Abnormal Reverse Osmosis Phenomenon in Dipalmitoylphosphatidylcholine Bilayers Enabled by Terahertz Waves

Area of Science:

• Membrane science and technology
• Biophysics
• Water treatment technologies

Background:

• Developing advanced membrane desalination technologies is critical for global water security.
• Reverse osmosis (RO) membranes are key to efficient and sustainable water purification.
• Understanding novel phenomena in membrane behavior is essential for technological advancement.

Purpose of the Study:

• To investigate the effect of terahertz (THz) waves on dipalmitoylphosphatidylcholine (DPPC) bilayers in a reverse osmosis (RO) model.
• To identify and characterize a novel RO phenomenon induced by THz radiation.
• To elucidate the underlying mechanism of THz-induced abnormal RO in biological membranes.

Main Methods:

• Utilizing a computational RO model with two DPPC bilayers separating saline and aqueous solutions.
• Applying terahertz (THz) waves at specific field strengths and frequencies to the DPPC bilayers.
• Analyzing ion behavior, hydration shells, potential of mean force (PMF) barriers, and membrane structural changes.

Main Results:

• Observed a significant net water flow from saline to aqueous solutions under specific THz stimuli, indicating an abnormal RO phenomenon.
• Demonstrated that THz waves cause ions to shed hydration shells and adsorb onto lipid heads, leading to lipid aggregation.
• Showcased how this aggregation breaks bilayer structural symmetry, facilitating RO permeation.
• Confirmed the mechanism through analysis of reduced PMF barriers, ion hydration numbers, and ion density.

Conclusions:

• Terahertz waves can induce a controllable, abnormal reverse osmosis phenomenon in DPPC bilayers.
• The mechanism involves THz-induced disruption of ion hydration and lipid bilayer structure.
• This discovery presents a new RO mechanism for biological membranes and a novel strategy for RO membrane design.