In this paper, we introduce a paper-based microfluidic device design that allows liquids to flow at a constant rate through the channels. The device pattern is designed based on a flow rate control test. Our proposed device can be easily manufactured by a wax printer and be printed on filter paper. The primary function of the paper device is to measure the concentration of hazardous chemicals such as heavy metals and bacteria in liquids. We also propose two new image analysis metrics, hue difference and chroma magnitude difference, for analyzing the color of images as a means of identifying the concentration of heavy metals in solutions. In addition, we discuss in detail the image processing pipeline for analyzing the devices from the initial image capturing to segmentation and analysis. This paper also discusses future goals and possible directions to take, such as handling the device from different viewpoints.
In this paper, we introduce an eight-channel paper-based microfluidic device that aims to detect multiple chemicals at once. The microfluidic device we propose is fabricated by wax printing on filter paper, which is trouble-free to handle, low cost, and easy to fabricate. As a hydrophobic material, wax (solid ink) defines the hydrophilic channels for testing. By using image processing techniques, we analyze the width change caused by heating of wax strokes and wax channels, which is a necessary step in the wax printing fabrications. In the same way, we test the minimum width of a channel that allows solutions to cross through and the minimum width of a barrier that is hydrophobic and blocks liquid flow. We also compare two different heating methods, the heat gun and the hot plate, by checking the wax channel width before and after heating based on our image processing pipeline. We conclude that a heat gun will be better for heating channels with relatively large widths. Using high resolution wax printing, we integrate multiple devices on a single paper, which makes this method very cost-effective. Lamination of wax-printed paper based devices is also analyzed, as leakage on the back side of paper is sometimes worth attention.