How TRPS Works
How does TRPS work?
The impedance of a nanopore in an electrolyte fluid cell is sampled 50,000 times per second. Sample particles are driven through the nanopore by applying a combination of pressure and voltage, and 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.1
- Blockade duration changes with the velocity of the particle and can be used to calculate the surface charge of each particle.2,3
- Blockade frequency is used to determine particle concentration.4
Magnitude, duration and frequency values are converted into respective particle properties by calibration with particles of known size, concentration and surface charge.
Why is TRPS inherently accurate?
Tunable Resitive Pulse Sensing guarantees highly accurate measurement of physicochemical properties of nanoparticles, such as concentration, size and surface charge. TRPS accuracy is predominantly based on its standardised calibration process with NIST traceable standards, the precise control of convective flow and electrokinetic forces via pressure and voltage actuation, and its single particle nature. Particles are counted on a particle by particle basis, without the use of any averaging algorithms, enabling highly accurate concentration 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. Particle size accuracy is further optimised by tuning the pore to the particulates at hand. The high accuracy in particle surface charge measurements is guaranteed through the combined effect of high electric fields within the pore and precise control of convection, electroosmosis and electrophoresis.
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Resources
- Quantitative sizing of nano/microparticles with a tunable elastomeric pore sensor, Analytical Chemistry (2011), 83, 3499.
- Simultaneous size and zeta potential measurements of individual nanoparticles in dispersion using size tunable pore sensors, ACS Nano(2012), 6 (8), 6990.
- Determination of zeta potential via nanoparticle translocation velocities through a tunable nanopore: Using DNA-modified particles as an example, Journal of Visualized Experiments (2016), (116), #e54577.
- Tunable pores for measuring concentrations of synthetic and biological nanoparticle dispersions, Biosensors & Bioelectronics (2011), 31(1), 17.
- Pulse size distributions in tunable resistive pulse sensing, Analytical Chemistry (2016), 88, 8648.
- Sizing of individual Au nanoparticles in solution with sub- nanometer resolution, ACS Nano (2015), 9 (7), 7186.