Ultra-long lifetime water bubbles stabilized by negative pressure generated between microparticles.

Bubbles blown up from a water surface can only last for seconds before bursting due to gravity, surface tension and evaporation. Although adding certain surfactants and depressing evaporation can significantly extend the bubbles' lifetime, there is still no method to prevent the bubble film from getting thinner and avoid the effects of evaporation. Here we report our experimental observation that centimeter length scale water bubbles can last for over a month at room temperature in the open natural environment with evaporation if they are covered with densely distributed microparticles on the bubble top surface. The underlying stability mechanism to balance out evaporation water loss is revealed to be the existence of negative pressure in the water between the two water-air interfaces of the film of the bubbles. This negative pressure is generated by surface tension of the locally curved water-air interfaces spanned over the particles and acts against gravity to suck water up from the water bulk and self-adaptively compensate the water loss due to evaporation. A theoretical model of the above water supplementary mechanism is built and computed numerically using Surface Evolver. A three-dimensional fluorescence experiment is also designed to verify the above water transfer process. This mechanism is generally valid for making ultra-long lifetime bubbles not only with water, but also for other liquids and suitable particles that satisfy certain contact angle requirements.