Electroactive Polymer Transducer Negative Bias Spring Optimization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electroactive polymer (EAP) actuators and transducers face limitations in achieving optimal force, stroke, and power output without increasing the amount of EAP material, necessitating improved biasing methods to enhance performance.
Innovation Solution
The use of selectively biased EAP transducers employing negative bias springs, combined with constant or positive rate springs, and novel spring configurations such as buckled beam springs and polymeric bias diaphragms, allows for progressive compression and optimized biasing rates to achieve desired performance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional biasing methods are used, then the transducer can operate, but force and power output are limited
Solution Approach 1:
The patent applies parameter changes by transitioning from conventional positive rate spring biasing to negative rate spring biasing. This changes the mechanical characteristic of the biasing element, allowing the EAP film to operate in a different region of its force-displacement curve where higher forces are generated during activation, thereby increasing power output without adding more EAP material.
Solution Approach 2:
The patent implements dynamics by making the biasing system adjustable and tunable. The negative rate spring mechanism can be configured with different spring rates and pre-loads to optimize performance for specific applications. This dynamic adjustment capability allows the system to adapt to different operating conditions and maximize power output from the same EAP material.
2Force
If more EAP material is used, then force and stroke output increase, but device size and cost increase
Solution Approach 1:
The patent changes the operational parameters of the EAP material by using negative rate spring biasing to increase the electric field strength and force density during activation. This allows existing EAP material to generate higher forces, eliminating the need to increase device size or material quantity to achieve greater force output.
Solution Approach 2:
The patent creates a composite system combining EAP material with negative rate spring biasing mechanisms. This composite approach leverages the electroactive properties of the polymer together with the mechanical energy storage and release characteristics of the negative rate spring, achieving enhanced force output from the same EAP material volume.
3Strength
If pre-straining is increased to improve dielectric strength, then higher field potentials are achieved, but the risk of material damage increases
Solution Approach 1:
The patent applies dynamics by implementing adjustable and tunable pre-straining levels through the negative rate spring mechanism. The system can dynamically adjust the pre-load applied to the EAP film, allowing operation at optimal dielectric strength levels without consistently maintaining maximum pre-strain that could lead to material fatigue and damage over time.
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
This approach enables increased force and stroke output while maintaining or reducing the amount of EAP material, leading to improved power and efficiency in applications like pumps, valves, and sensors, with tunable biasing mechanisms for specific performance requirements.
Implementation Method 1
When a voltage difference is applied to the electrodes, the oppositely-charged members attract each other producing pressure upon the polymer therebetween.
Implementation Method 2
The like (same) charge distributed across each elastic film electrode causes the conductive particles embedded within the film to repel one another expanding the elastic electrodes and dielectric attached polymer film.
Implementation Method 3
The selection of biasing according to the invention follows a negative bias spring model in which the spring force increases as the transducer's electroactive film moves from a preloaded position to its most highly activated position.
Data Source
Figure 1~3B
Figure 4~6
Figure 7~9
AI summary
Electroactive polymer transducers are disclosed. They are biased in a manner that provides for increased force and/or stroke output, thereby offering improved work potential and power output capacity. The biasing may offer additional or alternate functional advantage in terms of matching transducer performance with a given application such as a normally-closed valve. The improved biasing (including increased output biasing) may utilize negative spring rate biasing and/or a combination of negative or zero-rate biasing with positive rate biasing to achieve the desired ends.