Capillary Plasma Metering in Microfluidics Tolerant to Blood Variation
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Solution Overview
Problem
Existing microfluidic systems face challenges in autonomously extracting and metering plasma from whole blood with minimal user interaction, while accommodating variations in blood characteristics such as hematocrit and lipid content, leading to inconsistent flow and volume measurement.
Innovation Solution
A microfluidic device with distinct regions of varying flow resistance and a capillary means, utilizing a capillary force to transport and meter plasma, featuring a plasma extraction compartment, metering channel, and air vents to ensure consistent volume measurement independent of blood variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive metering structures are used in microfluidic devices, then device complexity is reduced, but flow resistance becomes highly sensitive to blood characteristic variations
Solution Approach 1:
The device is divided into distinct functional regions: a first region with inlet features for sample collection and a second region with a metering channel for precise volume measurement. This segmentation allows each region to be optimized independently - the first region handles variable blood flow while the second region ensures consistent metering, resolving the contradiction between simplicity and reliability.
2Adaptability or versatility
If active flow manipulation is used, then tolerance to blood characteristic variations is improved, but device complexity and power requirements increase
Solution Approach 1:
The microfluidic device uses passive capillary forces and surface tension effects to automatically regulate plasma flow from the first region to the second region. No external power sources or active control mechanisms are needed - the system self-regulates flow based on inherent fluid properties, achieving adaptability to blood variations while maintaining simplicity.
3Manufacturing precision
If centrifugation is used for plasma separation, then separation efficiency is improved, but time consumption and equipment requirements increase
Solution Approach 1:
The device replaces the mechanical centrifugation system with a passive microfluidic filtration mechanism. Plasma separates from whole blood through a porous membrane or filtration structure driven by capillary pressure, eliminating the need for centrifuges and significantly reducing processing time while maintaining separation efficiency.
4Extent of automation
If dissolvable membranes are used for metering, then passive metering is achieved, but measurement precision is affected by dissolution time variations
Solution Approach 1:
The metering channel is pre-designed with specific dimensions and hydrophobic coatings that control liquid flow rate before the actual measurement occurs. By establishing predetermined flow characteristics and using surface tension effects, the system achieves consistent volume metering without relying on dissolution time, thereby maintaining both automation and precision.
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 device achieves autonomous, time-independent plasma extraction and metering, tolerating variations in blood characteristics, ensuring precise volume measurement without external power sources, reducing complexity and cost.
Implementation Method 1
a capillary means in fluid communication with the outlet and configured to exert sufficiently strong capillary force to transport and absorb the metered plasma volume in the second region
Implementation Method 2
Separation of blood cells from plasma on the microscale can be achieved by either active (externally applied force such as electrical- or magnetic field) or passive (sedimentation, filtration or hydrodynamic effects induced by microfeatures
Data Source
AI summary
Disclosed herein is a microfluidic device and a method for transporting and sampling a defined volume of plasma, providing a fluid passageway from an inlet to an outlet comprising a first region with the inlet with a first high flow resistance configured to receive and collect a whole blood sample and to separate plasma; and a second region with the outlet lower flow resistance. The second region is in fluid connection with the first region and configured to meter the separated plasma by comprising a metering channel.