Counting leukocytes from whole blood using a lab-on-a-chip Coulter counter.

A microfluidic lab-on-a-chip Coulter counter was demonstrated to count micro particles and leukocytes from whole blood. Instead of electroplated or deposited metal electrodes, off-the-shelf gold pins were used as electrodes to simplify fabrication process, reduce cost, enhance device durability, and above all, achieve superior uniformity in E-field distribution for improved signal quality. A custom-designed, low-cost demodulation circuit was developed to detect the AC impedance signals of the particles and cells passing the detection area defined by the microfluidic channels. A mixture of polystyrene beads with three different sizes was used to characterize the device. The results showed high throughput at 2000 particles/s and clear separation among different sizes of beads with coefficients of variation (CV) of 13.53%, 10.35% and 5.67% for 7.66 µm, 10.5 µm and 14.7 µmbeads, respectively. To demonstrate the potential for a point-of-care or self-administered device for cancer patients going through chemotherapy, we have used the lab-on-a-chip device to count leukocytes from whole blood, generating encouraging preliminary results comparable to the results from a commercial flow cytometer.