Backlit Force Capacitive Touch Sensor with Segmented Conductive Plane
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Solution Overview
Problem
Capacitive touch sensors are prone to false triggering due to water, oil, mud, and metallic objects, and suffer from multiple activations when multiple sensors are closely arranged, with existing designs being mechanically thin and light opaque, preventing backlighting.
Innovation Solution
A capacitive touch sensor design featuring a substrate with a capacitive sensor element, a deformable spacer, and a conductive plane that changes capacitance upon mechanical force, combined with backlighting using light sources like LEDs or OLEDs through a light transmission cavity, allowing light to pass through for visual feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a deformable metal target layer is used to detect capacitance changes, then the sensor can detect touch input, but the metal layer is light opaque and prevents backlighting
Solution Approach 1:
The patent divides the target layer into multiple conductive elements (first conductive element and second conductive element) separated by a non-conductive material. This segmentation allows light to pass through the gaps between elements while maintaining capacitive coupling for touch detection, resolving the contradiction between backlighting capability and touch detection function.
2Area of stationary object
If capacitive touch sensors are arranged in a matrix with close proximity, then space is efficiently utilized, but neighboring sensors may be accidentally activated by the same touch
Solution Approach 1:
The patent segments the conductive target layer into distinct first and second conductive elements that are electrically isolated by non-conductive material. This segmentation creates independent capacitive coupling zones for each sensor element, preventing cross-activation between neighboring sensors while maintaining high array density.
Solution Approach 2:
The patent applies different electrical properties to different regions of the target layer - conductive regions for capacitive coupling and non-conductive regions for electrical isolation. This local differentiation of material properties enables precise control of capacitive coupling zones, ensuring that each sensor responds only to touches within its specific activation zone.
3Length of moving object
If simple flat spacer layers less than 50 micrometers thick are used, then the device is mechanically thin, but the structure lacks mechanical strength and deformability for physical force sensing
Solution Approach 1:
The patent uses a composite structure combining conductive elements, non-conductive material, and deformable spacer layers. This composite design provides both the mechanical strength needed for physical force sensing and the deformability required for capacitance change detection, while maintaining a thin overall profile.
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 design enhances immunity to false triggering and liquid contamination, prevents multiple sensor activations, and enables effective backlighting for improved visibility and user feedback.
Implementation Method 1
the capacitive sensor element changes capacitance when a mechanical force is applied to the conductive plane biased toward the capacitive sensor element
Implementation Method 2
backlighting using light sources like LEDs or OLEDs through a light transmission cavity, allowing light to pass through for visual feedback
Data Source
AI summary
A physical force capacitive touch sensor comprises a capacitive sensor element on a substrate, a physically deformable electrically insulating spacer over the capacitive sensor element and a conductive plane over the physically deformable electrically insulating spacer. A protective fascia may be placed over the conductive plane provides an environmental seal for physical and weather protection, but is not essential to operation of the capacitive touch sensor. Back lighting is accomplished with a light transmissive layer having a suspended metal target proximate to the capacitive touch sensor plate. When the light transmissive layer and metal target are displaced toward the capacitive touch sensor plate the capacitance value of the capacitive touch sensor plate changes and that change is detected.