The Flow Control Of Point-of-Care Test Chip Based On Specific Microstructure

Microfludic control is the core operation of point-of-care test (POCT) chips. All the fluid in POCT chips should be under controlled conditions in order to achieve rapid accurate detection. In this paper, several kinds of special shaped structures are designed to control sample introduction and meniscus of flow front. The finished work are as follows:(1) Based on the theory of contact line motion, micro wavelike buffers with different parameters are designed. In the capillary-driven microfludic POCT chips, the operation of manual sample injection often cause the velocity of liquid unsteady. The subsequent flow control such as flow time and mixing efficiency are affected by the unsteady sample injection, which result the last detection inaccurate and unrepeatable. So the wavelike buffer is designed to solve the problem above.16 kinds of wavelike buffer totally with three key parameters:the crest height, the number of waveform, the depth of wave are designed. The MEMS process such as lithography and dry etch are used to fabricate silicon mold. Then the PDMS and PMMA microfludic chips are fabricated by silicon mold. A series of fluid introduction experiments are carried out by controlling three key parameters of wavelike buffer and the effect of each parameter on performance of buffer is summarized. The experiment indicate that the non-specific and differential flow induced by sample introduction process in a POCT microfluidic device can be eliminated through a simple wavelike buffer. As the sample is injected into the device, its longitudinal flow will be changed to a transversal flow within the wavelike buffer. The form of the transversal flow can eliminate the disturbances induced during sample injecting process and generates a flat fluid front with steady and uniform flow velocity. Results have shown that the buffers with low waved peak height or fewer peak numbers will have better buffering performance. As the peak height decreases to 190um, the buffering time can reach 5s-7s. As the peak number reduces to 5, the buffering time will increase to 8s-10s.(2) A novel method which can control the shape of fluid front in a microfluidic channel is designed based on the theory of microfludic control. When samples flow in hydrophilic channel, the meniscus of sample is concave which is easy to introduct air bubbles into the channel or lead to uneven mixing and channel blockage. So channels with serrated edges are designed. The channel edges that are parallel to the direction of flow are designed to three types of serrated shapes, including semicircle, triangle and trapezoid. The effects of their length ratio(r), wavelength(w) and phase mode(p) on meniscus shape and curvature have been studied. Results have shown that the channel with serrated edges can generate convex liquid front, and the curvature of the front can be changed by adjusting r, w and p.