Microfluidic Interstitial Fluid Sampling via Thermal Ablation
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Solution Overview
Problem
Current methods for collecting interstitial fluid are invasive, time-consuming, and uncomfortable, limiting the practicality of using it as a source for cell-free non-coding RNA biomarkers, which are valuable for disease diagnosis and monitoring.
Innovation Solution
A microfluidic sampling device using thermal ablation micro-heaters and microchannels to non-invasively access and collect interstitial fluid, which is then mixed with analysis fluid for biomarker detection, utilizing a combination of Kapton and poly(dimethylsiloxane) layers and electrically controllable microheaters for efficient sample collection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If traditional invasive methods are used to collect interstitial fluid, then sufficient sample volume can be obtained, but the procedure becomes painful and time-consuming
Solution Approach 1:
The device divides the skin surface into multiple discrete heating zones, each with its own microheater array. This segmentation allows simultaneous collection from multiple sites, increasing sample volume while keeping each individual heating spot small and comfortable for the patient.
Solution Approach 2:
The microheaters pre-heat and ablate the stratum corneum before fluid collection begins. This preliminary thermal action creates microchannels that facilitate subsequent fluid extraction, reducing the need for invasive procedures and minimizing patient discomfort during the actual collection.
2Reliability
If invasive collection methods are used, then interstitial fluid can be accessed, but patient discomfort and procedure time increase
Solution Approach 1:
The device replaces mechanical puncture or surgical intervention with a thermal field approach. Electrically controllable microheaters create controlled thermal ablation of the stratum corneum, achieving reliable fluid access without physical invasion. This substitution dramatically reduces both patient discomfort and procedure time while maintaining collection reliability.
Solution Approach 2:
The microheaters induce phase transition in the stratum corneum material through controlled thermal ablation. This phase change creates permeable pathways in the skin barrier, enabling interstitial fluid to be drawn through microchannels via capillary action without requiring invasive mechanical penetration.
3Object-affected harmful factors
If the stratum corneum remains intact, then skin protection is maintained, but interstitial fluid cannot be accessed
Solution Approach 1:
The device applies localized thermal treatment only to specific microregions where fluid collection is needed, rather than compromising the entire skin barrier. Each microheater array creates localized microchannels through the stratum corneum, maintaining skin integrity in surrounding areas while enabling fluid access at discrete collection sites.
Solution Approach 2:
The microheaters act as intermediaries that temporarily modify the stratum corneum structure to enable fluid access. The thermal energy serves as a mediator that creates transient pathways through the skin barrier, allowing interstitial fluid to reach collection channels without requiring permanent or invasive disruption of the skin's protective function.
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
Enables painless, efficient, and non-invasive collection of interstitial fluid for cell-free non-coding RNA biomarker analysis, reducing the invasiveness and discomfort associated with existing methods, while providing a more reliable and efficient sample for disease monitoring.
Implementation Method 1
The ISF originates using, for example, thermal ablation micro-heaters 20... electrical components that control current to the micro-heaters... providing for individualized control of the heating pulse
Implementation Method 2
thermal ablation micro-heaters 20... that will be placed in contact with the top layer of skin containing dry, dead skin cells... The micro-heaters may be pulsed with a suitable alternating or direct current to provide local ablation
Implementation Method 3
The ISF is drawn up through the vertical micro-channels by capillary action
Data Source
AI summary
A system for determining the presence of cell-free non-coding RNA (cfNCR) biomarkers in interstitial fluid includes a microfluidic device for non-invasively and passively accessing interstitial fluid from a patient. The microfluidic device is formed of a substrate containing multiple vertical micro channels therethrough, wherein at a first end of each of the multiple vertical micro channels a microheater is formed for controllably ablating a portion of dry dead skin cells to access the interstitial fluid; and wherein at a second end of each of the multiple vertical micro channels is a horizontal micro channel for receiving accessed interstitial fluid from a vertical micro channel and guiding the accessed interstitial fluid to a common collection port.