Tunable Resistive Pulse Sensing Technology
Tunable Resistive Pulse Sensing (TRPS) technology enables measurements of nanoparticles suspended in electrolytes, as opposed to the estimates provided by light scattering techniques. A scientific measurement must be quantifiable and reproducible, delivering as a minimum:
1. The concentration of particles in the fluid as a number of particles per unit volume of fluid, across a specified detectable particle size range.
2. An accurate size distribution of these particles ideally plotted as a histogram of concentration v particle diameter (or volume).
TRPS is the only technology that delivers these fundamental requirements, and in addition can measure the surface charge of individual nanoparticles. See the technology comparison section for details of where competing technologies are failing.
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.
- Blockade duration changes with the velocity of the particle and can be used to calculate the surface charge of each particle.
- Blockade frequency is used to determine particle concentration.
Magnitude, duration and frequency values are converted into particle measurements by calibration with particles of known size, concentration and surface charge.
What is "Tunable" and Why?
Nanoparticle suspensions are complex systems. Characterising them fully requires an optimised setup and measurements of each sample under more than one condition.
- The Stretch "S" of the nanopore can be adjusted to optimise the nanopore size to the particle size range.
- The applied Pressure "P" can be tuned to adjust or even reverse the fluid flow through the nanopore - allowing adjustment of both blockade frequency and duration. Measurements at more than one pressure are required to calculate particle concentration, and very fine pressure control is required for single particle charge analysis.
- 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. Measurements at more than one voltage are required to calibrate single particle charge values.
Why is TRPS Inherently Accurate?
TRPS measurement of particles in electrolyte is more accurate than TEM. Learn more about the capabilities of TRPS by clicking on the Particle size, Particle concentration and Particle charge menu headings.
The video below shows TRPS in action with a qNano system.