Viscous Piezoresistive Strain Sensor for Medical Monitoring
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Solution Overview
Problem
Existing piezoresistive strain sensors have limited gauge factors, are temperature sensitive, and fragile, making them unsuitable for high-sensitivity medical monitoring applications, especially for long-term patient monitoring, which often results in inaccurate and spurious readings due to environmental stress and bulkiness.
Innovation Solution
A strain sensor comprising a viscous piezoresistive element encapsulated within a resilient packaging element, with contact means defining an electrical path that varies resistance with deformation, allowing for high sensitivity and fidelity, particularly suitable for wearable devices, using graphene-doped polysilicone and silicone materials, and a rigid support configuration for directional force sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a viscous piezoresistive material is used to achieve high gauge factor, then measurement precision is improved, but the sensor becomes fragile and temperature sensitive
Solution Approach 1:
The viscous piezoresistive material is encapsulated within a resilient packaging element, creating a nested structure where the sensitive material is protected inside a robust container. This allows the high gauge factor of the viscous material to be exploited while the packaging element shields it from environmental stress and mechanical damage.
Solution Approach 2:
The resilient packaging element acts as an intermediary between the external environment and the viscous piezoresistive material. It transmits mechanical deformation to the material while filtering out temperature sensitivity and fragility issues, enabling reliable operation in practical applications.
2Adaptability or versatility
If conventional piezoresistive sensors are used for medical monitoring, then device functionality is achieved, but reliability deteriorates due to environmental stress and bulkiness
Solution Approach 1:
The resilient packaging element functions as a flexible shell that encloses the viscous piezoresistive material. This flexible packaging allows the sensor to conform to body surfaces for medical monitoring while protecting the internal material from environmental stress, eliminating the bulkiness of conventional sensors.
3Duration of action of moving object
If the packaging element is made resilient to enable quick restoration, then duration of action is improved for time-varying force detection, but device complexity increases
Solution Approach 1:
The packaging element is designed with specific resilient properties that allow it to quickly restore to its original shape after deformation. By adjusting the material parameters of the packaging element, the sensor can detect time-varying forces while maintaining a relatively simple overall structure.
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 strain sensor provides a high gauge factor, reproducible, and monotonic resistance change, enabling sensitive and accurate detection of forces like pulse rates over extended periods with reduced environmental interference, suitable for medical monitoring, and is cost-effective and suitable for integration into wearable devices.
Implementation Method 1
Piezoresistive strain sensors use electrical conductance or electrical resistance as the sensed property. Under strain, the geometry of a conductor comprised in such a sensor deforms, changing the end-to-end resistance of the conductor.
Data Source
AI summary
A strain sensor includes a viscous piezoresistive element embedded or encapsulated within a solid, flexible, resilient packaging element, and a contact contactable from the exterior of the strain sensor and defining an electrical path through or along at least a portion of the viscous piezoresistive element, the resistance of the electrical path varying with deformation of the strain sensor. The invention allows the high gauge factor of a viscous piezoresistive material to be taken advantage of in a practical device by containing the material within a packaging element. The packaging element ensures a consistent output response as a function of deformation of the strain sensor and enables the strain sensor to detect time-varying forces due to the resilient nature of the packaging element.