High-Speed Multipass Coulter Counter with Ultrahigh Resolution

Area of Science:

• Nanotechnology
• Analytical Chemistry
• Biophysics

Background:

• Coulter counters measure particle size via resistive pulses, but Brownian motion limits resolution.
• Variability in particle translocation path affects accuracy.

Purpose of the Study:

• To develop a modified Coulter counter with enhanced nanoparticle size resolution.
• To overcome limitations of conventional Coulter counters caused by particle translocation variability.

Main Methods:

• Utilized programmable data acquisition hardware to modify a Coulter counter.
• Implemented a voltage-switching technique to repeatedly shuttle individual nanoparticles through a nanopipet orifice.
• Measured resistive pulses and determined mean pulse amplitude for individual particles.

Main Results:

• Achieved significantly improved size resolution compared to conventional Coulter counters.
• Demonstrated precise determination of mean blocking current for single polystyrene nanoparticles.
• Attained sub-angstrom size resolution through repeated particle measurements.

Conclusions:

• The modified Coulter counter offers superior accuracy and resolution for nanoparticle sizing.
• Repeatedly measuring individual particles significantly reduces translocation variability.
• This technique enables precise characterization of nanoparticles at the sub-angstrom level.