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Electrical Calcium Test for Measuring Barrier Permeability

National Renewable Energy Laboratory

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Technology Marketing Summary

Moisture or water vapor barriers are important in many types of packaging including moisture sensitive consumables and pharmaceuticals, as well as some photovoltaics applications, flexible displays and consumer electronics. Before barriers are used in packaging, they are tested for their Water Vapor Transmission Rate (WVTR) to determine how well they isolate the product from outside moisture. One current method for measuring WVTR through stand-alone barriers is an optical calcium test, which makes use of UV-Vis measurements of calcium corrosion as moisture permeates the barrier. Optical methods typically rely on use of an edge seal, which can interact partially with the calcium and require intimate contact of the calcium and the barrier to be tested. Deposition of calcium onto the barrier is a slow process requiring expensive glove-box integrated deposition systems. In addition, while such test methods can yield information on pinhole defects in films and their density, the total WVTR measurement data can be difficult to interpret. The present invention overcomes the limitations of optical calcium tests and provides an electrical measurement of WVTR of stand-alone barriers.


The current invention is an Electrical Calcium Test method and device that makes use of a thin-film conductor-patterned sensor test card to test moisture barriers under edge seal. The test cards contain patterned calcium sensors connected electrically to conductor lines in a four wire resistance measurement configuration so that changes in conductivity of the calcium sensors can readily be detected. The test card can also include a “witness line” to monitor the integrity of the edge seal itself to guard against false readings due to degradation of the edge seal rather than the barrier under test. An optional water impermeable spacer may be used to separate the test card from the barrier film to regulate the distance and aperture of the barrier exposed to the test card. The test cards can be created separately from the barriers, increasing ease of manufacture and use, and could be a disposable product.

  • Does not require intimate contact between barrier and calcium layer (and therefore avoids time consuming steps and expensive capital equipment)
  • Test cards can be created separately from barriers – could be off-the-shelf
  • In-situ/real-time measurement of WVTR and lag times without interrupting the test
  • System can be multiplexed for multiple concurrent tests of the same barrier
  • System can be multiplexed to test many barriers in parallel – can be used as a quality control technique on manufacturing lines or in barrier development in R&D environments
  • Readily integrated with multiple environmental chambers simultaneously
  • Flexibility in testing a variety of different permeation sensitivities (10-5 – 10-7 g/m2/day)
  • Automatically monitors integrity of edge seal separating edge effects from barrier transmission
  • Software techniques for data analysis improve speed and sensitivity of measurements

The technique has already been demonstrated with an edge seal that can perform for more than 1000 hours in 85C/85% RH conditions.

Applications and Industries
  • Photovoltaic encapsulation
  • Pharmaceutical packaging
  • Flexible electronics and displays
  • Organic LEDs
Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Patent 8,664,963
Test device for measuring permeability of a barrier material
A test device for measuring permeability of a barrier material. An exemplary device comprises a test card having a thin-film conductor-pattern formed thereon and an edge seal which seals the test card to the barrier material. Another exemplary embodiment is an electrical calcium test device comprising: a test card an impermeable spacer, an edge seal which seals the test card to the spacer and an edge seal which seals the spacer to the barrier material.
National Renewable Energy Laboratory 03/04/2014
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
NREL ROI 09-46DevelopmentAvailable08/04/201003/21/2016

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To: Erin Beaumont<>