Figure 1. Jetting parameters of titania ink: a) titania ink
photograph and particle size distribution by DLS method; b) dependence
of viscosity by ethylene glycol/titania sol ratio; c) drop analyze from
Dimatix printer stroboscopic camera; d) droplets of titania xerogel at
282 DPI; e) droplets of titania ink at 635 DPI
The advantages of nano-inks are their resulting large surface area and
high reactivity rates, as well as the possibility of uniform dense
packing of particles and passing through the cartridge nozzle without
clogging.
The viscosity of the initial sol was 1.5 cP, which is below the
recommended ink viscosity of 10 cP for Dimatix
cartridges26. Many research groups used various
organic additives for viscosity and surface tension modification to
configure the optimal print settings27. In our work we
used ethylene glycol to increase viscosity of titania sol to 9.3 cP
(Figure 1 b). The application of an organic component in our case
allowed to obtain an advanced porous surface capable to absorb the
analytes and react with them faster. Furthermore, to improve the
wettability of the nozzle and droplet formation, we set up the surface
tension of the ink reducing it from 45.7 to 30 mN•m−1
with 1% solution of DX4010N surfactant.
Then the ink was loaded into the cartridge compartment and the stability
of jetting and dropping were tested with a stroboscopic camera. By
latency test checking we found that print can be reproduced in a wide
range of time and printing frequency. We observed steady dropping
(Figure 1c) after exposure pause of 0.5 - 10 minutes without pre-washing
(purge of nozzles) indicating the stability and safety of the ink to
cartridge nozzles. At the same time the print frequency varying from 1
to 5 KHz and DPI (dots per inch) from 282 to 635 with stable printing
shape formation (Figure 1 d, e) identified the wide range of print speed
for our ink.