How lipids suppress cavitation in biological fluids.

Area of Science:

• Physical Chemistry
• Surface Science
• Biophysics

Background:

• Cavitation in liquids under tension often initiates at nanoscale hydrophobic surface defects.
• These defects stabilize pre-existing nanobubbles, acting as nucleation sites for cavitation.
• Surface imperfections are common in natural and engineered systems.

Purpose of the Study:

• To investigate the mechanism by which amphiphilic molecules suppress cavitation at hydrophobic surfaces.
• To test the hypothesis that polar lipids adsorb onto surface defects and eliminate nanobubble nucleation sites.
• To understand how these molecules enhance the stability of aqueous liquids against negative pressures.

Main Methods:

• Atomistic molecular dynamics simulations were employed.
• Classical nucleation theory was integrated into the models.
• Simulations modeled lipid bilayers and monolayer coatings on hydrophobic surfaces with nanoscale pits under negative pressures.

Main Results:

• Lipids readily adsorb onto hydrophobic surfaces, conforming to nanoscale features.
• Adsorbed lipids effectively eliminate bubble-hosting cavities, preventing cavitation initiation at defects.
• Cavitation resistance is significantly enhanced, shifting the limiting step to lipid bilayer rupture.

Conclusions:

• Amphiphilic additives, such as lipids, provide a molecular basis for enhancing liquid stability against cavitation.
• This mechanism explains how vascular plants maintain sap transport under substantial negative pressures despite vessel heterogeneities.
• The findings offer insights into preventing cavitation in various applications involving liquids under tension.