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An introduction to Spectradyne’s disposable cartridge technology

Lew Brown presents

…and here’s a transcript for your reading pleasure!

Hi, I’m Lew Brown from Spectradyne and today I’d like to talk to you a little bit more about the nCS1 measurement cartridges, which are really where the magic happens if you will in the nCS1.

Our customers just love our cartridges because they’re disposable so you don’t have to worry about cleaning. You don’t have to worry about cross contamination, etc. They only require 3 microliters of sample, which is really important for many people and they’re pre-calibrated. So you don’t have to calibrate for each individual cartridge; they’re already calibrated at the factory. So let’s take a closer look at them.

The cartridges themselves are actually quite small, measuring about half inch by a half inch square and consisting of 2 different pieces. I’ve taken one apart so that you can see the 2 pieces. The bottom piece is glass with gold electrodes for conductivity and in my right hand, you could see I’m holding the actual cast PDMS piece, which contains all the microfluidics.

To load the cartridge, one simply pipettes 3 microliters of sample into the sample port, which is located right on top of the cartridge. Once that has been pipetted in, it’s ready to be put into the instrument for measurement.

To briefly review the principle of resistive pulse sensing, particles are passed through a nano constriction where voltage is applied. The volume of the particle creates a change in electrical signal, which is what we measure. That change is proportional to the volume of the particle.

However, what would happen if all of a sudden a particle came through that was larger than the nano construction? It would clog it and that’s where microfluidics comes to the rescue.

In this over-simplified diagram you can see that how we’ve taken care of this problem is by placing a filter array between the sample port and the nano constriction where the actual measurement is made. Let’s take a closer look at that.

In order to let you see this a little bit closer what we did is we took a fluorescence microscope and looked into the cartridge as particles were going through it. The particles were fluorescent as well, which you can see is the green dots here. Now this is actually up near the filter array but it’s kind of hard to see. What I’m going to do is overlay an electron microscope image of the filter array on here, so you can see it.

The posts in the filter array are spaced exactly the same distance as the nano constriction. So what they do is they stop any particles that are large enough to clog the nano constriction from ever getting downstream where they could do that.

So I’ve zoomed out a little bit here and now you can see the particles moving from right to left as the flow is turned on and you see the larger particles of being trapped upstream.

Later on they actually get to the nano construction and here’s what it looks like and as you can see, there’s no clogging occurring. The system can run very fast, up to about 10,000 particles per second.

We use different size nano constructions in different types of cartridges in order to cover a very broad range, as shown in this map. For each size cartridge, the number represents the size of the nano constriction. So for example. the C400 cartridge has a 400nm nano constriction and you can see here that it covers from 65m to 400nm and an approximate concentration range from 1×107 particles/mL to 1×1011 particles/mL.

The overall instrument range is from 50nm to 10,000nm or 10 microns and you can see we cover a concentration range from about 1×104 particles/mL to 1011 particles/mL. Most customers only use one size cartridge, but if you need a broader range you can combine multiples together as shown here.

Here you see the same sample that has been run in 3 different cartridges in the nCS1. The software automatically stitches those 3 runs together from the different cartridges and you can see that they line up quite nicely in the overlap regions. So this overall represents a graph showing particle distribution from 65nm to 6000nm and it’s also showing over 8 orders of magnitude in concentration range.

Thanks for watching this video. I hope it was helpful to you. We’ve discussed the nCS1 cartridges in a little bit more detail. Please keep posted to our website. We will be adding more of these videos to talk about specific items related to the nCS1 over time. Thanks for your attention.