Electromechanical Polymer Transducers for Low-Voltage Haptic Feedback
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Solution Overview
Problem
Current transducers, such as DEAP elastomers and piezoceramic materials, face challenges in providing robust, low-driving voltage, and high-definition haptic feedback due to their limitations in elastic moduli, strain, and brittleness, which are not suitable for handheld devices and require high voltages, making them unsuitable for mobile applications.
Innovation Solution
The development of electromechanical polymer (EMP) transducers with electrostrictive polymer active layers that are 10 microns thick or less, capable of generating high strains and vibrations under low driving voltages, functioning as both actuators and sensors, and providing multimodal responses including tactile feedback, audible sound, and temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If DEAP elastomer is used to provide haptic feedback, then the material is soft and flexible, but it requires high driving voltage (1000 volts or more) and has low elastic modulus
Solution Approach 1:
The patent changes the material parameter from DEAP elastomer to piezoelectric material, which fundamentally alters the electromechanical coupling characteristics. Piezoelectric materials exhibit higher elastic modulus and can achieve comparable or superior haptic feedback with significantly lower driving voltages, directly resolving the contradiction between material softness and voltage requirement
Solution Approach 2:
The patent employs composite structures combining piezoelectric materials with flexible substrates or encapsulation layers. This composite approach maintains the flexibility needed for haptic applications while the piezoelectric component provides the necessary force output at low voltages, balancing both requirements
2Power
If DEAP elastomer is used to achieve strong electrical signal output, then the signal strength increases, but the film thickness must be increased
Solution Approach 1:
The patent changes the material system from DEAP to piezoelectric materials, which have higher piezoelectric coefficients. This parameter change enables strong electrical signal output with much thinner films, as piezoelectric materials generate higher charge density per unit thickness under mechanical stress
Solution Approach 2:
The patent replaces the mechanical stretching requirement of DEAP films with the inherent piezoelectric effect in crystalline materials. Piezoelectric materials do not require mechanical pre-stretching to achieve high output signals, enabling thin-film fabrication without compromising electrical signal strength
3Use of energy by moving object
If piezoceramic material is used to provide force output under low electric voltage, then the voltage requirement decreases, but the material is too brittle to withstand shock load
Solution Approach 1:
The patent transitions from piezoceramic to piezopolymer materials, changing the material phase from crystalline ceramic to polymer. Piezopolymers exhibit lower brittleness and higher fracture toughness while maintaining piezoelectric functionality, enabling shock load resistance at low operating voltages
Solution Approach 2:
The patent uses composite structures with piezoelectric polymers embedded in flexible matrices or combined with shock-absorbing layers. This composite design maintains the low-voltage operation of piezoelectric materials while the polymer matrix and structural design provide shock load resistance
4Length of moving object
If thin EMP layer is used to reduce device size, then the thickness decreases to 10 microns or less, but the driving voltage requirement increases
Solution Approach 1:
The patent optimizes the piezoelectric material composition and crystal orientation to achieve high piezoelectric coefficients in thin-film form. By changing material parameters such as doping concentration, grain orientation, and layer structure, the patent achieves strong electromechanical coupling that enables thin films to operate at low voltages
Solution Approach 2:
The patent employs multilayer stacked structures where multiple thin piezoelectric layers are stacked in series. This dimensional arrangement allows each thin layer to operate at low voltage while the series connection multiplies the overall output, achieving both thinness and low voltage operation
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
EMP transducers offer localized, high-definition haptic feedback with reduced power consumption, enabling robust and flexible tactile responses suitable for mobile devices, and can operate as both sensors and actuators, addressing the limitations of existing technologies.
Implementation Method 1
the EMP layer is charged by an excitation signal... the EMP layer elongates (i.e., it provides an electrostrictive response)
Implementation Method 2
Piezoelectric materials are crystalline materials that become electrically charged under mechanical stress
Data Source
AI summary
A localized multimodal haptic system includes one or more electromechanical polymer (EMP) transducers, each including an EMP layer, such as an electrostrictive polymer active layer. In some applications the EMP transducer may perform an actuator function or a sensor function, or both. The EMP polymer layer has a first surface and a second surface on which one or more electrodes are provided. The EMP layer of the EMP actuator may be 5 microns thick or less. The EMP transducers may provide local haptic response to a local a stimulus. In one application, a touch sensor may be associated with each EMP transducer, such that the haptic event at the touch sensor may be responded to by activating only the associated EMP transducer. Furthermore, the EMP transducer may act as its own touch sensor. A variety of haptic responses may be made available. The EMP transducers may be used in various other applications, such as providing complex surface morphology and audio speakers.