Fibre-Optic Sensor Microfabrication for Sealed Pressure Cavities
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Solution Overview
Problem
Existing methods for fabricating fibre optic sensors that measure pressure and temperature simultaneously are costly, require expensive capital equipment, and often fail to meet the high dimensional tolerances needed for physiological applications, limiting their performance and clinical usability.
Innovation Solution
The development of microfabrication methods using femtosecond laser-assisted etching and non-linear photon absorption to create free-form sensor elements with sealed cavities, allowing for the fabrication of both extrinsic and intrinsic sensing elements, enabling simultaneous pressure and temperature measurements with improved precision and reduced costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional anodic bonding methods are used to fabricate fibre optic pressure sensors, then the sensors can achieve pressure measurement capability, but the fabrication process becomes very expensive in terms of assembly time and capital equipment required
Solution Approach 1:
The patent replaces the conventional mechanical anodic bonding process with a microfabrication approach using photolithography and wet etching. The silicon diaphragm is released through chemical etching of sacrificial oxide layers rather than mechanical bonding, significantly reducing assembly time and equipment requirements while maintaining pressure sensor functionality
Solution Approach 2:
The patent changes the fabrication parameters from high-temperature anodic bonding to low-temperature photolithographic patterning and wet etching processes. This allows for precise control of diaphragm thickness and geometry at the micron scale without requiring expensive bonding equipment, reducing both capital costs and assembly time
2Measurement precision
If high dimensional tolerances at the micron-scale are required for diaphragm thickness and optical fibre interfaces, then sensor performance for clinical applications can be achieved, but the fabrication process becomes challenging and costly
Solution Approach 1:
The patent performs preliminary patterning of the silicon diaphragm structure using photolithography before final release. The active sensing regions, bonding areas, and release holes are all defined in advance through layered photomask processing, ensuring micron-scale dimensional tolerances are achieved without requiring complex post-fabrication adjustments
Solution Approach 2:
The patent uses sacrificial oxide layers as intermediary structures during fabrication. These temporary oxide layers allow for precise definition of diaphragm geometry through chemical etching, and are later removed to release the diaphragm structure. This intermediary approach simplifies the fabrication process while maintaining high dimensional precision
3Adaptability or versatility
If existing fabrication methods are used, then some sensors can measure pressure or temperature, but they fail to measure both pressure and temperature simultaneously with high performance
Solution Approach 1:
The patent designs a unified microfabricated platform that integrates both pressure sensing (through the silicon diaphragm deflection) and temperature sensing (through integrated thermal sensors) within the same device structure. The photolithographic fabrication process simultaneously creates both sensing elements, enabling simultaneous multi-parameter measurement while maintaining high dimensional tolerances for both sensor types
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
These methods enable the production of high-performance fibre optic sensors with precise dimensional control, capable of measuring pressure and temperature simultaneously, suitable for clinical applications, while reducing fabrication costs and equipment requirements.
Implementation Method 1
microfabrication methods using femtosecond laser-assisted etching and non-linear photon absorption to create free-form sensor elements
Data Source
AI summary
A method for making a housing that defines a cavity for a pressure sensor, the method comprising: providing a bulk of material that will form the housing; focusing a radiation beam on internal portions of the bulk of material so as to modify the internal portions, thereby defining the housing's shape, wherein upstream of the focus of the radiation beam other portions of the bulk material remain unmodified; and discarding either the modified portions or the unmodified portions of the bulk material so as to form the cavity.