Abstract: Described herein are cartridges and devices for operating said cartridges for analyzing a biological sample, such as a blood or saliva sample. Also described herein is an impedance sensor for analyzing a biological sample. Further described herein are methods of determining a cell count or detecting an analyte in a biological sample, which can include transporting the biological sample through a sensor comprising a channel or pore; applying an electrical current or voltage to the channel or pore; detecting an impedance within the channel or pore; and determining a cell count or detecting the analyte based on the detected impedance. Also described herein is an electrowetting electrode array that is configured to transport aqueous solutions using low voltage, such as about 50 volts or less. Further described herein are methods of transporting an aqueous liquid using electrowetting electrodes.