Piezoelectric Force Sensing Array for Non-Conductive Object Detection
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Solution Overview
Problem
Current touch sensing systems lack sensitivity, robustness, and energy efficiency, and often require an electrically conductive object for detection, limiting their functionality and usability.
Innovation Solution
A touch sensing system incorporating a force-sensing device with a substrate, an array of sensor pixel circuits, and a piezoelectric film layer, capable of detecting forces and converting mechanical energy into electrical signals, allowing for high-resolution fingerprint sensing and ultrasonic imaging without the need for conductive objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If projected capacitance methods are used for touch sensing, then the system can detect electrically conductive objects, but the system cannot detect non-conductive objects and requires the object to be electrically conductive
Solution Approach 1:
The patent replaces electrical detection methods (capacitance, resistance) with a mechanical sensing approach using piezoelectric materials. The piezoelectric layer converts mechanical pressure from any object (conductive or non-conductive) into electrical signals, eliminating the requirement for the detected object to be electrically conductive while maintaining sensor functionality
Solution Approach 2:
The piezoelectric layer acts as an intermediary between the mechanical touch input and the electrical signal output. It transduces mechanical energy from any object (regardless of conductivity) into electrical signals that can be processed by the sensor circuit, enabling detection of non-conductive objects that would otherwise be invisible to traditional capacitive sensors
2Reliability
If traditional touch sensing systems are used, then the system can operate with simple structures, but the systems lack sensitivity and robustness
Solution Approach 1:
The patent employs a composite structure combining piezoelectric material with a flexible substrate and protective layers. This composite design enhances sensor reliability by protecting the piezoelectric elements while maintaining their mechanical sensitivity, allowing the system to detect subtle forces and withstand various operating conditions
Solution Approach 2:
The force-sensing device is divided into discrete pixel elements arranged in an array, with each pixel containing its own piezoelectric element and associated circuitry. This segmentation allows independent optimization of each pixel's sensitivity and robustness while maintaining overall system functionality, improving reliability without requiring the entire sensor to be overly complex
3Measurement precision
If continuous operation is required for high-resolution sensing, then measurement precision is improved, but energy consumption increases
Solution Approach 1:
The patent implements periodic scanning of the piezoelectric pixel array rather than continuous readout. The control circuit sequentially activates and reads signals from pixel elements in a timed manner, maintaining measurement precision by periodically capturing force data while significantly reducing power consumption compared to continuous operation
Solution Approach 2:
The piezoelectric elements generate electrical signals automatically in response to applied mechanical force, eliminating the need for continuous external power supply to the sensing elements themselves. The signal generation is passive and driven by the mechanical input, reducing overall system power requirements while maintaining detection capability
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 provides enhanced sensitivity and energy efficiency, enabling detection of any object, including non-conductive ones, with the ability to function as both a fingerprint sensor and ultrasonic receiver, while maintaining low power consumption by converting user input into electrical energy.
Implementation Method 1
discrete elements of a piezoelectric film layer... converting mechanical energy into electrical signals
Data Source
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Figure 1B
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AI summary
A touch sensing system may include a pressure and force sensing device capable of sensing dynamic pressure or dynamic force applied to a piezoelectric sensing array. In such implementations, an applied force may be detected (and optionally recorded) during a period of time that the force is applied and changing. The force-sensing device may have a sufficiently high resolution to function as a fingerprint sensor. The touch sensing system may include one or more additional components capable of fingerprint sensing, such as an ultrasonic transmitter that allows the device to become an ultrasonic transducer capable of imaging a finger (or another object) in detail. The force-sensing device also may be capable of functioning as an ultrasonic receiver.