| Summary: | 博士 === 國立成功大學 === 生物醫學工程學系 === 101 === People are paying more and more attention for dietary needs and body health with advances in technology. Because people live longer and rich diet cause a variety of modern diseases (diabetes mellitus, hyperlipidemia, hyperuricemia, etc.), regular health check becomes very important for disease prevention. However, the clinical sample of blood is a complex mixture, which must undergo a variety of sample pre-treatment methods (centrifugation, culture, Filtration, etc.) to purify before analysis and testing. Furthermore, the conventional method requires a large amount of time, energy, cost, and at least extract a tube of venous blood to obtain detection results. To solve these problems, we develop four different chip design for sample pre-treatment based on electrokinetics for point-of-care testing (POCT).
(1) 3D dielectrophoresis-field flow fraction (DEP-FFF) chip, a new 3D DEP-FFF concept to achieve the precise separation of multiple particles by using an AC DEP force gradient in the z-direction. The interlaced electrode array not only focused the particles into a single stream of particles on the same starting position, but it also increased the spacing between each particle by the retardation effect to reduce particle aggregation. An inclined electrode was also designed to continuously and precisely separate different sizes of particles based on different magnitudes of DEP force at different positions in the z-direction of the DEP gate. Four different sizes of polystyrene beads (2, 3, 4, and 6um) were precisely sized fractionation to be four particle streams based on their different threshold DEP velocities that were induced by the field gradient in the z-direction, when a voltage of 6.5 Vp–p was applied at a flow rate of 0.6uL/min. We also performed several successful examples with blood cells and Candida albicans separation to demonstrate the ability of the chip.
(2) Electrothermal switching chip, electrothermal fluid flow generated by using two sides of lateral electrode pair to achieve continuous particle manipulation in the high conductivity solution. We demonstrated that electrothermal fluid flow is highly effective for particle manipulation with a wide range of conductivity solution (0.14-1.6 S/m), the maximum offset distance can reach approximately 100um by using two sides of lateral electrode pair to control the particle switch in the high conductivity solution (1.6 S/m). The offset distance of particle is proportional to the voltage and conductivity solution, which can be precise controlled by adjusting the voltage for particle manipulation. In biological application, the red blood cells, KU-812 cells, and yeast cells were successful switched at desired position by electrothermal fluid flow. The proposed chip enables combine with electrothermal switching and DEP trapping to achieve controllable single particle manipulation for single cell analysis and detection.
(3) Real-time blood cell and plasma separation chip, the chip can separate blood cells and plasma from whole blood by using capillary and negative dielectrophoretic forces. The chip size (1.4 × 2.6 cm) is miniaturized and the manual process of chip assembly is simple and rapid (within 1 min). In addition, the simulation results were shown to agree with the experimental results in order to obtain the optimal electrode design for blood cell separation. The chip not only achieved a separation efficiency of 90% within 30 sec when the hematocrit is in the range of 10-50%, but it is also capable of performing blood cell separation with a separation efficiency of 60% at high hematocrit (approximately 60%). An additional advantage of capillary dielectrophoretic chip is easy integrates with electrochemical detection. The proposed chip is suitable for application in immunosensor and other electrochemical sensor with detection substance of longer reaction time such as cholesterol detection.
(4) 3D capillary dielectrophoretic chip, the chip is developed to improve the disadvantage of 2D capillary dielectrophoretic chip. The 3D chip successfully short separation time with blood cell separation (approximately 10 sec) and enhance the separation efficiency from whole blood. The blood glucose measurement following blood cell separation from whole blood (hct = 40%) responds linearly to glucose concentrations of 50-550 mg/dl (R^2 = 0.996). Therefore, the 3D capillary dielectrophoretic chip successfully combines with the electrothermal blood glucose measurement to apply new detection method in diabetes. The results show that the chip not only can reduce blood cell interference to enhance the current response, but also can improve the hematocrit interference to decrease the detection error.
These novel methods of sample pretreatment can be applied in the microflow cytometry, electrochemical detection, immunosensor to prove rapid and portable medical devices for point-of-care testing.
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