Nanobubble Formation by Flow Regime Switching Using a Tesla Valve.

Nanobubbles (NBs) are very small gas cavities in solution, and when their sizes reach diameters around 200 nm, they exhibit special qualities with widespread application. We introduce a novel, cost-effective method for the generation of nanobubbles by flow regime cycling through a Tesla valve, a valvular condiut without moving parts. We compare the performance of Tesla valve flow regime cycling with other previously reported methods for laboratory-scale NB generation. NBs were created from CO or N and by flow regime swiching using the Tesla valve, ultrasonication, and pressure cycling. The comparison includes bubble diameter, bubble concentration, and zeta potential under individually optimized conditions. The average bubble diameter generated by the Tesla valve from CO was measured at 110 nm by NTA, which is similar to sonication but small compared to the bubbles produced by the pressure cycling method (140 nm). Additionally, the average concentration of bubbles created by the Tesla valve was 3.8 × 10 bubbles/mL, more than sonication at 3.0 × 10 bubbles/mL but fewer than pressure cycling at 2.6 × 10 bubbles/mL. The surface charge was recorded at -33 mV, just below sonication at -36 mV but larger than pressure cycling at -21 mV. The results indicate that flow cycling through a Tesla valve generates NBs in the 100-200 nm range, which compares favorably to the alternative laboratory-scale methods while promising low energy consumption and easy scalability for future industrial applications.