Abstract
A microfluidic chip with a microvalve based on a microhole array is proposed in this paper for the POCT of tumor marker proteins. In order to control the biochemical reaction time accurately and obtain a higher testing sensitivity, the parameters of the microhole array are optimized basing on the investigation of the effects of the variation of those parameters on the fluid rate and the residual liquid value in the microvalve region. By conducting liquid flow experiments using microvalves based on microhole arrays with varying microstructural parameters, the residual rate of reaction products is demonstrated to be proportional to the depth and diameter of the microholes and inversely proportional to the distance between the microhole centers. A comprehensive analysis indicates that a microhole depth of 95 μm, a microhole diameter of 230 μm, and a distance between microhole centers of 250 μm not only ensure a sufficiently long delay time, but also reduce the residual rate of reaction products, thereby providing an optimum microvalve performance that maximizes the detection efficiency and accuracy of microfluidic chips.
Highlights
Most POCT [1] technologies available worldwide for realtime in vitro diagnostic testing have been designed and developed based on microfluidic chips, and these have been generally applied for the detection of substances with a relatively high rate in the body fluids of patients, such as proteins [2] and blood sugar [3]
Low accuracy of the flow control and relatively large residual value are the main shortcomings of the microfluidic systems in such POCT chips, which results in inadequate biochemical reaction and large interassay imprecision. ese shortcomings mainly come from the microvalves integrated in the chips
E flow velocity difference between the two regions was at least 5 times. e lowest fluid head velocity in the microvalve region, which is attained by Chip C, is less than 1/10 of that in the capillary channel downstream. e phenomenon confirms that the microhole array has a significant delay effect on the fluid head when it was moving through the
Summary
Most POCT [1] technologies available worldwide for realtime in vitro diagnostic testing have been designed and developed based on microfluidic chips, and these have been generally applied for the detection of substances with a relatively high rate in the body fluids of patients, such as proteins [2] and blood sugar [3]. E mechanism of this kind of microvalves is based on the phenomenon that the surface parameters of the microstructures, such as contact angle and roughness, affect the capillary force and affect the flow state. We previously developed a capillary microvalve with the microhole array on one of the interior surfaces of the microchannel and investigated the effects of the parameters of the microhole array on the fluid head velocity [16]. In order to control the biochemical reaction time accurately and obtain a higher testing sensitivity, the parameters of the microhole array are optimized basing on the investigation of the effects of the variation of those parameters on the fluid rate and the residual liquid value in the microvalve region
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