Drop-on-demand printing of carbon black ink by electrohydrodynamic jet printing.

Electrohydrodynamic (EHD) jet printing is a technique using electric fields to eject inks through nozzle apertures. EHD jet printing is very attractive due to its non-contacting nature and compatibility with diverse materials and substrates. In this research, we have fabricated micron-sized dot arrays and line patterns with carbon black ink on Si wafer substrates using EHD jet printing. The effect of operating conditions such as applied voltage, working distance and stage speed on the size and shape of the jetted patterns and jetting cycles is investigated by using optical microscope, high speed camera and atomic force microscopy (AFM). We have also demonstrated the drop-on-demand feature of the EHD jet printing system by patterning carbon black ink lines with various widths and dot arrays with desired diameters and spacing by controlling the operating conditions.

Micro-contact printing of polydiacetylene liposomes using hydrophilic stamps.

Micron-sized polydiacetylene (PDA) liposome patterns have been fabricated on titanium (Ti) substrates using a micro-contact printing (micro-CP) technique. Two types of stamps (PDMS and agarose) and inking methods ("soaking" and "dropping") are used for micro-CP, and we compare their effect on the morphology of the PDA patterns. The size and morphology of the patterned PDA liposomes are analysized by optical and fluorescence microscopies and atomic force microscopy (AFM). When the agarose stamp is inked by the "dropping" method, PDA patterns are most efficiently transferred to the Ti substrate. However, the thickness of the transferred PDA patterns is not homogeneous, with the edge of the transferred pattern being thicker than its center. In contrast, when the PDMS stamp is used for micro-CP, the center of the pattern is thicker than the edge. Red fluorescence patterns are readily obtained by heat treatment of the PDA-immobilized solid substrate. The intensity of the fluorescence of the samples is consistent with the results of optical microscopy and AFM experiments.