Enclosed Amperometric Sensing Volume for Flow-Stable Readout
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Solution Overview
Problem
Miniaturized amperometric sensors with small electrodes are limited by diffusion of the target analyte, which is affected by fluid flow, leading to inaccurate concentration measurements due to the influence of external factors.
Innovation Solution
An amperometric sensor with an enclosing structure defining a sensing volume and a displaced electrode, allowing measurements within a time frame where the depletion layer is contained within the sensing volume, thereby isolating the measurement from external fluid flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If miniaturized electrodes are used to reduce sensor size and cost, then the sensor form factor is reduced, but diffusion of the target analyte becomes the limiting factor for steady-state current
Solution Approach 1:
The sensing system is segmented into distinct functional zones: a stagnant sensing volume where measurement occurs, and a bulk volume where fluid flow may occur. The enclosing structure segments the fluid domain to create a controlled measurement environment isolated from external flow disturbances.
Solution Approach 2:
The enclosing structure acts as an intermediary element between the electrode and the bulk fluid. It creates a stagnant sensing volume that mediates the interaction between the electrochemical reaction and the flowing fluid, allowing accurate measurement while maintaining connection to the bulk volume through the inlet.
2Adaptability or versatility
If fluid flow is present in the bulk volume, then the sensor can operate in dynamic environments, but the electrical signal is affected by both concentration and fluid velocity leading to inaccurate measurements
Solution Approach 1:
The fluid domain is segmented into a stagnant sensing volume and a flowing bulk volume. The enclosing structure creates this segmentation, allowing the sensor to operate in dynamic environments while maintaining a controlled measurement zone where fluid velocity does not affect the electrical signal.
Solution Approach 2:
The harmful effect of fluid flow on measurement accuracy is extracted and isolated from the sensing process. The enclosing structure removes the influence of bulk fluid velocity from the measurement zone, allowing the electrical signal to depend only on analyte concentration.
3Volume of moving object
If the sensing volume is made small to reduce device size, then the form factor is reduced, but the depletion layer may expand towards the inlet and be affected by external fluid flow
Solution Approach 1:
The aspect ratio of the sensing volume is optimized to ensure that during the measurement time frame, the depletion layer remains contained within the sensing volume. The dimensions are chosen such that h ≥ w/2, providing sufficient distance from the inlet to prevent external fluid flow from affecting the measurement.
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 provides accurate concentration measurements of the target analyte by insensitivity to fluid flow, enabling reliable sensing in environments with turbulent or unknown fluid conditions.
Implementation Method 1
An electroactive target analyte may then react with an electrode and produce another electrical signal (typically a current signal) which scales with concentration of the target analyte
Implementation Method 2
For small electrodes, such as electrodes having a size of 100 μm or less, diffusion of the target analyte in the fluid limits a steady-state current of the electrode
Data Source
Figure 1~2
Figure 3
Figure 4a~4b
AI summary
A device (100; 200; 300; 400; 500; 600) for amperometric sensing comprises: an enclosing structure (110; 210) defining a sensing volume (102; 202, 204a-e; 304a-e; 404a-c; 504a-c; 604a-c) and comprising at least one circumferential wall (112; 212; 412; 512), wherein the enclosing structure defines an inlet (114; 414; 514) in or at an end of the circumferential wall for allowing a target analyte to enter the sensing volume, an electrode (130; 230; 330a-e; 430; 530; 630) arranged in the sensing volume and displaced from the inlet; and a read-out circuitry (140; 240; 640) connected to the electrode and configured for read-out of an electrical signal from the electrode within a time frame during which a target analyte depletion layer around the electrode expands along the circumferential wall and is substantially contained within the sensing volume, wherein the electrical signal is representative of a concentration of the target analyte.