Thermal Calibration of PCB Sensors in Digital Microfluidics
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Solution Overview
Problem
Digital microfluidics systems face challenges in accurately monitoring and controlling temperature due to the production inaccuracies of printed circuit board (PCB)-based thermal sensors, which require costly trimming or calibration to maintain accuracy.
Innovation Solution
A method for thermal calibration of PCB-based sensors involving applying sense currents, determining resistance values, measuring reference temperatures, and generating calibration data to improve temperature measurement accuracy, allowing for adjustments within 1% of the desired temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If PCB-based thermal sensors are used in digital microfluidics systems, then manufacturing cost is reduced and ease of manufacture is improved, but temperature measurement accuracy deteriorates due to production inaccuracies in copper trace resistance
Solution Approach 1:
The patent applies preliminary action by performing thermal calibration of PCB-based sensors before they are used in actual digital microfluidics operations. The calibration process measures the actual resistance of copper traces at known temperatures and stores correction factors that are applied during subsequent measurements, thereby pre-compensating for manufacturing variations and improving temperature measurement accuracy without requiring costly trimming during production
Solution Approach 2:
The patent applies parameter changes by transforming the resistance measurement into a temperature measurement using a calibration-derived relationship rather than relying on nominal resistance values. By establishing an empirical correlation between resistance and temperature specific to each sensor through calibration, the system compensates for variations in copper trace resistance caused by manufacturing tolerances, thereby improving measurement precision while maintaining the simplicity of PCB-based sensors
2Measurement precision
If thermal calibration of PCB-based sensors is performed to improve temperature measurement accuracy, then measurement precision is improved, but calibration time and process complexity increase
Solution Approach 1:
The patent applies partial action by performing calibration at a single reference temperature (typically 20°C or 25°C) rather than across the entire operating temperature range. This single-point calibration provides sufficient accuracy for many applications and dramatically reduces calibration time compared to multi-point calibration methods, while still compensating for manufacturing variations in copper trace resistance
Solution Approach 2:
The patent applies self-service by enabling the calibration process to be performed automatically by the system itself without requiring external equipment or manual intervention. The calibration routine uses the sensor's own electrical properties and internally available temperature references to generate correction factors, making the process quick and self-contained
3Measurement precision
If trimming or calibration is performed on PCB-based sensors to maintain accuracy, then temperature measurement accuracy is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent applies copying by creating a digital copy or model of the sensor's actual electrical characteristics through calibration measurements. Instead of physically trimming or modifying the copper traces, the system creates a software-based correction model that replicates the sensor's behavior at known temperatures, thereby compensating for manufacturing variations without adding physical complexity or requiring access to the sensor during production
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 method enhances temperature measurement accuracy by up to 10% compared to resistance temperature detectors (RTDs) and reduces calibration time to under 60 seconds, improving the precision of thermocycling processes in digital microfluidic systems.
Implementation Method 1
An RTD is a passive sensor device whose resistance changes as its temperature changes. For example, the resistance increases as the temperature of the sensor increases. The resistance vs. temperature relationship is well known and is repeatable over time.
Implementation Method 2
In these DMF processes, thermocycling of the biological materials being processed may occur. For example, droplets of the biological materials may be cycled between two processing temperatures.
Data Source
AI summary
Described is thermal control in digital microfluidics (DMF) cartridges and more particularly to a DMF system, cartridge, and methods for thermal calibration of integrated heaters and sensors. In some embodiments, the presently disclosed subject matter provides a DMF system, cartridge, and methods for thermal calibration of integrated heaters and sensors. The presently disclosed DMF system provides a DMF cartridge (or device) having integrated heating. In some embodiments, the presently disclosed DMF system, cartridge, and methods may provide PCB-based sensors for monitoring the temperature at respective PCB-based heaters and wherein the PCB-based sensors may be, for example, copper sense traces of a PCB substrate. In some embodiments, the presently disclosed DMF system, cartridge, and methods may provide thermal calibration software and/or thermal control electronics for performing a thermal calibration process of a selected DMF cartridge.