Microfluidic Device for Non-Invasive Interstitial Fluid Collection
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Solution Overview
Problem
Current methods for collecting interstitial fluid are invasive, time-consuming, and uncomfortable, making them less desirable for clinical testing compared to blood draws.
Innovation Solution
A microfluidic device with vertically oriented microchannels and microheaters that ablate dry skin cells to access interstitial fluid, allowing for non-invasive and efficient collection using a substrate with polyimide and PDMS layers, and electrically controllable microheaters for thermal ablation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If suction method or blister method is used to collect interstitial fluid, then interstitial fluid can be collected for testing, but the procedure becomes invasive, time-consuming, and uncomfortable for patients
Solution Approach 1:
The device divides the skin surface into multiple discrete sampling sites, each with its own microheater and microchannel structure. This segmentation allows for distributed, minimally invasive access to interstitial fluid at multiple locations simultaneously, reducing the discomfort associated with single-point invasive procedures while maintaining adequate fluid collection volume.
Solution Approach 2:
The invention replaces mechanical suction methods and chemical blistering agents with a thermal field-based approach. Microheaters generate localized heat to create microchannels through the stratum corneum, enabling passive diffusion of interstitial fluid without mechanical suction or toxic chemical reactions, thereby eliminating the discomfort and safety concerns of previous methods.
2Quantity of substance
If suction method is used to collect interstitial fluid, then fluid can be obtained, but the procedure takes more than 2 hours to produce blisters
Solution Approach 1:
The microheater elements are pre-positioned on the device surface, ready for immediate activation. When applied to the skin, the heaters instantly begin thermal ablation of the stratum corneum, creating microchannels within seconds rather than requiring hours of suction application or chemical exposure. This preliminary preparation of the heating elements enables rapid fluid access.
Solution Approach 2:
The microheaters induce localized phase transitions in the stratum corneum material through thermal energy, transforming it from a intact barrier structure to a porous state that permits fluid passage. This thermal phase transition process occurs rapidly compared to the slow mechanical suction or chemical blister formation, reducing collection time from hours to minutes.
3Quantity of substance
If cantharides are applied to generate skin blisters, then interstitial fluid can be collected, but toxic reaction and adverse effects occur
Solution Approach 1:
The invention substitutes the chemical reaction mechanism of cantharides with a physical thermal field mechanism. Instead of using toxic chemicals to disrupt skin structure, localized heating creates microchannels through controlled thermal ablation, eliminating toxic reactions and adverse effects while achieving the same goal of interstitial fluid access.
Solution Approach 2:
The microheater acts as an intermediary between the external power source and the skin tissue, converting electrical energy to thermal energy in a controlled manner. This intermediary mechanism provides precise spatial and temporal control over the tissue interaction, avoiding the uncontrolled toxic reactions associated with cantharide application while still achieving effective microchannel creation.
4Quantity of substance
If micro-needles are used to draw interstitial fluid, then fluid can be collected, but the procedure becomes more invasive
Solution Approach 1:
The invention replaces mechanical needle penetration with a thermal field approach. Microheaters create microchannels through controlled thermal ablation of the stratum corneum, allowing passive diffusion of interstitial fluid without physical needle insertion. This eliminates the invasiveness and potential complications associated with micro-needle procedures while maintaining effective fluid 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
Enables painless, efficient, and non-invasive collection of interstitial fluid for clinical testing, facilitating the assessment of biomarkers using standard methods like mass spectrometry, with improved patient comfort and reduced recovery time.
Implementation Method 1
a microheater is formed for controllably ablating a portion of the dry dead skin cells to access the interstitial fluid
Implementation Method 2
ISF wicks up through a vertical microchannel by capillary action
Data Source
AI summary
A microfluidic device for non-invasively and passively accessing interstitial fluid from a patient includes 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.