2022 Fiscal Year Research-status Report
Colloidal-rods for examining polymer dynamics in complex flows
| Project/Area Number |
22K14738
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| Research Institution | Okinawa Institute of Science and Technology Graduate University |
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Principal Investigator |
CALABRESE Vincenzo 沖縄科学技術大学院大学, マイクロ・バイオ・ナノ流体ユニット, ポストドクトラルスカラー (40895413)
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| Project Period (FY) |
2022-04-01 – 2024-03-31
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| Keywords | colloidal rods / polymer solution / relaxation time / polymer dynamics |
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| Outline of Annual Research Achievements |
In FY2022, experiments were completed measuring the alignment of colloidal rods in different polymer solutions under steady shear flows. Testing different polymer solutions, we have been able to conclude that the polymer dynamics govern the onset of shear-induced alignment of colloidal rods. Specifically, the control parameter for the alignment of rods is the Weissenberg number of the polymer solution, quantifying the elastic response of the polymer to an imposed flow. Additionally, we find that the colloidal rods do not perceive the surrounding polymer solution as a continuous medium, but rather like a discrete medium and that the colloidal rods follow a universal trend of alignment that is independent of the surrounding polymer solution. These part of the project has been successfully completed and published in Macromolecules 2022-55-13.
In FY2022 we have also conducted experiments on the flow dynamics of worm-like block copolymers. We show that shear and extensional flows induce the alignment of the worm-like block copolymers. However, we find that extensional deformations are more effective than shear deformations at triggering the onset of alignment of the worm-like particles. We explain the difference in alignment between shear and extensional deformations based on the particle extensibility and flexibility. These part of the project has been successfully completed and published in Macromolecules 2022-55-22.
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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
The project has progressed very well through FY2022. As it was hoped, the core experiments are now complete and there is sufficient time in FY2023 to explore the effect of macromolecular flexibility on their alignment in shear and extensional flows. The rather quick progress was mainly due to the large amount of preliminary results conducted prior to the start of the project. Additionally, the facility at the Okinawa Institute of science and technology, ensured the smooth progress of the project.
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| Strategy for Future Research Activity |
We accomplished the objectives targeted for FY2022. In FY2023, the experiments regarding the macromolecular alignment in shear- and extensional flows should be ready together with a draft paper ready for submission. We will also perform experimental characterization of various macromolecules in “idealized porous media” to extend our understanding to mixed flows.
Characterization of the fluids will be performed combining flow-induced birefringence (to probe the extent of alignment of the rod-like particles) and flow velocimetry (to accurately quantify the shear and extensional deformation rates). For these experiments, we have already designed and tested the working principle of the microfluidic device using a Newtonian fluid. We have obtained (purchased or produced in our laboratory) and characterized multiple rod-like polymers and colloids with different flexibility, including DNA, filamentous viruses (Pf1 and fd), protein nanofibrils, hyaluronic acid, and cellulose-based polyelectrolytes. Comparison with theory for rigid rods is planned in order to compare with the experimental results.These experiments will allows generalization of the effect of shear and extensional flows at aligning macromolecules with different flexibility.
We believe that the results of this project will lead to significant new insights into the polymer physics community with strong implication in biophysics. By the end of FY2023, we hope to submit two or three additional research papers based on the results of the project.
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| Causes of Carryover |
We synthesised colloidal rods in our laboratory to have a better control of their morphology.
This enabled to have larger quantities of samples at a lower price.
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Research Products
(9 results)
