Polyester Track-Etch (PETE) FAQ

Polycarbonate (PC) and Polyester (PET) track-etch membrane filters are precision, two-dimensional microporous “screen” membranes with straight-through, cylindrical pores created by the track-etching process. Because the pore structure is uniform and non-tortuous, particles are captured primarily on the membrane surface, providing a highly accurate and reproducible separation cut-off compared to depth filter media. Track-etch membranes are known for having some of the most precise pore size distributions of any membrane filter, making them ideal for applications that require exact particle sizing and surface capture, such as microscopy, particle analysis, microbial enumeration, and sample preparation. These membranes are also very thin (typically ~6–15 µm) yet surprisingly durable, and can withstand high differential pressures (over 3,000 psi when properly supported). They are available in a range of appearances, from opaque to nearly transparent, including black options for enhanced contrast in imaging and microscopy.

Sterlitech Polycarbonate (PCTE) and Polyester (PETE) track-etched filter membranes offer ultra-low non-specific binding and a smooth, flat surface that captures particles on a single plane—ideal for microscopy, SEM, and particle analysis. Manufactured under Class 100 cleanroom conditions, they are contaminant- and pyrogen-free, with very low extractables and no fiber shedding. Both membranes are biologically inert, provide precise, uniform pore sizes, and deliver excellent chemical and thermal stability, with PETE offering higher solvent resistance.

Sterlitech Polyester Track-Etched (PETE) membrane filters are manufactured from polyethylene terephthalate (PET), a durable polyester film known for its excellent mechanical strength, dimensional stability, and chemical resistance. These properties make PETE membrane filters well suited for track-etched filtration, microscopy, particle analysis, and other demanding laboratory and analytical applications.

Generally, no. Polycarbonate Track-Etched (PCTE) and standard Polyester Track-Etched (PETE) membrane filters are not recommended as vent filters because they do not provide sufficient water entry pressure to reliably retain liquids while allowing gases to pass. Even hydrophobic PCTE membranes may allow water to pass under relatively low differential pressure. For gas venting, sterile vent filtration, or applications that require liquid retention with gas permeability, Sterlitech recommends hydrophobic PTFE membrane filters or hydrophobic/oleophobic PETE membrane filters, which offer significantly higher water entry pressure and are specifically designed for these applications.

Yes. Scanning Electron Microscopy (SEM) is commonly used to estimate the pore size of Polyester Track-Etched (PETE) membrane filters. However, measured pore diameters may vary due to SEM calibration, magnification, image resolution, sample preparation, and measurement technique, so they may not exactly match the manufacturer's specifications. For the most accurate results, use a calibrated scale standard, measure multiple pores across several fields of view, and report the average pore size along with the pore size distribution.

Cell adhesion to Polycarbonate Track-Etched (PCTE) membranes depends on the cell type and surface treatment. Many exfoliated human cells adhere naturally, while most epithelial cells attach more readily to plasma-treated or coated membranes. Endothelial cells generally do not adhere well to standard track-etched membrane filters without additional surface modification. For optimal results in cell culture and cell migration studies, membrane selection and surface treatment should be matched to the specific cell line.

Both polyester and polycarbonate track-etched membrane filters provide precise pore structures and excellent filtration performance, but each offers distinct advantages. Polyester track-etched membranes provide superior solvent resistance and are less prone to wrinkling during manufacturing. Polycarbonate track-etched (PCTE) membranes are widely used and have long been the industry standard, particularly for cell culture, microscopy, and cell-based assays, where they generally perform better with live or fixed cells. Both membrane types deliver high-quality, reproducible results and are suitable for a wide range of filtration, analytical, and life science applications.

The most common cause is accidentally installing the blue separator paper instead of the Track-Etched (PCTE) membrane filter. The separator paper is blue or printed and is for packaging only—it is not intended for filtration. The actual polycarbonate track-etched membrane is thin, translucent or opaque, and typically white with a slight yellow or green tint. If the correct membrane is installed, low or no flow is often caused by membrane clogging. Because track-etched membrane filters have precise cylindrical pores, they retain nearly all particles larger than the pore size, making them more susceptible to plugging. For samples with high particulate loads, use a glass fiber prefilter to capture larger particles before they reach the membrane. To further improve flow, especially in stainless steel filter holders, use a mesh spacer (drain disk) beneath the membrane. This promotes tangential flow, increases the effective filtration area, and helps maximize flow rates.

Yes. Sterlitech can provide custom Polycarbonate Track-Etched (PCTE) and Polyester Track-Etched (PETE) membrane filters with non-standard specifications, subject to manufacturing capabilities. Customization options may include pore size, pore density, membrane thickness, and surface treatments to meet specific application requirements. To discuss your application or inquire about the availability of custom track-etched membrane filters, please contact Sterlitech at [email protected].

Yes. When stored under the recommended conditions of 5–35°C (41–95°F) and 20–80% relative humidity, track-etched membranes maintain their pore size, pore density, bubble point, and thickness for up to 8 years. For best performance, store membranes in their original packaging away from direct sunlight, excessive heat, and moisture until use.

Polycarbonate Track-Etched (PCTE) and Polyester Track-Etched (PETE) membrane filters are extremely thin and can easily accumulate static electricity, making them difficult to handle, position, or separate from packaging. Using a static eliminator helps reduce static cling and electrostatic repulsion, improving membrane handling and minimizing the risk of damage or contamination during installation.

The polycarbonate track-etch (PCTE) membrane filters can be dissolved with dipolar aprotic solvents such as dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and n-methyl-2-pyrrolidone (NMP). The PCTE membrane filters can also be dissolved with the organic chlorinated solvents dichloromethane (DCM or methylene chloride) and trichloromethane (TCM or chloroform). PCTE membrane filters can also be dissolved with toluene and potentially with other similar aromatic hydrocarbon solvents. The polyester track-etch (PETE) membrane filters can be dissolved with m-Cresol, o-Chlorophenol, hexafluoroisopropanol, and trifluoroacetic acid (TFA). Both types of track-etch membranes can be dissolved with elevated temperature sodium hydroxide solutions.

Polyester Track-Etched (PETE) membrane filters can be autoclave sterilized using a steam-permeable autoclave pouch or wrap that allows direct steam contact with the membrane. Avoid packaging materials that block steam penetration, as they may reduce sterilization effectiveness. Proper steam exposure helps ensure reliable sterilization while maintaining PETE membrane performance.

Yes. Plasma treatment reduces the water contact angle of hydrophobic Polyester Track-Etched (PETE) membrane filters, making the membrane surface more hydrophilic. The process also introduces oxide and hydroxyl functional groups, which may improve cell attachment and surface interactions. While plasma treatment enhances membrane wettability and makes the pore structure easier to wet with cell culture media or buffers, a more hydrophilic surface does not necessarily result in better cell attachment for every cell type. The optimal surface depends on your specific cell culture application and cell line.

Polyester Track-Etched (PETE) membrane filters are absolute-rated membrane filters. Their track-etched manufacturing process produces highly uniform, cylindrical pores with tightly controlled pore size distribution, providing precise and reproducible particle retention. Like Polycarbonate Track-Etched (PCTE) membranes, PETE membrane filters are considered absolute-rated, making them ideal for applications requiring accurate particle sizing, microscopy, and analytical filtration.

Standard gold-coated Track-Etched membrane filters are coated as follows: Gold-coated Polycarbonate Track-Etched (PCTE) membranes: 40 nm gold coating on the front side and 20 nm on the back side.

Gold-coated Polyester Track-Etched (PETE) membranes: 100 nm gold coating on the front side. For specialized applications, custom gold coatings on both sides are available. Gold coating thicknesses of up to 100 nm or greater can be provided, subject to the membrane's adhesion characteristics. Additional plasma surface treatment or adhesion layers may be used to improve coating adhesion for specific membrane materials. Please contact [email protected] to discuss your application and custom coating requirements.