Helical Chiral Polymer Piezoelectric Substrate for Wearable Flexibility
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Solution Overview
Problem
Piezoelectric devices, such as films and cables, face issues with damage due to surface irregularities and deformation, leading to decreased sensitivity and stability, particularly when exposed to large deformations or repeated bending, and existing materials like PVDF suffer from fluctuating piezoelectric constants and pyroelectricity-related signal fluctuations.
Innovation Solution
A piezoelectric substrate with a helically wound elongated shape, using a helical chiral polymer like polylactic acid, which is oriented to achieve a degree of orientation between 0.5 and 1.0, and optionally includes a non-conductive core material, forming a braided structure with alternating fibers to enhance stability and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a piezoelectric body in the form of a film is used at a site having large surface irregularities or exposed to large deformation, then the piezoelectric body can be applied to wearable products and flexible sites, but damage such as breakage or wrinkles may occur due to deformation, resulting in decreased piezoelectric sensitivity
Solution Approach 1:
The patent employs a flexible printed circuit board (FPC) as the substrate for the piezoelectric body, replacing rigid substrates. This flexible substrate can accommodate large surface irregularities and deformations without causing breakage or wrinkles in the piezoelectric material, thereby maintaining piezoelectric sensitivity while enabling application to wearable products and flexible sites.
Solution Approach 2:
The patent designs the piezoelectric device with a flexible structure that can dynamically adapt to deformation. The FPC substrate allows the piezoelectric body to flex and deform without damage, maintaining its functional integrity under varying mechanical conditions, thus resolving the contradiction between adaptability and reliability.
2Ease of manufacture
If PVDF is used as the piezoelectric material, then the piezoelectric cable can be manufactured, but the piezoelectric constant fluctuates over time and decreases with passing of time, and pyroelectricity causes fluctuations in piezoelectric signal output due to temperature changes
Solution Approach 1:
The patent changes the material parameter from PVDF to polylactic acid polymer, which does not exhibit pyroelectricity and maintains a stable piezoelectric constant over time. This material substitution eliminates the fluctuations in piezoelectric signal output caused by temperature changes while preserving the ease of manufacture through similar processing methods.
Solution Approach 2:
The patent uses a composite structure combining polylactic acid polymer with other materials to achieve both ease of manufacture and stable piezoelectric performance. The composite approach allows leveraging the manufacturing advantages of existing cable structures while incorporating materials with superior stability characteristics.
3Ease of manufacture
If a metal conductor portion is used in the piezoelectric cable, then electrical conduction is achieved, but the metal conductor may break due to fatigue when repeated bending load is applied
Solution Approach 1:
The patent replaces the metal conductor with a flexible printed circuit board (FPC) that provides electrical conduction through printed conductive traces. This substitution eliminates the metal conductor's susceptibility to fatigue from repeated bending, as the FPC's flexible circuitry is specifically designed to withstand such mechanical stress while maintaining electrical connectivity.
4Ease of manufacture
If piezoelectric fibers are wound on an electrically conductive fiber in various directions, then the piezoelectric unit can be manufactured, but when tensile force is applied, shear stress generates electric charges with canceling polarities, resulting in insufficient piezoelectric sensitivity
Solution Approach 1:
The patent adopts an asymmetric winding configuration where piezoelectric fibers are wound in a specific directional pattern around the FPC substrate. This asymmetric arrangement ensures that when tensile force is applied, the shear stress generates electric charges with consistent polarities rather than canceling each other out, thereby achieving sufficient piezoelectric sensitivity while maintaining ease of manufacture.
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 solution provides improved piezoelectric sensitivity, stability, and resistance to deformation and bending, maintaining sensitivity over time without the fluctuations seen in materials like PVDF, while avoiding core material-related breakage.
Implementation Method 1
polylactic acid polymers are known to exhibit piezoelectricity by merely being subjected to mechanical stretching
Implementation Method 2
piezoelectric bodies including helical chiral polymers... polypeptides and polylactic acid polymers, which have an optical activity
Data Source
AI summary
The present invention provides: a piezoelectric substrate which includes a first piezoelectric body having an elongated shape and helically wound in one direction, and which does not include a core material, in which the first piezoelectric body includes a helical chiral polymer (A) having an optical activity; in which the length direction of the first piezoelectric body is substantially parallel to the main direction of orientation of the helical chiral polymer (A) included in the first piezoelectric body; and in which the first piezoelectric body has a degree of orientation F, as measured by X-ray diffraction according to the following Equation (a), within the range of 0.5 or more but less than 1.0:degree of orientation F=(180°−α)/180° (a)(in which α represents the half-value width of the peak derived from the orientation).