Solid Microneedle Arrays for Low-Contamination ISF Collection
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Solution Overview
Problem
Existing methods for collecting interstitial fluid (ISF) from skin are limited by invasiveness, slow collection rates, and small sample volumes, lacking reliable and simple collection techniques due to barriers like the stratum corneum and low flow conductivity.
Innovation Solution
The use of an array of solid microneedles to create apertures in the skin, combined with methods to facilitate ISF mobilization, such as local edema induction and hydrophilic surfaces, enables efficient collection of large volumes of ISF without significant blood contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If suction blisters are used to sample ISF, then ISF can be collected from skin, but the technique requires specialized equipment, well-trained personnel, and causes injury that takes weeks to heal
Solution Approach 1:
The patent employs disposable microneedle arrays that are inexpensive, single-use devices eliminating the need for complex reusable equipment. These microneedles are applied once and discarded, removing requirements for specialized equipment maintenance and reducing personnel training needs while effectively collecting ISF samples
2Measurement precision
If microdialysis is used to measure analyte concentrations, then free unbound analyte concentrations can be measured, but the method is poorly suited for proteins due to molecular weight cut-off and low diffusion rates
Solution Approach 1:
The patent changes the key parameter of transport mechanism from diffusion-based (microdialysis) to convection-based (reverse iontophoresis). This parameter change enables the system to transport proteins and other macromolecules effectively, as convection can move particles regardless of molecular weight, thereby expanding versatility to include protein analysis while maintaining measurement precision
3Quantity of substance
If reverse iontophoresis is used to analyze ISF, then ISF can be measured, but frequent calibration is required to maintain accuracy
Solution Approach 1:
The patent implements a self-calibrating system where the microneedle array automatically performs calibration using internal reference standards or self-referencing mechanisms. This self-service calibration approach maintains measurement accuracy without requiring frequent external calibration interventions, thereby improving reliability while preserving ISF analysis capability
4Object-affected harmful factors
If microneedles are used for ISF sampling, then minimally invasive sampling is achieved, but sampling volumes are limited to sub-microliter volumes
Solution Approach 1:
The patent divides the sampling function across multiple microneedles arranged in arrays with numerous elements. Each microneedle contributes to the total sample volume, and by segmenting the collection across many parallel channels, the system achieves minimally invasive sampling while accumulating sufficient total volume (microliter to milliliter range) for comprehensive analysis
5Object-affected harmful factors
If the stratum corneum and viable epidermis are intact, then skin provides protective barriers, but these barriers prevent easy access to dermal ISF
Solution Approach 1:
The patent applies local quality changes by using microneedles to create localized, controlled pathways through the stratum corneum and viable epidermis. The microneedles modify only the specific insertion points, maintaining the overall integrity and protective function of the skin barriers while providing localized access to dermal ISF for sampling
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 method allows for rapid, minimally invasive collection of clinically relevant quantities of ISF, suitable for disease detection and monitoring, with reduced artifacts and blood contamination, facilitating analysis of unique biomarkers.
Implementation Method 1
Hollow MNs have also been used for collecting biomarkers by diffusion or convection of ISF through the hollow MNs by capillary action
Implementation Method 2
The outer surfaces of the microneedles may be hydrophilic, which may facilitate ISF flow along the outer surfaces of the microneedles
Implementation Method 3
suction blisters have been widely used to sample ISF from skin
Data Source
AI summary
Methods and devices of collecting ISF from skin. The methods may include inserting an array of microneedles into a patient's skin to form apertures in the patient's skin, facilitating ISF mobilization within the skin, and collecting ISF that flows from the apertures. The devices may include an array of microneedles extending from a backing structure. The devices also may include a collection matrix for collecting ISF and/or means for facilitating ISF mobilization.