Flexible Force Sensor With Tilted Electrodes for Pressure and Shear Detection
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Solution Overview
Problem
There is a need for a force sensor that can be arranged on a flexible support without preventing flexing, capable of sensing both shear forces and pressure, and suitable for high-volume manufacturing.
Innovation Solution
A force sensing device comprising a flexible substrate with sensor units having first and second electrodes, an intermediate structure, trenches, bridging structures, and a rigid projecting structure embedded in elastic material, allowing decoupled detection of pressure and shear forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a force sensor is arranged on a flexible support, then the sensor can be used in flexible electronics and soft robots, but the sensor may prevent flexing of the support
Solution Approach 1:
The force sensor is divided into multiple discrete sensor units arranged in an array on the flexible substrate. Each sensor unit is electrically isolated and mechanically segmented, allowing the flexible substrate to flex between units while maintaining sensing capability. This segmentation resolves the contradiction by enabling both flexibility (through substrate bending between units) and structural integrity (through distributed sensing elements).
Solution Approach 2:
The sensor employs thin-film electrodes and intermediate structures deposited on a flexible substrate. The thin-film nature of the components allows the overall structure to flex without breaking, while still providing sufficient mechanical stability for force sensing. This approach maintains both flexibility and structural rigidity simultaneously.
2Adaptability or versatility
If the sensor unit uses multiple electrodes and layers, then it can detect shear forces and pressure independently, but the device complexity increases
Solution Approach 1:
The sensor unit uses a multi-layer electrode structure where the same basic configuration (first layer electrodes, intermediate structure, second layer electrodes) serves multiple detection functions. By arranging electrodes in specific patterns and utilizing the intermediate structure's mechanical properties, the system can detect both shear forces and pressure using the same structural framework, reducing overall complexity despite enhanced capabilities.
Solution Approach 2:
The sensor adds a third dimension to force detection by measuring not only in-plane shear forces but also out-of-plane pressure forces. This is achieved by incorporating the intermediate structure between electrode layers that can deform in response to pressure, while the electrode patterns detect shear forces. This dimensional expansion enables multi-axis force sensing without proportionally increasing structural complexity.
3Measurement precision
If the sensor unit is made rigid for accurate force detection, then measurement precision improves, but the flexible substrate cannot flex
Solution Approach 1:
The sensor is segmented into discrete units with rigid sensing elements distributed across a flexible substrate. Each sensor unit maintains rigid internal structures for accurate local force measurement, while the flexible substrate connects these units, allowing overall bending. This segmentation enables simultaneous rigidity (for measurement precision) and flexibility (for adaptability).
Solution Approach 2:
The sensor employs composite construction combining rigid materials for the electrode layers and intermediate structure with flexible materials for the substrate and encapsulation. This composite approach allows the rigid components to provide measurement precision while the flexible components enable substrate bending, resolving the contradiction between rigidity and flexibility.
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 device accurately senses forces in multiple dimensions, including shear and pressure, while maintaining flexibility and durability, facilitating high-volume manufacturing and three-dimensional force detection.
Implementation Method 1
an intermediate structure arranged between the first layer and the second layer, wherein the intermediate structure is configured to change characteristics of the force sensing device between the at least one first electrode and the at least one second electrode upon a force being received by the sensor unit
Implementation Method 2
a rigid projecting structure arranged on the second layer projecting therefrom and connected to the at least one second electrode, wherein the rigid projecting structure is embedded in an elastic material for allowing the rigid projecting structure to be tilted in relation to the first layer upon receiving a force
Implementation Method 3
the rigid projecting structure is embedded in an elastic material for allowing the rigid projecting structure to be tilted in relation to the first layer upon receiving a force
Data Source
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Figure 5
AI summary
A force sensing device (100) comprises: a flexible substrate (102); a sensor unit (112) arranged thereon comprising: at least one first electrode (114a-d) in a first layer (116); at least one second electrode (120) in a second layer (122); wherein a plurality of first electrodes (114a-d) and/or second electrodes is provided; an intermediate structure (130) between the first and second electrodes for changing characteristics upon a force being received; trench(es) (140) in the second layer (122) partially surrounding the second electrode(s) (120), wherein bridging structure(s) (142) provides an anchoring position defining a fixed relation between the first and second layers (116; 122); a rigid projecting structure (150) projecting from the second layer (122) and connected to the second electrode(s) (120), wherein the rigid projecting structure (150) is embedded in an elastic material (152) for allowing the rigid projecting structure (150) to be tilted in relation to the first layer (116).