KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Settings

Author: search.filters.author.Atthi, Nithi

Search Results

Now showing 1 - 5 of 5
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Item,
    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.
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Item,
    Enhancement of Bacterial Anti−Adhesion Properties on Robust PDMS Micro−Structure Using a Simple Flame Treatment Method
    (2022-02-01)
    Houngkamhang, Nongluck
    ;
    Chaisawat, Ploymanee
    ;
    Joksathit, Waisaree
    ;
    Samart, Sutichai
    ;
    Chutipaijit, Sutee
    Biofilm−associated infections caused by an accumulation of micro−organisms and pathogens significantly impact the environment, health risks, and the global economy. Currently, a non−biocide−releasing superhydrophobic surface is a potential solution for antibacterial purposes. This research demonstrated a well−designed robust polydimethylsiloxane (PDMS) micro−structure and a flame treatment process with improved hydrophobicity and bacterial anti−adhesion proper-ties. After the flame treatment at 700 ± 20 °C for 15 s, unique flower−petal re−entrant nano−structures were formed on pillars (PIL−F, width: 1.87 ± 0.30 μm, height: 7.76 ± 0.13 μm, aspect ratio (A.R.): 4.14) and circular rings with eight stripe supporters (C−RESS−F, width: 0.50 ± 0.04 μm, height: 3.55 ± 0.11 μm, A.R.: 7.10) PDMS micro−patterns. The water contact angle (WCA) and ethylene glycol contact angle (EGCA) of flame−treated flat−PDMS (FLT−F), PIL–F, and C–RESS−F patterns were (133.9 ± 3.8°, 128.6 ± 5.3°), (156.1 ± 1.5°, 151.5 ± 2.1°), and (146.3 ± 3.5°, 150.7 ± 1.8°), respectively. The Escherichia coli adhesion on the C−RESS−F micro−pattern with hydrophobicity and superoleophobicity was 42.6%, 31.8%, and 2.9% less than FLT−F, PIL−F, and Teflon surfaces. Therefore, the flame−treated C−RESS−F pattern is one of the promising bacterial anti−adhesion micro−structures in practical utilization for various applications.
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Item,
    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.
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Item,
    Fabrication of MEMS-based capacitive silicon microphone structure with staircase contour cavity using multi-film thickness mask
    (2019-02-01)
    Jantawong, Jirawat
    ;
    Atthi, Nithi
    ;
    Leepattarapongpan, Chana
    ;
    Srisuwan, Awirut
    ;
    Jeamsaksiri, Wutthinan
    In this work, a silicon capacitive microphone structure with a three-dimensional staircase style contour cavity (S-CTC) is developed using a newly developed Multi Film Thickness photo lithography process. This newly developed Multi Film masking process overrides the conventional wisdom in which the staircase style cavity is formed using multiple exposures of mask and multiple etchings of silicon. With this newly developed photo lithographic technique, a Multi Film Thickness (MFT) mask is fabricated with varying chromium film thicknesses such as 0, 4, 14, and 114 nm thick. The mask was then evaluated to fabricate a microphone structure with a three-dimensional staircase style cavity. Once the mask was patterned onto a substrate, a single dry etching of silicon was carried out and a desired three-dimensional stair cavity pattern was achieved. Surprisingly, our results show that a capacitive sensor with an S-CTC structure has an increased absolute capacitance value by an average of 30% in comparison to a conventional box cavity (BC) structure. This may indeed improve SNR as we anticipated. The capacitance value changed from 2.2pf to 2.9pf for the same dimension of devices. This promising technology renders an opportunity to improve the next generation of ultra-low-pressure sensors for microphone applications.
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Item,
    Fabrication of Contour Cavity Using Multi-Exposure Lithography for MEMS Capacitive Microphone
    (2018-07-02)
    Jantawong, Jirawat
    ;
    Atthi, Nithi
    ;
    Leepattarapongpan, Chana
    ;
    Jeamsaksiri, Wutthinan
    ;
    Austin, Anu
    This paper presents a novel technique to optimize a capacitive pressure sensor with multi-exposure dose lithography. As part of achieving high signal to noise ratio (SNR) in microphone, a new design was implemented. The new design defies the conventional wisdom of parallel plate theory and implement a concept of contour cavity (backplate) to follows the diaphragm deflection. This 3-dimensional contour cavity (CC) is fabricated by multi-exposure dose lithography with single silicon etching process. The CC structure with different etched depth of 0.65, 1.15, and 1.57 micron were fabricated by multi-exposure dose of 92, 120, and 210 mJ/cm<sup>2</sup>on 5.0 micron thick photoresist and single step etching with CF<inf>4</inf>/O<inf>2</inf>plasma (Si/PR etch selectivity: 1.3). Due to this novel contour cavity design, polysilicon membrane with 0.8 micron thick and a diameter of 930 micron structure produces the capacitance value of 2.88 pF, which is 28.6% higher than that of conventional parallel plate capacitive sensor.