  Bubble nucleation in water induced by boiling, gas supersaturation or
cavitation usually originates from pre-existing gas cavities trapped into solid
defects. Even though the destabilization of such gas pockets, called nuclei,
has been extensively studied, little is known on the nuclei dynamic. Here,
nuclei of water-particle suspensions are excited by acoustic cavitation, and
their dynamic is investigated by monitoring the cavitation probability over
several thousand pulses. A stable and reproducible cavitation probability
emerges after a few thousand pulses and depends on particle concentration,
hydrophobicity, and dissolved gas content. Our observations indicate that a
stable nuclei distribution is reached at a later-time, different from
previously reported nuclei depletion in early-time. This apparent paradox is
elucidated by varying the excitation rate, where the cavitation activity
increases with the repetition period, indicating that the nuclei depletion is
balanced by spontaneous nucleation or growth of nuclei. A model of this
self-supporting generation of nuclei suggests an origin from dissolved gas
adsorption on surfaces. The method developed can be utilized to further
understand the spontaneous formation and distribution of nano-sized bubbles on
heterogeneous surfaces.
