| Summary: | 碩士 === 國立交通大學 === 機械工程系所 === 103 === Diluting sample to be different concentrations using buffer or related reagents is called as sample dilution which is important pre-procedure in various biomedical detections. Increasing number of diluted sample concentrations could enhance accuracy of detection; For some specifically applications like genetic detection, raising dilution ratio (~1/50) is necessary; Because of small bio-samples and expensive reagents, operation needs less liquid. In commercial dilution products of liquid solute, there has not a device with dilution of high flexibility (In high dilution ratio, has numerously diluted sample concentrations), and its amount of liquid demand is large. In references, there has not any design with dilution of high flexibility either. In commercial dilution products of solid solute, the devices are high flexibility, but it needs large buffer and solid sample which is unsuitable for bio-application with mostly liquid sample. Therefore, developing the device with dilution of high flexibility and less liquid amount is the goal in this research.
Here, the concept of device is EWOD-based microfluidic chip with constant gap between top and bottom plate. In this chip, the electrodes connect to buffer reservoir are totally 5 kinds of sizes - 1、2、4、8、15 unit area, and only 1 unit area electrodes connect to sample reservoir. Consequently, it could create buffer droplets of 5 kinds of volume and single sample droplet of fixed volume, and then calculate the dilution method of 1/2~1/50 totally 49 kinds of volume concentrations.
Changing driving voltage in creating droplets to control droplet volume could get more precise concentration. By experiment, the volume of created sample droplets are more identical with driving voltage 60V, and define the volume as 1 unit. Buffer droplets of 1、2、4、8 and 15 target unit volume are created with driving voltage 120、60、60、60 and 60V, respectively. Use this operating condition to dilute sample, including measurement of high concentration(1/2、1/10)、middle concentration range(1/21~1/25) and low concentration range(1/46~1/50). Max amount of liquid demand is 4.768 μL in dilution of concentration 1/50. Moreover, it could be observed that the error results and target concentrations is positive correlation. Max error is 1.86% (concentration 1/2), and most of errors are less than 1%. Except utilizing error results to determine precision of single concentration, it is proved adjacent concentration could be distinguished or not. No matter it is at middle concentration range or low concentration range, all of adjacent concentration values are not overlap. Although low concentration range is distinguished hardest part of all concentration range, it still could be distinguished. Therefore, it is proved that all range of concentration values are not overlap. Based on the above, the EWOD-based dilution chip of this research can achieve liquid sample dilution of high flexibility (1/2~1/50), and completes the goal of less liquid with max amount of liquid demand 4.768 μL in dilution of single concentration.
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