Touch Surface Sensor Stack for Proximity and Force Measurement
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Solution Overview
Problem
Existing touch sensors are unable to accurately detect and measure the intensity of a touch force, as they typically employ all-or-nothing detection methods that do not account for variations in force application.
Innovation Solution
A combined proximity and force sensor system is developed, featuring a capacitive sensor and a force sensor based on conductive or semi-conductive nanoparticles, which allows for precise detection and measurement of touch force by adjusting sensitivity and compensating for environmental factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitive or resistive sensors are used for touch detection, then proximity and touch can be detected, but the intensity of the applied force cannot be measured
Solution Approach 1:
The patent combines a capacitive sensor and a force sensor into a single integrated sensor unit. The capacitive sensor detects proximity and touch events, while the force sensor (using piezoresistive or piezoelectric elements) measures the intensity of the applied force. By merging these two sensor types into one device, the system achieves both touch detection and force quantification without requiring separate sensor systems, thus resolving the contradiction between measurement precision and device complexity.
2Measurement precision
If ultrasound devices with piezoelectric elements are used for combined proximity and force detection, then both functions can be detected, but energy consumption increases substantially
Solution Approach 1:
The patent replaces the ultrasound-based detection system with an electrical field-based capacitive sensor for proximity detection. Instead of using piezoelectric elements that generate and detect ultrasound waves (which consume substantial energy), the capacitive sensor detects changes in electrical capacitance caused by the proximity of conductive objects. This substitution dramatically reduces energy consumption while maintaining the ability to detect both proximity and touch events.
3Measurement precision
If multiple sensor systems are superimposed for combined detection, then both proximity and force can be detected, but the touch surface becomes relatively thick
Solution Approach 1:
The patent merges the capacitive sensor and force sensor into a single integrated sensor unit with a common substrate and shared structural elements. The capacitive sensor layers (conductive electrodes and dielectric layers) are combined with the force sensor elements (piezoresistive or piezoelectric layers) in a unified structure. This integration allows both proximity and force detection functions to coexist in a thin profile, avoiding the thickness increase that would result from superimposing separate sensor systems.
4Measurement precision
If force sensors are made highly sensitive to detect touch intensity, then measurement precision improves, but sensitivity to environmental factors such as temperature increases causing drift
Solution Approach 1:
The patent incorporates temperature compensation mechanisms that use feedback from temperature sensors to adjust the readings of the force sensor. By continuously monitoring the temperature and applying correction algorithms, the system compensates for the drift caused by thermal effects on the piezoresistive or piezoelectric elements. This feedback approach allows the force sensor to maintain high sensitivity to touch intensity while reducing the impact of environmental temperature variations on measurement accuracy.
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 system effectively measures touch force intensity, reduces drift and hysteresis phenomena, and is adaptable to both flexible and rigid substrates, enhancing the interactivity and functionality of touch-sensitive surfaces.
Implementation Method 1
The capacitive detection detects the presence of an hovering object at a short distance from the sensor, by changing the capacitance of an electrical circuit due to the presence of this object.
Implementation Method 2
a force sensor consisting of an assembly of conductive or semi-conductive nanoparticles in colloidal suspension in a ligand which is electrically insulating and deposited on said substrate
Data Source
AI summary
The invention relates to a touch surface comprising:a carrier substrate (510, 610) comprising 2 opposite faces (511, 512) one (511) of the faces being exposed to touch;and comprising on the face (512) opposite the face (511) exposed to touch, a combined proximity and force sensor (300) comprising:an insulating substrate (210); —conductive tracks (221, 222) deposited on said substrate (210) and configured to produce a capacitive sensor;a force sensor (230) consisting of an assembly of conductive nanoparticles in colloidal suspension in an electrically insulating ligand;a protective layer (310) covering the conductive tracks and the nanoparticle assembly.The invention also relates to a method for detecting and measuring the force applied by a touch against such a touch surface.