Micro functions make all the difference in microfluidics
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Porex Virtek® PTFE Hydrophobic vents
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Microfluidic design challenges solved with a unique yet simple functional material

Diagnostics innovators are continually working to diagnose and detect nearer, faster and at a lower cost within a smaller device footprint. Devices like lab-on-chip or cartridge-based point-of-care (PoC) systems help to bring the world of diagnostics closer to everyone.

Yet taking lab processes onto a micro-device requires optimizations to meet or exceed lab test accuracy. Subtle interactions of microfluidic cartridge design and materials cause changes in fluid dynamics and create challenges, such as bubbling that can lead to poor optical detection.

Porex Virtek® PTFE hydrophobic vent membranes support all microfluidic device functions and designs, from a true lab-on-chip PoC setting to lab-based molecular diagnostics.

Mitigate micro-bubbling

Virtek PTFE Debubbling Mechanism

Bubbling challenges in microfluidics are common and can lead to major downstream issues, like inaccurate optical readings. They distort fluid flow and are difficult to remove, especially with chip materials like PDMS.

Porex Virtek® hydrophobic vents are permeable to gas and not liquid – enabling as an effective passive debubbling mechanism:

  • Air and fluid pressure migrate bubbles towards vent membrane
  • Air passes through, yet keeps sample liquid within
  • Microbubbles release and break on the membrane surface

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Venting solutions

Strengthen test accuracy by minimizing contamination

Porex Virtek® pure PTFE has extremely high viral filtration efficiency (VFE) (>99.9999) and bacterial filtration efficiency (BFE) (>99.9999%) ratings to preserve samples and reagents from contamination as well as protect workers from bloodborne pathogen exposure:

  • A barrier against viral and bacterial particles, critical to sample integrity
  • Keeps liquids and other environmental contaminants out
  • 100% pure PTFE; no leachable additives or coatings leading to sample contamination

Achieve up to 5x lower MVTR for better moisture control

A sintered microporous liquid tight barrier with up to 5x lower moisture vapor transmission rates (MVTR) than other stretched or cast membranes1:

  • Minimizes sample evaporation and expulsion of PCR reagents, keeping liquids inside – critical to test sensitivity
  • Supports storage of lyophilized enzyme-based reagents to avoid early reconstruction
  • Helps minimize moisture and humidity exposure from outside of the device
Filtration solutions

Maintain a leak-proof closed system design

A vent that won’t allow water to be drawn through under typical vacuum and pressure conditions, with water entry pressure ranges typically between 3.9 – 14.5 psi:

  • Prevents leakage where user handling error may occur
  • Manage biological waste after disposal to minimize spread of biohazards
  • Surface continues to vent after contact with liquid, unlike other membrane materials
Pressure equlization

Allow for pressure equalization and fluid alignment

A hydrophobic membrane for proper venting that allows free air movement, and trapped air to escape:

  • Bypass air during heating and cooling cycles
  • Air displacement to support fluid movement
  • Allow fluid alignment for accurate volume metering where excess sample fluid is a concern2

1. Data on file via third party independent group. Tested via ASTM E96-16 method in 23±2 ̊C, 50±10%rH chamber conditions
2. A. Schneider, P. Pop and J. Madsen, “A novel metering component for volume management in flow-based microfluidic biochips,” 2018 Symposium on Design, Test, Integration & Packaging of MEMS and MOEMS (DTIP), 2018, pp. 1-6,.

Standard venting products

Products available in standard width sized rolls and discs. Custom sizes, shapes, and other formats upon request.

ItemThickness mm
Nominal
Typical Airflow
I/hr/cm2 at 70 mbar
Dry Filtration
Efficiency*
>99.99%
BFE** %
Nominal
VFE*** %
Nominal
Typical WEP****
mBar
MD100.13107 (min 70)0.5 µm>99.99270 (min 175)
MD10L0.385 (min 48)0.5 µm>99.99270 (min 175)
MD150.1875 (min 45)0.4 µm>99.99370 (min 265)
MD200.2525 (min 16)0.1 µm>99.9999>99.999520 (min 350)
MD220.117 (min 5)0.2 µm>99.99765 (min 500)
MD250.197 (min 2)0.1 µm>99.99991050 (min 750)
Oleophobic treatments available
* According to IEST RP-CC007.2 2009
** Bacterial Filtration Efficiency (BFE) data is based on a modified version of ASTM F2101
*** Viral Filtration Efficiency (VFE), † Not tested but similar results to MD20 expected.
**** WEP (Water Entry Pressure)
Properties are typical and not meant for specifications. Selected options and adhesives may affect properties. Complete testing data and information is available upon request – all exceeded the standard BFE value of 98% RoHS, WEEE, REACH Compliant (PFOA Free)

PTFE Membrane Material

Polytetrafluoroethylene (PTFE)
For applications in need of ultra-hydrophobicity, high temperature tolerances, high chemical resistance, and excellent robustness, sintered and skived PTFE membrane technology is a perfect choice.

Made from 100% pure PTFE free of PFOA, Porex Virtek® PTFE contains no additives, supporting layers, or processing aids, which ensures that the outstanding physical properties of PTFE are utilized to their full potential.

Related Resources:

Webinar: The Science INSIDE Webinar series: Increase Microfluidic Cartridge Efficiency with Porous Polymers

Video Icon Demonstration video: Porex Virtek PTFE membrane vs cast and non-woven membranes

Learn more about Porex Sample Analysis solutions