Particle Sensor Using Thermophoretic Force Concentration
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Solution Overview
Problem
Existing particle sensors take a long time to provide stable readings at low concentrations of particles, such as pollen, and increasing the air flow rate to speed up detection can lead to flow restriction issues.
Innovation Solution
A particle sensing system that uses a heating arrangement to create a thermal gradient, applying a positive thermophoretic force to concentrate particles within a detection volume, allowing for faster and more accurate detection without affecting the overall fluid flow rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the flow rate is increased to detect more particles at low concentrations, then the detection speed is improved, but the sensor size increases due to larger air pumps required
Solution Approach 1:
The patent applies local quality by creating a thermal gradient specifically within the detection volume to concentrate particles locally, rather than increasing the overall flow rate throughout the entire sensor. The heating element generates a temperature gradient that causes thermophoretic migration of particles into a concentrated region at the detection volume, enabling faster detection without requiring larger pumps or increasing sensor size.
2Measurement precision
If channel narrowing is used to increase particle concentration, then the detection sensitivity is improved, but the fluid flow through the sensor is restricted
Solution Approach 1:
The patent uses thermal energy as an intermediary mechanism to concentrate particles without physically narrowing the channel. The heating element creates a temperature gradient that acts as a mediator, inducing thermophoretic forces that migrate particles into a concentrated region at the detection volume while maintaining the original channel geometry and fluid flow characteristics.
3Quantity of substance
If thermophoretic force is applied to concentrate particles, then the particle concentration in detection volume is increased, but additional heating energy is required
Solution Approach 1:
The patent applies partial action by using a heating element that creates a localized thermal gradient only in the region where particle concentration is needed (at the detection volume), rather than heating the entire fluid stream. This selective heating approach minimizes energy consumption while achieving sufficient particle concentration for detection.
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 system significantly reduces the time to obtain a stable reading at low particle concentrations by concentrating particles within the detection volume, while maintaining the same flow rate through the sensor, and allows for adjustable heating levels based on particle concentration.
Implementation Method 1
a heating arrangement for generating a thermal gradient perpendicular to the fluid flow direction thereby applying a positive thermophoretic force to particles entrained in the fluid
Implementation Method 2
the thermophoretic force is used to constrict the space occupied by the particles within the flow and thereby concentrate the particles within the detection volume
Data Source
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AI summary
A particle sensing system is for sensing particles entrained in a fluid. The system comprises a flow channel having a longitudinal direction along which the fluid is to be passed, a heating arrangement for heating the fluid and thereby applying a positive thermophoretic force on the fluid in a direction perpendicular to the longitudinal direction of the flow channel and a first sensor for sensing the particles in the fluid after heating by the heating arrangement. The thermophoretic force increases the concentration of the particles at the first sensor.