Piezoresistive Flexible Sensor Structure for Wearable Bending Detection

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Solution Overview

Problem

Existing sensors integrated into intelligent wearable devices struggle with accuracy and convenience in detecting bending conditions, which is crucial for precise human body movement recognition.

Innovation Solution

A sensor comprising a flexible substrate with a multilayer structure that includes conductive layers, where the resistance of a second conductive layer changes with substrate deformation, allowing for accurate detection of bending conditions through differential processing of signals from symmetrically arranged sensing structures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a sensor uses a simple single-layer conductive structure, then the device complexity is reduced, but the measurement precision of bending conditions deteriorates

Engineering Contradiction:

Improvesensor structure complexityVSAvoidbending detection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The sensor is divided into multiple independent conductive layers (first conductive layer, second conductive layer, third conductive layer) with distinct functions. The second conductive layer specifically detects bending through resistance changes, while other layers provide structural support and electrical connections, allowing each segment to be optimized for its specific function.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The sensor employs a composite multilayer structure combining conductive materials with different electrical conductivity properties. The second conductive layer has lower electrical conductivity to enhance its piezoresistive effect for bending detection, while other layers use higher conductivity materials for efficient signal transmission and grounding.

Inventive Principle:

Principle #40Composite materials

2Measurement precision

If a sensor integrates multiple functional layers, then the measurement precision improves, but the device complexity increases

Engineering Contradiction:

Improvebending detection accuracyVSAvoidsensor structure complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Multiple sensing functions are merged into a compact multilayer structure where the first, second, and third conductive layers work together in close proximity. This integration allows the sensor to detect bending conditions effectively while maintaining a space-efficient design suitable for wearable devices.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

Different regions of the sensor have specialized properties: the second conductive layer is positioned and configured specifically where bending detection is most critical, with its unique low conductivity property localized to maximize piezoresistive effect in the bending zone while other areas maintain structural and electrical functions.

Inventive Principle:

Principle #3Local quality

3Measurement precision

If the second conductive layer has low electrical conductivity, then the sensitivity to bending deformation improves, but the signal strength deteriorates

Engineering Contradiction:

Improvebending sensitivityVSAvoidsignal strength

Core Design Contradiction:

Measurement precisionVSPower

Solution Approach 1:

The first and third conductive layers with higher electrical conductivity act as intermediaries that couple the weak signal from the low-conductivity second layer to the external circuitry. These intermediary layers amplify and transmit the bending-induced resistance changes from the second layer without directly experiencing the bending themselves.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The electrical conductivity parameter is strategically varied across different layers: the second layer uses low conductivity to maximize piezoresistive sensitivity to bending, while the first and third layers use high conductivity to ensure strong signal transmission. This parameter optimization balances sensitivity and signal strength requirements.

Inventive Principle:

Principle #35Parameter changes

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

Enhances the accuracy and convenience of detecting bending conditions by simplifying the collection of resistance parameters, reducing common-mode interference, and improving sensitivity through differential signal processing.

Implementation Method 1

a resistance of the second conductive layer changes with a deformation of the flexible substrate

Methodology Applied

Scientific EffectPiezoresistive effect: Piezoresistive Effect

Data Source

PatentEP4628849A1sensor

Publication Date: 2025.10.08 SHENZHEN SHOKZ CO LTD

Figure 1A
Figure 1B~2B
Figure 2C~3

AI summary

The present disclosure relates to a sensor, including: a flexible substrate (11) and a first sensing structure (12), wherein the first sensing structure (12) includes a multilayer structure disposed on a side surface of the flexible substrate (11) along a thickness direction; and each layer of the multilayer structure of the first sensing structure (12) is stacked along the thickness direction of the flexible substrate (11); and the multilayer structure of the first sensing structure (12) includes a first conductive layer (121) and a second conductive layer (122) which are disposed adjacent to each other; the second conductive layer (122) is disposed between the first conductive layer (121) and the flexible substrate (11); and a resistance of the second conductive layer (122) changes with a deformation of the flexible substrate (11).