Single-step centrifugal hematocrit determination on a 10-$ processing device.
We present a novel concept to process human blood on a spinning polymer disk for the determination of the hematocrit level by simple visual inspection. The microfluidic disk which is spun by a macroscopic drive unit features an upstream metering structure and a downstream blind channel where the centrifugally enforced sedimentation of the blood is performed. The bubble-free priming of the blind channel is governed by centrifugally assisted capillary filling along the sloped hydrophilic side-wall and the lid as well as the special shape of the dead end of the two-layer channel. The hematocrit is indicated at the sharp phase boundary between the plasma and the segregated cellular pellet on a disk-imprinted calibrated scale. This way, we conduct the hematocrit determination of human blood within 5 min at a high degree of linearity (R(2) = 0.999) and at a high accuracy (CV = 4.7%) spanning over the physiological to pathological working range. As all processing steps including the priming, the metering to a defined volume as well as the centrifugation are executed automatically during rotation, the concept is successfully demonstrated in a conventional PC-CDROM drive while delivering the same performance (R(2) = 0.999, CV = 4.3%).
Riegger
L
L
Laboratory for MEMS Applications, Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges-Koehler-Allee 106, 79110 Freiburg, Germany. lriegger@imtek.de
Grumann
M
M
Steigert
J
J
Lutz
S
S
Steinert
C P
CP
Mueller
C
C
Viertel
J
J
Prucker
O
O
Rühe
J
J
Zengerle
R
R
Ducrée
J
J
D002498:Centrifugation / Q000295:instrumentation* / Q000379:methods; D003362:Cost-Benefit Analysis; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005858:Germany; D006400:Hematocrit / Q000295:instrumentation* / Q000379:methods; D044085:Microfluidics / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity