Stopped-Flow Lateral Flow Strips for Multi-Step Assays
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Solution Overview
Problem
Conventional lateral flow devices are limited to single-step assays due to reliance on capillary action, lacking sensitivity and quantitative capabilities, while complex microfluidic systems are costly and require external pumps, making them unsuitable for point-of-care applications.
Innovation Solution
The development of stopped-flow microfluidic devices that utilize porous elements with distinct materials and pressure differentials to control fluid flow, enabling multi-step assays and amplification processes without external equipment, suitable for low-resource settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional lateral flow devices use capillary action for fluid transport, then the devices are simple and disposable, but they are limited to single-step assays and lack sensitivity
Solution Approach 1:
The device is divided into multiple porous elements with distinct flow characteristics arranged in series. Each element can perform a specific function (e.g., sample loading, mixing, incubation, detection), enabling multi-step assays while maintaining overall device simplicity and disposability.
Solution Approach 2:
Different regions of the device have locally optimized properties - some porous elements have higher capillary pressure for rapid flow, others have lower pressure for mixing or incubation. This local differentiation enables complex assay functions within a simple capillary-driven architecture.
2Ease of manufacture
If conventional lateral flow devices rely on wicking flow, then the devices are affordable and user-friendly, but they have limited analytical sensitivity
Solution Approach 1:
Reagents are pre-loaded into the porous elements in dried or concentrated form. When sample fluid flows through, it automatically rehydrates and activates the reagents at the appropriate time, eliminating the need for separate reagent addition steps while enabling sensitive detection.
Solution Approach 2:
The use of porous elements with controlled pore sizes and capillary pressures enables concentration of analytes and extended interaction times between analytes and reagents, significantly improving analytical sensitivity while maintaining the affordability of the disposable format.
3Adaptability or versatility
If microfluidic systems incorporate complex disposable components for multi-step assays, then the devices can perform sophisticated functions, but manufacturing costs increase significantly
Solution Approach 1:
The porous element architecture provides a universal platform where different assay functions (mixing, incubation, separation, detection) are achieved by varying the physical and chemical properties of the porous materials rather than adding complex mechanical components, keeping manufacturing costs low.
Solution Approach 2:
The device uses the sample fluid itself to drive flow, activate reagents, and perform mixing through capillary action. No external pumps, valves, or complex actuation mechanisms are needed, eliminating expensive manufacturing steps while enabling sophisticated multi-step assays.
4Reliability
If lateral flow assays use capillary flow control, then the devices are entirely disposable, but flow control is limited and quantitative analysis is difficult
Solution Approach 1:
The device controls flow by changing parameters of the porous materials themselves - pore size, porosity, and capillary pressure gradients are precisely engineered in different elements to achieve desired flow rates, mixing, and incubation conditions while maintaining the disposable format.
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
Enables automated, cost-effective, and sensitive multi-step assays with enhanced detection capabilities, suitable for processing large sample volumes and complex samples, such as urine, without the need for external pumps or valves.
Implementation Method 1
fluid transport occurring due to the capillary pressure of the strip material
Implementation Method 2
flow of fluid through the LFT usually occurs by wicking through a membrane
Implementation Method 3
utilize porous elements with distinct materials and pressure differentials to control fluid flow
Data Source
AI summary
The present technology generally relates to stopped-flow microfluidic devices. Select embodiments of the present technology include microfluidic devices having a first porous element configured to receive a first fluid and a second porous element configured to receive a second fluid. The second porous element can have one or more legs overlapping with the first porous element. The device can be configured such that (a) delivery of the first fluid to the first porous element causes the first fluid to flow along the length of the first porous element without substantially wetting the one or more legs, and (b) delivery of the second fluid to the second porous element causes the second fluid to flow into the overlapping regions of the first porous element, thereby substantially stopping flow of the first fluid along at least a portion of the first porous element.