Miniaturized pH Sensor with Flat Electrodes for Microliter Samples
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional pH measurement technologies face challenges in accurately measuring small sample volumes due to probe design limitations, contamination risks, evaporation issues, and the need for frequent maintenance, especially in semi-solid samples, which restricts high-throughput analysis and accuracy.
Innovation Solution
The development of miniaturized analyte sensors with flat sensing surfaces and conductive composite materials that allow for precise containment and measurement of small sample volumes, using voltammetric or amperometric methods, and a conductive analyte barrier to stabilize reference electrode potential, enabling multi-channel measurements and reduced maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional glass probes are used for pH measurement, then measurement accuracy is maintained, but sample volume requirement increases to milliliter levels
Solution Approach 1:
The probe is segmented into distinct functional components: a solid-contact working electrode with ion-selective membrane, a separate reference electrode with liquid junction, and a counter electrode. This segmentation allows miniaturization of each component while maintaining their individual functions, enabling operation in microliter-scale samples
Solution Approach 2:
The invention transitions from traditional three-dimensional bulbous glass electrodes to planar, two-dimensional electrode configurations. The flat electrode surfaces allow for better packing density and more efficient use of sample volume, enabling accurate pH measurement in constrained microliter samples
2Quantity of substance
If glass probes are used for small volume samples, then sample volume requirement decreases, but probe positioning and sample contact become difficult
Solution Approach 1:
The invention employs planar, flat electrode surfaces rather than curved bulbous shapes. This planar geometry provides stable, predictable positioning in microliter samples and ensures consistent contact between the electrode active area and the sample, eliminating positioning difficulties associated with small-volume glass probes
3Quantity of substance
If glass probes are used for small volume samples, then sample volume requirement decreases, but contamination from electrode mass transfer increases
Solution Approach 1:
The solid-contact working electrode uses a thin film ion-selective membrane on a small-area electrode, minimizing the amount of glass and other materials that could contaminate the sample. The reduced material mass compared to traditional glass probes significantly decreases contamination risk in microliter samples
4Quantity of substance
If glass probes are used for small volume samples, then sample volume requirement decreases, but evaporation effects become more significant
Solution Approach 1:
The thin film ion-selective membrane on the solid-contact electrode minimizes the volume of sample required for measurement. By reducing the necessary sample volume to the minimum required for film wetting and ionic conduction, the invention reduces evaporation effects while maintaining measurement reliability in microliter-scale samples
5Productivity
If glass probes are used for high throughput measurement, then measurement speed increases, but measurement accuracy decreases due to steady state requirements
Solution Approach 1:
The solid-contact working electrode with ion-selective membrane provides continuous, stable potentiometric response without requiring extended steady-state equilibration. The direct ion-to-electron transduction at the solid contact enables rapid, continuous measurements while maintaining accuracy, supporting high-throughput analysis
6Ease of manufacture
If glass probes are used for repeat use, then cost efficiency improves, but maintenance frequency increases due to fouling
Solution Approach 1:
The invention changes the fundamental parameters of the electrode materials and interfaces: using solid-contact electrodes with ion-selective membranes instead of traditional glass membranes, and employing specific reference electrode electrolytes and junction materials. These parameter changes reduce fouling by minimizing interactions with proteins, sugars, and other sample constituents, thereby reducing maintenance frequency while maintaining cost efficiency
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
These sensors enable precise measurement of analyte concentrations in microliter-scale samples with improved stability and reduced maintenance, overcoming the limitations of traditional glass probes by allowing for accurate, high-throughput analysis of small volumes without significant reduction in sensitivity.
Implementation Method 1
As pH measurement using a glass electrode requires that a potentiometric signal reach steady state
Implementation Method 2
Proper functioning of the reference electrode depends on fluid communication between the analyte and the internal reference solution through a porous junction such as a frit
Implementation Method 3
One or both anvils have embedded in them one or more electrodes of the analyte sensor in conductive contact with a surface of the anvil having a containment area wetted by the sample
Data Source
AI summary
Voltammetric sensors prepared from composite materials and optionally using microfabrication techniques enable detection of analyte in sample volumes under ten microliters.