Imaging of ink jet penetration in uncoated paper using microscopic techniques

Ink penetration in paper is influenced by the structure of the interfiber and intrafiber void spaces and the surface characteristics of the fibers. This report describes new techniques to determine the influence of the fiber surfaces and the cell wall internal structure on ink spreading and penetration. The location and penetration of ink is demonstrated by optical, scanning electron, confocal laser scanning, and transmission electron (TEM) microscopy methods. Ink penetration, as determined by each of these methods, is compared. The hemicellulose of the fiber’s internal void surfaces can be determined by immunochemical labeling in conjunction with TEM imaging. We demonstrate this by using primary monoclonal antibodies with specificity for hemicellulose with a secondary colloidal gold marker. This technique provides a way to visualize the location of hemicelluloses inside the cell wall and on the surfaces of nanopores. Combining paper structure with fluid spreading and wicking models can identify the influence of fiber surfaces and the cell wall on drop absorption.