Microfabricated Electrochemical Gas Sensor Using Surface Tension
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Solution Overview
Problem
Conventional electrochemical gas sensors are large, costly, and difficult to miniaturize due to challenges in incorporating liquid electrolytes and membranes, which results in high response times and limited manufacturability, making them unsuitable for portable applications.
Innovation Solution
Microfabrication techniques are used to create micro cavities within a stack of conductor and insulator layers, filled with a liquid electrolyte that exhibits a low contact angle with electrodes but a high contact angle with the outer insulator, allowing the electrolyte to be retained by surface tension, eliminating the need for membranes and reducing response time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional electrochemical gas sensors are miniaturized using microfabrication, then size is reduced, but retaining liquid electrolyte becomes challenging
Solution Approach 1:
The patent applies local quality by creating different surface properties in different locations of the microfabricated sensor. The cavity walls are engineered to have specific wettability characteristics that differ from other surfaces, enabling the liquid electrolyte to be retained in the cavity through controlled capillary forces while maintaining miniaturization. This localized surface property modification allows the sensor to keep its small size without sacrificing electrolyte retention reliability.
2Device complexity
If ionic liquid electrolyte is used to eliminate membranes, then device complexity is reduced, but response time increases due to low diffusion coefficient
Solution Approach 1:
The patent applies parameter changes by modifying the physical dimensions of the electrolyte containment cavity. By creating a micro-scale cavity with specific volume and surface area characteristics, the patent changes the mass transport parameters for the ionic liquid electrolyte. This reduces the diffusion path length and increases the surface-to-volume ratio, thereby improving the response time of the gas sensor while maintaining the simplicity of using ionic liquid without membranes.
3Manufacturing precision
If microfabrication techniques are used, then manufacturing precision is improved, but ease of manufacture deteriorates due to difficulty in incorporating electrolytes and membranes
Solution Approach 1:
The patent applies the extraction principle by removing the membrane component from the sensor structure entirely. By using ionic liquid electrolyte in a microfabricated cavity with engineered surface properties, the patent eliminates the need for separate membrane incorporation steps. This simplifies the manufacturing process while maintaining the precision benefits of microfabrication, as the electrolyte is retained through capillary forces rather than requiring membrane containment.
4Reliability
If ordinary membranes are used to contain electrolyte, then electrolyte retention is achieved, but cost increases and manufacturability decreases
Solution Approach 1:
The patent applies self-service by enabling the microfabricated cavity structure to retain the ionic liquid electrolyte through its own inherent surface properties rather than requiring external membrane components. The cavity walls are engineered with specific wettability characteristics that create capillary forces to hold the electrolyte, making the structure self-containing. This eliminates the need for separate membrane components, reducing cost and improving manufacturability while maintaining reliable electrolyte 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 solution enables the miniaturization of electrochemical gas sensors, reducing size and cost while maintaining sensitivity and selectivity, and achieving faster response times by utilizing surface tension to retain the liquid electrolyte within micro cavities.
Implementation Method 1
the liquid electrolyte is kept in the micro cavities by surface tension
Implementation Method 2
The electrolyte exhibits low contact angle over the electrodes and high contact angle when in contact with the surface of the outer insulator
Data Source
AI summary
This invention describes an electrochemical gas sensor that utilizes microfabrication to achieve miniaturization without using a membrane. The sensor is comprised of thin film electrodes and insulators, and micro cavities in them. The micro cavities are filled with a liquid electrolyte that is kept in the micro cavities by surface tension.