A survey of over 100 manufacturers indicated that leaks are the most common failure mode in microfluidic diagnostic devices.
Unintended leaking, even in the smallest of occurrences, cause catastrophic issues to testing device performances including analyte losses, causing sample redraws, triggering safety concerns from leaching of amplicons, and ultimately impacting physician decision-making. For the IVD test device, the state of human health and safety remains in the balance of mitigating leaks from a device design standpoint.
So What Does This Mean for Device Designers?
As the FDA remains focused on supporting the industry with a new regulatory science tool—which will likely set a precedent for published guidelines in future—device designers must consider all early development phase opportunities in their designs. Knowing what standardized and proven materials or modular subcomponents pre-exist to aid a leak-proof closed system design is critical. For a new device concept like microfluidics, can we draw upon inspiration from other medical device applications?Since a dedicated analysis to microfluidic device design does not yet exist, working with material suppliers who have seen many devices come to market successfully may be the gap for a lack of evidence of leakages in this space. Start with the Microfluidic FDA Program’s list of concentrated areas of where leaks are prevalent, listed as connected components like micropumps, integrated chip interconnections, mechanics of flow control, and filters. Then look to understand your device’s weakest spot.
Every engineer will have heard the expression that a device is only as good as its weakest component or part, so we know this is where failures in design stem. For closed system devices, the weakest point in design stands to be any openings, seals, welded parts, vent ports, etc. This is where leaks are prevalent. This is also confirmed when we look at past recorded FDA recalls of on-market devices withdrawn due to leakages.
The opening or vent might be required on a closed system design for a number of reasons, a few being: to pressure equalized from mechanical working components, optimize fluid flow, or allow air to escape. For this, materials and components that are developed specifically for the purpose of IP-Rated protection of vents and seal openings for water ingress will validate them for leakages in design. To maintain a closed system with vent openings, refer to filtration efficiency ratings to mitigate unwanted contaminates. Using this language and terminology sets a precedent for suppliers to meet and allows us all to work toward a greater standard.
A factor we then consider a new challenge in this space is the added complexity of moving towards the micro-size device. For most of these devices, fluid flow through micro-channels occurs in a laminar flow fashion. Fluid dynamics of flow and viscosities at the micrometer scale behave so differently in these volumes, they bring along new leak root causes. One of these lesser-known challenges to causing leaks due to small volume of fluids is micro-bubbling.
Subject matter experts in microfluidics speak on the topic of micro and macro size bubble formation as a growing concern in IVD point-of-care devices. It is quickly becoming one of the leading root causes of leakages in these device types. Bubbling is a liquid flow related occurrence, where bubbling or foaming is created due to: directional changes in channel flow; pressure conditions from micropumps; heating during thermal cycling steps; clogging of micro-liquids in channels due to viscosity of liquid types; and many others. The IVD device space has begun bringing in new terminologies such as “debubbling” as a requirement to material suppliers in their vented or open-port designs to mitigate leakages.
This brings us back to question current methods of leak detection testing, which are mostly based on a human eye visual detection of leak/bubble occurrence. We can assume the challenge of validating a design to be leak-proof at the micrometer level to be even greater. So we move upstream, back to the material supplier and seek evidence for leak-proof before the device reaches final form—where we can only rely on up to date regulatory test methods to validate.
A Perspective from a Supplier
Your material supplier is the stakeholder to the microfluidic community, to help bridge knowledge gaps and improve the point-of-care device performance—to overcome challenges like leaks and air bubble formation by setting new standards in design.POREX is a porous polymer material science, product design, and manufacturing expert that develops custom engineered porous solutions to customers to help overcome complexities of product development challenges—from medical devices to industrial applications. Our materials absorb, apply, filter, diffuse, vent, wick, etc. Leaks are a common design challenge we receive across every known sector and application—and we help to solve them. We validate our material specifications for leakages using standard and non-standard approaches, which gives us the confidence to provide a solution we know works regardless of how far the industry has come along in their methods of validating at the final finish device point.
We support the microfluidic device community by taking our learnings as a material expert and calling for homogeneity of specifications and requirements to help set a new standard in design, the ultimate goal being to minimize failure modes (like leakages) in devices that make an impact to human health and safety.
Click here to learn more about POREX >>>>>