Piezoelectric Touch Panel for Wet Environment Detection
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Solution Overview
Problem
Conventional touch panels, especially projected capacitance and capacitive touch panels, fail to function reliably when wet or submerged, and struggle to detect touches made with non-conductive objects or through gloves, leading to unreliable user interaction detection.
Innovation Solution
A touch panel design incorporating a layer of piezoelectric material between sensing electrodes and a counter electrode, with a touch controller that switches between force-based, capacitance-based, and mixed force-capacitance modes to determine user interactions, allowing operation even in wet conditions and environments with high electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If capacitive sensing is used for touch detection, then the touch panel can detect conductive touches, but it fails to function reliably when wet or submerged
Solution Approach 1:
The patent combines capacitive sensing and piezoelectric force detection into a single touch panel system. The capacitive sensing layer detects touches through conductive objects, while the piezoelectric force-detection layer detects applied force. By merging these two sensing mechanisms, the system can reliably detect touches even when wet, as the piezoelectric effect is not affected by water interference.
Solution Approach 2:
The touch panel is designed to perform multiple functions: capacitive touch detection for standard interactions, force-based detection for wet or submerged conditions, and mixed mode for enhanced accuracy. This multi-functionality allows the same device to adapt to various environmental conditions and input methods, including wet touches, gloved fingers, and stylus inputs.
2Strength
If projected capacitance touch panel with glass exterior is used, then the surface is resistant to scratching, but it struggles to detect touches made with non-conductive objects or through gloves
Solution Approach 1:
The patent merges capacitive sensing with piezoelectric force detection to create a hybrid system. The capacitive layer handles conductive touches, while the piezoelectric force-detection layer handles non-conductive objects and gloved fingers by detecting the mechanical force applied to the panel, thus maintaining ease of operation across different input types while preserving the scratch-resistant glass surface.
3Device complexity
If a single sensing mode is used, then the system is simpler to implement, but it cannot adapt to different environmental conditions and input methods
Solution Approach 1:
The touch controller dynamically switches between capacitive mode, force-based mode, and mixed mode based on environmental conditions and input characteristics. This dynamic adaptability allows the system to optimize performance for different scenarios (dry/wet conditions, conductive/non-conductive inputs) without requiring multiple separate devices, balancing complexity and versatility.
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 and accurate detection of user interactions without interruption, even when the panel is wet or submerged, and in environments with high interference, enhancing usability in wearable devices like smart watches.
Implementation Method 1
a layer of piezoelectric material disposed between a number of sensing electrodes and at least one counter electrode
Implementation Method 2
The touch controller is configured to determine one or more capacitance values
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An apparatus (2, 22) is described which includes a touch panel (1, 21). The touch panel (1, 21) includes a layer of piezoelectric material (4) disposed between a number of sensing electrodes (5, 23, 24) and at least one counter electrode (6). The apparatus (2, 22) also includes a touch controller (3) connected to the touch panel (1, 21). The touch controller (3) is configured to determine, in response to receiving piezoelectric signals (7) from one or more of the sensing electrodes (5, 23, 24), a location (9) and an applied force (10) corresponding to a user interaction (11) with the touch panel (1, 21). The touch controller (3) is configured to determine a capacitance value (20) of one or more of the sensing electrodes (5). The touch controller is configured to operate in a force- based mode, a capacitance-based mode or a mixed force-capacitance mode depending on the type of input received.