Microfluidic Flow Measurement via Pressure Differential
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current micro-fluidic flow measurement methods are inaccurate, sensitive to environmental conditions, and prone to clogging due to complex setups and high sensitivity requirements, lacking a simple and reliable solution for precise and fast flow control in micro-fluidic applications.
Innovation Solution
A system using a reservoir with a gaseous top and a pressure sensor measuring the pressure difference between the gas and liquid downstream of a hydraulic resistance, allowing for precise flow measurement and control using a single pressure sensor element, with a capillary tube or restriction to maintain hydraulic resistance and prevent clogging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermal sensors are used to measure micro-fluidic flow, then flow measurement is achieved, but measurement precision deteriorates due to inaccuracy and environmental sensitivity
Solution Approach 1:
The patent replaces thermal measurement methods with a mechanical pressure-based measurement system. A pressure sensor measures the pressure difference across a restriction element, and flow is calculated using the pressure differential and known hydraulic resistance. This mechanical approach eliminates the environmental sensitivity and inaccuracy issues of thermal sensors.
Solution Approach 2:
The patent introduces a restriction element (capillary tube or micro-fluidic channel) as an intermediary component. This element creates a measurable pressure drop that is directly related to flow rate through its known hydraulic resistance, providing a reliable intermediate measurement point that links pressure to flow without the complications of direct thermal measurement.
2Measurement precision
If differential pressure sensors with two liquid pressure sensors are used, then flow measurement is achieved, but device complexity increases
Solution Approach 1:
The patent combines the gas pressure measurement and liquid pressure measurement into a single differential pressure sensor. This integrated approach measures the pressure difference directly between the gas phase (above liquid in reservoir) and liquid phase (downstream of restriction) using one sensor element, thereby reducing system complexity while maintaining measurement precision.
Solution Approach 2:
The differential pressure sensor serves multiple functions simultaneously: it measures the pressure difference across the restriction, provides a signal for flow calculation, and can be used for flow control feedback. This multi-functionality reduces the need for separate sensors and control components.
3Measurement precision
If small diameter restrictions are used to measure flow, then measurement precision improves, but reliability deteriorates due to clogging
Solution Approach 1:
The patent changes the physical parameters of the restriction element by using a capillary tube with relatively large diameter (compared to typical micro-fluidic channels) or a micro-fluidic channel with optimized dimensions. This parameter change allows sufficient hydraulic resistance for accurate measurement while maintaining large enough aperture to prevent clogging, thus resolving the contradiction between precision and reliability.
4Measurement precision
If complex flow measurement systems are implemented, then measurement precision improves, but ease of operation deteriorates
Solution Approach 1:
The system uses a passive restriction element (capillary tube or micro-fluidic channel) that automatically creates the pressure drop needed for measurement without requiring active control or adjustment. The hydraulic resistance is inherent to the geometry of the restriction, eliminating the need for complex control mechanisms and simplifying operation.
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
This approach provides a reliable, fast, and accurate method for measuring micro-fluidic flow with reduced risk of clogging, achieving a good balance between reliability, speed, and cost-effectiveness by using a single pressure sensor and larger diameter restrictions, enabling precise control of liquid flow in micro-fluidic circuits.
Implementation Method 1
pressure sensor means including a first input connected to the gaseous top and a second input connected to the liquid output P2, the output of the pressure sensor means delivering a signal depending on the difference in pressures (P1−P2) representative of the liquid flow
Implementation Method 2
a capillary tube or restriction to maintain hydraulic resistance and prevent clogging
Data Source
AI summary
A system to measure the flow rate of a liquid in a microfluidic circuit. The system includes a vessel that is partially filled with the liquid, a gaseous ceiling above the vessel and a pressure regulator to maintain the pressure of the gas in the gaseous ceiling at a predetermined value P1. A capillary pipe to extract the liquid from the vessel and to output the liquid at a pressure P2 lower than P1. A first inlet of the pressure sensor is connected to the gaseous ceiling, a second inlet of the pressure sensor is connected to the capillary pipe, and the outlet of the pressure sensor outputs a signal as a function of the pressure difference (P1−P2), which is a measurement representing the flow rate of pressurized P2 liquid supplied to the microfluidic circuit.