Unconventional Application of Direct Ink Writing: Surface Force-Driven Patterning of Low Viscosity Inks

A new concept for the direct ink writing (DIW) of model titanium dioxide inks through capillary action (no applied pressure during printing) is investigated through the use of diluted low viscosity inks for micropatterning. The inks are characterized with respect to rheological, thermal, and surface properties. Printed structures are characterized by profilometry, atomic force microscopy (AFM), scanning electron microscopy (SEM), and photocatalytic degradation of methylene blue. By use of the concept of surface force-driven DIW and by control of the writing speed and ink composition for different substrate surfaces, the heights of profiles of printed structures can be tailored from under 100 nm to over 1 μm. Furthermore, it is demonstrated that the surface roughness of the titanium dioxide films can be reduced up to 60% by increasing writing speed and line-to-line spacing. This work highlights a new concept of low viscosity solution micropatterning that currently can only be performed by other methods such as inkjet printing. It is believed that this novel approach will hold the key to patterning a range of low viscosity inks for various thin film technological applications.