Foldable Piezoelectric Pressure Sensor with Orthogonal Electrodes
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Solution Overview
Problem
Existing pressure sensors used in folding structures, such as foldable smartphones, face challenges in detecting pressure with high sensitivity when in a folded state due to the cancellation of charges generated by piezoelectric sheets in overlapping layers.
Innovation Solution
A pressure sensor configuration that includes a foldable piezoelectric film with a first electrode on one surface and multiple second electrodes on the other, orthogonal to the folding line, along with a folding detection unit and processing unit that adjusts signal processing based on the folded state, allowing for sensitive detection even when the film is folded.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a piezoelectric sheet is used for pressure detection in a folding structure, then pressure detection function is provided, but detection sensitivity deteriorates in folded state due to charge cancellation between overlapping layers
Solution Approach 1:
The piezoelectric sheet is divided into multiple independent piezoelectric elements arranged in an array. Each element can generate and process signals independently, allowing the system to select and process signals from elements that are not in overlapping positions when folded, thereby avoiding charge cancellation and maintaining detection sensitivity.
Solution Approach 2:
The system dynamically adjusts its operation based on the folding state. A detection unit identifies whether the device is folded or unfolded, and the control unit dynamically selects appropriate piezoelectric elements for signal processing. In folded state, elements that would produce canceled signals are excluded from processing, while in unfolded state, all elements can be used for maximum sensitivity.
2Stability of the object's composition
If overlapping layers of piezoelectric sheet are used to maintain structural integrity in folded state, then structural stability is improved, but charge cancellation occurs reducing detection accuracy
Solution Approach 1:
By segmenting the piezoelectric sheet into multiple independent elements, the system can structurally utilize overlapping layers for stability while selectively processing signals only from non-overlapping elements, thus maintaining both structural integrity and detection accuracy.
Solution Approach 2:
Different regions of the piezoelectric sheet are treated differently based on their spatial position. Elements in overlapping regions are identified and excluded from signal processing, while elements in non-overlapping regions are used for detection. This local differentiation maintains structural stability from overlapping layers while preserving detection accuracy from non-overlapping elements.
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 high-sensitivity pressure detection in both folded and unfolded states by reversing or adjusting signal polarities and gains, preventing charge cancellation and improving accuracy.
Implementation Method 1
a piezoelectric sheet 91 of the pressure sensor 90 is distorted in a pressed direction. The piezoelectric sheet 91 is distorted only in one direction, and therefore generates a charge of predetermined polarity.
Data Source
AI summary
A pressure sensor for use in a folding structure that includes a foldable piezoelectric film, a first electrode disposed on a first main surface of the piezoelectric film, a plurality of second electrodes disposed side by side on a second main surface of the piezoelectric film so as to face the first electrode and to be positioned along a direction orthogonal to a folding line of the piezoelectric film, a folding detection unit that detects a folded state of the piezoelectric film, and a processing unit that changes processing of at least one of signals generated on the second electrode when the piezoelectric film receives a pressing operation and the folding detection unit is detecting the folded state of the piezoelectric film.