Design Day 1 Follow-up

1) What are the pressure and temperature differentials between the surface and the altitudes we're interested in sampling at?

2) What are the specifications for our button sampler vacuum pumps?

• NiMH battery
• operating temperature range: 0 to 45 C
• altitude: "Do not use pump beyond 7500 ft"
• 12 hrs at 2000 ml/min
• up to 30 inches water back pressure

3) What are the specifications for the filters we've been using in the button samplers. Does the Mixed cellulose ester (1.2 um) - we have used these with the button sampler

• burst strength: > 10 psi
• porosity: 74-77%
• maximum working temperature: 130 C

Cellulose nitrate (0.2 um) - we have used these with larger pumps

• burst strength: > 2 psi
• porosity: 66-84%
• maximum working temperature: 80 C

*** I have not been able to find specific information effects of low temperatures on pore size.
5) We need a way to sample a huge volume of air with no pressure differential. We should look into methods other than filtration for collecting cells, maybe impaction onto foams or other porous materials that particles could stick to. For example glass wool (but touch for bead beating), furnace for houses, 'open cell foam', or polyurethane foam. Think about difference between impingement & impaction.


Impaction onto porous surfaces is a good option and one that we have some experience with. We have used gelatin filters with large pore sizes to trap microbes. Cells end up stuck to the sticky gelatin. The large pore size of the "filter" allows for a higher flow rate.


6) Another way to avoid "sucking" is to explore "pushing" air through a filter. We would need 3-4 psi. What about using a cooling fan harvested from used computer can run off a 9V battery (see image below). Can we use this to move air through a filter? Or onto a surface? We could put these blowers in series. Another idea is a brushless DC blower (a larger) or a "squirrel cage blower" fan.