Soft Capacitive Pressure Sensors with Wrinkled Gold Films
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Solution Overview
Problem
Current capacitive pressure sensors have low pressure sensitivities and are not suitable for long-term, continuous monitoring of radial pulse pressures due to stiff substrates and brittle electrodes, which limit their ability to conform to the body and accurately measure arterial pulse waveforms.
Innovation Solution
Development of soft capacitive pressure sensors with wrinkled metallic thin films and micro-ridged structures that create air gaps, allowing for high pressure sensitivity and dynamic range, along with neural network calibration for accurate beat-to-beat blood pressure monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If stiff substrates are used in capacitive pressure sensors, then structural stability is improved, but conformability to the body deteriorates
Solution Approach 1:
The patent replaces stiff substrates with flexible thin film structures, including wrinkled metallic thin films for electrodes and thin dielectric layers, enabling the sensor to conform to curved body surfaces while maintaining structural integrity through the wrinkled geometry that accommodates bending and stretching
Solution Approach 2:
The patent employs composite material structures combining metallic thin films with dielectric materials and elastomeric substrates, creating a multi-layered flexible sensor system that integrates conductivity, insulation, and mechanical compliance properties in a single conformable assembly
2Device complexity
If conventional capacitive sensors are used, then device simplicity is improved, but pressure sensitivity deteriorates
Solution Approach 1:
The patent uses ultra-thin dielectric layers (few nanometers to micrometers thick) between capacitive electrodes, which dramatically increases capacitance change per unit pressure while maintaining the simple capacitive sensing mechanism and requiring only standard thin film deposition techniques
Solution Approach 2:
The patent modifies the dielectric layer thickness parameter to the nanometer/micrometer scale and introduces wrinkled geometries in the metallic thin films, which amplifies the capacitance response to pressure stimuli while preserving the fundamental capacitive sensor design and fabrication simplicity
3Ease of manufacture
If brittle electrodes are used, then manufacturing ease is improved, but durability deteriorates
Solution Approach 1:
The patent fabricates electrodes as wrinkled metallic thin films deposited on flexible substrates, which inherently accommodate bending, stretching, and torsional deformations without cracking or delamination, enabling durable wearable sensors through standard thin film deposition processes
Solution Approach 2:
The patent introduces wrinkled or curved geometries in the metallic thin film electrodes, which distribute mechanical stress away from critical regions and prevent crack propagation during repeated deformation cycles, significantly enhancing durability while maintaining ease of manufacture through conventional deposition methods
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 sensors achieve high pressure sensitivity and quick response times, enabling continuous and accurate measurement of arterial pulse pressures, comparable to FDA-approved devices, with improved durability and conformability to the body.
Implementation Method 1
compression of the dielectric layer leads to an increased capacitance which is equal to: C = ε0εrA/d
Implementation Method 2
sr is the relative permittivity of the dielectric material
Data Source
AI summary
Soft capacitive pressure sensors for continuous wearable health monitoring applications are described herein. Wrinkled gold thin films on elastomeric substrates are used as robust parallel plate electrodes to create a robust integration with the polymer, allowing repeated normal force to deform the thin film without failure. By incorporating micro-ridged structures that support the counter electrodes to create air cavities within the elastomeric dielectric layer, pressure sensitivity is further increased. The pressure sensors are configured to measure human physiological signals such as pressure exerted from a radial pulse on a skin's surface. The radial pulse pressure detected by the sensor can be correlated to an arterial blood pressure. Calibration of said pressure sensors using a neural network allows for determination of absolute blood pressure.