Spatially Offset Raman Spectroscopy for Non-Invasive pH Detection
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Solution Overview
Problem
Conventional methods for measuring pH require direct contact with the sample, which is undesirable or impractical in many applications, especially in clinical and industrial settings where contamination risks are high or the sample does not present an exposed surface, such as measuring pH beneath the skin or within a bioreactor.
Innovation Solution
The use of spatially offset Raman spectroscopy with embedded SERS nanoparticles allows for non-invasive, subsurface monitoring of pH by directing probe light to one region and collecting it from another, spatially offset region, enabling pH determination without contact through analysis of Raman spectral features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct contact electrodes are used for pH measurement, then measurement precision is improved, but contamination risk increases and non-invasive measurement becomes impossible
Solution Approach 1:
The patent replaces the mechanical/electrical contact-based pH measurement system with an optical detection system. Raman spectroscopy uses light scattering to obtain pH information without physical contact, thereby eliminating contamination risks while maintaining measurement precision through spectral analysis of pH-sensitive molecules
Solution Approach 2:
The patent introduces pH-sensitive reporter molecules as intermediaries that interact with the sample environment to provide pH information. These molecules serve as mediators between the measurement system and the sample, allowing indirect pH measurement without direct electrode contact, thus preventing contamination while preserving measurement accuracy
2Measurement precision
If direct contact electrodes are used for pH measurement, then measurement precision is improved, but applicability to sub-surface measurement deteriorates
Solution Approach 1:
The patent replaces contact-based electrical measurement with non-contact optical measurement using Raman spectroscopy. This substitution enables penetration through scattering media such as tissue, allowing sub-surface pH measurement while maintaining precision through the optical properties of pH-sensitive molecules that can be detected through diffuse scattering
Solution Approach 2:
The patent uses pH-sensitive reporter molecules as intermediaries that can be introduced into or near the sub-surface region of interest. These molecules serve as mediators that provide pH information from deep within the sample through their optical signatures, enabling non-invasive sub-surface measurement while maintaining measurement precision
3Ease of operation
If conventional Raman spectroscopy is used, then non-contact measurement is achieved, but measurement precision deteriorates in diffusely scattering samples
Solution Approach 1:
The patent employs Surface Enhanced Raman Spectroscopy (SERS) nanoparticles with locally enhanced optical properties. These nanoparticles provide localized signal enhancement at specific positions within the diffuse scattering medium, allowing precise pH measurement despite the challenging optical environment by concentrating the Raman signal from specific locations
4Measurement precision
If SERS nanoparticles are embedded in the sample, then sensitivity is improved, but device complexity increases
Solution Approach 1:
The patent utilizes changes in the optical parameters of SERS nanoparticles in response to pH variations. By monitoring shifts in Raman spectral features caused by pH-induced changes in the nanoparticle environment or surface chemistry, the system achieves high detection sensitivity while managing complexity through optical parameter analysis rather than physical reconfiguration
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 enables accurate, non-invasive pH measurement at various depths within diffusely scattering samples, reducing contamination risks and enhancing sensitivity through SERS, allowing for applications such as subcutaneous tissue analysis and bioreactor monitoring.
Implementation Method 1
using embedded SERS nanoparticles with pH sensitive nanoparticle labels, using a technique of spatially offset Raman spectroscopy
Implementation Method 2
collecting the probe light, following scattering within the sample, from one or more second, collection regions some or all of which may be separate from and/or spaced from and/or spatially offset from the one or more entry regions
Implementation Method 3
The collected light then contains spectral features arising from Raman scattering within the sample which can be analysed to determine one or more pH measurements
Data Source
AI summary
We disclose methods and apparatus for measuring pH in a sub-surface volume of a diffusely scattering sample. Probe light is directed to an entry region on the sample surface, and collected from a collection region on the sample surface following diffuse scattering within the sample. The collection region is spatially offset from the entry region, so that when one or more Raman spectral features are detected in the collected probe light, a pH of the sub-surface volume can be determined from the spectral features.