A new design of atomic layer deposition (ALD) system for deposition on to moving flexible substrates has been demonstrated. The basic design is a cylindrical drum to which the substrate is attached which rotates inside a reaction chamber fitted with a number of different precursor and purge zones. It is intended as a vehicle for determining the parameters which are important in the design of a roll-to-roll ALD system. The system shows that deposition takes place according to the typical ALD model where there is dose saturation above a certain dose levels and that the thickness of film deposited is proportional to the number of ALD cycles carried out. The deposition rate for a reaction temperature of 100 degrees C is similar to 1 angstrom/cycle. Good uniformity across the width of a 300 mm x 100 mm flexible substrate is demonstrated. The deposition process shows some deviations from classical ALD behaviour which can be understood taking into account the movement of the substrate. (C) 2011 Elsevier B.V. All rights reserved.