Optical Sensor Polymer Graft Opacity Stability
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Solution Overview
Problem
Implanted sensors face errors in analyte readings due to changes in the opacity of the polymer graft over time, which can be caused by changes in the sensing medium, leading to variations in light absorption and emission that are unrelated to the analyte concentration.
Innovation Solution
A sensor design with a polymer graft that maintains a consistent opacity over time, allowing no more than a specified percentage of light to pass through, thereby minimizing changes in the measurement signal caused by opacity variations, ensuring accurate analyte readings. The polymer graft can be made of materials like polymer hydrogel including acrylic acid and polyethylene glycol, and may be configured to remain stable for extended periods, such as one month or longer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a polymer graft is used in the sensor, then the sensor can measure analyte concentration, but the opacity of the graft varies over time causing errors in readings
Solution Approach 1:
The patent modifies the physical and chemical parameters of the polymer graft by incorporating specific concentrations of scattering particles (0.1-10% by weight) and adjusting the graft's cross-linking density. These parameter changes enable the graft to maintain stable light scattering properties over time while preserving analyte sensing capability
Solution Approach 2:
The patent creates a composite polymer graft structure combining multiple materials: the base polymer matrix, fluorescent indicator molecules, and optically scattering particles. This composite structure provides both stable optical properties for accurate light transmission measurement and chemical sensitivity for analyte detection
2Duration of action of stationary object
If the polymer graft opacity changes over time, then the sensor structure remains functional, but light absorption and emission vary causing measurement errors
Solution Approach 1:
The patent pre-compensates for potential opacity changes by incorporating optically scattering particles into the polymer graft matrix before implantation. These particles create a stable light scattering environment that cushions against variations in graft opacity over time, ensuring consistent light transmission characteristics throughout the sensor's operational lifespan
Solution Approach 2:
The patent implements a measurement system that monitors light transmission through the polymer graft and uses this information to compensate for opacity variations. By comparing expected light transmission with actual measurements, the system can correct for opacity changes and maintain accurate analyte concentration readings over extended periods
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 consistent opacity of the polymer graft reduces errors in analyte readings by maintaining a stable light transmission percentage, ensuring that changes in the measurement signal are primarily indicative of analyte concentration rather than opacity variations, thus providing reliable and accurate measurements over time.
Implementation Method 1
fluorescent indicator molecules may reversibly bind glucose and, when irradiated with excitation light (e.g., light having a wavelength of approximately 378 nm), emit an amount of light (e.g., light in the range of 400 to 500 nm)
Implementation Method 2
A light source (e.g., light emitting diode (LED)) may emit the excitation light, which may then be absorbed by the indicator molecules in the polymer graft
Data Source
AI summary
A sensor (e.g., an optical sensor) that may be placed within a living animal (e.g., a human) and may be used to measure an analyte (e.g., glucose or oxygen) in a medium (e.g., interstitial fluid) within the animal. The sensor may include a sensor housing and a polymer graft including indicator molecules and covering at least a portion of the sensor housing. The opacity of the polymer graft may remain substantially the same (i.e., may have little or no variation) over time. The sensor may include a photodetector, and variation in the opacity of the polymer graft does not cause a significant change in a measurement signal output by the photodetector. The polymer hydrogel may be made of polymers including acrylic acid and/or polyethylene glycol.