In this study, we propose a novel and simple fabrication method of the microfluidic device, with high-aspect-ratio (HAR) microchannel for microparticle separation under viscoelastic fluid flow. To fabricate the HAR (> 10) microfluidic device comprised of the Si channel and PDMS mold, basic MEMS processes such as photolithography, reactive ion etching and anisotropic wet etching of Si wafer were used, and then plasma bonding with mechanical alignment between the Si channel and PDMS mold was conducted. The width of the microchannels was determined by the difference between the Si channel width and the master width for the PDMS mold. On the other hand, the heights of the Si channel and PDMS mold could be controlled by the KOH etching time and spin-coating speed of SU-8, respectively. The HAR microfluidic device whose microchannel had 10 μm width and 100 μm height was successfully fabricated, and used to separate microparticles without other external forces. The effect on the particle focusing position and focusing width under viscoelastic fluid was investigated, depending on the flow rate and the microparticle size. It is expected that precise manipulation as well as high-throughput separation of microparticles, can be achieved using the microfluidic device with HAR microchannel.
Citations
Citations to this article as recorded by
Process for the Fabrication of Nickel Material High Aspect-ratio Digital PCR Partition GeeHong Kim, HyungJun Lim, SoonGeun Kwon, Hak-Jong Choi Journal of the Korean Society for Precision Engineering.2024; 41(8): 663. CrossRef
In this paper, we propose acoustophoretic microfluidic devices with an acoustic transparent polymer wall using a simple and low-cost fabrication method followed by MEMS (Micro-Electromechanical Systems) processes. Generally, due to the acoustic standing wave between two opposing walls in microfluidic channel, the particle focusing lines are fixed according to the applied frequency. In the proposed device, however, it is possible to place the particle focusing lines in the arbitrary position within the fluidic domain through the optimized width of polymer wall. The PDMS (Polydimethylsiloxane) mold with thin layer was used as the sealing layer between the Si substrate and cover glass, as well as the decoupling layer between the acoustic boundary and fluidic boundary. The thickness of PDMS mold needed to be minimized to decrease the heating by the acoustic energy absorption of PDMS layer, which was successfully made using the spin-coating of PDMS and the UV tape transfer method. The acoustophoretic device with thin PDMS layer and optimized width of PDMS wall can be applied, for biotechnological applications such as the separation of blood cells and micro-particles.
Recently, many attempts have been made to use microalgae as raw material for next generation biodiesel. Since conventional microalgae detection is performed in the laboratory after collecting algae in the field, it is necessary to develop a portable fluorescence measuring device that can effectively reduce detection duration in the field. In this study, we developed a portable fluorescence measurement device composed of an optical system and a control system to detect microalgae in the field. The optical system stimulates excitation light suitable for algae to be measured and determines the amount of algae by measuring the amount of emitted light through the PMT sensor. The optical system facilitates seamless change of filters and lenses according to kinds of algae. This was validated by checking the amount of light measured according to concentration of CC125. Reliability of the fluorescence measuring device was verified through repeated experiments.
Fabrication of inverse-tapered structure remains as a problem in the fabrication of oleophobic surface mostly due to the complications and the high cost of processes. In this paper, we propose a simple and low-cost fabrication method of inverse-tapered structured oleophobic surface using micromolding in capillaries (MIMIC) and microtransfer molding followed by MEMS processes. Silicon wafer molds for the formation of inverse-tapered structure were made using MEMS processes such as photolithography and anisotropic KOH etching of silicon wafer. The geometry of structure could be changed by controlling the etching depth of the silicon wafer mold. After covering the surface of the mold using flat UV tape, the formed space between mold and UV tape was filled with pre-cured PDMS by capillary force and then cured in oven. The tapered structure on UV tape was transferred and bonded to glass wafer by O₂ plasma treatment. The fabricated inverse-tapered structure was coated with a fluoroalkylsilane monolayer to reduce its surface energy. The wetting behaviors were investigated by the contact angle (CA) measurement of hexadecane droplets. This study demonstrates that an inversetapered structure can be fabricated on a substrate using micromolding in capillaries and microtransfer molding, whose surface shows the superoleophobicity.
Citations
Citations to this article as recorded by
Fabrication of Acoustophoretic Device with Lateral Polymer Wall for Micro-Particle Separation Sungdong Kim, Su Jin Ji, Song-I Han, Arum Han, Young Hak Cho Journal of the Korean Society for Precision Engineering.2022; 39(5): 379. CrossRef
Fabrication of anisotropic wetting surface with asymmetric structures using geometrical similarity and capillary force Ye-Eun Lee, Dong-Ki Lee, Young Hak Cho Micro and Nano Systems Letters.2019;[Epub] CrossRef
In this paper, we propose a novel and simple fabrication microchannel with parallelogram cross-section using anisotropic wet etching of Si wafer, and self-alignment between Si channel and PDMS mold. Single crystal Si wafer was used to fabricate microchannel and master for PDMS mold, using photolithography and anisotropic KOH etching. Si structure for microchannel and master were formed on the same Si wafer by KOH etching, and the PDMS mold was made from Si master. Thus, we could fabricate the Si microchannel and PDMS mold, with same structural height. Finally, a microchannel with parallelogram cross-section could be easily formed, through self-alignment between them. Si microchannel and PDMS mold were permanently bonded, using O₂ plasma treatment. It is expected that the fabricated microchannel with parallelogram cross-section, can be used to study inertial focusing, widely used to separate particles continuously and with high-throughput.
Citations
Citations to this article as recorded by
The Fabrication of a High-Aspect-Ratio Microfluidic Device for Microparticle Separation under Viscoelastic Fluid Sung Woo Kim, Joo Yong Kwon, Jihong Hwang, Young Hak Cho Journal of the Korean Society for Precision Engineering.2022; 39(10): 725. CrossRef
Experimental Study on Heat Transfer Performance of Microchannel Applied with Manifold Jungmyung Kim, Hoyong Jang, Heesung Park Journal of the Korean Society for Precision Engineering.2022; 39(12): 923. CrossRef
High-Aspect-Ratio Microfluidic Channel with Parallelogram Cross-Section for Monodisperse Droplet Generation Hyeonyeong Ji, Jaehun Lee, Jaewon Park, Jungwoo Kim, Hyun Soo Kim, Younghak Cho Biosensors.2022; 12(2): 118. CrossRef
Fabrication of microfluidic channels with various cross-sectional shapes using anisotropic etching of Si and self-alignment Dong-Ki Lee, Joo Yong Kwon, Young Hak Cho Applied Physics A.2019;[Epub] CrossRef
In this paper, we propose a simple and low-cost fabrication method for PMMA (Poly (Methyl Methacrylate)) acoustophoretic microfluidic chips using plasma-assisted bonding followed by MEMS (Microelectromechanical Systems) processes. A metal mold for replicating the PMMA polymer was fabricated using MEMS processes, and the microfluidic channel was imprinted on the PMMA polymer using a hot-embossing process. The closed fabricated microfluidic channel was achieved by means of the plasma-assisted bonding between the PMMA channel and the flat PMMA cover. The plasma treatment and hot-embossing conditions for PMMA-PMMA bonding were studied and evaluated. The particle separation test confirmed that the PMMA acoustophoretic microfluidic chips could be used. We expect the Si-based acoustophoretic microfluidic chip to be replaced by the presented polymer chip in such applications as blood or droplet separation.
Citations
Citations to this article as recorded by
Fabrication of Acoustophoretic Device with Lateral Polymer Wall for Micro-Particle Separation Sungdong Kim, Su Jin Ji, Song-I Han, Arum Han, Young Hak Cho Journal of the Korean Society for Precision Engineering.2022; 39(5): 379. CrossRef
Microfluidic Chip Fabrication of Fused Silica Using Microgrinding Pyeong An Lee, Ui Seok Lee, Dae Bo Sim, Bo Hyun Kim Micromachines.2022; 14(1): 96. CrossRef
PMMA Thermal Bonding System Using Boiling Point Control Dong Jin Park, Taehyun Park Journal of the Korean Society for Precision Engineering.2021; 38(8): 613. CrossRef
Microchannel Fabrication on Glass Materials for Microfluidic Devices Jihong Hwang, Young Hak Cho, Min Soo Park, Bo Hyun Kim International Journal of Precision Engineering and Manufacturing.2019; 20(3): 479. CrossRef
In this paper, we propose a simple and low-cost fabrication method of polymer microlens using solvent-vapor-assisted reflow (SVAR). Metal molds for replication of polymer were fabricated using micro milling and the cylindrical shape of polymer was imprinted using hot-embossing process. The cylindrical shape of polymer was changed to hemispherical lens shape by SVAR. The characteristics of fabricated microlens were evaluated according to the condition of SVAR such as temperature and time. The focal length of polymer microlens could be controlled more easily in low-temperature and long-time condition than in high-temperature and short-time condition. That is, the level of concentrated light to focal point could be improved through the control of temperature and time. Also, we confirmed that toluene was more appropriate solvent than acetone in fabrication of PMMA polymer microlens using SVAR.
Today, there are lots of progresses in the field of lens researches, especially in the microlens fabrication. Unlike normal lenses, microlens has been widely used as a role of improving the performance of photonic devices which increase the optical precision, and also used in the fields of the display. In this paper, polymer microlenses with 300 μm diameter were replicated through hot-embossing from nickel mold which was fabricated by micro-EDM. After hot-embossing process, the polymer microlenses have a rough surface due to the crater formed by micro-EDM process, which is projected onto the surface of the lenses. The surface of polymer microlenses was polished using solvent vapor to improve the surface roughness of the microlenses without changing their shape. In the experiment, the surface roughness was improved with the processing time and vapor temperature. Also, the roughness improvement was greatly affected by the solubility difference between polymer and solvent.
We present a simple and low-cost method to fabricate poly(methyl-methacrylate) (PMMA) nanochannels with various shapes by combining the standard optical lithography with a PMMA layer transfer and collapse technique. We utilized PMMA membrane reflowing/collapsing phenomena into microchannels to fabricate nanochannels at both corners of arbitrarily-shaped microchannels. This allows nanochannels with various shapes such as curved nanochannels as well as straight nanochannels to be easily fabricated since the shape of the microchannel determines the shape of the nanochannels. This nanochannel fabrication method is simple, flexible, and low-cost since the standard optical lithography with low-resolution optical masks can be used to fabricate nanoscale channels as small as 100 nm wide with various shapes. Also, the sealing of nanochannels can be naturally achieved while the nanochannels are formed through the polymer layer transfer and collapse.
In this paper, we present details on fabrication of single-cell electroporation microdevice, practical experiments of single-cell electroporation with our fabricated microdevice. Also, the continuous electroporation for the continuous flow of cells is used for high-throughput electroporation. The delivery efficiency and cell viability tests are provided and the successful GFP transfection into cells is also evaluated with a fluorescent microscope after electroporation. This device enables to reduce the size of samples and thus the use of small amount of reagents. Also, it makes it possible to permit to avoid cell discrimination (transfected cells versus non-transfected cells) encountered when traditional bulk electroporation is held.
First
Prev
