Stacked Strain Gauge Sensor for Rapid Wearable Detachment
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Solution Overview
Problem
Existing wearable strain gauge sensors attached to body surfaces like fingernails face challenges in efficient detachment due to slow adhesive removal processes and limited surface area constraints, which hinder their practical application in clinical settings.
Innovation Solution
The development of stacked strain gauge sensors with increased electrical resistance, featuring multiple layers with aligned holes for adhesive remover access and interconnects between layers, allowing for quick and easy detachment without increasing the sensor footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive is used to bond the sensor to the body surface, then strong adhesion is achieved, but removal becomes time-consuming and tedious
Solution Approach 1:
The sensor is divided into multiple detachable layers (substrate layer, sensor layer, encapsulation layer) that can be separated from the body surface independently. The adhesive is applied only to specific portions of the substrate rather than the entire sensor assembly, allowing selective removal of the sensor layer while leaving the substrate behind, dramatically reducing removal time from 30+ minutes to seconds.
Solution Approach 2:
The adhesive is extracted and applied only to specific portions of the substrate layer rather than covering the entire sensor. This allows the sensor layer to be removed quickly by peeling it away from the adhesive, while the adhesive remains on the substrate which stays on the body. This extraction of adhesive from the complete sensor structure enables rapid sensor removal without compromising initial adhesion strength.
2Measurement precision
If the sensor footprint is increased to improve signal strength, then better measurement is achieved, but the available body surface area is exceeded
Solution Approach 1:
The sensor design transitions from a single-plane layout to a multi-layer stacked configuration. By stacking the substrate layer, sensor layer, and encapsulation layer vertically, the effective sensor area is multiplied across layers while maintaining a compact footprint on the body surface. This dimensional transition allows the sensor to achieve enhanced signal strength through increased active area without exceeding the limited body surface area available for attachment.
3Measurement precision
If multiple sensor layers are stacked to increase electrical resistance, then sensitivity is improved, but device complexity increases
Solution Approach 1:
The sensor structure employs a nested doll configuration where the sensor layer is positioned between the substrate layer and encapsulation layer, with each layer containing and protecting the others. The strain gauge pattern is nested within the substrate layer, and the entire assembly is nested within a compact footprint. This nesting approach increases electrical resistance and sensitivity through multiple layers while maintaining structural simplicity and ease of fabrication.
Solution Approach 2:
Multiple functional layers (substrate, sensor, encapsulation) are merged into a single integrated stacked structure with aligned through-holes for interconnects. The adhesive application patterns on different layers are merged to create a unified bonding structure. This merging of layers and functions achieves increased sensitivity through stacked configuration while simplifying the overall device structure and reducing manufacturing complexity.
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
This design enables rapid adhesive release and efficient data collection, reducing removal time from minutes to seconds, while maintaining high sensitivity and adherence to small body surfaces, enhancing clinical usability.
Implementation Method 1
Each of the substrates can include: a film (e.g., a polyurethane film, a polyester film and/or a polyimide film) and an adhesive layer (e.g., an acrylate and/or acrylic adhesive)
Implementation Method 2
A biocompatible adhesive bonds the device to the body. The adhesive ensures strong adhesion to the fingernail
Implementation Method 3
applying an adhesive remover via the through holes to release the one or more stacked strain gauge sensors from the at least one body surface
Data Source
AI summary
In one aspect, forming a stacked strain gauge sensor with increased electrical resistance includes: forming multiple sensor layers, wherein the sensor layers include strain gauge sensor wires on substrates; forming holes in the substrates; stacking the sensor layers, one on top of another, to form a stack with the holes aligned in one or more locations forming through holes in the stack; and forming interconnects in the holes in one or more other locations interconnecting the strain gauges sensor wires between adjacent sensor layers to form a stacked strain gauge sensor. A stacked strain gauge sensor and method of use thereof are also provided.