One-Sided Thin-Film Touch Sensor Layout to Prevent Backside Triggers
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Solution Overview
Problem
Conventional capacitive touch sensors are costly and complex, making them impractical for low-cost applications like games, toys, and interactive books due to their two-sided sensitivity and requirement for expensive components.
Innovation Solution
A thin film capacitive touch sensor system with a capacitive touch sensor layer, a separation layer, and a conductive ground plane or air gap layer to create a one-sided sensing capability, reducing complexity and cost while maintaining sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional capacitive touch sensors are used, then touch sensing capability is achieved, but cost and device complexity increase
Solution Approach 1:
The sensor is divided into multiple independent trace elements arranged in a matrix pattern, where each trace element can be independently controlled and read. This segmentation allows the sensor to achieve full touch sensing capability with simpler individual elements, reducing overall system complexity while maintaining reliability.
Solution Approach 2:
The same trace elements serve multiple functions: they act as both driving electrodes and sensing electrodes, and the same read circuitry is used for all trace elements through multiplexing. This multi-functionality reduces the number of dedicated components needed, thereby reducing device complexity while maintaining sensing capability.
2Reliability
If conventional capacitive touch sensors are used, then touch sensing capability is achieved, but cost increases
Solution Approach 1:
The read circuitry is shared across all trace elements through time-multiplexed operation, eliminating the need for dedicated read circuits for each element. This universal use of read circuitry significantly reduces component count and manufacturing cost while maintaining full sensing capability across the sensor array.
Solution Approach 2:
The sensor uses thin-film deposited trace elements on a flexible substrate, which can be manufactured using low-cost deposition techniques. This approach replaces expensive rigid capacitor structures with affordable thin-film technology, reducing manufacturing cost while maintaining sensing reliability.
3Ease of manufacture
If thin film capacitive touch sensors are used, then cost is reduced, but two-sided sensitivity causes false triggering
Solution Approach 1:
The capacitive field is localized to the front surface by designing trace elements that extend only to the front contact layer, with deliberate gaps at the back surface. This local concentration of capacitance at the front ensures that touches on the backside do not significantly affect the measured capacitance, eliminating false triggering while maintaining low-cost thin-film construction.
Solution Approach 2:
Instead of trying to prevent backside touches from affecting the sensor, the design accepts that backside touches occur but configures the trace elements such that their capacitive effect is minimal at the back surface. This inversion of the problem-solving approach—accepting the phenomenon rather than preventing it—eliminates false triggering while maintaining manufacturing simplicity.
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 inexpensive, simple, and effective touch sensing in handheld devices and interactive applications, such as games, toys, and books, with reduced false triggering and improved user interaction.
Implementation Method 1
a conductive ground plane layer adjacent the separation layer to shield a backside of the capacitive touch sensor layer
Implementation Method 2
A capacitive touch sensor typically is a small capacitor enclosed in an electrical insulator. The capacitor is a device that has an ability to store an electrical charge, referred to as capacitance.
Data Source
AI summary
Thin film capacitive touch sensors and applications thereof are described herein. Embodiments include construction of one-sided and two-sided thin film capacitive touch sensors with partial fill patterns, one-sided thin film capacitive touch sensors including conductive ground plane layers, one-sided thin film capacitive touch sensors including air gap layers, one-sided thin film capacitive touch sensors including a combination of both separation layers to create air gap layers and conductive ground plane layers.