WM-DPTR Glucose Sensor Using Mid-IR Laser Differential Detection
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Solution Overview
Problem
Current non-invasive glucose monitoring methods are inadequate for continuous, real-time measurement due to discomfort, pain, and high risk of infection from frequent skin punctures, and existing optical technologies face challenges with sensitivity and specificity, particularly in the near-IR spectral range where water absorption dominates glucose signals.
Innovation Solution
The use of Wavelength-Modulated Differential Laser Photothermal Radiometry (WM-DPTR) with two modulated CO2 laser beams of different wavelengths to co-irradiate tissue, employing phase-sensitive detection to isolate glucose absorption peaks from water and other tissue absorptions, providing a non-invasive and accurate glucose concentration measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequent skin puncture is used for glucose monitoring, then accurate glucose concentration data is obtained, but patient discomfort, pain and risk of infection increase
Solution Approach 1:
The patent replaces the mechanical skin puncture method with an optical measurement system using mid-IR laser radiation. The glucose concentration is measured non-invasively by detecting the absorption of laser radiation at the 9.7 μm wavelength through the skin and underlying tissue, eliminating needles and blood sampling while maintaining measurement capability
Solution Approach 2:
The patent introduces an optical intermediary system consisting of laser sources, optical fibers, and detection equipment that mediates between the glucose molecules in tissue and the measurement instrument. The mid-IR radiation acts as an intermediary that interacts with glucose molecules to provide measurement information without direct mechanical contact or invasion
2Loss of energy
If near-IR spectral range is used for optical glucose monitoring, then water absorption is reduced, but glucose signal detection precision deteriorates due to overlapping absorption bands
Solution Approach 1:
The patent changes the spectral parameter from near-IR to mid-IR range, specifically targeting the 9.7 μm wavelength where glucose has a strong, isolated absorption peak. This parameter change exploits the unique vibrational modes of glucose molecules in the mid-IR region to achieve both low water absorption and high glucose signal specificity
Solution Approach 2:
The patent applies local quality by focusing measurement energy at a specific wavelength (9.7 μm) where glucose absorption is maximized and isolated from interfering absorptions. The system uses narrow-band laser sources and selective detection to concentrate measurement sensitivity at this specific spectral location rather than using broad-band near-IR illumination
3Measurement precision
If mid-IR region is used for glucose monitoring, then glucose absorption peaks are isolated from interfering peaks, but water absorption coefficient increases and dominates the signal
Solution Approach 1:
The patent changes the measurement parameter from broad-band mid-IR to a narrow, specific wavelength (9.7 μm) where glucose absorption is maximized. By using tunable laser sources and narrow-band detection, the system exploits the fact that at this specific wavelength, the glucose absorption cross-section is high while the path length through water is minimized due to the optical properties of tissue at this wavelength
Solution Approach 2:
The patent replaces conventional broad-band optical detection with a laser-based differential absorption technique. The system uses two laser beams at slightly different wavelengths (one at the glucose absorption peak, one as reference) to measure the differential absorption, which isolates the glucose signal from the dominant water absorption background
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 method offers precise, non-invasive glucose monitoring with enhanced signal resolution and noise reduction, capable of detecting glucose concentrations within the normal range of 90-120 mg/dl, reducing interference from water absorption and other tissue components, and enabling real-time baseline corrections for universal calibration.
Implementation Method 1
Wavelength-Modulated Differential Laser Photothermal Radiometry (WM-DPTR) with two modulated CO2 laser beams of different wavelengths to co-irradiate tissue
Implementation Method 2
employing phase-sensitive detection to isolate glucose absorption peaks from water and other tissue absorptions
Implementation Method 3
providing a non-invasive and accurate glucose concentration measurement
Data Source
AI summary
There is provided a glucose monitoring method and apparatus based on the principle of Wavelength-Modulated Differential Laser Photothermal Radiometry (WM-DPTR). Two intensity modulated laser beams operating in tandem at specific mid-infrared (IR) wavelengths and current-modulated synchronously by two electrical waveforms 180 degrees out-of-phase, are used to interrogate the tissue surface. The laser wavelengths are selected to absorb in the mid infrared range (8.5-10.5 μm) where the glucose spectrum exhibits a discrete absorption band. The differential thermal-wave signal generated by the tissue sample through modulated absorption between two specific wavelengths within the band (for example, the peak at 9.6 and the nearest baseline at 10.5 μm) lead to minute changes in sample temperature and to non-equilibrium blackbody radiation emission. This modulated emission is measured with a broadband infrared detector. The detector is coupled to a lock-in amplifier for signal demodulation. Any glucose concentration increases will be registered as differential photothermal signals above the fully suppressed signal baseline due to increased absorption at the probed peak or near-peak of the band at 9.6 μm at the selected wavelength modulation frequency. The emphasis is on the ability to monitor blood glucose levels in diabetic patients in a non-invasive, non-contacting manner with differential signal generation methods for real-time baseline corrections, a crucial feature toward precise and universal calibration (independent of person-to-person contact, skin, temperature or IR-emission variations) in order to offer accurate absolute glucose concentration readings.