Capillary Channels for Uniform Sweat Collection
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Solution Overview
Problem
Existing wearable sweat sensing devices face challenges in consistently and uniformly collecting and transporting sweat due to issues with flow rate variability and fluid loss caused by G-forces, especially during motion, and require complex flow dynamics for analyte detection.
Innovation Solution
A multilayered article with an adhesive layer, a microstructured film layer containing capillary channels, and a cover layer that utilizes capillary action for uniform sweat collection and transportation, minimizing fluid loss and enabling continuous analyte detection without the need for hermetic seals or individual vent holes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sweat collection devices are used, then sweat can be collected, but flow rate variability and fluid loss occur due to G-forces during motion
Solution Approach 1:
The device segments the sweat collection area into multiple discrete capillary channels within the film layer, each independently transporting sweat from the adhesive layer to the cover layer. This segmentation prevents fluid loss by confining sweat within individual channels and allows consistent collection by distributing sweat across multiple parallel pathways, reducing the impact of G-forces on overall collection reliability.
Solution Approach 2:
The invention replaces complex mechanical flow control systems with passive capillary action. The microstructured film layer utilizes capillary channels that automatically transport sweat through surface tension forces without requiring active pumping or complex mechanical components. This substitution eliminates fluid loss associated with mechanical systems under G-forces and ensures consistent collection during motion.
2Adaptability or versatility
If complex flow dynamics are used for analyte detection, then detection capability is improved, but device complexity increases
Solution Approach 1:
The invention replaces complex active flow control systems with passive capillary action for sweat transport. The microstructured film layer with capillary channels provides sufficient flow dynamics for analyte detection without requiring complex mechanical components, pumps, or valves. This substitution maintains adaptability for detecting various analytes while significantly reducing device complexity.
Solution Approach 2:
The capillary channels in the film layer are self-service structures that automatically transport sweat from the adhesive layer to the cover layer without external control. The channels' inherent capillary properties provide the necessary flow dynamics for analyte detection, eliminating the need for complex external flow control systems and reducing overall device complexity.
3Reliability
If hermetic seals and individual vent holes are used, then fluid containment is improved, but manufacturing complexity increases
Solution Approach 1:
The invention extracts the venting function from individual vent holes and integrates it into the overall multilayer structure. The film layer with capillary channels naturally allows air displacement during sweat collection without requiring separate vent holes in each channel. This extraction simplifies manufacturing by eliminating the need for precise vent hole placement while maintaining reliable fluid containment through the layered architecture.
Solution Approach 2:
The film layer serves multiple functions simultaneously: it provides fluid containment through the capillary channels, allows air displacement during sweat collection, and enables analyte detection. This multi-functionality eliminates the need for separate hermetic seals and individual vent holes, simplifying manufacturing while maintaining reliable fluid containment and proper pressure equalization during sweat collection.
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 solution provides a small, consistent, and uniform collection of sweat, ensuring reliable analyte detection by maintaining fluid within capillary channels even under G-forces, and simplifies manufacturing with roll-based processes.
Implementation Method 1
each of the plurality of capillary channels is in fluid communication with the second aperture and extends toward a perimeter of the film layer. A surface of each of the capillary channels exhibits spontaneous wicking when contacted with an aqueous fluid.
Data Source
AI summary
The present disclosure provides articles including an adhesive layer; a film layer bonded to the adhesive layer having a microstructured surface including numerous capillary channels; and a cover layer disposed on the capillary channels and attached to the adhesive layer. The adhesive layer is hydrophobic and includes an aperture for fluid (e.g., sweat) collection from a skin surface. The film layer also includes an aperture that overlaps the adhesive layer aperture to direct collected fluid to the capillary channels of the microstructured surface, which have a hydrophilic surface. Optionally at least one indicator chemistry can be present in the channels to facilitate optical (e.g., visual) determination of total fluid volume and/or concentration of at least one analyte in the fluid as a function of time.