Disposable Reference Sensor With Vapor-Activated Salt Layer
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Solution Overview
Problem
Existing single-use planar electrochemical sensors face challenges in maintaining a stable and reproducible junction potential due to the limited size of the salt reservoir in the reference electrode, which is quickly washed away by aqueous solutions, and previous attempts to address this issue have resulted in complex manufacturing processes or sensor failures.
Innovation Solution
A single-use disposable potentiometric reference sensor is developed, incorporating an amorphous polysaccharide/salt layer with a semipermeable cover membrane that allows for water vapor absorption, enabling the sensor to activate at the point of use and maintain a stable junction potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a limited size salt reservoir is used in the reference electrode, then the sensor can be made small and disposable, but the salt is quickly washed away by aqueous solutions causing unstable junction potential
Solution Approach 1:
A semipermeable membrane is introduced as a thin film layer between the salt reservoir and the external environment. This membrane allows water vapor to pass through while restricting the outward diffusion of salt ions, thereby preventing rapid salt depletion and maintaining stable junction potential in a compact sensor design
Solution Approach 2:
The semipermeable membrane is designed with controlled porosity to allow selective transport of water vapor while blocking salt ions. This porous structure enables the membrane to permit necessary vapor exchange for membrane stability while preventing salt leakage, resolving the contradiction between small sensor size and potential stability
2Reliability
If hydrophilic electrolytes are used to enable ion transport, then the reference electrode functions properly, but long shelf life becomes difficult to achieve due to complex packaging requirements
Solution Approach 1:
The semipermeable membrane acts as a protective barrier that seals the hydrophilic electrolyte and salt reservoir from external moisture and contaminants. This membrane packaging allows the sensor to maintain its hydrophilic electrolyte environment for long-term storage without requiring complex sealed packaging systems
Solution Approach 2:
The sensor is designed as a single-use disposable device with integrated semipermeable membrane packaging. The membrane protects the hydrophilic electrolyte throughout the sensor's service life and is discarded with the sensor after use, eliminating the need for complex reusable packaging systems and extending effective shelf life
3Reliability
If hydrophobic cover membranes are used to prevent salt washing away, then salt reservoir stability improves, but water vapor diffusion is poor and salt permeability is too slow or too fast
Solution Approach 1:
The semipermeable membrane is engineered with optimized porosity to achieve balanced transport properties. The porous structure provides sufficient pathways for water vapor diffusion to maintain membrane stability while restricting salt ion permeability to prevent rapid salt depletion, resolving the contradiction between stability and diffusion rate
Solution Approach 2:
The membrane's physical and chemical parameters (porosity, thickness, material composition) are optimized to control selective permeability. By adjusting these parameters, the membrane achieves appropriate water vapor transmission while blocking salt ions, solving the contradiction between reservoir stability and vapor diffusion speed
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 achieves a stable and reproducible junction potential, suitable for blood analysis, with minimal manufacturing complexity and reduced sensor failure rates, while being cost-effective and convenient for use.
Implementation Method 1
a semipermeable cover membrane disposed over the internal layer where the semipermeable cover membrane has water vapor and ion permeability
Implementation Method 2
an amorphous polysaccharide/salt layer with a semipermeable cover membrane that allows for water vapor absorption, enabling the sensor to activate at the point of use
Implementation Method 3
maintain a stable junction potential
Data Source
AI summary
A single-use disposable potentiometric reference sensor includes an insulating base substrate, a reference electrode disposed on the insulating base substrate where the reference electrode is a silver-silver chloride electrode, an internal layer disposed on the reference electrode where the internal layer is an amorphous salt layer that includes an amorphous polysaccharide and a salt having equi-mobility cations and anions, and a semipermeable cover membrane disposed over the internal layer where the semipermeable cover membrane has water vapor and ion permeability.