This article is sponsored by Porex. In this Voices interview, Medical Design & Outsourcing spoke with Dr. Gerda Ricken, PhD, Head of Research and Development, Track-Etched Membrane, Life Science at Porex, to discuss their track-etched membrane filtration technology and its applications.
Medical Design & Outsourcing: To start off, tell us a bit about yourself and your role at Porex.
Gerda Ricken: My role is head of R&D for the life science division of our track-etched membrane technology platform. I lead the R&D team for product development. Our sites in Germany (Automotive/Industrial) and Switzerland (Life Science) produce track-etched membrane products for filtration applications within life sciences, medical, automotive and industrial uses.
My background is in molecular biology, which is especially helpful on our focus within life science applications.
What is track-etched membrane technology, and how is it made?
We start out with a polymer base film and only use polyethylene terephthalate (PET). There are two main processing steps that turn that film into a functional membrane.
First, we do a high-energy exposure. The film goes into a particle accelerator — in this case, a large cyclotron — where we expose it to heavy ion beams. This high-energy particle beam creates tracks in the base film, which is where the “track” part of the name comes from. This determines how many pores we have in the film.
The second processing step is the etching. We place the film with tracks into an etching bath to turn the film into a porous material. We tightly control how the tracks form into the individual pores. When you look at the base film under a microscope, you see a flat film with holes punched in it. This makes it incredibly unique compared to many other porous materials that are not very structured.
We tightly control the pore geometry: how big they are, how cylindrical they are, and at which angle they pass through the base film. We also control the density of the pores, which creates unique functionality with very tight parameters. The pores are the basis for all other parameters like airflow, water flow, burst strength or any functionality the customer needs.
Track-etched membranes have been around for a while, but are not as widely used as some other materials. Why, and what’s changing now?
Track-etched membranes can be used in a wide variety of applications, so it’s not so much a niche product from our perspective; it all depends on a customer’s application and whether they are looking for something highly precise with certain parameters. For example, if a customer is looking for a specific particle size cutoff, they need a solution with an exact pore size that allows only certain sizes of particles to pass through.
This level of accuracy is necessary for lots of applications in life sciences and medical diagnostics, but there are also automotive and industrial venting applications. We hope the niche product status will change with more customers looking for very tightly controlled, reproducible materials that have very low batch-to-batch variability and tight tolerances.
Track-etched membranes allow for very precise control over pore size. How does Porex deliver that level of control, and why is it important for filtration?
The quality control comes from our proprietary control system for the two processing steps discussed earlier — making the tracks first, and then etching the pores — because we have 100% control over the whole length of the batch, where the base film can be hundreds of meters long. From the beginning of the batch to the end, we know the exact pore density and pore size on each square centimeter, and the exact thickness of the membrane.
Controlling these three geometries allows us to dictate all the functionalities that come afterwards, such as flow rates, burst pressure rates, and particle retention rates. All of this can be kept within very tight tolerances with a clean cutoff for all parameters.
There’s often a distinction between hydrophilic and hydrophobic membranes. Where does Porex stand on each, and what’s still in development?
Porex has a comprehensive portfolio that includes hydrophilic and hydrophobic material with different pore sizes.
In a hydrophilic application, water flows through the membrane or it is immersed in water. In either instance, you want to have a good flow rate, where the particles that should pass through the pores do so, while the rest remain in place. In these applications — such as cell culturing, cell filtration, or other processes where particles need to flow from one side of the membrane to the other — you want hydrophilic materials. Our base PET material is hydrophilic, and we can increase the hydrophilicity with additional treatments that reduce the surface tension.
With hydrophobic applications, you need to have a liquid barrier to keep moisture or liquid on one side of your system while still allowing air to pass through. For hydrophobic solutions, we use our base material with an additional hydrophobic coating covalently bonded to the surface of the PET film. This production-ready material has an ultra-low PFAS content and is also oleophobic, a barrier for oils and surfactants.
For both hydrophilic and hydrophobic applications, there can be a need for sterile filtration or sterile venting. This requires selecting pore size and confirming performance to help prevent microbial ingress while still enabling air or water to pass.
What are the primary applications using track-etched membranes today?
Applications fall into our two base markets – life sciences and industrial.
The life science market includes healthcare, pharmaceutical, and cosmetics and beauty industry products. For example, our customers need to test cosmetic products on cells to make sure they are safe to use. In medical diagnostics, there are many filtration applications where someone needs to grow cells on one side of the membrane and allow certain particles to pass through. The track-etched membrane, with its flat surface and precisely defined pores, is great for having a single layer of cells to image them clearly without having a large patch of cells stuck together.
There are also venting applications, such as in microfluidic devices where fluid passes through and an air vent is needed to prevent pressure buildup that would impede the flow. There are medical device applications, where protecting a sensor from moisture with a liquid barrier, while maintaining venting capability is necessary. Lastly, there is sterile filtration, where air passes through, but bacteria or viruses remain on the other side. It can also be used as a catch filter to capture a low number of bacteria in a sample on an even membrane surface.
In the consumer electronics and automotive industries, there is a large range of venting applications, such as in batteries or sensors. Sometimes customers need pressure compensation or dust and water protection. Other times, they need a burst membrane, where pressure builds and the membrane bursts to release the excess pressure, like in emergency pressure release vents. Sensors, actuators, and electronic lamps may need a liquid barrier and a specific vent for air pressure buildup.
Cell culture inserts are another major application. We produce different sizes and designs of cell culture inserts that are used to grow cells. These include a plastic housing and the track-etched membrane secured with heat sealing, produced in a cleanroom environment with sterile surroundings and packaging.
What can customers expect from Porex in terms of manufacturing readiness, cleanroom requirements, and certifications when using track-etched membranes for medical or other high-requirement applications?
Our track-etched membrane is not only highly specific and reproducible as a material — it is also highly scalable. We use roll stock material and can scale up processing and conversion. With conversion, we can easily integrate the membrane into a plastic housing using heat sealing, ultrasonic sealing, or pressure-sensitive adhesives. We can also do overmolding or injection molding to produce a membrane integrated into a housing part that we provide to the customer.
Our portfolio includes production-ready hydrophilic and hydrophobic solutions with membrane thicknesses from 8 to 36 micrometers, and pore sizes from 0.2 micrometers (for sterile-grade application when validated) up to 8 micrometers.
We can provide biocompatibility certifications for the PET-based material, as well as cytotoxicity certification for backing materials and adhesives. We can also provide sterile venting or cell filtration certificates for materials intended for sterile use, and certificates for REACH, PFOA, RoHS, and other required certifications for biocompatibility or general material information for medical-grade products.
For medical devices and medical diagnostics, our track-etched membrane is highly compatible with most common sterilization techniques used in large-scale production including gamma, X-ray, e-beam, ethylene oxide, and in certain applications, even steam and autoclaving.
Our production sites in Switzerland are certified according to ISO 9001 and ISO 14001, and our German site, which focuses on automotive and industrial applications, holds ISO 9001 and IATF 16949 certification. We can provide customers with Certificates of Conformance (COCs) to specifications defined at the beginning of a collaboration, and product-specific certificates confirming there are no extractables, leachables, or low particle shedding from our materials.
Ultimately, Porex combines global scale with local agility to ensure materials and components move seamlessly from prototype to high-volume production. By integrating end-to-end manufacturing capabilities with ISO-certified facilities across three continents, we provide the security of supply and technical responsiveness required in today’s market. Our commitment to advanced engineering and continuous improvement ensures that every component—no matter how complex the geometry—delivers reliable, high-performance results at any scale. We don’t just manufacture porous materials, we provide the infrastructure and precision control necessary to bring our customers’ products to life.
For more than 60 years, Porex has been a trusted co-creation partner, helping medical device, diagnostics and life science professionals solve complex functional challenges and create life-saving products through advanced material science engineering and precision manufacturing. Leveraging our comprehensive portfolio of precision-engineered materials and global manufacturing presence, we deliver optimal solutions tailored to your specific performance requirements. To learn more, visit Porex.com.