Needle-Integrated Miniature pH Electrode for Viscous Biofluid Sensing
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Solution Overview
Problem
Conventional glass-rod pH sensors are bulky and prone to inaccuracies in viscous bodily fluids due to elevated junction potentials, hindering miniaturization and reliability for in vivo monitoring.
Innovation Solution
A miniature pH-sensing electrode design featuring a flexible substrate with iridium oxide as the working-material layer and silver/silver chloride as the reference-material layer, deposited using sol-gel or printing techniques, which can be inserted into a needle for in vivo monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional glass-rod pH sensors are used, then reliable pH sensing in aqueous solutions is achieved, but the sensors are bulky and prone to inaccuracies in viscous solutions due to elevated junction potentials
Solution Approach 1:
The patent extracts and eliminates the salt bridge component from the conventional pH sensor design, replacing it with a direct-contact electrode structure. This removes the source of junction potentials that cause inaccuracies in viscous solutions, while maintaining reliable pH sensing through the exposed glass electrode membrane that directly contacts the biofluid.
Solution Approach 2:
The patent segments the pH sensor into distinct functional components: the glass electrode membrane for pH sensing, the reference electrode, and the wire leads, allowing each component to be optimized independently. The glass membrane is specifically designed for aqueous solution contact, while the reference electrode is configured for stable potential in viscous fluids, resolving the contradiction between reliability and precision.
2Reliability
If conventional glass-rod pH sensors are used, then stable pH responses in aqueous solutions are achieved, but miniaturization is hindered by their bulky design
Solution Approach 1:
The patent implements a nested structure where the glass electrode membrane is positioned within a protective housing that contains the reference electrode and wire connections. This compact nested arrangement maintains the stable pH response of the glass membrane while significantly reducing the overall sensor volume, enabling miniaturization without sacrificing reliability.
Solution Approach 2:
The patent employs thin-film construction for the electrode housing and flexible wire leads, reducing the mechanical bulk of the sensor. The glass membrane is maintained as a thin film structure that provides stable pH sensing while minimizing the volume required for the electrode assembly, facilitating miniaturization.
3Measurement precision
If salt bridges are used to mitigate protein adsorption effects, then measurement accuracy in viscous fluids is improved, but the sensors become bulky
Solution Approach 1:
The patent removes the salt bridge component entirely from the sensor design. Instead of using a salt bridge to mitigate protein adsorption, the invention employs a direct-contact glass electrode membrane that is hydrophilic and resistant to protein fouling, eliminating the need for additional volume-consuming salt bridge structures while maintaining measurement accuracy.
Solution Approach 2:
The patent changes the surface properties of the glass electrode membrane to be more hydrophilic and protein-resistant, altering the interaction parameters between the sensor and biofluid. This parameter change reduces protein adsorption directly at the sensing interface, eliminating the need for salt bridges and reducing sensor volume.
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 miniature pH-sensing electrode enables reliable and accurate pH monitoring in both aqueous and viscous solutions, facilitating insertion into tissues and blood vessels without, providing effective and cost-effective pH sensing in tissues.
Implementation Method 1
a working-material layer disposed on a first surface of the substrate; wherein the pH-sensing electrode is sized for placement in or into a tissue, or completely or partially inside a blood vessel
Implementation Method 2
a reference-material layer disposed on a second surface of the substrate
Implementation Method 3
The working-material layer is deposited on the substrate by at least one of: a sol-gel method, electroplating, electrodeposition, physical vapor deposition, or metal-organic chemical vapor deposition
Implementation Method 4
the pH-sensing electrode is inserted into a needle
Data Source
AI summary
Provided herein are systems and methods related to a pH-sensing electrode including a substrate; a working-material layer disposed on a first surface of the substrate; and a reference-material layer disposed on a second surface of the substrate, wherein the second surface is opposite the first surface; wherein the pH-sensing electrode is configured to be inserted into a needle for placement in or into a tissue, or completely or partially inside a blood vessel.