PVDF Ionic-Liquid Piezoelectric Films Without Stretching Distortion
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Solution Overview
Problem
Existing piezoelectric polymer films used in electrophoretic displays are brittle, require high concentrations of polarizable regions, and suffer from inhomogeneities in thickness and optical distortions due to stretching, making them unsuitable for thin, transparent applications.
Innovation Solution
Forming piezoelectric films from a mixture of polyvinylidene fluoride (PVDF) and ionic liquids, which increases beta phase concentration without stretching, resulting in thin, transparent films suitable for electrophoretic displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If piezoelectric polymer films are stretched to increase beta phase concentration, then piezoelectric response is improved, but film thickness uniformity deteriorates and optical distortions occur
Solution Approach 1:
The patent changes the chemical composition parameter by incorporating ionic liquids into the PVDF polymer matrix. This compositional change enables the polymer chains to adopt beta phase conformation without mechanical stretching, thereby maintaining film thickness uniformity while achieving high piezoelectric response. The ionic liquids act as plasticizers that facilitate chain alignment in the beta phase configuration.
Solution Approach 2:
The patent creates a composite material system by combining PVDF polymer with ionic liquids. This composite approach allows the ionic liquid components to interact with the polymer chains and promote beta phase formation through molecular-level interactions, eliminating the need for stretching processes that cause thickness non-uniformity and optical distortions.
2Power
If charged inorganic particles are added to increase local polarizability, then piezoelectric effect is enhanced, but film transparency is lost
Solution Approach 1:
The patent changes the type of additive from inorganic particles to ionic liquids. The ionic liquid molecules, being molecular-scale and transparent, can enhance local polarizability and promote beta phase formation without causing light scattering or absorption. This maintains film transparency while achieving the desired piezoelectric effect enhancement.
3Length of moving object
If piezoelectric polymer films are made thin for flexibility, then device thickness is reduced, but sufficient beta phase concentration becomes difficult to achieve
Solution Approach 1:
The patent changes the compositional parameter by incorporating ionic liquids that promote beta phase formation at the molecular level. This enables thin films to achieve sufficient beta phase concentration without requiring stretching processes, as the ionic liquids facilitate beta phase conformation throughout the film matrix during fabrication.
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 films are optically clear, flexible, and do not require external power, enabling applications such as security markers, authentication labels, and strain sensors, with uniform thickness and no optical distortions.
Implementation Method 1
The power supply could also be a piezoelectric element which creates charge through physical motion or thermal expansion
Implementation Method 2
Other phases, such as beta and gamma, have fluorine atoms predominantly in the same direction, and have much greater piezoelectric response. To achieve sufficient beta phase concentrations, it is often necessary to stretch piezoelectric polymer films
Data Source
AI summary
Piezoelectric films including ionic liquids and methods of making piezoelectric films including ionic liquids. The resulting films have higher levels of beta phase and can be poled using external fields without additional treatment, such as stretching. The films are light-transparent. In some embodiments, the piezoelectric material is used to create piezo-electrophoretic films that can be patterned for use as security markers, authentication films, or sensors. The films are generally flexible. Some films are less than 100 μm in thickness. Electrophoretic displays formed from the piezoelectric films do not require an external power source.