Introduction to the Membrane Flow Analysis Device for Gas (MFAD-G), QC Model

Introduction

The Membrane Flow Analysis Device for Gas (MFAD-G), Quality Control Model, is the first* of a 3-version series of devices that, altogether, will allow use-specified measurement of flow rate and flow pressure of gas and liquid media through chip-mounted membranes. The QC Model has a rudimentary form of the general system and acts as both a prototype for laboratory-grade versions as well as a functional device sufficient for chip quality-control testing by SiMPore.

Concept Art

The driving need behind the design is that membrane porosity, mechanical strength, and uniformity thereof are critical aspects being developed in nanoporous and microporous membrane chips. By measuring the flow rate through a system containing a measured positive pressure that is partially isolated from the environment by a membrane (the rate of gas escaping), we can approximate these properties for an individual chip with respect to the theoretical model and previous sampling.

Basic Representation

Basic Representation

*The MFAD is an improved and published descendant of a setup developed and commonly used by other laboratory researchers at McGrath Lab. Improvements are in ease of use and accuracy.
 

The MFAD-G QC Model system diagram:

System Flow Diagram for MFAD-G QC Model

Besides the aforementioned functions, you can see that the device also features:

  • A pressure-release valve for resetting and reducing system pressure
  • A rotameter bypass path for burst-pressure testing that prevents jolting of the rotameter bead into the top face of the tube.

 

Brief explanation of components:

  1. Nitrogen Tank and Tank Regulator: A large N2 tank equipped with a Harris 0-100 psi welding gas regulator preserves and controls pressure in the system. All MFAD components are rated for >100 psi.TankRegPic
  2. Rotameter: Gives an  analog measure of flow rate by channeling flow past a bead in a tapered tube (higher flow -> greater height of bead suspension). Uses simply interchangeable 0-.20, 0-2.0, and 0-20. L/min flow tubes for 2% accuracy at a wide range. (see manual for tube changing instructions).RotameterPic
  3. Manometer: A proven model that gives a digital read-out measure of 0-100 psig flow pressure with .1 psi resolution.DigitalManometer
  4. Chip Holder: A component that seals the chip across the end of the MFAD. Any holders customized to chip sizes and testing applications can be used as long as they have a 1/4″ OD input tube for attachment with the end ball valve. Below are two existing holders for SEPCON chips:
Flow Rate Measurement Holder

Flow Rate Measurement Holder

Burst Pressure Measurement Holder

Burst Pressure Measurement Holder

 

5.  Frame [Not in Flow Diagram]: All versions of the MFAD will be frame-mounted for organization and storage purposes.

FramedPic

Measurement Comparison with Previous System:

From “Wafer-scale permanence test” by Meghan Kazanski and Josh Winans, NRG Archive for Data:

Average SEPCON Flow Rate: 500 ± 21 mL/min

Pressure = 1 psi

n = 5

From testing with the MFAD-G QC Model:

Average SEPCON Flow Rate: 605 ± 14 mL/min

Pressure = 1.03 psi

n = 5

After further testing and discussion, the difference was explained by a combination of leakage and a lack of significant figures in the old system.

Next Steps

The MFAD-G Electronic Model will be a laboratory-grade device with electronic transducers, digital data collection.

System Flow Diagram for Electronic MFAD-G

System Flow Diagram for Electronic MFAD-G

  • Error reduction
  • Faster Sampling/Larger Sample Sizes

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