Nondestructive evaluation of polymeric paints and coatings using two-photon laser scanning confocal microscopy

A 120 μm thick tri-layer polymer paint on an aluminium substrate was imaged in three-dimensions using multichannel two-photon confocal laser scanning microscopy. Each layer is doped with a different fluorophore so that the fluorescence emission from the layers can be separated into different channels. Use of i.r. excitation light allows deeper penetration in the polymer layers. The image reveals fine details within each layer, as well as information about the interfaces between layers. The substrate features are also visible with excellent resolution in negative contrast. This technique provides a nondestructive method to probe thick multilayer polymer materials.