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J. Xu et al.
Fig. 8.5 Schematic diagrams of a the procedure for the manufacture of electrofluidic devices in
glass, b spatially selective metallization of glass channels, and c water-assisted fs laser ablation of
channel sidewalls. d 45° and e 60° tilted optical micrographs of a metal pattern and an electrode pad
formed on sidewall surfaces after electroless copper plating, respectively. f Top-view and g titledview photographs of electrode-integrated glass channels with different configurations. The inset
shows a close-up of the sidewall indicated by the arrow in g [56, 88–90]
microcracks due to the inhomogeneous distribution of induced stress or the redeposition of debris on and around the ablated regions, both of which can degrade the
metal patterning produced during the electroless plating step. The introduction of
water to the ablation site has been suggested as a means of mitigating this problem
(Fig. 8.5c) [88]. In the case of volumetric writing performed by repeating layer-bylayer scanning from the top to the bottom of the sidewalls to produce ablation, the
introduction of water during irradiation was found to effectively remove the ablation
debris. This allowed the fabrication of crack-free, edged, well-defined structures in
a spatially selective manner. The presence of water also compensates the refractive
index mismatch at the interface between air and glass, thus improving the focusing
geometry during sidewall ablation. For these reasons, water-assisted fs laser ablation
greatly improves the ablation quality while ensuring that the ablated surfaces are
modified to the extent necessary for selective metallization (Fig. 8.5d, e). An initial
application of electroless copper plating is necessary to enhance the adhesion of thin
metal films to the glass surface. Subsequently, electroless gold plating is performed
to cover the copper films in order to enhance both the chemical stability and biocompatibility of the metal surfaces [91, 92]. In general, the geometric aspects of plated
J. Xu et al.
Fig. 8.5 Schematic diagrams of a the procedure for the manufacture of electrofluidic devices in
glass, b spatially selective metallization of glass channels, and c water-assisted fs laser ablation of
channel sidewalls. d 45° and e 60° tilted optical micrographs of a metal pattern and an electrode pad
formed on sidewall surfaces after electroless copper plating, respectively. f Top-view and g titledview photographs of electrode-integrated glass channels with different configurations. The inset
shows a close-up of the sidewall indicated by the arrow in g [56, 88–90]
microcracks due to the inhomogeneous distribution of induced stress or the redeposition of debris on and around the ablated regions, both of which can degrade the
metal patterning produced during the electroless plating step. The introduction of
water to the ablation site has been suggested as a means of mitigating this problem
(Fig. 8.5c) [88]. In the case of volumetric writing performed by repeating layer-bylayer scanning from the top to the bottom of the sidewalls to produce ablation, the
introduction of water during irradiation was found to effectively remove the ablation
debris. This allowed the fabrication of crack-free, edged, well-defined structures in
a spatially selective manner. The presence of water also compensates the refractive
index mismatch at the interface between air and glass, thus improving the focusing
geometry during sidewall ablation. For these reasons, water-assisted fs laser ablation
greatly improves the ablation quality while ensuring that the ablated surfaces are
modified to the extent necessary for selective metallization (Fig. 8.5d, e). An initial
application of electroless copper plating is necessary to enhance the adhesion of thin
metal films to the glass surface. Subsequently, electroless gold plating is performed
to cover the copper films in order to enhance both the chemical stability and biocompatibility of the metal surfaces [91, 92]. In general, the geometric aspects of plated