The SeaFlow cytometer was invented by Jared Swalwell of the University of Washington Armbrust Lab. One major SeaFlow innovation is patented "virtual core" technology. Most cytometers form a single-file line or "core" of cells by injecting the cells into a stream of "sheath fluid" when then flows past the light excitation beam. Seaflow eliminates the need for an actual core and sheath fluid by utilizing three positional detectors and software to determine which cells are in proper position relative to the excitation beam, rejecting measurements that don't fall within the measurement region. Swalwell is developing the next generation SeaFlow, called SeaLabel. SeaLabel significantly reduces instrument size and power usage.
2013 MBARI CytoAUV MBARI proposal (not finally submitted; includes SeaLabel description [CONFIDENTIAL])
Performance notes
Measurement time, event rate, power - Swalwell et al describe seawater flow rates on page 472 of their recent paper. Seawater is pumped into the the instrument at a "nominal" rate of 15 ml/min. Only particles in the inner part of the stream are detectable, and only a fraction of those particles are in focus. Only the in-focus "optically-positioned particles" (OPP) can be analyzed. The flow rate of detectable particles is ~1/10 the flow rate of the stream while the flow rate of OPP is ~1/100 the flow rate of the detectable particles. Thus the flow rate of the OPP is ~15 uL/min = 2.5 x 10^-4 ml/sec.
Compute time 'T' to measure N OPP cells at this flow rate 'f', for given values of number density 'p':
T = N / (f * p)
We assume that cells are not necessarily all the same size, but they are all detectable, and assume that each cell is individually detected (i.e. we don't see multiple cells counted as one).
| N=1000 (sigma=3.1%) |
N=500 (sigma=4.4%) | N=100 (sigma=10%) |
|
|---|---|---|---|
| p = 10^2 cell/ml |
40000 s |
20000 s |
4000 s |
| p = 10^3 cell/ml |
4000 s |
2000 s |
400 s |
| p = 10^4 cell/ml |
400 s |
200 s |
40 s |
| p = 10^5 cell/ml |
40 s |
20 s |
4 s |
Note that the virtual core size (and hence OPP flow rate) is adjustable. The example value of ~15 uL/min corresponds to a virtual core diameter of ~6 microns (the physical stream diameter is ~200 microns). For a low number density, the virtual core diameter and OPP flow rate could be increased with only small risk of coincident counting, resulting in shorter counting times. Science likely wants to resolve several constituent populations with different number densities, in which case statistical uncertainties will vary with target population.
Seaflow-Limnology-and-Oceanography.pdf (application/pdf)
CytoAUV_proposal_2013-v3.pdf (application/x-pdf)
