By Sean Fenske, Editor-in-Chief

The COVID-19 pandemic left us with a number of takeaways across many industries and lifestyles. The experience resulted in a rethinking of many activities and offered a view of alternatives that may not have otherwise been explored. Healthcare was certainly one such area impacted by the period, and perhaps nowhere more so than with regard to diagnostics.

Accurate and timely testing was crucial during the pandemic. People wanted to know if a sniffle or cough marked the start of allergies, the common cold, or the virus. It was critical to have information about one’s own health to ensure proper treatment was sought out (as needed) and to avoid those in more vulnerable populations to decrease the risk of exposure. The world came out of the pandemic with a significantly greater appreciation for diagnostics.

As a result, diagnostic firms are increasing the number of tests being developed. As such, they are seeking expertise on specialized components needed for these solutions. In the following Q&A, Shane Sheedy, Head of Innovation & Commercial Strategy at Porex Membrane Technologies, has responded to a series of questions around filtration materials for blood that can be used in point-of-care (POC) diagnostics.

Sean Fenske: Can you speak to some of the current trends in diagnostics, specifically in the point-of-care diagnostic space?

Shane Sheedy: Diagnostics is an essential enabler of the broader healthcare system. As technology continues to evolve and we transition to value-based healthcare, diagnostics will play an increasingly vital role in enhancing patient outcomes.

POC diagnostics is one of the most dynamic areas in healthcare today. The global POC diagnostics market continues to expand rapidly and is expected to almost double over the next 10 years, reaching ~$90 billion by 2033. We believe three key trends are driving this growth.

Consumerization and at-home testing represent the first driver. Technology improvements have accelerated the push toward decentralized and patient-centric testing. Many consumers are taking more control of their health with the use of smart watches and other digital devices to track general health and fitness. Increasing consumer ownership, supported by advances in technology that enable non-invasive, self-administered tests, has rapidly increased the amount of control and transparency consumers have over their own health and health outcomes. During the COVID-19 pandemic, for example, the convenience and scalability of rapid at-home tests highlighted the value of POC diagnostics for delivering immediate results to large populations.

The second trend is improving technology and miniaturization. POC tests are becoming more portable and are being developed to provide lab-quality results within minutes, at the bedside, in clinics, or even at home. This reduces the wait for reports and considerably simplifies and shortens diagnosis timelines. As a result, the market is seeing better patient outcomes and a lower economic burden on the healthcare system.

Finally, data system integration and AI compose the third driver. Many new POC devices connect to smartphones or cloud platforms, which are beginning to be integrated across multiple data sources to enable accelerated data analysis and provide a more holistic view of patient health. Additionally, these datasets are being analyzed by AI to enable clinical decision support, accelerating diagnoses and providing best-in-class healthcare in remote or resource-limited settings.

With a growing emphasis on wellness and prevention, we expect POC diagnostics to continue evolving, with improvements in speed, connectivity, and patient empowerment.

Fenske: Why is it important to be able to separate blood into blood cells and plasma at the point of care?

Sheedy: The key requirement for POC diagnostics is the delivery of a result with lab-level accuracy, in a time that allows the clinician or user of the test to provide optimal treatment to a patient before they leave the clinic.

The key steps in the testing process are: Sample Collection, Sample Application, Detection Method, Signal Processing, and Results. The Sample Collection step collects the relevant input sample at the POC. For most blood-based tests, plasma (the cell-free liquid component) is the key input into the Detection Method as the cellular components can interfere with the detection of analytes.

Blood cells, especially red blood cells, can cause interference with Detection Methods and subsequent signal processing steps. This can be as simple as optical interference (for example, the red color of hemoglobin can obscure colorimetric readings) and may non-specifically bind or alter target molecules. By removing these cells, we minimize interference in analyte detection and improve the sensitivity and specificity of the test. In fact, cell/plasma separation is considered one of the most basic and vital steps in disease diagnostics; it yields a cleaner sample so biomarkers can be measured reliably.

In a point-of-care setting, achieving this separation is especially important because the goal of these tests is to work with very small sample volumes (~10 µl, which equates to one to two drops of blood from a single finger-prick) without the need for complex lab equipment such as centrifuges.

In these tests, plasma contains the molecules of interest (glucose, proteins, markers, etc.) in a uniform solution. To obtain lab-quality results, we need to quickly and accurately isolate the plasma. Traditionally, laboratories use centrifugation to spin down blood and separate plasma, but this isn’t feasible in most POC scenarios. There have been advancements in this over the past several years, with membrane filtration starting to become a viable solution for this isolation step. That said, there is still room for considerable improvements with these technologies, especially with handleability, consistency, and replicability.  

In summary, on-site blood separation into plasma ensures POC diagnostic devices can run properly, yielding accurate results without the confounding effects of blood cells. It enables rapid testing for critical biomarkers (for example, in infectious disease or metabolic monitoring) without having to transport samples to a central lab, which is crucial for timely decision-making in remote clinics, ambulances, or at-home care.

Fenske: How is this type of blood separation traditionally achieved, and what are the challenges or disadvantages of these methods?

Sheedy: Whole blood separation methods primarily include centrifugation, sedimentation, microfluidic techniques, and filtration. The key considerations for all these various methods are plasma yield, speed, replicability, and practicality, with each method having trade-offs.

Centrifugation is the standard laboratory method; a blood sample in a tube is spun at high speed so dense cells pack to the bottom and plasma remains on top. While centrifugation is very effective in a lab, it is impractical for POC use. It requires large sample volumes, bulky equipment, electrical power, and trained operators, and the process is relatively slow with multiple handling steps. High rotational forces can also stress or damage delicate cells (causing hemolysis), which may alter sample integrity.

With gravity sedimentation, whole blood sits undisturbed, allowing cells to settle under gravity. This gentle, equipment-free approach preserves cell integrity, but it is extremely slow and imprecise while requiring large sample volumes. Waiting hours for cells to naturally separate is not feasible when rapid results are needed, making sedimentation unsuitable for most timely diagnostics.

Newer miniaturized devices employ microscale channels or forces (capillary action, inertial focusing, acoustic or magnetic fields) to isolate plasma on-site (i.e., microfluidic separation). They offer high precision and can operate with small blood volumes, yet they come with practical drawbacks. Active microfluidic techniques that use external fields/pumps achieve efficient separation but add complexity and are hard to integrate into compact, power-free devices. Fully passive chip designs (relying on channel geometry or flow effects) avoid external power but can be prone to clogging and have very strict flow rate and channel requirements. Moreover, most microfluidic separators handle limited throughput—scaling up for larger sample volumes or faster processing is difficult.

Many POC kits use a porous membrane or microfilter (e.g., glass fiber pads or polymer membranes) to trap blood cells while plasma wicks through. This method is relatively simple and easily integrated into many test forms, assuming the material does not have handleability challenges. However, maintaining both speed and purity can be challenging. Irregular pore sizes in traditional filters mean some red cells can slip through (contaminating the plasma) while others clog and slow the flow. Filters also absorb a portion of the sample (reducing plasma yield), and forcing blood through fine pores can rupture cells, releasing hemoglobin, which may interfere with the test reading.

For optimal product performance, we believe it is important to consider the separation method as early as possible in the product development process.

Fenske: What advantages does the Porex track-etched membrane provide for the blood separation process?

Sheedy: Porex’s track-etched membranes (TEM)—branded as Oxyphen—are thin, porous polymer membranes that have unparalleled control of pore size and density, producing extremely uniform, cylindrical pores created by an ion track and chemical etching process. Leveraging this TEM technology, Porex has been developing a new membrane to specifically address the challenges observed in the current blood separation process, namely plasma yield, speed, replicability, and practicality.

This new membrane allows for precise filtration with high yield: the pores can be tuned to a diameter that effectively blocks red blood cells (which are about 6-8 µm in size) while letting plasma through. Because all pores are the same size, within a very low tolerance, you get a very sharp cutoff and high filtration efficiency, producing high plasma yield with low cell hemolysis. This contrasts with fibrous or paper membranes where pore sizes vary and some cells might bypass. The result is high plasma purity and yield, which means more of the plasma from a small blood sample (and the analytes within it) is available for testing.

This new membrane is a true surface filter, meaning blood doesn’t have to travel through a “tortuous-path” matrix structure. The flow-through is essentially a straight path, which enables very rapid separation. Additionally, this ensures there is no held-up volume in the membrane itself, vastly decreasing the amount of blood required to produce plasma for the test. Faster separation directly translates to faster test results, a crucial benefit in POC settings where timely answers are needed. The membrane is designed to work with a true finger-prick volume of blood, targeting 10 µL of blood, as sufficient for many test forms. This opens the door to less invasive and more frequent testing, improving patient comfort and compliance.

Our TEMs have a long track record of product integration, and this new membrane has been developed with replicability and handleability as core points of differentiation versus existing blood filtration membranes. Unparalleled control of pore size and density results in improved test replicability when compared to “tortuous-path” membranes, which can have larger variation through the final product. Additionally, Porex’s membrane is easy to handle and unsusceptible to surface clogging if touched or manipulated. Final form factors can easily be adjusted to support integration into existing manufacturing processes.

Finally, our new membrane has practical benefits for POC diagnostics. Our studies show existing membrane products require larger volumes of blood to attain similar levels of output plasma, while having consistency and product integration challenges. Our membrane addresses these concerns while improving the overall patient experience and increasing confidence in these tests for final product producers.

In summary, the new Porex blood separation membrane leverages track-etched membrane technology to offer precise control over filtration, speed, and efficiency and facilitate separation of high-quality plasma from minimal blood volumes—all of which are game-changing advantages for POC blood testing. It enables lab-like sample preparation in a tiny disposable component, paving the way for faster and more reliable POC diagnostics.

Fenske: How is the membrane incorporated into a diagnostic device? Can Porex offer design assistance with this?

Sheedy: Porex has extensive experience integrating our membranes into a wide variety of devices and products. Our TEM portfolio ranges from cell culture inserts to drug delivery devices and methods such as ultrasonic welding and heat sealing. For blood separation devices in particular, the membrane is generally used as a built-in filtration element where blood is introduced into the test. The blood is placed on the membrane before the plasma flows through the membrane and onto a collection substrate. This substrate can be a part of the test strip or a collection chamber before flowing into a microfluidic channel. Integration is typically straightforward: the membrane might be housed in a plastic frame or sandwiched between layers of the device; it can be cut into various shapes and final form factors (e.g., standard roll stock or pre-punched discs) to support easy integration with existing or new manufacturing processes.

Porex takes pride in our collaborative approach to product design, development, manufacturing integration, and subsequent product support. Our team of engineers has extensive experience in the material science product development cycle. We partner with customers to understand key technical requirements of the final product to ensure we provide optimal design solutions throughout the development process, cost management, and long-term regulatory compliance. This level of support is critical because integrating a membrane isn’t just about the membrane itself; it’s about how that membrane interacts with the sample fluid dynamics and overall device architecture. We believe this collaborative approach helps manufacturers produce a working design faster with confidence that the filtration component will meet their needs.

Fenske: When seeking filtration material for diagnostics or another medical device application, what are the most important selection factors manufacturers need to consider?

Sheedy: Selecting the right filtration material is crucial to determining the success of a diagnostic device. To optimize material selection, we recommend engaging with us early in the process so we can understand the key technical requirements of the final product and provide design solutions. With that said, there are several factors manufacturers should consider.

Sample Volume & Format Constraints: Consider the volume of sample you’re working with and how the filter material handles it. In diagnostics, you often want to work with very small samples (finger-prick volumes). The filtration medium should be effective, even at micro-volume scales, providing sufficient output for the assay. Also, factor in whether the membrane needs to be pre-treated or primed for use—for example, does it require wetting agents or anticoagulants, and are those compatible with your test? Materials like track-etched membranes have the advantage of functioning with very small volumes and can be made hydrophilic to start wicking immediately. Always match the membrane’s capabilities to the sample size and type (blood, saliva, urine, etc.) relevant to the application.

Pore Size & Uniformity: The pore size must be appropriate to capture or exclude the target particles. Equally important is how uniform those pores are across the membrane. True pore-size control (as in track-etched membranes) ensures consistent filtration performance. Irregular pore materials might have oversized pores that let unwanted particles through, or undersized ones that slow the flow. Thus, knowing the membrane’s pore size distribution and cutoff is critical.

Filtration Efficiency & Speed: Especially in point-of-care tests, time is of the essence. Manufacturers should evaluate how quickly the membrane can process the required sample volume. High flow rates at low pressure and quick plasma separation times (on the order of seconds to a couple of minutes) are desirable. For instance, advanced blood separation membranes can achieve separation in as fast as ~60 seconds per cm² area (depending on sample hematocrit). Efficiency also means maximizing plasma yield—the membrane should retain cells but let through as much of the plasma (and analytes) as possible, even from a small drop of blood. In short, consider the trade-off between speed and completeness of filtration, and choose materials that meet your test’s timing requirements without sacrificing sample quality.

Material Compatibility & Purity: The filtration media should not introduce any contaminants or interfere with the assay chemistry. This means it should have low extractables (no chemicals leaching into the sample) and low nonspecific binding. An inert material that is resistant to protein binding is ideal, so it won’t soak up antibodies, antigens, or other analytes and skew the results. Also, consider the membrane’s chemical compatibility with reagents: if your test involves solvents or enzymes, the membrane must remain stable and not inhibit the reaction. For instance, some membranes might have surfactants or additives that could affect an immunoassay or PCR; those should be identified and avoided. Porex emphasizes using certified non-leachable, non-extractable media with superior purity for precisely this reason. Essentially, the filter should be biologically and chemically inert in the context of your test.

Mechanical & Design Integration: The physical form of the material and how it fits into your device is a practical factor. Can the membrane be produced in the needed size or shape? Does it come in sheets, rolls, or pre-cut formats that suit your assembly process? A good filtration material for devices should be available in dimensions that match high-volume manufacturing (e.g., roll stock for automated assembly) or be easily cut without fraying (if it’s fibrous). Thickness and sturdiness matter too—a very thin membrane might need a support or lamination to prevent tearing during handling, whereas a very thick one might not fit in a slim cartridge. Manufacturers should also consider how the membrane will be sealed or mounted (e.g., thermal bonding, adhesives, ultrasonic welding, etc.) and choose materials that are compatible with those methods. In some cases, suppliers offer custom sizing and even adhesive-backed membranes to simplify integration.

Regulatory Compliance & Biocompatibility: Since these materials are used in medical devices or diagnostics, they should meet regulatory and safety standards. Look for membranes that come from ISO 13485-certified manufacturing lines and have consistent lot-to-lot quality.

Biocompatibility (if the material will contact patient samples or reagents that go into a patient) is another consideration. For example, compliance with USP Class VI or ISO 10993 for cytotoxicity ensures the material itself is not harmful.

Additionally, with evolving regulations, avoidance of hazardous substances is key: ensure the membrane is free from things like heavy metals, BPA, or certain perfluorinated compounds (PFAS) that might be restricted. For instance, Porex certifies our materials contain no detectable PFOA and are latex-free to align with global safety standards. Manufacturers must factor in these compliance issues early, as using a non-compliant material could derail a project late in development.

Performance Validation & Support: Finally, consider what support or data is available from the supplier. Reputable suppliers will provide detailed specifications (pore size, flow rate, protein binding characteristics) and application data relevant to diagnostics. They may offer samples for feasibility testing and have technical experts to help optimize usage. It’s wise for manufacturers to partner with suppliers that can demonstrate the filter’s performance in scenarios similar to their application and reliably supply the material at scale. Consistency is crucial—you want to be confident the membrane in every production lot behaves the same, which ties back to choosing a supplier with strong quality control (again, an ISO 13485 process or similar).

In summary, selecting a filtration material is a multidimensional decision: you need the right technical specs (pore size, flow, binding), practical fit (format, integration), and assurance of quality and safety. Balancing all these factors will lead to a reliable choice for your diagnostic or medical device.

Fenske: Do you have any additional comments you’d like to share based on these topics, or something you’d like to tell medical device manufacturers?

Sheedy: As I have mentioned several times throughout this Q&A, I believe early engagement significantly improves final product outcomes and accelerates development timelines. Filtration (and venting in many cases) can be complex, with innovation in this sector accelerating. Porex can help you find creative solutions to challenges (like handling tiny fluid volumes or meeting a new regulatory requirement) faster. At Porex, we take pride in our customer relationships, not just as a supplier, but as a trusted development partner. We strive to understand the needs of device design, patient safety, and regulatory compliance, and we build those considerations into our materials from the outset. Additionally, I think it is very important to note we approach these discussions with a commercial mindset. We understand cost is a key consideration and offer transparency on the trade-offs between price and performance throughout the development process. Finally, I would be remiss to not discuss the expertise we bring to the product development cycle, supporting through the design control process and, in many cases, enabling material selection, which helps accelerate regulatory approval timelines.

I’d also like to reiterate how optimistic I am about the current landscape. Patient outcomes are the ultimate measure of success for our industry, and I am excited to see how new technologies and broader macro trends enable us to reach more patients and to deliver care in a more decentralized, patient-friendly way. We’re at a point where advanced materials—like the track-etched membranes and Porex’s new blood separation—are enabling diagnostics that were thought impossible at the point-of-care a decade ago.

At Porex, our goal as materials developers is to empower healthcare innovators. As we incorporate these innovations, we maintain a focus on quality and reliability. When device makers don’t have to worry about whether a filter will clog or if a separator will alter the sample, they can concentrate on the big picture of diagnosing and treating disease. So, in closing, I’d tell my colleagues in the medical device space: think of materials not as off-the-shelf commodities, but as integral parts of your device’s design. By selecting the right materials and partnering with companies that prioritize innovation and compliance, you can bring safer, more effective, and more user-friendly medical devices to the market—and do so with greater confidence and speed. The future of diagnostics is very bright; together, we can continue to push the boundaries of what’s possible at the point of care, ultimately making the world safer, healthier, and more productive.

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