Microfluidic Flow Sensor Calibration via Drop Ejection
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Solution Overview
Problem
Real-time calibration of flow sensors in microfluidic devices is challenging due to the need for independent calibration at manufacture, and existing methods are not effective for microfluidic applications.
Innovation Solution
A microfluidic sensor calibration system that integrates a drop ejector within the microfluidic channel, which expels droplets to create a low-pressure region, allowing for real-time calibration of flow sensors using calibration electronics that correlate electrical signals with flow rates based on the geometry of the channel and the volume of ejected droplets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If independent calibration at manufacture is performed, then calibration accuracy is achieved, but device complexity increases and real-time recalibration becomes difficult
Solution Approach 1:
The patent combines the calibration function with the main microfluidic channel by integrating a drop ejector directly into the channel structure. This merging eliminates the need for separate calibration equipment and allows calibration to be performed in-situ within the same device, thereby maintaining calibration accuracy while reducing overall device complexity.
Solution Approach 2:
The system enables self-calibration by using the drop ejector to introduce known volumes of fluid directly into the microfluidic channel. The flow sensor measures these known volumes, allowing the device to automatically correlate electrical signals with actual flow rates without requiring external calibration equipment or manual intervention.
2Measurement precision
If separate calibration componentry is used, then calibration functionality is achieved, but device complexity and size increase
Solution Approach 1:
The calibration functionality is merged with the main microfluidic channel by integrating the drop ejector directly into the channel structure. This eliminates the need for separate calibration equipment, reducing device complexity while maintaining calibration capability.
Solution Approach 2:
The drop ejector serves multiple functions: it acts as both a fluid delivery mechanism for normal operation and a calibration tool by ejecting droplets of known volume. This multi-functionality eliminates the need for separate calibration componentry, as the same structure performs both operational and calibration roles.
3Measurement precision
If traditional calibration methods are used, then initial calibration is achieved, but frequent recalibration becomes difficult
Solution Approach 1:
The system enables easy recalibration by allowing users to manually trigger the drop ejector to release known volumes of fluid through the microfluidic channel. This self-service calibration mechanism can be performed frequently without requiring external equipment, making recalibration as easy as initiating a simple ejection sequence.
Solution Approach 2:
The calibration process is designed to be periodic, where the drop ejector releases droplets at predetermined intervals or on demand. This periodic calibration action allows for frequent recalibration to maintain measurement accuracy over time, as the same calibration sequence can be repeated without complexity.
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 real-time, in-situ calibration of flow sensors without separate componentry, facilitating frequent recalibration and improving accuracy by directly linking electrical signals to fluid flow rates within the microfluidic channel.
Implementation Method 1
actuation of the drop ejector causes a droplet of liquid to be expelled from the microfluidic channel... creates a low-pressure region within the microfluidic channel which results in adjacent fluid being drawn to occupy the low-pressure region
Data Source
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Figure 5
AI summary
A droplet of fluid having a predetermined drop weight is ejected from a microfluidic channel. Electrical signals are received from a sensor in the microfluidic channel, wherein the electrical signals vary in response to the ejection of the droplet of fluid. The electrical signals of the sensor are calibrated to a rate of flow of fluid through the microfluidic channel based on a number of droplets ejected and the predetermined drop weight of each droplet.