We present a method for the read-out of five serially arranged SOI ring resonator-based biosensors at a speed of 3 Hz/sensor and at a fixed wavelength of 1550 nm. The system uses the high thermo-optical coefficient of silicon by applying AC voltages to periodically heat up electrodes adjacent to each sensor. A time-division multiplex scheme allows the allocation of the measured optical output from the mutual spectrum to each specific resonator. We demonstrate our system by immobilizing two different antibodies (biotin and a hexa-His-peptide) at the surface of selected resonators and successfully showing the selective binding characteristics of analyte-probing in a microfluidics supported experiments.