Liquid flame spray (LFS)-technique was used to create multifunctional nanoparticle coatings. LFS process is continuous roll-to-roll process and it operates in ambient conditions up to line speed of 200 m/min. LFS-process is presented in Figure 1.
Figure 1. LFS coating process
Titanium dioxide (TiO2) nanoparicle coatings were generated on heat sensitive packaging materials, i.e. board, paper, and low density polyethylene (LDPE), as seen in the Figure 2. Coating amounts were 30‒50 mg/m2, average particle size was 25‒30 nm and the porosity of nanoparticle coating ~90%.
LFS-coatings have several functionalities, for example permanent superhydrophobicity (TiO2: CAW >150°) or superhydrophilicity (SiO2: CAW <10°), self-cleanability and adjustable wettability by surface stimulation (e.g. UV, plasma, heat treatments) or by changing ratio of TiO2 and SiO2-precursors. In addition, LFS/TiO2 coating has SLIPS (Slippery Liquid Infused Porous Surface)-properties.
In the end, LFS-process has great potential for industrial use because it operates roll-to-roll at high line speeds, the coating amounts are very low and it possess several different functionalities. However, the main limitations are low yield (25-30%) of the LFS-process and poor durability of the LFS-coating.
