Microfluidic Bypass Channel Mitigates Sample Drift
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Solution Overview
Problem
Point-of-care sample testing systems face challenges in mitigating fluid sample drift over sensors during electrochemical assays, leading to inefficiencies and potential cross-sensor interference in micro-environment sensor structures.
Innovation Solution
Incorporating a bypass channel into the microfluidics of test cartridges, where the first channel has an upstream region with a larger cross-sectional area than the downstream region, and a second channel with a cross-sectional area between the upstream and downstream regions, to relieve pressure and mitigate sample drift by acting as an additional resistive element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single channel is used for fluid sample flow, then the device structure is simple, but sample drift occurs over the sensor leading to cross-sensor interference
Solution Approach 1:
The single channel is segmented into multiple regions with different cross-sectional areas: an upstream region with larger area, a downstream region with smaller area, and a bypass channel with intermediate area. This segmentation allows different flow paths to be created within the same channel structure, enabling pressure relief and drift mitigation without adding completely separate channels.
Solution Approach 2:
The invention introduces a bypass channel that branches off from the main channel, creating a two-dimensional flow path configuration. This bypass channel provides an alternative route for excess sample flow, relieving pressure buildup that would otherwise cause drift over the sensor. The bypass channel effectively adds a spatial dimension to the flow path without significantly increasing overall device complexity.
2Reliability
If the channel cross-sectional area is uniform, then the manufacturing is easier, but pressure builds up causing sample drift over the sensor
Solution Approach 1:
The channel is designed with non-uniform cross-sectional areas at different locations. The upstream region has a larger cross-sectional area to accommodate incoming sample flow, the bypass channel has an intermediate area, and the downstream region has a smaller area. This local variation in geometry creates the necessary pressure gradient to prevent drift while remaining manufacturable using standard microfabrication techniques.
3Loss of time
If the sample flows quickly through the channel, then the analysis time is reduced, but the sample does not remain over the sensor long enough for complete analysis
Solution Approach 1:
The flow dynamics are made variable through the bypass channel mechanism. During initial sample introduction, the bypass channel allows excess flow to pass through, preventing pressure buildup. Once the sample reaches the sensor region, the reduced cross-sectional area in the downstream region naturally slows the flow, allowing the sample to remain over the sensor for the required analysis duration without extending the overall assay time.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The bypass channel effectively reduces sample drift, allowing the fluid sample to sit over the sensor long enough for complete analysis, improving the accuracy and efficiency of electrochemical assays in point-of-care testing devices.
Implementation Method 1
a bypass channel into the microfluidics of test cartridges, where the first channel has an upstream region with a larger cross-sectional area than the downstream region, and a second channel with a cross-sectional area between the upstream and downstream regions, to relieve pressure and mitigate sample drift by acting as an additional resistive element
Data Source
AI summary
The present disclosure relates to analytical testing devices comprising microfluidics and methods for performing an assay on a fluid sample received within the microfluidics, and in particular, to mitigating drift of fluid samples over a sensor by incorporating a bypass channel into the microfluidics. For example, a test cartridge device is provided that includes a fluid sample entry port and holding chamber connected to a bifurcation junction of a sensor channel and a bypass channel. The sensor channel includes an upstream region and a downstream region, and an analyte sensor is in the upstream region. As a cross-sectional area of the bypass channel is greater than the cross-sectional area of the downstream region of the sensor channel, the bypass channel is a preferred path for excess sample flow and pressure, and thus sample drift above the analyte sensor is mitigated.