Potentiometric Reference Sensor With Salt-Retaining Membrane
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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 solutions like hydrophobic membranes have poor water vapor diffusion properties or slow ion permeability, leading to complex manufacturing processes and high failure rates.
Innovation Solution
A single-use disposable potentiometric reference sensor is developed with an amorphous polysaccharide/salt layer combined with a semipermeable cover membrane, allowing for water vapor and ion permeability, ensuring a stable and reproducible junction potential by incorporating an amorphous polysaccharide and equi-mobility salts within a hydrophobic polymer layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a concentrated aqueous salt solution is used in the reference electrode to maintain stable reference potential, then the reference potential stability is improved, but the salt reservoir is quickly washed away by aqueous solutions due to limited size in planar sensor arrays
Solution Approach 1:
A hydrophobic membrane coating is applied to the reference electrode, forming a thin film barrier that prevents aqueous solutions from washing away the concentrated salt reservoir while allowing the electrode to maintain its stable reference potential. The hydrophobic nature of the coating creates a water-repellent barrier that retains the salt solution within the limited planar space.
Solution Approach 2:
The invention changes the physical and chemical parameters of the membrane coating, specifically using hydrophobic materials with controlled porosity and surface energy. By adjusting the coating thickness, hydrophobicity, and pore size, the system maintains salt reservoir stability while controlling ion transport, resolving the contradiction between retaining salt and allowing function.
2Loss of substance
If hydrophobic cover membranes are used to prevent salt reservoir washing away, then salt retention is improved, but water vapor diffusion properties are poor and ion permeability is slow or too fast
Solution Approach 1:
The hydrophobic membrane coating is designed with controlled porosity, creating a porous structure that allows selective transport. The pores are sized and distributed to permit ion passage at appropriate rates while maintaining hydrophobicity to prevent salt solution leakage. This porous hydrophobic structure resolves the contradiction between salt retention and ion permeability.
Solution Approach 2:
The membrane coating is formulated as a composite material combining hydrophobic polymer matrix with controlled pore structure and potentially hydrophilic domains. This composite structure provides both the hydrophobic barrier needed for salt retention and the ion transport pathways necessary for proper electrode function, balancing retention and permeability.
3Loss of substance
If the salt reservoir size is increased to prevent washing away, then salt retention is improved, but the device size increases which contradicts the small size requirement for disposable electrodes
Solution Approach 1:
The hydrophobic membrane coating forms a thin film encapsulation around the salt reservoir, creating an effective barrier against washing away without requiring a large physical reservoir volume. This thin film approach allows the salt to be retained in a compact configuration, maintaining small electrode size while preventing salt loss.
Solution Approach 2:
The hydrophobic coating is applied in advance to the reference electrode structure, creating a pre-established protective barrier before the electrode is exposed to aqueous samples. This preliminary protection allows the use of smaller salt reservoirs since the anti-washing mechanism is already in place, resolving the contradiction between small size and salt retention.
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 across varying ionic strengths, reducing manufacturing complexity and failure rates while maintaining a constant reference potential for extended periods, suitable for disposable use.
Implementation Method 1
the semipermeable membrane has water vapor and ion permeability
Implementation Method 2
the semipermeable membrane has water vapor and ion permeability
Implementation Method 3
ensuring a stable and reproducible junction potential by incorporating an amorphous polysaccharide and equi-mobility salts within a hydrophobic polymer layer
Data Source
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Figure 3~4
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.