Microelectrode Sensor for Non-Invasive Tear Fluid Monitoring
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Solution Overview
Problem
Current electrochemical sensors for measuring analyte concentrations in tear fluid are invasive and lack efficient non-invasive methods for continuous monitoring, especially for diabetic patients who need to track glucose levels.
Innovation Solution
An ophthalmic sensing platform embedded in a contact lens with a microelectrode-based electrochemical sensor that wirelessly communicates with an external reader, using a polymeric material for mounting on the corneal surface and powered by ambient energy, allowing for non-invasive, continuous monitoring of tear fluid analyte concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional electrochemical sensors are used for analyte detection, then measurement capability is achieved, but the sensing platform occupies excessive area and consumes excessive power
Solution Approach 1:
The sensor platform is divided into functionally independent microelectrodes (working electrode, counter electrode, reference electrode) that can be spatially separated and optimized individually. This segmentation allows each electrode to be miniaturized to micrometer scale while maintaining their respective detection, current completion, and potential reference functions, thereby reducing the overall platform area.
Solution Approach 2:
Each electrode is designed with specific local properties: the working electrode has catalytic coating for analyte detection, the counter electrode provides current completion pathway, and the reference electrode maintains stable potential. This localized functional differentiation enables efficient space utilization where each micrometer-scale electrode performs its specialized function without requiring excessive area.
2Measurement precision
If conventional electrochemical sensors are used for analyte detection, then measurement capability is achieved, but power consumption is excessive for implantable applications
Solution Approach 1:
The electrochemical sensing operates through periodic electrochemical cycles where the working electrode alternates between oxidation and reduction states. This periodic operation at microelectrode scale enables analyte detection while minimizing continuous power consumption, as the system only requires brief energy input for each measurement cycle rather than continuous power supply.
Solution Approach 2:
The microelectrode system utilizes the natural electrochemical properties of the analyte and electrode materials to generate detectable signals with minimal external power input. The catalytic working electrode spontaneously reacts with target analytes, and the small electrode geometry creates self-sustaining electrochemical fields that reduce the power required for continuous operation.
3Reliability
If polymeric material with high resistance is used for mounting, then biocompatibility and corneal mounting are improved, but voltage loss increases
Solution Approach 1:
The polymeric material is applied locally only where needed for biocompatibility and mounting stability, rather than as a complete coating. This localized application minimizes the total resistance encountered by electrical currents while preserving the biocompatible interface with corneal tissue. The polymer is strategically positioned to provide tissue compatibility without creating excessive electrical barriers.
Solution Approach 2:
The sensor platform design creates asymmetric electrical pathways where high-resistance polymeric material is positioned away from critical current flow paths. The mounting surface contacts corneal tissue through polymer for biocompatibility, while the electrochemical measurement pathway uses direct conductive connections that bypass high-resistance regions, thereby minimizing voltage loss while maintaining tissue compatibility.
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
Enables continuous, non-invasive monitoring of analyte concentrations in tear fluid, providing clinically relevant readings and reducing the need for invasive blood sampling, with efficient analyte diffusion and reduced voltage loss due to high resistance in the electrolyte material.
Implementation Method 1
An electrochemical amperometric sensor measures a concentration of an analyte by measuring a current generated through electrochemical oxidation or reduction reactions of the analyte at a working electrode of the sensor
Implementation Method 2
efficient analyte diffusion
Data Source
AI summary
An eye-mountable device includes an electrochemical sensor embedded in a polymeric material configured for mounting in front of a surface of an eye. The electrochemical sensor includes a working electrode, a reference electrode, and a reagent that selectively reacts with an analyte to generate a sensor measurement related to a concentration of the analyte in a fluid to which the eye-mountable device is exposed. The working electrode can have at least one dimension less than 25 micrometers. The reference electrode can have an area at least five times greater than an area of the working electrode. A portion of the polymeric material can surround the working electrode and the reference electrode such that an electrical current conveyed between the working electrode and the reference electrode is passed through the at least partially surrounding portion of the transparent polymeric material.