Haptic Display Electrodes with Simultaneous Sensing and Actuation
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Solution Overview
Problem
Current touch interfaces for surface haptic devices lack effective multi-point haptics, as existing technologies like vibration-based systems and electrostatic actuation face challenges in providing independent haptic effects to separate fingers and accurate multi-touch sensing due to issues with electrode placement, resistance, and interference between haptic and sensing mechanisms.
Innovation Solution
The implementation of a touch interface with simultaneous sensing and actuation (SSA) using mirrored electrodes, where a top layer of electrodes for haptics and a bottom layer for sensing are aligned in a similar pattern, enabling strong capacitive coupling and independent control of haptic effects on each finger, while also addressing the problem of scratches by allowing sensing to continue even if the top surface electrodes are compromised.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If vibration-based haptic feedback is used, then tactile feedback is provided to the user, but the entire device vibrates causing effects to be felt throughout the hand rather than localized to the fingertip
Solution Approach 1:
The device divides the haptic actuation function into multiple independent electrostatic actuators distributed across the touch surface, each capable of generating localized electrostatic forces at specific fingertips without causing whole-device vibration. This segmentation allows independent control of haptic effects at different locations.
Solution Approach 2:
The patent replaces mechanical vibration-based haptic actuators with electrostatic actuators that generate forces through electric fields. This substitution eliminates mechanical vibrations that propagate through the device structure, confining haptic effects to the immediate contact point between fingertip and screen.
2Adaptability or versatility
If multiple electrodes are used for electrostatic haptics, then multi-point haptics capability is enabled, but electrical connection to non-edge electrodes becomes difficult resulting in slow charging
Solution Approach 1:
The patent transitions from planar electrode layouts to a three-dimensional stacked architecture with transparent conductive layers arranged at different depths within the substrate. This vertical stacking enables electrical connection to all electrodes through conductive traces on multiple layers, eliminating the charging speed limitation of edge-only connections while maintaining multi-point haptics capability across the entire surface.
3Measurement precision
If projected capacitive sensing is used for multi-touch detection, then fingertip locations can be sensed, but the electrostatic haptics and sensing mechanisms interfere with each other
Solution Approach 1:
The patent segments the electrode functions by assigning different roles to electrodes at different locations and time periods. Haptic electrodes and sensing electrodes are spatially and temporally separated, allowing both functions to operate independently without interference. The controller alternates between haptic actuation and sensing modes for different electrode groups.
Solution Approach 2:
The controller implements periodic switching between haptic actuation and capacitance sensing operations. During haptic mode, electrostatic forces are applied to designated electrodes; during sensing mode, the same or different electrodes are used to measure fingertip locations. This time-division multiplexing eliminates mutual interference while enabling both functions.
4Device complexity
If a single electrode layer is used for both haptics and sensing, then device complexity is reduced, but scratches on the surface compromise both functions
Solution Approach 1:
The patent adds a vertical dimension to the electrode architecture by stacking multiple transparent conductive layers at different depths within the substrate. This three-dimensional arrangement ensures that scratches on the surface affect only the top layer, leaving lower layers intact and functional. Both haptic and sensing functions can continue using undamaged electrodes from deeper layers.
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 reliable multi-point haptics with improved signal-to-noise ratio and resolution, allowing for accurate finger position sensing and independent control of haptic effects on each finger, while ensuring that sensing remains functional even if the top surface electrodes are scratched.
Implementation Method 1
a finger touch capacitively couples a respective one or more bottom surface or deeper layer electrodes
Implementation Method 2
The electric field is established at the point of contact between the fingertip and the touch surface
Implementation Method 3
electrostatic actuation has been explored as a means to generate vibrations localized to the fingertip
Implementation Method 4
electrostatic forces to create vibrations of the fingertip
Data Source
AI summary
A haptic touch interface having simultaneous sensing and actuation including an insulating substrate having a front surface and a rear surface and one or more front surface electrodes connected to the front surface of the substrate, wherein the front surface electrodes are arranged in a first pattern. The touch interface further includes one or more rear surface electrodes connected to the rear surface of the substrate, wherein the rear surface electrodes are arranged in a second pattern and the front surface electrodes have a substantial mutual capacitance with the rear surface electrodes. Flying logic is used to control voltages applied to at least one of the front and rear surface electrodes.