Coated Substrates for Extended Shelf Life in Microfluidic Diagnostics
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Solution Overview
Problem
Microfluidic point of care diagnostic devices, particularly capillaries and channels, face a short shelf life due to adventitious carbon deposition, leading to decreased wettability and impaired capillary action, requiring complex handling and skilled operation for accurate blood sampling.
Innovation Solution
Coating substrates with layers comprising carboxylate functions, amine functions, or combinations thereof, such as polyelectrolytes, to maintain low contact angles and prevent the adverse effects of adventitious carbon deposition, ensuring consistent capillary filling regardless of orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If uncoated glass capillaries are used, then initial wettability is good, but shelf life is short due to aging and adventitious carbon deposition
Solution Approach 1:
The capillary is pre-coated with a hydrophilic substance (such as silane, polysiloxane, or other hydrophilic coatings) before use. This preliminary coating establishes a stable hydrophilic surface that resists adventitious carbon deposition and maintains wettability throughout the shelf life, preventing the aging effect that occurs with uncoated glass.
Solution Approach 2:
A hydrophilic coating layer is introduced as an intermediary between the glass surface and the blood sample. This coating layer acts as a protective barrier that prevents direct interaction between adventitious carbon in the environment and the glass surface, thereby maintaining consistent wettability properties over time.
2Reliability
If capillary aging occurs, then contact angle increases and wettability decreases, but cleaning can restore surface properties
Solution Approach 1:
The hydrophilic coating is applied in advance during manufacturing, creating a stable surface that maintains its wettability properties throughout the product's shelf life and usage. This preliminary protective action eliminates the need for cleaning operations before use, as the coating prevents aging effects from occurring in the first place.
Solution Approach 2:
The hydrophilic coating provides self-protecting properties to the capillary surface, continuously maintaining low contact angles and high wettability without requiring external cleaning or maintenance. The coating inherently resists adventitious carbon deposition and maintains performance throughout the product lifecycle.
3Productivity
If capillary inversion is required to assist filling, then gravity compensates for decreased wettability, but device complexity increases
Solution Approach 1:
The capillary is pre-coated with hydrophilic material to ensure consistent wettability and reliable capillary action throughout its shelf life and during use. This preliminary protective measure ensures that the capillary will fill reliably in the intended orientation without requiring users to invert the device to compensate for wettability loss.
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 coated substrates exhibit extended shelf life, maintaining low blood contact angles and high capillary filling efficiency over time, allowing for reliable and user-friendly operation by untrained personnel, reducing manufacturing complexity and costs.
Implementation Method 1
The coating may prolong the shelf life of the capillary and enhance its usefulness in the collection of biological fluids... maintaining low blood contact angles
Implementation Method 2
the aging of capillary or microfluidic channel surfaces may be influenced by the deposition of adventitious carbon (AC)... ameliorate the effects of adventitious carbon deposition on the wettability of the substrate
Implementation Method 3
reliably and accurately fill a pre-determined volume of a capillary or channel... fill to a predetermined volume using capillary forces alone
Data Source
AI summary
The present disclosure relates to coated substrates, capillaries and microfluidic channels which exhibit an extended shelf life compared to uncoated substrates. More specifically the disclosure relates to charged coatings at physiological pH which may prolong the shelf life of the substrate, capillary or microfluidic channel before being applied to biological fluids. Said shelf life is measured by the ability to provide a low fluid contact angle after an extended storage interval in ambient atmospheric conditions.