Injection-Molded Polymer Piezoelectric Element for Shear Stress Sensing
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Solution Overview
Problem
Shear stress in polymer piezoelectric materials, particularly those made from helical chiral polymers like polylactic acid, is difficult to utilize effectively for practical applications due to its opposing directional nature, making it challenging to apply in devices such as sensors and actuators.
Innovation Solution
An injection-molded article of polymer piezoelectric material is created with a uniaxial orientation of b-axes and a configuration that includes electrode layers, utilizing a manufacturing apparatus with controlled temperature zones to ensure phase transition and orientation of helical chiral polymers, allowing for effective piezoelectricity and responsiveness to rotational and shear stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shear stress is applied to helical chiral polymer structures, then piezoelectric charge is generated, but the opposing directional nature of shear stress makes it difficult to utilize for practical applications
Solution Approach 1:
The patent applies asymmetry by uniaxially orienting the b-axes of the helical chiral polymer crystals in a specific direction (thickness direction) while allowing c-axes to be oriented in the plane direction. This asymmetric orientation configuration enables the material to respond to both shear stress and rotational stress effectively, converting the previously problematic opposing directional nature into a useful dual-response characteristic that enhances practical applicability
2Shape
If polymer piezoelectric materials are shaped using three-dimensional shaping apparatus, then desired three-dimensional structures are obtained, but the manufacturing process requires precise temperature control to achieve proper molecular orientation
Solution Approach 1:
The patent applies parameter changes by precisely controlling the temperature of the support surface to be at or above the phase transition temperature (where metastable phase transitions to stable phase) but below the melting point of the helical chiral polymer. This specific temperature parameter control enables the polymer chains to orient properly during injection molding, achieving both the desired three-dimensional shape and the required molecular orientation for piezoelectricity
Solution Approach 2:
The patent utilizes phase transitions by heating the support surface to trigger the transition from metastable phase to stable phase of the helical chiral polymer. This phase transition occurs at a specific temperature range that allows the polymer to crystallize with proper orientation while maintaining the three-dimensional structure, thereby achieving both shape fidelity and molecular alignment
3Reliability
If the support surface temperature is increased to achieve phase transition and molecular orientation, then piezoelectric constants increase, but the temperature must remain below the melting point to maintain material integrity
Solution Approach 1:
The patent applies parameter changes by optimizing the support surface temperature to a specific range: at or above the phase transition temperature (for maximum piezoelectric constant) but below the melting point (for material integrity). This precise parameter control allows the material to achieve its highest piezoelectric response without compromising structural stability
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 enables a piezoelectric element that can detect and generate rotational and shear stresses effectively, enhancing the practicality and performance of devices like sensors and actuators by increasing piezoelectric constants and mechanical strength.
Implementation Method 1
a temperature of the support surface is greater than or equal to a phase transition temperature of the helical chiral polymer at which a phase transition from a metastable phase to a stable phase takes place
Implementation Method 2
heating a raw material containing a helical chiral polymer to obtain a molten material
Data Source
AI summary
An injection-molded article of polymer piezoelectric material includes: a helical chiral polymer constituted by a polymer chain and having a unit cell with an a-axis, a b-axis, and a c-axis as crystal axes, wherein b-axis<a-axis<c-axis in terms of lengths of the crystal axes, the c-axis is parallel to a long chain direction of the polymer chain, the helical chiral polymer is a crystal in which the b-axis is uniaxially oriented, and the injection-molded article has piezoelectricity.