Biomedical Engineering Reference
In-Depth Information
Fig. 3.5
Left
: Prototype of a compact, low-cost, battery-powered, handheld flow cytometer. We
used off-the-shelf components to assemble the
2-in. instrument which weighs less than
1 lb. A battery pack of similar weight is sufficient for more than 10 h of continuous operation.
Right
: Intensity histogram of a sample of 2 m Rainbow calibration beads (RCP20-5)
5
3
A representative density plot is shown in Fig.
3.4
b with patterns for the major
constituents of white blood cells (WBC). For comparison and benchmarking,
measurements were performed on the same samples with a FACSCount (BD
Biosciences). The patterns from the two instruments were in good agreement as
discussed in [
30
].
Measurements of absolute CD4 were also successfully performed on samples
with much higher blood concentrations of up to 1:2. The ability to analyze a
large amount of whole blood per unit time enables either reduced analysis time
or improved data statistics.
3.2.4
Handheld Prototype
The first generation of a compact, single-parameter optofluidic detector based on the
spatial modulation technique is shown in Fig.
3.5
. Its size is
2 in., and we
anticipate that the dimensions will shrink further in the final, engineered layout that
will include laser diodes for excitation. For detection, we use a small high numerical
aperture aspheric lens (NA 0.6, 6.3-mm diameter) and a basic pin photodiode rather
than a photomultiplier tube (PMT). The prototype was assembled with off-the-shelf
components (
5
3
$350, excluding pumps and housing), and the optical unit can be
battery powered (2
9 V, 4
1:5 V AA-type are sufficient for >10 h continuous
operation).
