Capacitive Touch Sensor Resistive Thread Multi-Touch
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Solution Overview
Problem
Capacitive touch sensors struggle with accurate multi-touch detection, often resulting in 'ghosting' or misplaced location sensing, and face challenges in production cost, weight, washability, and bio-compatibility, especially when implementing large sensing areas.
Innovation Solution
A capacitive touch sensor utilizing a support layer with electrically resistive threadlike elements, such as biopolymer-based yarns filled with conductive materials, integrated into fabrics, which change capacitance values upon touch, allowing for efficient multi-touch detection without 'ghosting' and being lightweight, washable, and bio-compatible.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Mutual Capacitance Sensing technique is used to solve ghosting problem, then multi-touch detection accuracy is improved, but device complexity and manufacturing difficulty increase significantly
Solution Approach 1:
The patent divides the sensing function into independent sensing threads woven into the fabric. Each thread operates independently as a self-capacitance sensor, eliminating the need for complex mutual capacitance measurements between intersecting wires. This segmentation approach maintains multi-touch detection capability while greatly simplifying the overall system architecture.
Solution Approach 2:
The patent replaces the complex electrical measurement system of mutual capacitance sensing with a simpler self-capacitance measurement approach. By using resistive threadlike elements that generate their own sensing signal, the system eliminates the need for complex controller-based sequential evaluation of mutual capacitance values at wire intersections.
2Measurement precision
If traditional capacitive touch sensor with metal sensing wires is used, then sensing accuracy is achieved, but weight and washability are compromised
Solution Approach 1:
The patent changes the material parameters of the sensing elements from heavy metal wires to lightweight resistive threadlike elements. These threads have controlled electrical resistance properties that enable capacitive sensing functionality while dramatically reducing weight. The resistive nature of the threads allows them to function as both structural and sensing components.
Solution Approach 2:
The patent uses composite threadlike elements that combine resistive materials with textile properties. These composite threads integrate sensing functionality into fabric structures, enabling the sensor to be lightweight, flexible, and washable while maintaining touch detection accuracy. The composite nature allows simultaneous achievement of electrical functionality and mechanical flexibility.
3Measurement precision
If high frequency clock and high accuracy measurement are used in mutual capacitance sensing, then measurement precision is improved, but energy consumption increases
Solution Approach 1:
The resistive threadlike elements serve multiple functions simultaneously: they provide structural support, enable sensing through their resistance properties, and generate the necessary electrical signals for detection. This self-service approach eliminates the need for separate high-frequency clock circuits and complex measurement systems, thereby reducing energy consumption while maintaining measurement precision.
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 accurate multi-touch detection without 'ghosting' and reduces production costs, while being lightweight, washable, and bio-compatible, by using resistive threadlike elements in fabrics that change capacitance values upon touch.
Implementation Method 1
each sensing threadlike element has a capacitance value that changes when an object touches it
Implementation Method 2
the electrical resistance per unit of length of each electrically resistive threadlike element is comprised between 10 kΩ/m and 10 MΩ/m
Data Source
AI summary
It is disclosed a capacitive touch sensor (10) comprising a support layer (1) having a plurality of sensing threadlike elements (2) coupled thereto and configured to be electrically connected to a detection device (5) for evaluating the capacitance value (C) of each sensing threadlike element (2) of said plurality of sensing threadlike elements, characterized in that said sensing threadlike elements (2) comprise a plurality of electrically resistive threadlike elements (2r), wherein the electrical resistance per unit of length of each electrically resistive threadlike element (2r) is comprised between 10 kΩ/m and 10 MΩ/m. An article comprising the capacitive touch sensor (10) and a method for detecting a touch event on a support layer (1) are also disclosed.