Barrier Test
Barrier Test Overview

Ultra Barrier TestPermeation Rate Measurements of Ultra Barriers Using Cavity Ring-Down Spectroscopy


Barrier-quality advancements of various materials have pushed the sensitivity limits of commercially available water vapor permeation equipment.  There is a need for techniques to test the next generation of Ultra Barriers.


There are emerging technologies for markets such as packaging, construction / habitat, healthcare, electronics, energy.


We need a barrier measurement technique that is:


  • fast
  • reliable
  • DL = 10-6 g/(m2-day) 


Comparison of WVTR Techniques for Ultra Barriers


Comparison of WVTR Techniques


Cavity Ring Down Spectroscopy (CRDS)


The key to our Ultra Barrier test is the CRDS (Cavity Ring Down Sensor).  In this sensor, a pulsed laser is directed into a cavity capped with partially reflective mirrors.  This allows an extremely long path of many kilometers for the laser energy to be absorbed by a few molecules of water or oxygen.  The detector is capable of sensing water vapor presence as low as 0.4 ppb.


Cavity Ringdown Spectroscopy (CRDS)




Permeation Rate


The permeation rate of a material is determined by the rate of decay of light intensity over time.  The lower the permeation rate, the longer it takes to absorb and decay the laser energy.


CRDS Light Intensity



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