into a glass of warm milk. Here, we report controlled experiments injecting a fluid into a miscible phase and show that, above a critical injection velocity, layering emerges over a time scale of minutes. We identify critical conditions to produce the layering, and relate the results quantitatively to double-diffusive convection. Based on this understanding, we show how to employ this single-step process to produce layered structures in soft materials, where the local elastic properties vary step-wise along the length of the material. The ability to form density layering in a fluid in a simple and repeatable way is of relevance to a number of industrial and environmental processes. Here Xue et al. show formation of layers by simple injection of a hot liquid into a warm one at a predetermined critical pouring velocity.
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Affiliation(s)
- Nan Xue
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, 08544, USA
| | - Sepideh Khodaparast
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, 08544, USA
| | - Lailai Zhu
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, 08544, USA.,Linné Flow Centre and Swedish e-Science Research Centre (SeRC), KTH Mechanics, Stockholm, SE, 10044, Sweden
| | - Janine K Nunes
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, 08544, USA
| | - Hyoungsoo Kim
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, 08544, USA.,Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Deajeon, 34141, South Korea
| | - Howard A Stone
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, 08544, USA.
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Abstract
Inks of permanent markers and waterproof cosmetics create elastic thin films upon application on a surface. Such adhesive materials are deliberately designed to exhibit water-repellent behavior. Therefore, patterns made up of these inks become resistant to moisture and cannot be cleaned by water after drying. However, we show that sufficiently slow dipping of such elastic films, which are adhered to a substrate, into a bath of pure water allows for complete removal of the hydrophobic coatings. Upon dipping, the air-water interface in the bath forms a contact line on the substrate, which exerts a capillary-induced peeling force at the edge of the hydrophobic thin film. We highlight that this capillary peeling process is more effective at lower velocities of the air-liquid interface and lower viscosities. Capillary peeling not only removes such thin films from the substrate but also transfers them flawlessly onto the air-water interface.
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Affiliation(s)
- Sepideh Khodaparast
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - François Boulogne
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA
- Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Orsay 91400, France
| | - Christophe Poulard
- Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Orsay 91400, France
| | - Howard A Stone
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA
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24
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Abstract
We study the process of coating the interface of a long gas bubble, which is translating in a horizontal circular capillary tube filled with a colloidal suspension. A typical elongated confined bubble is comprised of three distinct regions: a spherical front cap, a central body that is separated from the tube wall by a thin liquid film, and a spherical cap at the back. These three regions are connected by transitional sections. Particles gradually coat the bubble from the back to the front. We investigate the mechanisms that govern the initial accumulation of the particles and the growth of the particle-coated area on the interface of the bubble. We show that the initial accumulation of particles starts at the stable stagnation ring on the rear cap of the bubble, and the particles will completely coat the spherical cap at the back of the bubble before accumulating on the central body. Armoring the central interface of the bubble with particles thickens the liquid film around the bubble relative to that around the particle-free interface. This effect creates a rather sharp step on the interface of the bubble in the central region, which separates the armored region from the particle-free region. After the bubble is completely coated, the liquid film around the body of the bubble will adjust again to an intermediate thickness. We show that the three distinct thicknesses that the liquid film acquires during the armoring process can be well described analytically.
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Affiliation(s)
- Yingxian Estella Yu
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA.
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25
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Abstract
Moving air-liquid interfaces, for example, bubbles, play a significant role in the detachment and transport of colloids and microorganisms in confined systems as well as unsaturated porous media. Moreover, they can effectively prevent and/or postpone the development of mature biofilms on surfaces that are colonized by bacteria. Here we demonstrate the dynamics and quantify the effectiveness of this bubble-driven detachment process for the bacterial strain Staphylococcus aureus. We investigate the effects of interface velocity and geometrical factors through microfluidic experiments that mimic some of the confinement features of pore-scale geometries. Depending on the bubble velocity U, at least three different flow regimes are found. These operating flow regimes not only affect the efficiency of the detachment process but also modify the final distribution of the bacteria on the surface. We organize our results according to the capillary number, [Formula: see text], where μ and γ are the viscosity and the surface tension, respectively. Bubbles at very low velocities, corresponding to capillary numbers Ca < 5 × 10-5, exhibit detachment efficiencies of up to 80% at the early stage of bacterial adhesion. In contrast, faster bubbles at capillary numbers Ca > 10-3, have lower detachment efficiencies and cause significant nonuniformities in the final distribution of the cells on the substrate. This effect is associated with the formation of a thin liquid film around the bubble at higher Ca. In general, at higher bubble velocities bacterial cells in the corners of the geometry are less influenced by the bubble passage compared to the central region.
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Affiliation(s)
- Sepideh Khodaparast
- Department of Mechanical and Aerospace Engineering, Princeton University , Princeton, New Jersey 08544, United States
| | - Minyoung Kevin Kim
- Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States
| | - Justin E Silpe
- Department of Molecular Biology, Princeton University , Princeton, New Jersey 08544, United States
| | - Howard A Stone
- Department of Mechanical and Aerospace Engineering, Princeton University , Princeton, New Jersey 08544, United States
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Nojoomi F, Ghasemian A, Eslami M, Khodaparast S. Antibiotic Susceptibility Profile, ESBL Production and blaCTX-M1, blaSHV and blaTEM Types Among Escherichia coli Blood Isolates. Int J Enteric Pathog 2016. [DOI: 10.15171/ijep.2017.03] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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27
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Alikhani MY, Shahcheraghi F, Khodaparast S, Mozaffari Nejad AS, Moghadam MK, Mousavi SF. Molecular characterisation of Klebsiella oxytoca strains isolated from patients with antibiotic-associated diarrhoea. Arab J Gastroenterol 2016; 17:95-101. [PMID: 27344094 DOI: 10.1016/j.ajg.2016.03.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Revised: 01/29/2016] [Accepted: 03/07/2016] [Indexed: 11/29/2022]
Abstract
BACKGROUND AND STUDY AIM Colitis is a common complication after treatment with antibiotics such as β-lactams, quinolones, and aminoglycosides. Recently, Klebsiella oxytoca has been implicated in this type of diarrhoea. The prevalence and characterisations of K. oxytoca isolated from patients with antibiotic-associated diarrhoea were investigated. The K. oxytoca isolates were also tested for cytotoxin production. PATIENTS AND METHODS This study was conducted from May 2011 to Dec 2013. Faecal samples were collected from hospitalised patients receiving antibiotic treatment. Initial cultivation was performed on specific media. The clinical isolates were confirmed by polymerase chain reaction (PCR) using the specific K. oxytoca polygalacturonase (pehX) gene. The double-disc diffusion test was used to detect extended-spectrum beta-lactamase (ESBL)-producing strains. Tracking of ESBL-encoding genes was performed via PCR. The organism was cultured on Hep-2 cell lines for cytotoxin production. RESULTS Out of 331 samples collected from patients, 40 were confirmed molecularly to be clinical isolates of K. oxytoca. Fourteen (35%) ESBL-producing strains were isolated using the double-disc diffusion method. Among the molecularly confirmed K. oxytoca isolates, seven (17.5%) tested positive for the blaSHV gene, 12 (30%) for blaTEM, 10 (25%) for blaCTX-M, three (7.5%) for blaOXA, nine (22.5%) for blaCTX-M-15, and seven (17.5%) for blaTEM-1. Five (12%) isolates showed cytotoxin activity below 30%, 12 (30%) strains showed moderate cytotoxin activity between 30% and 60%, and 23 (58%) strains showed cytotoxin activity ⩾60%. CONCLUSIONS The cytotoxin-producing K. oxytoca is found to be one of the causes of antibiotic-induced colitis. Discontinuing treatment and allowing normal intestinal flora to be established or prescribing appropriate medication after antibiogram can help patients with antibiotic-induced haemorrhagic colitis in a timely manner.
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Affiliation(s)
- Mohammad Yousef Alikhani
- Department of Microbiology, School of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Fereshteh Shahcheraghi
- Microbiology Research Center & Department of Microbiology, Pasteur Institute of Iran, Tehran, Iran
| | - Sepideh Khodaparast
- Department of Microbiology, School of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Amir Sasan Mozaffari Nejad
- Department of Microbiology, Osmania University, Hyderabad, Andhra Pradesh (AP), India; Department of Microbiology, Research Center for Molecular Medicine, Hamadan University of Medical Sciences, Hamadan, Iran
| | | | - Sayed Fazlollah Mousavi
- Microbiology Research Center & Department of Microbiology, Pasteur Institute of Iran, Tehran, Iran.
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