How lipids suppress cavitation in biological fluids.

Abstract

Hypothesis: Cavitation in water under tension is often initiated at nanoscale hydrophobic surface defects that stabilize preexisting nanobubbles. We hypothesize that amphiphilic molecules, such as polar lipids, can adsorb onto these defects and suppress cavitation by removing nanobubble nucleation sites.

Simulations: To test this mechanism, we performed atomistic molecular dynamics simulations in combination with classical nucleation theory to model lipid bilayers and monolayer coatings at hydrophobic surfaces containing nanoscale pits and to investigate their response to applied negative pressures.

Findings: We find that lipids readily adsorb onto hydrophobic surfaces, conform to nanoscale features, and eliminate bubble-hosting cavities. This passivation shifts the cavitation-limiting step from nanobubble expansion at defects to rupture of lipid bilayers, which exhibit much higher cavitation resistance. These results provide a molecular basis for how amphiphilic additives enhance the stability of aqueous liquids against cavitation, even in the presence of unavoidable surface imperfections. This mechanism also offers a physically grounded explanation for how vascular plants sustain sap transport under substantial negative pressures despite structural heterogeneities in their water-conducting vessels.