Flexible Polyimide Sensor Stack for Curved Acoustic Sensing
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Solution Overview
Problem
Existing sensing technologies, particularly in flexible or foldable devices, face challenges with signal strength and performance due to the use of conventional sensors that do not adequately transmit or receive acoustic signals, especially ultrasonic waves, leading to reduced sensing capabilities on curved or distorted surfaces.
Innovation Solution
A flexible acoustic sensor system is developed, comprising a flexible substrate made of polyimide and a sensor stack with a piezoelectric layer, a receiver element, and a coupling element, which allows for the transmission and detection of acoustic signals on non-planar surfaces, enhancing signal propagation and detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sensors are used in flexible devices, then device flexibility is maintained, but signal strength and sensing performance deteriorate on curved surfaces
Solution Approach 1:
The patent employs a flexible substrate made of polyimide with thickness between 5 and 80 μm that can conform to curved surfaces while maintaining structural integrity. This flexible substrate supports the sensor stack and allows the device to adapt to non-planar geometries without compromising sensing performance, directly resolving the contradiction between maintaining flexibility and ensuring reliable sensing on curved surfaces.
Solution Approach 2:
The patent specifically designs the sensor system to operate on curved and distorted surfaces, with the flexible substrate capable of conforming to various surface geometries. The coupling element is configured to maintain optimal contact with curved body parts, enabling the sensor to function reliably on non-planar surfaces such as skin, which directly addresses the contradiction between surface geometry and sensing performance.
2Adaptability or versatility
If conventional rigid sensor structures are used, then manufacturing precision is easier to achieve, but adaptability to flexible and curved surfaces deteriorates
Solution Approach 1:
The flexible substrate serves as the foundation for the entire sensor stack, providing both structural support and flexibility. This allows the sensor to adapt to curved surfaces while maintaining manufacturing precision through controlled deposition and assembly processes on the flexible substrate, resolving the contradiction between adaptability and manufacturing precision.
Solution Approach 2:
The sensor system is divided into distinct functional layers including the flexible substrate, piezoelectric layer, receiver element, and coupling element. Each layer can be manufactured and assembled separately with controlled precision, then integrated into the final flexible sensor system. This segmentation enables maintaining manufacturing precision while achieving adaptability to curved surfaces through the flexible substrate.
3Length of moving object
If thin flexible substrates are used, then device flexibility and form factor are improved, but signal transmission quality deteriorates
Solution Approach 1:
The patent uses a composite structure consisting of multiple functional layers including the flexible polyimide substrate, piezoelectric layer, receiver element, and coupling element. Each material is selected for its specific properties: the substrate provides flexibility with minimal thickness, while the piezoelectric and receiver components ensure high-quality signal transmission. This composite approach resolves the contradiction between thin substrate thickness and signal transmission quality.
Solution Approach 2:
The flexible substrate is designed with optimized thickness between 5 and 80 μm to maintain flexibility while supporting the sensor stack. The thin-film structure allows the substrate to be flexible enough for wearable applications while still providing sufficient mechanical support and acoustic coupling for reliable signal transmission, resolving the contradiction between substrate thickness and signal quality.
4Measurement precision
If piezoelectric materials are added to enhance acoustic detection, then signal sensitivity is improved, but device complexity increases
Solution Approach 1:
The patent combines the piezoelectric layer and receiver element into an integrated sensor stack that works together to detect acoustic signals. The piezoelectric materials are positioned to directly interface with the acoustic waves, converting mechanical vibrations to electrical signals that are then detected by the receiver element. This merged structure improves signal sensitivity while managing device complexity through functional integration.
Solution Approach 2:
The piezoelectric layer acts as an intermediary between the acoustic waves and the receiver element, converting acoustic energy to electrical signals. This intermediary function enhances signal sensitivity by providing efficient energy conversion, while the modular nature of the piezoelectric layer allows it to be integrated without excessive complexity increase.
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 flexible sensor system maintains high resolution and reliability on curved surfaces, improving signal sensitivity and enabling applications in flexible devices like foldable displays and wearable biosensors, while providing non-invasive measurement of physiological characteristics.
Implementation Method 1
a piezoelectric layer; and a receiver element disposed adjacent to the piezoelectric layer and configured to detect one or more signals received through the flexible substrate
Implementation Method 2
a light source system disposed on a flexible printed board, the light source system configured to transmit one or more optical signals toward a target object
Implementation Method 3
a flexible and optically transparent substrate disposed on the flexible printed board... configured to detect one or more acoustic signals received through the flexible substrate
Data Source
AI summary
Flexible sensing apparatus and various configurations of sensor stacks associated therewith are disclosed. Example embodiments may include a sensing system having: a flexible printed board; a sensor stack including: a flexible and optically transparent substrate disposed on the flexible printed board, the flexible and optically transparent substrate comprising polyimide; and a flexible sensor element disposed adjacent to the flexible substrate, the flexible sensor element including a first stack of materials, the first stack of materials including: a piezoelectric layer; and a receiver element disposed adjacent to the piezoelectric layer and configured to detect one or more acoustic signals received through the flexible substrate; and a control system configured to determine a physiological characteristic associated with a target object based on the one or more acoustic signals, electrical signals generated by the piezoelectric layer, or optical signals detected by the receiver element.