Method and system for determining a pressure of a liquid flowing in a channel
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Solution Overview
Problem
Existing pressure sensors in microfluidic channels provide erroneous values due to their placement outside the channel, leading to measurement drift and fouling, especially when used over long periods.
Innovation Solution
A measurement system that determines pressure through thermal measurement and a predetermined calibration function, using a flow actuator, thermal measurement device, and processing unit to calculate pressure from temperature differences within the channel, avoiding the need for remote pressure sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pressure sensor with membrane is used to measure pressure in microfluidic channel, then pressure measurement is possible, but the sensor must be disposed upstream or downstream of the channel where transverse dimensions are sufficiently large, leading to erroneous values
Solution Approach 1:
The patent replaces the mechanical pressure sensor system with a thermal measurement system. Instead of using a membrane-based pressure sensor that requires remote placement, the invention uses temperature measurement combined with thermoelastic effects to determine pressure. The processing unit calculates pressure from temperature differences using the relationship between thermal and elastic properties of the channel material, eliminating the need for mechanical contact sensors outside the channel.
Solution Approach 2:
The patent introduces temperature as an intermediary parameter to measure pressure indirectly. Rather than measuring pressure directly with a sensor, the system measures temperature changes in the channel wall caused by pressure-induced thermoelastic effects. This intermediary measurement allows pressure determination without physical contact, solving the problem of sensor placement and fouling.
2Stability of the object's composition
If pressure sensor is disposed outside the microfluidic channel, then the channel structure remains intact, but pressure values become erroneous and measurement drift occurs due to fouling
Solution Approach 1:
The patent replaces mechanical pressure sensors that are susceptible to fouling with a thermal measurement system. The thermal measurement device measures temperature through the channel wall without contacting the liquid, eliminating fouling issues. Pressure is derived from temperature measurements using thermoelastic relationships, maintaining channel integrity while ensuring accurate, drift-free measurements.
Solution Approach 2:
The patent creates a thermal copy of the pressure information. Instead of directly sensing pressure, the system measures temperature changes that replicate pressure effects through thermoelastic coupling. This thermal copy allows accurate pressure determination without physical intrusion into the fluid path, preventing fouling while maintaining measurement accuracy.
3Reliability
If thermal measurement device is used to determine pressure from temperature, then measurement reliability is improved, but the system requires predetermined calibration function and specific compressibility conditions
Solution Approach 1:
The patent changes the measurement parameter from direct pressure sensing to temperature measurement. By measuring temperature and using the calibrated relationship between temperature and pressure (based on thermoelastic properties), the system achieves reliable pressure determination. The calibration function establishes the specific parameter relationship for different channel materials and geometries, converting thermal measurements into pressure values.
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
Provides reliable pressure measurement directly in the channel, reducing measurement errors and drift by utilizing thermoelastic effects for incompressible liquids, ensuring accurate pressure determination without disturbing the flow.
Implementation Method 1
a thermal measurement device, adapted to measure at least one temperature Theq of the liquid of interest flowing in the channel
Implementation Method 2
The thermal measurement device can be adapted to detect infrared radiation emitted by the liquid of interest and transmitted by a peripheral wall of the channel
Implementation Method 3
a processing unit, adapted to determine pressure Pheq from the temperature Theq measured and a predetermined calibration function f, expressing a course of a pressure difference ΔP between the pressure Pheq and a predefined reference pressure Peq of the liquid of interest at rest in the channel, as a function of a temperature difference ΔT between the temperature Theq measured and a predefined reference temperature Teq of the liquid of interest at rest in the channel
Data Source
AI summary
A measurement system is configured to determine a pressure of a liquid of interest having compressibility km flowing in a channel of radius rint, which are selected such that the product km×rint is less than or equal to 12.5×10−11 mm/Pa. The system includes a flow actuator for flowing the liquid of interest in the channel at a Mach number less than or equal to 0.3, a thermal measurement device for measuring a temperature of the liquid of interest flowing in the channel, and a processing unit configured to determine the pressure from the temperature measured and a predetermined calibration function.