Humidity Sensor Detection Film Surface Roughness
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Solution Overview
Problem
Sensors face durability issues due to capacitance changes over time, particularly in humidity sensors, which affect measurement accuracy and wear resistance, especially when used for extended periods and subjected to bending forces.
Innovation Solution
A sensor design featuring a detection film with rough surfaces having a root mean square roughness of 0.3 μm to 3.0 μm, where at least one electrode is a plated film, and the detection film is formed from a resin composition, including a polyimide resin component, to improve wear resistance and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a smooth detection film surface is used, then manufacturing is easier and initial capacitance is stable, but wear resistance deteriorates and capacitance changes over time
Solution Approach 1:
The detection film surface is pre-treated to create fine irregularities with a specific roughness (Sq: 0.03-3.0 μm) before electrode formation. This preliminary surface preparation ensures that when electrodes are later deposited, they form a mechanical interlock with the rough surface, significantly improving wear resistance and preventing capacitance drift over time without complicating the overall manufacturing process
Solution Approach 2:
The surface roughness is controlled to have fine irregularities only in the electrode contact regions, while other areas of the detection film maintain their inherent properties. This localized surface modification optimizes wear resistance at the electrode-film interface without affecting the overall detection film performance or requiring complete surface reconstruction
2Adaptability or versatility
If the detection film is made thinner to improve flexibility, then flexibility improves, but wear resistance and durability deteriorate
Solution Approach 1:
The surface roughness treatment is applied specifically to regions where electrodes contact the detection film, creating localized mechanical interlocking zones. This allows the detection film to remain thin for flexibility while the roughened surfaces at critical contact points provide enhanced wear resistance and structural integrity
Solution Approach 2:
The detection film is constructed as a composite structure combining a thin flexible base layer with a surface treatment layer creating fine irregularities. This composite approach maintains the flexibility of the thin film while the surface structure provides enhanced durability and wear resistance at electrode interfaces
3Reliability
If a rough surface with fine irregularities is created on the detection film, then wear resistance and durability improve, but manufacturing precision requirements increase
Solution Approach 1:
The surface roughness is controlled within a broad acceptable range (Sq: 0.03-3.0 μm) rather than requiring ultra-precise values. This parameter optimization allows standard manufacturing processes to achieve the required surface quality without needing specialized equipment or extremely tight process controls, balancing durability improvement with manufacturing feasibility
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 exhibits superior durability with suppressed capacitance changes over time and enhanced wear resistance, maintaining a capacitance retention rate of 50% or more, effectively addressing the durability concerns in humidity sensors and similar applications.
Implementation Method 1
a first electrode provided on a first surface of the detection film; wherein the first surface of the detection film includes a rough surface having fine irregularities with a root mean square roughness (Sq) of 0.3 μm to 3.0 μm in a portion that is in contact with the first electrode
Data Source
AI summary
A sensor including a detection film formed from a resin composition, a first electrode provided on a first surface of the detection film, and a second electrode provided on a second surface of the detection film, wherein the first surface of the detection film includes a rough surface having fine irregularities with a root mean square roughness (Rq) of 0.3 μm to 3.0 μm in a portion that is in contact with the first electrode.