A Circuit Model of Human Whole Blood in a Microfluidic Dielectric Sensor

This brief reports on the analysis of a circuit model for human whole blood in a microfluidic dielectric sensor. The sensor employs a novel, 3-D, parallel-plate, capacitive sensing structure with a floating electrode integrated onto a microfluidic channel with 9 μL of sample volume. A circuit model is developed that accurately captures the characteristics of the capacitive double-layer formed due to the ionic content of blood, as well as the characteristics of the dispersion region attributed to interfacial polarization of the red blood cells. The sensor-measured permittivity of human whole blood and blood samples with hematocrit levels of 0.2, 0.4, and 0.6 show an excellent agreement to simulated data from the circuit model, with rms errors less than 2.14% and 1.17% for the real and imaginary parts of permittivity, respectively, for all samples and over the full measurement frequency range of 10 kHz-100 MHz.