On the spontaneous electric-bipolar nature of aerosols formed by mechanical disruption of liquids

• Bipolar charged aerosols are spontaneously formed after mechanical disruption.
• Aerosol is usually non-electroneutral.
• Charge partition at interfaces results in positive and negative charged droplets.

Aqueous aerosols are widely found on the Earth's atmosphere and they participate from any anthropic environment. We show here that aerosols produced by a nebulizer based on splashing contain both positive and negative droplets, this means, it is bipolar but the overall aerosol charge is usually non-zero. Charge distribution within the aerosol is by itself fractal, as previously observed in other cases of mechano-chemical charge formation that is an important mechanism for producing triboelectricity in solids. The present information added to the other authors' work leads to a particle charging mechanism based on charge partition at interfaces combined to the variability of interfacial area/volume ratio in aqueous droplets, thus explaining the formation of bipolar aerosol. The demonstration of charge bipolar distribution within aerosols contributes to explain the ubiquity of electric charge patterns in solid surfaces that is receiving growing evidence and contributes to understand both beneficial and damaging outcomes of electrostatic charging.

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