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 CO₂ or N₂ 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 CO₂ 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 × 10⁸ bubbles/mL, more than sonication at 3.0 × 10⁸ bubbles/mL but fewer than pressure cycling at 2.6 × 10⁹ 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.