Fluorescence microscopy of inkjet prints
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Date
25/11/2010Author
Castro Spencer, Maria Diana
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Abstract
Inkjet printing technology has been developing rapidly during recent years, pressing the ink
and paper manufacturers to develop a better understanding of the mechanism of fixation of
inkjet dye into the substrate.
The aim of the work described in this thesis was to investigate the three-dimensional
distribution of inkjet dye in paper and the interaction between dye and paper using advanced
fluorescence microscopy techniques, Confocal Laser Scanning Microscopy (CLSM), and
Two-photon Fluorescence Lifetime Imaging Microscopy (2P-FLIM).
It has been shown that CLSM is a valuable, non-destructive, rapid technique for threedimensional
imaging of printed samples and evaluation of print quality. The intrinsic
fluorescence of both the inkjet dye and the paper substrate can be used to determine the
spread and penetration of ink droplets in different inkjet papers. The optical sectioning
capability of CLSM enables the position of the ink layer relative to the paper surface and the
penetration depth of the ink to be quantified. It was observed that while in the microporous
type of inkjet paper the penetration depends on the quantity of ink in the printed sample, in
the swellable type of inkjet paper the penetration is almost the same for different amounts of
ink.
2P-FLIM has been employed to spatially map, in three-dimensions, fluorescence lifetimes by
measuring the lifetime at each pixel in the image. Fluorescent molecules in both the ink and
paper were analysed. Because the fluorescence lifetime is affected by the local molecular
environment, the fluorescence lifetime maps provide information on the interaction between
inkjet dye and paper. Analysis of fluorescence lifetime maps reveals the interaction between
dye molecules and silica or alumina particles in the paper, variations of the molecular
environment within a single ink dot and that interaction between dye and paper is affected by
pH.