Bipolar Haptics with Segmented Electrodes for Multi-Touch
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Solution Overview
Problem
Existing haptic devices struggle to provide robust multi-touch sensing and electroadhesion-based haptics simultaneously, especially in transparent touch surfaces, due to challenges with voltage distribution, scratch resistance, and the need for reliable friction modulation across varying conditions.
Innovation Solution
An integrated system with a substrate having top and bottom electrodes, a position sensor, and a friction modulator that applies bipolar electrical signals to detect touch locations and modulate friction, utilizing a layered electrode configuration for capacitive coupling and robust sensing, while ensuring durability and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electroadhesion is applied on a transparent touch surface, then haptic feedback is provided to the user, but the surface cannot reliably track multiple finger positions simultaneously
Solution Approach 1:
The touch surface is divided into multiple independently addressable electrode regions. Each region can be independently controlled for haptic feedback while the entire surface maintains capacitive sensing capability for multi-touch location detection. This segmentation allows simultaneous operation of haptic actuation and precise touch tracking without interference.
2Force
If voltage is increased to improve electroadhesion effect, then friction modulation is enhanced, but radiated emissions and safety concerns increase
Solution Approach 1:
High voltage is applied only to specific localized electrode regions where haptic feedback is needed, rather than across the entire surface. This localized application reduces overall radiated emissions and improves safety while maintaining strong electroadhesion effect at the point of contact. The voltage distribution is optimized to provide maximum friction modulation with minimum harmful emissions.
3Strength
If a top insulating layer is added to protect the touch surface, then durability is improved, but voltage drop across the insulating layer reduces the available voltage for electroadhesion
Solution Approach 1:
The insulating layer thickness and material properties are optimized to minimize voltage drop while maintaining adequate protection. The electrode geometry and spacing are adjusted to compensate for the voltage loss across the insulating layer. By changing these parameters, the system achieves both durable surface protection and sufficient voltage for effective electroadhesion.
4Force
If the touch surface is made conducting to improve electroadhesion, then friction modulation is enhanced, but the surface becomes more susceptible to abrasion and wear
Solution Approach 1:
The touch surface uses a composite structure combining transparent conductive material with protective insulating coating. The conductive layer provides the necessary electrical properties for electroadhesion, while the insulating coating provides abrasion and wear resistance. This composite approach allows the surface to maintain both electrical functionality and mechanical durability.
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
Enables highly robust multi-touch sensing and effective electroadhesion-based haptics, maintaining performance across different grounding conditions and environmental factors, with reduced radiated emissions and improved safety features.
Implementation Method 1
Electroadhesion depends on the formation of an electric field that acts across the air gap that exists between the fingertip and the surface it is touching. The electric field in the air gap exerts an attractive force between bound or polarized charge contained in the skin and the surface.
Implementation Method 2
a first set of electrodes arranged on a top surface of the substrate and a second set of electrodes arranged on a bottom surface of the substrate
Data Source
AI summary
An indirect haptic device includes a substrate having a top surface and a bottom surface, and a plurality of haptic electrodes and a plurality of island electrodes arranged on the top surface. The device further includes a plurality of transmit electrodes and a plurality of receive electrodes arranged on the bottom surface, a position sensor, and a friction modulator. The device further includes a control device configured to apply bipolar electrical signals to the plurality of transmit electrodes to detect touch locations of a user's appendage and to modulate the friction between the user's appendage and the touch surface. Each of the plurality of haptic electrodes are substantially aligned with and capacitively coupled to a corresponding two of the plurality of transmit electrodes.