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Subject: search.filters.subject.Microfluidics

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    Fabrications of Low-Cost Poly(methyl methacrylate) Microfluidic Devices for Precise Passive Flow Control
    (2024-01-01)
    Kaewtae, Wattana
    ;
    Tanasapsakul, Warinthorn
    ;
    Pattamang, Pattaraluck
    ;
    Ranron, Norabadee
    ;
    Sripumkhai, Witsaroot
    Microfluidics serve as effective platforms for conducting point-of-care diagnostics and biochemical assays which require precise control over flow rates and incubation times. To enable their uses in resource-limited settings, a pump-free approach is essential for driving fluid flow within the microfluidics. In this study, we introduced cost-effective methodologies for fabricating poly(methyl methacrylate) (PMMA)-based microfluidic devices driven passively by capillary pressure. We explored three fabrication techniques including two-layer CNC micro-milling, two-layer laser engraving, and three-layer laser cutting. Among these methods, three-layer laser cutting proved to be the most reproducible method, yielding devices with consistent channel dimensions and contact angles. Consequently, this fabrication technique enables better control over flow rates within microfluidic systems. Our findings demonstrate the feasibility of fabricating low-cost, pump-free microfluidic devices for precise flow control, with potential applications in disease detection and biomedical research.
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    Mutation detection of urinary cell-free DNA via catch-and-release isolation on nanowires for liquid biopsy
    (2023-08-15)
    Takahashi, Hiromi
    ;
    Yasui, Takao
    ;
    Hirano, Masaki
    ;
    Shinjo, Keiko
    ;
    Miyazaki, Yusuke
    Cell-free DNA (cfDNA) and extracellular vesicles (EVs) are molecular biomarkers in liquid biopsies that can be applied for cancer detection, which are known to carry information on the necessary conditions for oncogenesis and cancer cell-specific activities after oncogenesis, respectively. Analyses for both cfDNA and EVs from the same body fluid can provide insights into screening and identifying the molecular subtypes of cancer; however, a major bottleneck is the lack of efficient and standardized techniques for the isolation of cfDNA and EVs from clinical specimens. Here, we achieved catch-and-release isolation by hydrogen bond-mediated binding of cfDNA in urine to zinc oxide (ZnO) nanowires, which also capture EVs by surface charge, and subsequently we identified genetic mutations in urinary cfDNA. The binding strength of hydrogen bonds between single-crystal ZnO nanowires and DNA was found to be equal to or larger than that of conventional hydrophobic interactions, suggesting the possibility of isolating trace amounts of cfDNA. Our results demonstrated that nanowire-based cancer screening assay can screen cancer and can identify the molecular subtypes of cancer in urine from brain tumor patients through EV analysis and cfDNA mutation analysis. We anticipate our method to be a starting point for more sophisticated diagnostic models of cancer screening and identification.
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    Development of a Serological Dilution Microfluidic Chip for Immunoassay Applications
    (2022-07-01)
    Thienthong, Therdthai
    ;
    Juntasaro, Ekachai
    ;
    Khemthongcharoen, Numfon
    ;
    Sripumkhai, Witsaroot
    ;
    Houngkamhang, Nongluck
    This work aims to develop a multiple dilution microfluidic chip that is capable of diluting the human serum by means of two-fold dilution for seven levels from 1:2 to 1:128 with phosphate-buffered saline (PBS) buffer. The dilution in this work is processed in parallel in order to reduce the accumulated errors that the standard pipetting technique generates in the micro-well plate. The serum and PBS buffer are precisely delivered to the micromixers by controlling their flow rates. The dilution is achieved by the passive mixing process for which the serpentine geometry is designed in order to continually generate the Dean vortices along the serpentine microchannel to effectively mix serum and PBS buffer in the microfluidic chip. The prototype of this multiple dilution microfluidic chip is fabricated by using polydimethylsiloxane (PDMS). The dilution-in-parallel capability of this prototype is validated by using the UV-vis absorption method. The results reveal that the measured values of the seven dilution ratios obtained are in good agreement with the exact values. Finally, this prototype is evaluated for serological MOG-IgG detection in order to verify the reliable operation of this multiple dilution microfluidic chip. The prototype can successfully detect MOG-IgG at all volume concentration ratios.
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    Mixing-performance evaluation of a multiple dilution microfluidic chip for a human serum dilution process
    (2021-09-30)
    Thienthong, Therdthai
    ;
    Juntasaro, Ekachai
    ;
    Sripumkhai, Witsaroot
    ;
    Houngkamhang, Nongluck
    ;
    Chanasakulniyom, Mayuree
    This paper is aimed to propose a numerically designed multiple dilution microfluidic chip that can simultaneously deliver several serum dilutions in parallel. The passive mixing scheme is selected for dilution and achieved by the serpentine mixing channel in which Dean vortices are induced to increase the contact area and time for better diffusion. The mixing performance at the exit of this dilution chip is numerically evaluated using five commonly-used mixing indices with the goal that the homogeneity of the mixture over the exit cross-sectional area of the mixing channel must be greater than 93.319% to fulfill the six-sigma quality control.
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    Microfluidic magnetic switching valves based on aggregates of magnetic nanoparticles: Effects of aggregate length and nanoparticle sizes
    (2017-01-15)
    Jiemsakul, Thanakorn
    ;
    Manakasettharn, Supone
    ;
    Kanharattanachai, Sivakorn
    ;
    Wanna, Yongyuth
    ;
    Wangsuya, Sujint
    We demonstrate microfluidic switching valves using magnetic nanoparticles blended within the working fluid as an alternative microfluidic flow control in microchannels. Y-shaped microchannels have been fabricated by using a CO<inf>2</inf> laser cutter to pattern microchannels on transparent poly(methyl methacrylate) (PMMA) sheets covered with thermally bonded transparent polyvinyl chloride (PVC) sheets. To examine the performance of the microfluidic magnetic switching valves, an aqueous magnetic nanoparticle suspension was injected into the microchannels by a syringe pump. Neodymium magnets were then employed to attract magnetic nanoparticles and form an aggregate that blocked the microchannels at a required position. We have found that the maximum volumetric flow rate of the syringe pump that the magnetic nanoparticle aggregate can withstand scales with the square of the external magnetic flux density. The viscosity of the fluid exhibits dependent on the aggregate length and the size of the magnetic nanoparticles. This microfluidic switching valve based on aggregates of magnetic nanoparticles has strong potentials as an on-demand flow control, which may help simplifying microfluidic channel designs.
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    Isolation of circulating tumor cells under hydrodynamic loading using microuidic technology
    (2014-01-01)
    Zhao, Cong
    ;
    Lee, Yi Kuen
    ;
    Xu, Rui
    ;
    Liang, Chun
    ;
    Liu, Dayu
    Cancer is a leading cause of mortality worldwide causing human deaths. Circulating tumor cells (CTCs) are cells that have detached from a primary tumor and circulate in the bloodstream; they may constitute seeds for subsequent growth of additional tumors (metastasis) in different tissues. The detection of CTCs may have important prognostic and therapeutic implications but, because their number is very small, these cells are not easily detected. Circulating tumor cells are found in the order of 10-100 CTCs per mL of whole blood in patients with metastatic disease. Isolation of tumor cells circulating in the blood stream, by immobilizing them on surfaces functionalized with bio-active coating within microfluidic devices, presents an interdisciplinary challenge requiring expertise in different research areas: cell biology, surface chemistry, fluid mechanics and microsystem technology. We first review the fundamental of cell biology of CTCs and summarize the key microfluidic techniques for isolation of CTCs via cell-ligand interactions, magnetic interactions, filtration; detection and enumeration of CTCs; in vivo CTCs imaging.