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.