Sample Prep part 2

 We are particle people.  We consider that our job begins by collecting particles; from air, surfaces, and liquids.  Then, we deliver the particles for detection or identification as the case may be, in the best possible way.  So, to collect the particles we build aerosol inlets, aerosol collectors of different kinds, surface samplers, and water samplers.  For the best possible sample delivery to detectors and identifiers, we build the concentrators (Slide 7).  The concentrator forms the link between the real-world sample volumes and the micro-volumes required by the modern identifiers that we described earlier.
 
Our wet foam elution is very efficient because foam has some interesting and unique characteristics.  All the shear and particle removal forces of a foam are made to bear right at the very surface that they contact (Slide 8).  Very small particles, like bacteria, viruses, and proteins in the micron and below size ranges adhere unbelievably tightly to surfaces.  Think about geckos and the way they can walk on the ceiling.  They can do it because the hairs on the bottoms of their feet are so small that the small molecular forces become proportionally very large in comparison to the tiny size of the hairs.  It is the same for biological particles.  And it means that you need a strong dislodging force, like our wet foam elution, to remove the particles from surfaces. 
 
Another great thing about foam is that it moves more like a plug than like a liquid, and since it’s been expanded with gas, it’s like flushing with five or ten times more fluid than you end up with when it collapses back down to a liquid.  We make the foam by carbonating it.  The foam collapses fast because the carbon dioxide off-gasses quickly, kind of like the way soda pop goes flat fast if you foam it up.  If you want to see soda pop go flat really fast, try opening a can of soda pop and putting it in an ultrasonic bath sometime.  Turn it on and stand back.  And Make sure everyone is wearing their safety glasses!  In fact, don’t try this in the lab like we did; go outside.
 
In Slide 9, you can see wet foam eluting particles from a dry filter.  The filter in the specially designed cartridge shown is made to connect to a hand-held cartridge of wet foam elution fluid.  When the cartridge is attached, the foam shoots through the filter and extracts the particles from the filter.  We tested this with microspheres and spores and it is essentially 100% efficient.    When particles are collected in the hollow membrane fiber cells of the Concentrator, the wet foam elution removes them and delivers them efficiently in a preset small volume of identifier-friendly fluid (Slide 10).