Optical Fiber Bragg Grating Freeze Dryer Monitoring
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Solution Overview
Problem
Conventional temperature sensors used in freeze dryers are invasive, not representative of the entire batch, and limited in sensitivity and precision, making it difficult to control the drying process effectively, especially for pharmaceutical products.
Innovation Solution
The use of optical sensing fibers with fiber Bragg gratings that allow for non-invasive, simultaneous temperature monitoring at multiple sites within the dryer, providing high sensitivity and the ability to detect minute energetic transitions, and can also measure other physical parameters like force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional temperature sensors (thin wire thermocouples or resistance thermal detectors) are used for product temperature monitoring, then temperature measurement capability is provided, but the sensors are invasive and not representative of the entire batch due to variations in nucleation and freezing behaviour
Solution Approach 1:
The patent replaces conventional electrical temperature sensors (thermocouples, resistance thermal detectors) with optical sensors that use light-based measurement. This substitution eliminates the mechanical/invasive contact that disrupts ice formation, as optical sensors can measure temperature through the vial wall without physically interfering with the product's freezing and drying processes.
Solution Approach 2:
The patent introduces an intermediary medium (optical signal/light) to transfer temperature information from the product to the measurement system. Instead of direct electrical contact with the product, the optical sensor uses light transmission through the vial wall and interaction with the product to obtain temperature data, thereby avoiding direct interference with the ice formation process.
2Loss of information
If multiple temperature sensors are used to monitor different locations, then measurement coverage is improved, but handling with numerous wires becomes difficult and container closure is negatively affected
Solution Approach 1:
The patent combines multiple temperature measurement functions into a single optical sensor system. Instead of using multiple separate electrical sensors each requiring individual wiring, the optical sensor integrates multiple measurement capabilities through a unified optical fiber connection, eliminating the complexity of handling numerous wires while maintaining comprehensive temperature distribution monitoring.
3Measurement precision
If conventional temperature sensors are used in samples of limited space or volume, then temperature measurement is possible, but multiple measuring points in one sample or vial can hardly be achieved
Solution Approach 1:
The patent transitions from a single-point measurement approach to a distributed measurement approach by positioning the optical sensor to measure temperature at multiple locations simultaneously or sequentially. The optical fiber can be configured to contact the product at various points along its length, enabling multiple measuring points within a single vial without requiring additional sensors or increasing vial volume.
4Measurement precision
If conventional temperature sensors are used, then temperature monitoring is provided, but overall sensitivity and precision are rather limited
Solution Approach 1:
The patent changes the measurement parameter from electrical resistance/voltage (conventional sensors) to optical properties (light transmission, reflection, or absorption). This parameter change enables higher sensitivity and precision in temperature measurement, as optical sensors can detect subtle temperature-induced changes in the product's optical characteristics with greater accuracy than electrical sensors, thereby improving process control reliability.
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 solution enables precise control of the drying process, improves sensitivity and sampling rate, and allows for better monitoring of temperature profiles and other parameters, enhancing the quality assurance and process understanding in freeze drying.
Implementation Method 1
The monitoring device comprises an optical sensing fiber having at least one fiber Bragg grating
Data Source
AI summary
The invention provides a monitoring device (32) for a dryer (10) includes a means for sensing a physical parameter, such as temperature or strain, at a sensing locus within the dryer (10), for example at a vial (20). The sensing means comprises an optical sensing fiber (38) having at least one fiber Bragg grating (54). Moreover, the invention provides a dryer, in particular a freeze dryer (10), which is equipped with such monitoring device (32).