Methods are described for detecting pathogens, infectious diseases, and physiological conditions by quantifying change of impedance over time of when a biological sample is applied onto a lab-on-a-chip. The lab-on-a-chip utilizes alternating-current electrokinetic (ACEK) phenomena such that molecules move or are carried in an electric field generated by the application of an electrical signal of predetermined magnitude and frequency to an electrode array of the lab-on-a-chip.