Annular Piezoelectric Touch Sensing for Wet Cover Glass
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Solution Overview
Problem
Capacitive-type touch sensing systems face performance issues due to conductive, electrically-floating objects such as water droplets, and require complex stack-ups for operation, which can lead to reduced reliability and increased manufacturing complexity.
Innovation Solution
An acoustic touch sensing system utilizing a mechanically integrated annular piezoelectric structure with shear poled piezoelectric segments, which simplifies structural integration, provides improved water sealing, and allows for efficient detection of touch events even in wet environments without the need for complex stack-ups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If capacitive-type touch sensing systems are used, then touch detection capability is provided, but performance is reduced due to conductive objects such as water droplets and manufacturing complexity increases
Solution Approach 1:
The patent replaces capacitive sensing (electrical field-based) with acoustic sensing (mechanical wave-based). The piezoelectric transducers generate and detect acoustic waves that propagate through the cover glass, making the sensing mechanism immune to interference from conductive objects like water droplets since acoustic waves are mechanical vibrations rather than electrical fields.
Solution Approach 2:
The patent changes the fundamental sensing parameter from electrical capacitance to acoustic wave properties (frequency, amplitude, propagation time). By using acoustic waves with specific frequencies that propagate through the cover glass and reflect off touch points, the system achieves reliable detection without being affected by the electrical conductivity of external objects.
2Adaptability or versatility
If multiple discrete transducers are integrated to the surface, then touch sensing functionality is achieved, but structural integration complexity increases and manufacturing reliability decreases
Solution Approach 1:
The patent merges multiple discrete transducer functions into a single integrated piezoelectric structure. This annular piezoelectric structure can simultaneously generate and detect acoustic waves across multiple zones of the cover glass, eliminating the need for multiple separate transducer components and their associated mounting, wiring, and alignment procedures.
Solution Approach 2:
The single piezoelectric structure performs multiple functions: it acts as both the acoustic wave source and the detection sensor across different regions of the cover glass. The annular structure can generate acoustic waves that propagate in multiple directions and detect reflections from various touch locations, providing comprehensive touch sensing coverage with one component.
3Adaptability or versatility
If discrete transducers are mounted individually to the surface, then touch sensing is enabled, but water sealing performance deteriorates
Solution Approach 1:
By integrating the piezoelectric structure directly into the cover glass as a unified component rather than mounting discrete transducers, the patent eliminates gaps and interfaces where water could penetrate. The single integrated structure provides continuous coverage and maintains the structural integrity needed for effective water sealing.
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 system offers reliable and stable touch sensing capabilities in wet conditions, with improved manufacturing efficiency and structural integrity, enabling effective detection of touch positions and presence using ultrasonic waves.
Implementation Method 1
The piezoelectric material in the annular structure can be shear poled such that a poling direction of the piezoelectric material can follow the curvature of the annular piezoelectric structure
Implementation Method 2
acoustic touch sensing systems that can be fabricated using a mechanically integrated structure including multiple acoustic transducers
Data Source
AI summary
Acoustic touch sensing systems can include a mechanically integrated structure including multiple acoustic transducers. For example, an annular structure including one or more piezoelectric segments can be fabricated and then coupled to a front crystal/cover glass. A single structure can simplify the structural integration of the device, can provide a mechanically reliable and stable structure for improved structural integrity of the system, and can provide for improved water sealing for a waterproof or water resistant device. The piezoelectric material in the annular structure can be shear poled such that a poling direction of the piezoelectric material can follow the curvature of the annular piezoelectric structure.