Electroactive Polymer Haptic Layer with Negative CTE Coating
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Solution Overview
Problem
Existing touch-sensitive devices face challenges in providing immediate and delicate haptic feedback due to the limitations of vibration motors like eccentric rotating mass (ERM) and linear resonant actuators, which require increased mass for higher vibration levels, have slow response speeds, and are opaque, making them unsuitable for placement above display panels.
Innovation Solution
A touch-sensitive element featuring an electroactive layer with a hard coating layer having a negative coefficient of thermal expansion, which enhances vibration efficiency and surface hardness, allowing for a transparent and sensitive haptic experience at low driving voltage, and improves impact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If vibration motors (ERM or LRA) are used to increase vibration level, then vibration strength is improved, but device mass must be increased and response speed becomes slow
Solution Approach 1:
The patent replaces traditional mechanical vibration motors (ERM/LRA) with an electroactive polymer-based haptic device that generates vibrations through electrostatic actuation. This substitution eliminates the need for heavy rotating masses while achieving comparable or superior vibration strength through direct electrostatic force application to the polymer membrane.
Solution Approach 2:
The patent changes the fundamental actuation mechanism from mechanical rotation to electrostatic field application. By controlling voltage parameters applied to the electroactive polymer, the system achieves variable vibration strength and frequency without changing physical mass, enabling rapid parameter adjustment for different haptic effects.
2Reliability
If vibration motors are used, then vibration feedback is provided, but response speed becomes very slow
Solution Approach 1:
The electroactive polymer system replaces mechanical inertia-based actuation with electrostatic field-driven deformation. This allows near-instantaneous response to voltage changes, enabling the haptic device to quickly follow touch events and provide immediate feedback without the lag inherent in mechanical vibration motors.
Solution Approach 2:
The patent utilizes high-frequency periodic voltage application to the electroactive polymer to generate controlled vibrations. The electrostatic actuation can be modulated at various frequencies to produce different haptic sensations, with the ability to rapidly switch between frequencies for dynamic feedback scenarios.
3Force
If eccentric rotating mass or resonant actuator is used, then vibration is generated, but the material is opaque making it difficult to dispose above display panel
Solution Approach 1:
The patent changes the material composition from opaque metals and ceramics to transparent electroactive polymers and transparent conductive oxides. This material parameter change enables the haptic device to be positioned above the display panel without blocking light, maintaining display visibility while providing haptic feedback.
Solution Approach 2:
The patent employs composite structures combining transparent electroactive polymer membranes with transparent conductive oxide electrodes. This composite approach maintains both the electrostatic actuation functionality and optical transparency, allowing the haptic device to be integrated into the display structure without compromising visual output.
4Reliability
If shape memory alloy or electro-active ceramics are used, then haptic effect is achieved, but the material has low durability against external impact and is opaque
Solution Approach 1:
The patent changes from brittle ceramics and metal alloys to flexible electroactive polymer materials. The polymer's inherent flexibility and elasticity provide superior impact resistance, as it can absorb external shocks without fracturing, while maintaining its electrostatic actuation properties for haptic feedback generation.
Solution Approach 2:
The patent uses composite structures with flexible polymer substrates and thin-film electrodes that provide both haptic functionality and mechanical durability. The flexible nature of the polymer composite allows the device to withstand external impacts and bending stresses that would damage rigid ceramic or metal-based haptic actuators.
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 significantly increases vibration acceleration and reduces the required driving voltage, providing a transparent and durable touch-sensitive element with enhanced haptic feedback and impact resistance.
Implementation Method 1
an electroactive layer which is formed of electroactive polymer (EAP)
Implementation Method 2
a hard coating layer which is disposed on the electroactive layer and the electrode and has a negative coefficient of thermal expansion (CTE)
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
Provided are a touch sensitive element and a display device including the same. According to the exemplary embodiment of the present disclosure, a touch sensitive element, includes: an electroactive layer which is formed of electroactive polymer (EAP); an electrode which is disposed on at least one surface of the electroactive layer; and a hard coating layer which is disposed on the electroactive layer and the electrode and has a negative coefficient of thermal expansion (CTE). Therefore, vibration effect in a vertical direction is maximized and impact resistance may be improved.