Transonic Flow Focusing Delivers 99% Monolayer Graphene Exfoliation in Single Surfactant-Free Step

The preprint describes a contact-free process in which liquid suspensions are focused into jets at transonic speeds, generating combined shear and extensional flows within microsecond residence times at the meniscus. Experiments with commercial graphene nanoplatelets in isopropanol produced flakes 300-400 nm laterally and nanofragments 10-15 nm across, both verified as monolayers by HRTEM and AFM, while water runs reached 92.9% monolayer fraction.

Existing liquid-phase exfoliation routes such as probe sonication or shear mixing typically require surfactants or oxidation steps that leave residues and lower electronic quality. The TFF approach avoids these additives entirely, achieving viscous power densities near 10^10 W/m^{3} that rival or exceed turbulent mixers yet operate in a confined, scalable geometry.

Because the method works with both alcohol and pure water and yields predominantly monolayer material in one pass, it could reduce purification costs that currently dominate top-down graphene production. Remaining questions center on throughput scaling and defect density under continuous operation.

Pilot reactors with parallel jet arrays would need to demonstrate gram-scale hourly output while preserving monolayer fraction above 95% to displace incumbent methods in electronics-grade supply chains.