Papers by Keyword: Microfluidic Device

Abstract: Chemotaxis microfluidic devices are one type of lab-on-a-chip (LOC) devices that functions to minimize the volume of sample used and the testing time by conducting an analysis on a smaller scale. Chemotaxis microfluidic devices consist of micro-scale features that are delicate to be produced using conventional manufacturing methods. Chemotaxis microfluidic devices are generally manufactured using soft lithography. This study attempts to apply hot embossing process to replace soft lithography process, in which the hot embossing mould was fabricated using 3D printing, especially digital light processing (DLP) methods. This project investigates the challenges of fabricating the hot embossing mould of chemotaxis microfluidic device using DLP 3D printing. Three printed orientations for the moulds were produced and compared. The three moulds are subsequently used in the hot embossing process to produce chemotaxis microfluidic devices on poly(methyl methacrylate) (PMMA) substrate. The performance of the moulds is compared to the mould produced by micro-milling process using qualitative (visual analysis) and quantitative (dimensional analysis) methods. The analysis shows that DLP 3D printed moulds have comparable quality with those produced by micro-milling. The printing orientation has significant effect on the dimensional differences between the mould and design with mould WT (area of width and thickness attached to the platform) has the smallest dimensional differences.

Abstract: Illegal cooked oil is a serious food safety issue in China, while an effective authentication method is still lacking. In this paper, a microfluidic device was applied for the discrimination of low-grade oil from edible oil, by creating water droplets of different sizes in different oils.

Abstract: This study presents a new method for surface modification of polymeric materials by using pulsed UV laser welding technology. The bonding procedures including ablation treatment, Oxygen plasma treatment, adhesive layer bonding and cured by pulsed UV laser writing system was exhibited. The investigation of various parameters for UV laser writing system was performed and discussed by using water contact angle measurement. This technique has been successfully applied to bond dissimilar polymer substrates (polydimethylsiloxane (PDMS) to polymethylmethacrylate (PMMA)). The scanning electron microscopy (SEM) image reveals clearly that there was no clogging in the microchannel or deformation observed between PDMS and PMMA. The method was straightforward and the integrity of microfluidic features was successfully preserved after bonding.

Abstract: Monitoring body fluids such as sweat composition can provide useful information about the physiological status. Physiological monitoring of body fluids such as sweat with a textile-based system has the advantage of being non-invasive and easily accessible and such monitoring is beneficial to indicate information about body's physiological status. In the present study, it is aimed to design a textile-based system with non-invasive methods which can be used to monitor a sportsman's performance. A novel, disposable and wearable biochemical analytical device was designed and fabricated by patterning micro channels and reservoirs using SU-8 photoresist through photolithography technique on an absorbant bicomponent Evolon® nonwoven substrate. It was obtained that hydrophilic reservoirs were well defined and demarcated by hydrophobic barriers. Therefore, no liquid leakage was observed around the reservoirs which was crucial for achieving a proper enzyme immobilization and the successful detection of the color change after the simulated sweat was deposited on the hydrophilic reservoir areas. Analyte optimization studies revealed that color change became more evident with the increasing analyte concentration until 20 mM and started to decrease with further increase due to analyte inhibition. Also, on textile fabrics, color densities started to decrease after 40 mM analyte concentration.

Abstract: Membrane-based microfluidic devices have been demonstrated in recent literature to show a significant potential in developing low-cost but high-efficient analytical devices. Usually, the step of sampling and sample preparation is the most importance processes in the whole analytical experiments. This study designed and manufactured a low-cost kit for water sampling and sample preparation of waterborne pathogens, especially protozoan parasites. Subsequently, Saccharomyces cerevisiae was employed as the model microbe to verify the function of kit. The concepts of green design and agile manufacturing were reflected throughout this work. In the devices, membrane filters were fixed and locked in a pair of disposable filter holders, and then the filter set would be assembled with a volumetric sample container to filter the microorganism in water samples. After the sampling process, the used filter holder with microbes on the membrane would be taken out and conserved in a preservation buffer, which could protect the DNA/RNA molecules inside the cells. When these filter holders were transported to a remote laboratory, the sample preparation cassette will be used in the on-site extraction of the DNA/RNA from the cells on the membrane. At last, the eluate was made for further identification, i.e. NASBA tests. Eight kinds of candidate membrane filters were evaluated in the kit, and the function of the kit was verified.

Abstract: This paper describes the use of a printing circuit technology to generate hydrophilic channels in a filter paper. Pattern was first designed using Protel soft, and printed on a blank paper. Then, the pattern was transferred on a sheet copper using a thermal transfer printer. The sheet copper with pattern was dipped in a ferric trichloride solution to etch the whole pattern of the sheet copper. At last, the etched sheet copper was coated with paraffin, then with a filter paper and heated at the other side of the sheet copper with an electric iron. The melting paraffin penetrated full thickness of the filter paper and formed a hydrophobic “wall”. Colorimetric assays for the presence of protein and glucose were demonstrated in the paper-based device. The work is helpful for researching paper-based microfluidic devices for monitoring health and detecting disease.

Abstract: A new low cost microfluidic device has been designed and fabricated. Three thread microchannels were fabricated using tape and three indicting filter papers were also made by dipping three filter papers into sodium nitrite with different concentration. The side of the thread microchannels was connected to the indicting filter papers and then mounted on a 128⁰ yx-LiNbO₃ piezoelectric substrate, on which an interdigital transducer and reflector were fabricated using microeletric technology. PDMS film was coated to avoid the evaporation of microfluid transporting in the thread based microchannels. When a 25.5MHz RF signal with 25.4dBm power was applied on the IDT, the microfluid on the piezoelectric substrate was actuated by surface acoustic wave and transported along the thread microchannels, and reacted with nitrite ion in the indicting filter paper. Experimental results show that the thread-piezoelectric substrate microfluidic device can be used for biological or chemical analysis.

Abstract: This paper presents a simple but reliable fabrication process for microfluidic devices on glass substrate using wet etching technology. Instead of using expensive Pyrex glasses as substrates and depositing expensive metal or polysilicon/amorphous silicon as etch masks in conventional method, glass slide is used as substrate and a single-layer negative photoresist RFJ-220 is used as the etching mask. The etch rates, generation of defects, undercut ratio and surface roughness are studied. In order to achieve high etching depth and smooth surface, buffered oxide etching with hydrochloric acid as additive is proposed. By proper cleaning and long-time hard baking, the undercut ratio can approach to 1. An 110μm depth microchannel with smooth surface is achieved. This fabrication process leads to a considerable reduction of process steps, fabrication time and material consumption. With this technique, we successfully fabricated a microfluidic device, which is used in the capture of hepatoma cells HepG2.

Abstract: A biochip for building up self assembled ferromagnetic structures was designed. The magnetic structures are self assembling onto magnetic seeding points which are arranged in a periodic hexagonal structure on the bottom of the chip. The individual shapes of the ferromagnetic structures can be controlled by an applied external magnetic field. This periodic arrangement of adaptable ferromagnetic structures is well suited for selective and dynamic cell trapping. A biochip designed for lab experiments and a simulation model for optimizing the magnetic structures is presented.

Abstract: Poly(lactic acid) (PLA) is a biodegradable and biocompatible aliphatic polyester whose lactic acid monomers are derived from renewable resources such as corn and sugar beet. As a thermal plastic it can be processed through compounding and injection. As such, we have developed a microfludic device using PLA aimed at blood dialysis application. To quantify the degradation of PLA, its hydrolysis at different pH value was studied. To study the bioresorbable property of these fabricated devices, its decomposition was tested by morphology observation and weight change measurements after embedding in soil under simulated environmental conditions. Upon contact with a hydrophobic surface, platelets and prothrombin are always activated to attach to the surface, resulting in blood clot. This would block the blood flow through the dialysis channels in the microfluidic device. To improve the hydrophilicity, hence the blood compatibility, chemical grafting of a hydrophilic polymer, poly(ethylene oxide) methacrylate (PEGmA), onto the surface of PLA microfluidic device was carried out and the changes in hydrophilicity was monitored through measuring the water contact angle. Our results indicate that chemical grafting of PEGmA significantly improves the hydrophilicity of the device surface.