What Nanoparticle Properties Can Tunable Resistive Pulse Sensing Measure?

Tunable Resistive Pulse Sensing (TRPS) technology enables accurate measurements of nanoparticles. Such measurement must be quantifiable and reproducible. At a minimum, a particle measurement technology should deliver:


Concentration measurement: given as the number of particles per unit volume of fluid.


Size measurement: given as an accurate size distribution generated by single particle sizing data.

TRPS is the only technology capable of delivering these fundamental requirements. As you can see, light scattering techniques such as DLS and NTA fail to resolve particle data which TRPS resolved with ease.

Even more impressively, TRPS also measures the surface charge of individual particles.  

Figure 1.

Tunable Resistive Pulse Sensing (TRPS), Nanoparticle Tracking Analysis (NTA) and Multi-angle Dynamic Light Scattering (MADLS) measurements of quadrimodal sample C (CPN100/CPN150/CPN200/CPN240 at 25/25/25/25). TRPS, NTA and MADLS measurements were averaged over 3 runs. TRPS identifies all four sub populations clearly. NTA was able to identify that multiple sub populations were present. MADLS was not about to identify any sub populations.


How Does Tunable Resistive Pulse Sensing Work?

The impedance of a nanopore in an electrolyte fluid cell is sampled 50,000 times per second. As particles are driven through the nanopore by applying a combination of pressure and voltage, each particle causes a resistive pulse or “blockade” signal that is detected and measured by the application software.


Blockade magnitude is directly proportional to the volume of each particle.


Frequency of blockades is directly proportional to the sample concentration.


Measuring against calibration particles of known size, concentration and surface charge ensures the accuracy of measurements.

Particle diameters are calculated from resistive pulse heights. These are proportional to particle volume as opposed to particle diameter, resulting in increased accuracy of particle diameter when compared with optical based methods.

Measurements for each sample are taken in triplicate to ensure accuracy and reproducibility. Results can be displayed as histograms, scatter plots or exported as raw data.

The Nanopore and Tunability of TRPS

Nanoparticle suspensions are complex and often polydisperse. Characterising them fully requires a tunable system which allows you to customise the measurement for your sample.


The Stretch “S” of the nanopore can be tuned to optimise the nanopore size to the particle size range within your sample.


The applied Pressure “P” can be tuned to adjust or even reverse the fluid flow through the nanopore. This adjusts blockade frequency and duration.


The applied Voltage “V” can be tuned to attract particles of different surface charge or polarity through the nanopore, and optimise the signal-to-noise ratio of the system.

TRPS uses an optimised setup which measures each sample under more than one condition. Measurements at more than one pressure are required to calculate particle concentration. Measurements at more than one voltage are required to calibrate single particle charge values.


The Exoid: The World's Most Advanced TRPS System

The Exoid is Izon’s Tunable Resistive Pulse Sensing (TRPS) system. Unlike with the qNano Gold, where parameters were adjusted manually, pressure, voltage and pore stretch are adjusted directly from your Exoid-connected device. Significant hardware improvements reduce noise levels significantly over the qNano, meaning that smaller particles can be measured more reliably. The Exoid also has a clean user interface which provides guidance throughout the setup and measurement process.

Learn more about the Exoid

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