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Justin Koh J, Pang P, Chakraborty S, Kong J, Sng A, Anukunwithaya P, Huang S, Koh XQ, Thenarianto C, Thitsartan W, Daniel D, He C. Presence, origins and effect of stable surface hydration on regenerated cellulose for underwater oil-repellent membranes. J Colloid Interface Sci 2023; 635:197-207. [PMID: 36587573 DOI: 10.1016/j.jcis.2022.12.109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [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: 09/15/2022] [Revised: 12/13/2022] [Accepted: 12/19/2022] [Indexed: 12/24/2022]
Abstract
HYPOTHESIS Underwater oil-repellency of polyelectrolyte brushes has been attributed mainly to electric double-layer repulsion forces based on Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Many non-polyelectrolyte materials also exhibit oil-repellent behaviour, but it is not clear if there exist similar electric double-layer repulsion and if it is the sole mechanism governing their underwater oil-repellency. EXPERIMENTS/SIMULATIONS In this article, the oil-repellency of highly amorphous cellulose exhibiting is investigated in detail, through experiments and molecular dynamics simulations (MDS). FINDINGS It was found that the stable surface hydration on regenerated cellulose was due to a combination of long-range electrostatic repulsions (DLVO theory) and short-range interfacial hydrogen bonding between cellulose and water molecules (as revealed by MDS). The presence of a stable water layer of about 200 nm thick (similar to that of polyelectrolyte brushes) was confirmed. Such stable surface hydration effectively separates cellulose surface from oil droplets, resulting in extremely low adhesion between them. As a demonstration of its practicality, regenerated cellulose membranes were fabricated via electrospinning, and they exhibit high oil/water separation efficiencies (including oil-in-water emulsions) as well as self-cleaning ability.
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Affiliation(s)
- J Justin Koh
- Institute of Materials Research and Engineering, Agency for Science, Technology, and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore; Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore
| | - Pengfei Pang
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore
| | - Souvik Chakraborty
- Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, 16-16 Connexis North, Singapore 138632, Singapore
| | - Junhua Kong
- Institute of Materials Research and Engineering, Agency for Science, Technology, and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore
| | - Anqi Sng
- Institute of Materials Research and Engineering, Agency for Science, Technology, and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore
| | - Patsaya Anukunwithaya
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore
| | - Shujuan Huang
- NUS Environment Research Institute, National University of Singapore, 5A Engineering Drive 1, Singapore 117411, Singapore
| | - Xue Qi Koh
- Institute of Materials Research and Engineering, Agency for Science, Technology, and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore
| | - Calvin Thenarianto
- Institute of Materials Research and Engineering, Agency for Science, Technology, and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore
| | - Warintorn Thitsartan
- Institute of Materials Research and Engineering, Agency for Science, Technology, and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore
| | - Dan Daniel
- Institute of Materials Research and Engineering, Agency for Science, Technology, and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore; Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia.
| | - Chaobin He
- Institute of Materials Research and Engineering, Agency for Science, Technology, and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore; Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore.
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Li S, Sng A, Daniel D, Lau HC, Torsæter O, Stubbs LP. Visualizing and Quantifying Wettability Alteration by Silica Nanofluids. ACS Appl Mater Interfaces 2021; 13:41182-41189. [PMID: 34424661 DOI: 10.1021/acsami.1c08445] [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] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
An aqueous suspension of silica nanoparticles or nanofluid can alter the wettability of surfaces, specifically by making them hydrophilic and oil-repellent under water. Wettability alteration by nanofluids has important technological applications, including for enhanced oil recovery and heat transfer processes. A common way to characterize the wettability alteration is by measuring the contact angles of an oil droplet with and without nanoparticles. While easy to perform, contact angle measurements do not fully capture the wettability changes to the surface. Here, we employed several complementary techniques, such as cryo-scanning electron microscopy, confocal fluorescence and reflection interference contrast microscopy, and droplet probe atomic force microscopy (AFM), to visualize and quantify the wettability alterations by fumed silica nanoparticles. We found that nanoparticles adsorbed onto glass surfaces to form a porous layer with hierarchical micro- and nanostructures. The porous layer can trap a thin water film, which reduces contact between the oil droplet and the solid substrate. As a result, even a small addition of nanoparticles (0.1 wt %) lowers the adhesion force for a 20 μm sized oil droplet by more than 400 times from 210 ± 10 to 0.5 ± 0.3 nN as measured by using droplet probe AFM. Finally, we show that silica nanofluids can improve oil recovery rates by 8% in a micromodel with glass channels that resemble a physical rock network.
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Affiliation(s)
- Shidong Li
- Institute of Chemical and Engineering Sciences (ICES), Agency for Science, Technology and Research (A*STAR), 1, Pesek Road, Jurong Island, Singapore 627833
| | - Anqi Sng
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634
| | - Dan Daniel
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634
| | - Hon Chung Lau
- Department of Civil and Environmental Engineering, National University of Singapore, 1 Engineering Drive 2, Singapore 117576
| | - Ole Torsæter
- PoreLab - Norwegian Center of Excellence, S. P. Andersens vei 15b, Trondheim, Norway 7031
- Department of Geoscience and Petroleum, Norwegian University of Science and Technology (NTNU), S.P. Andersens veg 15a, Trondheim, Norway 7031
| | - Ludger P Stubbs
- Institute of Chemical and Engineering Sciences (ICES), Agency for Science, Technology and Research (A*STAR), 1, Pesek Road, Jurong Island, Singapore 627833
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Daniel D, Lin M, Luhung I, Lui T, Sadovoy A, Koh X, Sng A, Tran T, Schuster SC, Jun Loh X, Thet OS, Tan CK. Effective design of barrier enclosure to contain aerosol emissions from COVID-19 patients. Indoor Air 2021; 31:1639-1644. [PMID: 33876847 PMCID: PMC8250690 DOI: 10.1111/ina.12828] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [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: 12/10/2020] [Revised: 03/14/2021] [Accepted: 03/16/2021] [Indexed: 05/04/2023]
Abstract
Facing shortages of personal protective equipment, some clinicians have advocated the use of barrier enclosures (typically mounted over the head, with and without suction) to contain aerosol emissions from coronavirus disease 2019 (COVID-19) patients. There is, however, little evidence for its usefulness. To test the effectiveness of such a device, we built a manikin that can expire micron-sized aerosols at flow rates close to physiological conditions. We then placed the manikin inside the enclosure and used a laser sheet to visualize the aerosol leaking out. We show that with sufficient suction, it is possible to effectively contain aerosol from the manikin, reducing aerosol exposure outside the enclosure by 99%. In contrast, a passive barrier without suction only reduces aerosol exposure by 60%.
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Affiliation(s)
- Dan Daniel
- Institute of Materials Research and EngineeringA*STAR (Agency for Science, Technology and ResearchInnovisSingapore
| | - Marcus Lin
- School of Mechanical and Aerospace EngineeringNanyang Technological UniversitySingapore
| | - Irvan Luhung
- Singapore Centre For Environmental Life Sciences Engineering (SCELSENanyang Technological UniversitySingaporeSingapore
| | - Tony Lui
- Ng Teng Fong General HospitalSingaporeSingapore
| | - Anton Sadovoy
- Institute of Materials Research and EngineeringA*STAR (Agency for Science, Technology and ResearchInnovisSingapore
| | - Xueqi Koh
- Institute of Materials Research and EngineeringA*STAR (Agency for Science, Technology and ResearchInnovisSingapore
| | - Anqi Sng
- Institute of Materials Research and EngineeringA*STAR (Agency for Science, Technology and ResearchInnovisSingapore
| | - Tuan Tran
- School of Mechanical and Aerospace EngineeringNanyang Technological UniversitySingapore
| | - Stephan C. Schuster
- Singapore Centre For Environmental Life Sciences Engineering (SCELSENanyang Technological UniversitySingaporeSingapore
| | - Xian Jun Loh
- Institute of Materials Research and EngineeringA*STAR (Agency for Science, Technology and ResearchInnovisSingapore
| | - Oo Schwe Thet
- School of EngineeringNgee Ann PolytechnicSingaporeSingapore
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Daniel D, Florida Y, Lay CL, Koh XQ, Sng A, Tomczak N. Quantifying Surface Wetting Properties Using Droplet Probe Atomic Force Microscopy. ACS Appl Mater Interfaces 2020; 12:42386-42392. [PMID: 32799518 DOI: 10.1021/acsami.0c12123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The functional properties of a surface, such as its anti-fogging or anti-fouling performance, are influenced by its wettability. To quantify surface wettability, the most common approach is to measure the contact angles of a liquid droplet on the surface. While well established and relatively easy to perform, contact angle measurements were developed to describe macroscopic wetting properties and are difficult to perform for submillimetric droplets. Moreover, they cannot spatially resolve surface heterogeneities that can contribute to surface fouling. To address these shortcomings, we report on using an atomic force microscopy technique to quantitatively measure the interaction forces between a microdroplet and a surface with piconewton force resolution. We show how our technique can be used to spatially map topographical and chemical heterogeneities with micron resolution.
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Affiliation(s)
- Dan Daniel
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis, 138634 Singapore
| | - Yunita Florida
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis, 138634 Singapore
| | - Chee Leng Lay
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis, 138634 Singapore
| | - Xue Qi Koh
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis, 138634 Singapore
| | - Anqi Sng
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis, 138634 Singapore
| | - Nikodem Tomczak
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis, 138634 Singapore
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Daniel D, Lay CL, Sng A, Jun Lee CJ, Jin Neo DC, Ling XY, Tomczak N. Mapping micrometer-scale wetting properties of superhydrophobic surfaces. Proc Natl Acad Sci U S A 2019; 116:25008-25012. [PMID: 31772014 PMCID: PMC6911201 DOI: 10.1073/pnas.1916772116] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
There is a huge interest in developing superrepellent surfaces for antifouling and heat-transfer applications. To characterize the wetting properties of such surfaces, the most common approach is to place a millimetric-sized droplet and measure its contact angles. The adhesion and friction forces can then be inferred indirectly using Furmidge's relation. While easy to implement, contact angle measurements are semiquantitative and cannot resolve wetting variations on a surface. Here, we attach a micrometric-sized droplet to an atomic force microscope cantilever to directly measure adhesion and friction forces with nanonewton force resolutions. We spatially map the micrometer-scale wetting properties of superhydrophobic surfaces and observe the time-resolved pinning-depinning dynamics as the droplet detaches from or moves across the surface.
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Affiliation(s)
- Dan Daniel
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), Innovis, Singapore 138634;
| | - Chee Leng Lay
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), Innovis, Singapore 138634
| | - Anqi Sng
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), Innovis, Singapore 138634
| | - Coryl Jing Jun Lee
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), Innovis, Singapore 138634
| | - Darren Chi Jin Neo
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), Innovis, Singapore 138634
| | - Xing Yi Ling
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371
| | - Nikodem Tomczak
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), Innovis, Singapore 138634
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Janca A, Lillee A, Sng A. Social Rituals and Early Detection of Mental Disorders. Eur Psychiatry 2015. [DOI: 10.1016/s0924-9338(15)30237-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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