Chemo-Optical Sensor Conditioning for Transcutaneous CO2 Monitoring
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Solution Overview
Problem
Current transcutaneous CO2 sensors experience sensitivity changes due to molecular perturbations, such as water transport, leading to inaccurate measurements in osmotically unbalanced environments like the skin, requiring frequent calibration.
Innovation Solution
A chemo-optical sensor unit is conditioned with a contact medium containing propylene glycol and sodium chloride, allowing the sensor to operate in an osmotically equilibrated environment, reducing sensitivity changes and eliminating the need for additional calibration steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transcutaneous CO2 sensors are used in osmotically unbalanced environments like skin, then gas measurement function is achieved, but sensitivity changes occur due to molecular perturbations such as water transport
Solution Approach 1:
The patent changes the osmotic parameters of the contact medium by adding propylene glycol to match the osmolarity of skin interstitial fluid. This parameter change prevents water transport into or out of the sensor membrane, eliminating sensitivity drift while maintaining reliable gas measurement function.
Solution Approach 2:
The patent introduces a specially formulated contact medium as an intermediary between the sensor membrane and the skin. This intermediary layer with matched osmolarity prevents direct osmotic interaction that would cause water transport and sensitivity changes, thereby maintaining measurement precision.
2Ease of operation
If transcutaneous CO2 sensors operate in skin environment, then non-invasive monitoring is achieved, but frequent calibration is required due to sensitivity alterations
Solution Approach 1:
The patent performs preliminary action by pre-equilibrating the contact medium with propylene glycol to match skin osmolarity before sensor application. This preliminary osmotic balancing prevents sensitivity drift during operation, eliminating the need for frequent calibration and reducing time loss.
Solution Approach 2:
The sensor system with osmotically balanced contact medium becomes self-regulating, automatically maintaining its sensitivity without external calibration intervention. The matched osmolarity creates a stable environment that prevents molecular perturbations, allowing the sensor to self-maintain measurement accuracy.
3Reliability
If contact medium is used between sensor and skin, then transcutaneous gas permeability is achieved, but osmotic imbalance causes water transport and sensitivity changes
Solution Approach 1:
The patent changes the osmotic parameter of the contact medium by adding propylene glycol to achieve osmolarity matching with skin interstitial fluid. This parameter change prevents water transport that would alter sensor membrane composition, maintaining stability while enabling reliable gas measurement.
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 sensor maintains stable optical responses, providing accurate CO2 measurements without sensitivity alterations, ensuring reliable transcutaneous gas monitoring without the need for frequent recalibration.
Implementation Method 1
the propylene glycol is present in the chemo-optical sensor unit in essentially the same concentration as in the contact medium
Implementation Method 2
adapted to pass gas whose concentration is to be measured through the gas-permeable layer towards the sensing layer
Implementation Method 3
a sensor comprising an electrochemical pH sensor and reference electrode; and an algorithm to compensate for temperature effects and skin metabolism
Data Source
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AI summary
The present invention relates to a chemo-optical sensor unit for transcutaneous measurement of a concentration of a gas, comprising: at least one sensing layer adapted to be irradiated with a predetermined radiation; and at least one gas-permeable layer adjacent to one side of the at least one sensing layer, adapted to pass gas whose concentration is to be measured through the gas-permeable layer towards the sensing layer; wherein said chemo-optical sensor unit is adapted to operate with a contact medium between the gas-permeable layer and the skin, wherein said contact medium comprises a first compound other than water; wherein said chemo-optical sensor unit is characterized in that said at least one gas-permeable layer and said at least one sensing layer are permeable to said first compound; and wherein the chemo-optical sensor unit is adapted to measure an optical response of the at least one sensing layer, whose optical response depends on the concentration of the gas. The present invention also relates to a system comprising such a chemo-optical sensor, as well as to a method for conditioning a chemo-optical sensor unit for measuring a concentration of a gas and a thereby obtainable conditioned sensor.