2019 Fiscal Year Research-status Report
Effect of liquid flow on the forces and physical properties of surfaces in liquids
| Project/Area Number |
19K05264
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| Research Institution | Shinshu University |
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Principal Investigator |
マクナミー キャシー 信州大学, 学術研究院繊維学系, 准教授 (40504551)
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| Co-Investigator(Kenkyū-buntansha) |
小川 智之 東北大学, 工学研究科, 准教授 (50372305)
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| Project Period (FY) |
2019-04-01 – 2022-03-31
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| Keywords | Experiment planning / Force experiments / data analysis / discussion |
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| Outline of Annual Research Achievements |
We determined how a liquid flow affects the forces between two negatively charged surfaces (silica particle and silicon wafer) in aqueous solutions containing surfactants by using a combined Atomic Force Microscope-peristaltic pump system.
When the charge of the surfactant was same as the surface, the application of a flow reduced the magnitude and range of the repulsive force. The adsorption of the surfactant to the like-charged surfaces is reasoned not to increase with a liquid flow, due to the repulsive electrostatic forces acting between the surface and the surfactants. When the charge of the surfactant was opposite to the surface, a flow changed the adsorption of the surfactants to the silica/silicon wafer surfaces. This changed the magnitude of the attractive force acting between the silica/silicon wafer surfaces. Increasing the flow rate increased the degree to which the surfactant adsorption changed, and could result in the charge reversal of the silica/silicon wafer surfaces at lower concentrations than that required in the absence of a flow. Thus, in addition to the existing method of controlling the aggregating ability of charged particles in the presence of oppositely charged ionic surfactants via the surfactant concentration,it may be possible to control the aggregating ability of charged particles via the flow rate, if the appropriate surfactant type and concentration is used.[Langmuir, 2020, 36, 1887-1897]
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
In 2019, we planned to study the effect of a liquid flow on hydrophobic surfaces stabilized by surfactants adsorbed via physical forces. However, due to difficulties associated with measuring forces of hydrophobic surfaces in aqueous solutions, the effect of a flow on hydrophilic surfaces stabilized by surfactants adsorbed via physical forces was studied instead. One article has been accepted for publication [Langmuir, 2020, 36, 1887-1897].
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| Strategy for Future Research Activity |
In year 2020, we plan to study the effect of flow on surfaces stabilized by polymers adsorbed via chemical forces.
In the absence of a flow, the chemical adsorption of polymers to a surface causes a steric repulsion, which can make normally aggregating particles disperse. The strength of the steric repulsion increases with the length of extension of the polymers that are attached to the surfaces. We will determine if the presence of a flow changes the extension of these polymers due to a change in their conformation, by establishing whether the magnitude of the steric repulsion changes with a liquid flow. The force-distance curves will be measured between a silica probe and a silicon substrate to which have polymers of different molecular weights have been chemically attached.
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| Causes of Carryover |
The remaining money from year 2019 will be used to help fund the consumable items (cantilevers, substrates, particles, chemicals, etc) used in the research in Year 2020, publication costs (open access fees etc) and travel. These amounts are expected to cost more than the previous year. Additionally, new cantilevers and other consumables will be required to perform the planned research of Year 2020. The costs of these materials are more expensive than originally planned. The results from the research in Year 2019 could not all be presented at conferences, so money from Year 2019 will go towards participation in international conferences.
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