Life Sciences – Diagnostics – Microfluidic Cartridges

Microfluidic Debubbler and Vent Membranes

Successfully Degass Air Bubbles in Microfluidic Devices

Porex PTFE Hydrophobic Vents Act as Microfluidic Bubble Trap

Air bubbles are considered to be one of the most common design challenges associated with microfluidic devices used in point-of-care diagnostic testing. Poor bubble removal can impact quantitative measurements which can lead to improper device functioning and inaccurate optical readings. Porex Virtek® PTFE hydrophobic vents can successfully eliminate bubble occurrences – even in low vacuum conditions – and thus promote fluid flow through microchannels that otherwise may have become obstructed.

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

How it works

Porex Virtek® Hydrophobic Vents are permeable to gas but repel liquids – enabling an effective debubbling mechanism where:

Air and fluid pressure migrate bubbles towards the vent membrane
Bubbles release and break on the membrane surface
Air passes through, yet the sample liquid does not pass

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Technical & Design Challenges Integrating Porous Membranes in Microfluidics

Options for standard and custom microfluidic debubbler and vent membranes

Key Features & Benefits

Strengthen test accuracy by minimizing contamination – Porex Virtek® PTFE membranes have high viral and bacterial filtration efficiencies (>99.9999%) to preserve samples and reagents while also protecting workers from bloodborne pathogen exposure
No leachable additives or coatings
5X lower moisture vapor transmission rates (MVTR) compared to other stretched or cast membranes – minimizes sample evaporation and expulsion which is critical to test sensitivity
Minimizes moisture and humidity exposure from outside of the device
Supports storage of lyophilized enzyme-based reagents to avoid early reconstruction
Does not allow water to be drawn through under typical vacuum and pressure conditions, with water entry pressure ranges typically between 3.9 and 14.5 psi
Allows for pressure equalization and fluid alignment

Vent Membrane Options

Porex’s standard venting products are available in standard width sized rolls and discs. Custom sizes, shapes, and other formats are available upon request.

Item	Thickness mm Nominal	Typical Airflow I/hr/cm² at 70 mbar	Dry Filtration Efficiency^* >99.99%	BFE^** % Nominal	VFE^*** % Nominal	Typical WEP^**** mBar
MD10	0.13	107 (min 70)	0.5 µm	>99.99	†	270 (min 175)
MD10L	0.3	85 (min 48)	0.5 µm	>99.99	†	270 (min 175)
MD15	0.18	75 (min 45)	0.4 µm	>99.99	†	370 (min 265)
MD20	0.25	25 (min 16)	0.1 µm	>99.9999	>99.999	520 (min 350)
MD22	0.1	17 (min 5)	0.2 µm	>99.99	†	765 (min 500)
MD25	0.19	7 (min 2)	0.1 µm	>99.9999	†	1050 (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)

Geometric Options

Sheets
Slit rolls
Molded & die-cut discs and plugs
Self-adhesive discs
Custom 3D sizes, chapes, and other formats

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Microporous PTFE Successfully Degasses Air Bubbles in Microfluidic Devices

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