Nanobubbles in Ultrapure Water Can Self-Propel

Area of Science:

• Physics
• Colloid Science
• Nanotechnology

Background:

• Nanobubbles are sub-micron gas entities with diverse scientific applications.
• Their movement is typically assumed to follow Brownian motion.

Purpose of the Study:

• To investigate the motion of oxygen bulk nanobubbles in ultrapure water at body temperature.
• To characterize the observed motion using fractal analysis and stochastic process descriptors.

Main Methods:

• Observation of oxygen bulk nanobubble trajectories in ultrapure water.
• Application of fractal analysis, including structure function, velocity autocorrelation, skewness, and kurtosis calculations.
• Classification of the observed motion as a stochastic process.

Main Results:

• Oxygen nanobubbles demonstrate self-propelled motion, not solely Brownian diffusion.
• The motion exhibits self-affine characteristics with different scaling exponents along the x- and y-axes.
• Analysis confirms a quasi-Gaussian stochastic process classified as fractional Brownian motion.
• Superdiffusion is observed in over 50% of x-axis trajectories, and 30% of y-axis trajectories.

Conclusions:

• Oxygen nanobubbles exhibit self-propelled, fractional Brownian motion in ultrapure water.
• The motion's characteristics are influenced by the anisotropic nature of the field of view.
• This finding challenges the conventional understanding of nanobubble diffusion and opens new research avenues.