National Physical Laboratory

Measuring the performance of barrier layers


One of the biggest challenges for emerging technology based on organic electronics and graphene is assuring the lifetime of the product. These materials are highly sensitive to moisture and oxygen and metrology to underpin quantitative degradation studies of the active components and performance measurements of encapsulating barrier materials is essential for future success of the technology.

NPL facility

Water Vapour Transmission Rate (WVTR) facility

NPL has developed a new approach to measuring WVTR directly, based on cavity ring-down infra-red spectroscopy. The system operates with a dry chamber separated from two wet chambers of known temperature and relative humidity by the barrier material under test. Water vapour permeating through the film is collected by a flow of dry nitrogen and measured. A major source of error in methods used to measure ultra-low levels of water vapour transport is leakage around the perimeter of the sample under test where it is clamped into the measurement system. The measurement cell described here uses a novel design to minimise leakage through the seal and hence to eliminate water ingress to the dry chamber. This approach is a significant advance beyond existing methods and provides accuracy and traceability with a detection limit below 5 x 10-5 g m2 day. This method is underpinned by a unique facility at NPL for generating reference standards of water vapour in nitrogen between 5 and 2000 nmol mol-1 with an estimated relative expanded uncertainty of 2 %.

Research focus

Current research activities include:

  • Stable electrical impedance sensors to support measurements of trace water vapour
  • A portable, dynamic calibration device to support measurements of the influence of water on new materials used in organic electronic devices and assess the suitability of encapsulating barrier layers
  • Traceable measurements of oxygen transmission rate

Investigating the feasibility of producing high performance barrier films using self-healing multilayers of high quality chemical vapour deposition graphene and atomic layer deposited amorphous alumina multilayers

Contact us

Customer enquiry tel: +44 20 8943 8715

Last Updated: 10 Dec 2014
Created: 13 Oct 2010


Please note that the information will not be divulged to third parties, or used without your permission