Single Particle Zeta Sizer
December 7, 2021
Background / Context / Abstract:
The inventor’s research group has been studying sensor technologies using ultra-thin solid nanopores for the structural analysis of single particles. More specifically, the technology detects the motions of particles passing through nm-sized fluidic channels through measuring the ionic current that enables an analysis of their size and zeta potential at the single particle level.
Resistive pulse sensors have widely been used to deduce the size, and sometimes also the zeta potential, of analytes from the ionic current signal waveforms. However, the measurement waveforms tended to be distorted due to the effects of particles entering (entry effect) or passing through the nanopore off the central axis (off-axis effect), and so it was not always possible to measure an accurate signal waveform. The invention of the single-particle zeta sizer with the “pores-in-series” structure has solved this problem, and the correct zeta potential can now be obtained for each particle.
Invention of a particle size measurement device for a single particle/molecule with multiple nanopores connected in series, classified as a type of resistive pulse method.
This technology can simultaneously measure the size and surface zeta potential of individual particles by a simple electrical measurement.
・As shown in the figure above, octet-channel architecture (eight nm-sized constrictions) was installed in series allowing eight times of resistive pulse detections in one measurement. It was confirmed that the signal waveforms acquired in the narrowed portions of the later stage channel were more similar to the original signal waveforms due to the reduction of the off-axis effect thereby enabling accurate estimations of the particle sizes from the resistive pulse heights.
・The positions of the eight pulses tell us when a particle electrophoretically passed through which of the eight constrictions. This information is useful in knowing how fast it moved in the fluidic channel and to accurately estimate the single-particle zeta potential from the resistive pulse spacing under the suppressed off-axis effect at the channel downstream.
・Kishimoto S., Tsutsui M., et al. “Inertial focusing and zeta potential measurements of single-nanoparticles using octet-nanochannels” Lab Chip, 2021, 21, 3076.
・Size and zeta potential measurement of individual particles and molecules with only a single measurement.
・High accuracy: Particles of interest are less susceptible to “entry effect” and “off-axis effect.”
Potential Applications / Potential Markets:
A sensor with multiple nanopores connected in series for simultaneous measurements of the size and zeta potential of a single particle or molecule in liquid.
State of Development / Opportunity / Seeking:
・Available for exclusive and non-exclusive licensing
・Exclusive/non-exclusive evaluation for defined period (set up for options)
Applied in Japan (JPO), not yet published.
The series nanopore structure reduces the influence of the “entry effect” and “off-axis effect.”
Ion current waveform of a particle passing through a series of nanopores; particle transit time can be measured.