Fingerprint Sensor Fluoropolymer Coating for Wet Finger Accuracy
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Solution Overview
Problem
Conventional fingerprint identification apparatuses have poor hydrophobic and oleophobic properties, leading to reduced accuracy and speed when used with a wet finger due to moisture or oil stains, which affect the capacitance sensing mechanism.
Innovation Solution
A fingerprint identification apparatus with a substrate, sensing chip, and a dual-layer coating system where the second layer is made from a fluoropolymer with a hydrophobic and oleophobic coating, applied using a solvent like dipropylene glycol methyl ether, and optionally enhanced with silicone-modified or organic fluorine-modified resins in the first layer to improve surface hydrophobicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional coating is used on the sensing chip, then the device structure is simple and easy to manufacture, but the hydrophobic and oleophobic properties are poor, leading to reduced fingerprint identification accuracy and speed for wet fingers
Solution Approach 1:
The patent applies a composite coating structure consisting of a first covering layer (protective coating) and a second covering layer (fluoropolymer coating with hydrophobic and oleophobic properties). This composite structure combines the protective function of the first layer with the water and oil repellent properties of the second layer, thereby improving fingerprint identification accuracy for wet fingers while maintaining manufacturing feasibility
Solution Approach 2:
The patent changes the chemical composition parameters of the coating by introducing fluoropolymer materials and adjusting the ratio of hydrophobic and oleophobic components. Specifically, the fluoropolymer content in the second covering layer is controlled at 5-20 wt%, which optimizes the contact angle properties and enhances the coating's ability to repel water and oil, thus improving fingerprint sensing performance
2Productivity
If no hydrophobic and oleophobic coating is applied, then the manufacturing process is simple, but moisture and oil stains spread on the coating surface, increasing the affected sensing region and reducing identification speed
Solution Approach 1:
The patent modifies the surface energy parameters of the coating by incorporating fluoropolymer materials with low surface energy. The contact angle of water on the coated surface is increased to greater than 110 degrees, and the contact angle of oil is increased to greater than 90 degrees. This parameter change prevents moisture and oil stains from spreading, reduces the affected sensing region, and maintains fast fingerprint identification speed
Solution Approach 2:
The fluoropolymer coating acts as an intermediary layer between the sensing chip and the external environment (water and oil). This intermediate layer prevents direct contact between moisture/oil and the sensing chip, thereby preventing spread of contaminants and maintaining high identification speed even when fingers are wet
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 enhanced hydrophobic and oleophobic properties of the surface significantly improve fingerprint identification accuracy and speed in wet environments by reducing the contact area of moisture or oil stains, allowing clearer and faster fingerprint detection.
Implementation Method 1
the second covering layer is an oleophobic and hydrophobic coating
Implementation Method 2
the second covering layer is an oleophobic and hydrophobic coating
Data Source
AI summary
The present disclosure relates to the technical field of biometric identification, and in particular, a fingerprint identification apparatus. The fingerprint identification apparatus includes: a substrate, a sensing chip, a first covering layer, and a second covering layer; wherein the sensing chip is arranged on the substrate, the first covering layer is coated over the sensing chip, the second covering layer is coated on an upper surface of the first covering layer, and the second covering layer is an oleophobic and hydrophobic coating. In the fingerprint identification apparatus according to the embodiment of the present disclosure, a hydrophobic and oleophobic coating is arranged on the surface of the fingerprint identification apparatus, where the density of the hydrophobic components is increased and the hydrophobic as well as oleophobic capabilities are enhanced, and thus the fingerprint identification accuracy and fingerprint identification speed in a wet-finger use environment are improved.