Microfluidic Systems for Epidermal Sampling with Capillary Burst Valves
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Solution Overview
Problem
There is a need for wearable microfluidic systems that can reliably collect, monitor, and analyze biofluids under various environmental conditions and during different physical activities, including extreme conditions, while minimizing biofluid loss and efficiently handling both low and high flow regimes.
Innovation Solution
The development of microfluidic systems with flexible substrates and multiple networks, each configured to manage biofluids in specific flow regimes using capillary burst valves and colorimetric sensors, along with biofluid gelling agents and absorbents to minimize loss and enhance collection efficiency, and the use of patterned gratings for optical detection of biofluid amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single microfluidic network is used, then device complexity is reduced, but the system cannot effectively handle both low flow and high flow regimes
Solution Approach 1:
The system divides the microfluidic network into multiple independent networks (first microfluidic network and second microfluidic network), each optimized for specific flow regimes. The first network handles low flow regimes while the second network handles high flow regimes, allowing the system to adapt to varying sweat production conditions without requiring a single complex network design.
Solution Approach 2:
Each microfluidic network is designed with multi-functionality to handle different operational requirements. The networks incorporate universal components such as reservoir chambers, capillary burst valves, and sensors that can operate across different flow conditions, enabling the system to maintain versatility while managing complexity through standardized modular designs.
2Productivity
If microfluidic geometry and size are adjusted for different flow regimes, then flow control is improved, but manufacturing precision requirements increase
Solution Approach 1:
The system employs capillary burst valves with different burst pressures to control fluid flow into reservoir chambers. By changing the pressure parameter rather than relying solely on precise geometric dimensions, the system achieves effective flow control for different regimes while reducing the stringency of manufacturing precision requirements for the microfluidic channels and chambers.
3Measurement precision
If capillary burst valves with unique burst pressures are used, then flow control accuracy is improved, but device complexity increases
Solution Approach 1:
Each reservoir chamber is equipped with a capillary burst valve having a uniquely tuned burst pressure specific to its operational requirements. This local optimization allows precise control and measurement of fluid flow into each chamber based on its specific function (e.g., sweat collection vs. interstitial fluid collection), while the overall system complexity is managed through the modular repetition of this localized solution across multiple chambers.
4Adaptability or versatility
If multiple microfluidic networks are implemented, then flow regime coverage is improved, but biofluid loss increases
Solution Approach 1:
The system incorporates reservoir chambers that pre-capture and retain biofluids before analysis. The capillary burst valves are designed to open only when specific pressure thresholds are met, ensuring that fluids are retained in the collection channels until the reservoir chambers are ready to receive them. This preliminary action prevents premature loss or evaporation of biofluids while maintaining the ability to handle multiple flow regimes.
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
These systems enable reliable and efficient measurement and characterization of biofluids across different flow regimes, maintaining accuracy and reliability under diverse conditions, and effectively manage biofluid loss, facilitating real-time monitoring and analysis.
Implementation Method 1
a plurality of capillary burst valves fluidically connected with the microfluidic conduit network, each capillary burst valve positioned between fluidically adjacent reservoir chambers
Implementation Method 2
a plurality of colorimetric sensors, each positioned in a unique reservoir chamber to monitor the biofluid property
Implementation Method 3
biofluid gelling agents and absorbents to minimize loss and enhance collection efficiency
Data Source
AI summary
A microfluidic system includes a flexible substrate having a skin-facing surface and a back-facing surface; a microfluidic network at least partially embedded in or supported by the flexible substrate; a sensor fluidically connected to the microfluidic network, wherein the microfluidic network is configured to transport a biofluid from a skin surface to the sensor; and a capping layer, having a capping layer skin-facing surface and a back-facing surface, wherein the back-facing surface of the capping layer is attached to the skin-facing surface of the substrate. The flexible substrate is at least partially formed of a thermoplastic elastomer or a polymer configured to provide a high barrier to vapor or liquid water transmission.