Novel microfluidic structures for wireless passive temperature telemetry medical systems using radar interrogation techniques in ka-band

We present a new miniaturized (below 1 mm³) temperature sensor based on microfluidic technology and radar passive interrogation principles, which can be easily applied for temperature telemetry for medical applications. The chipless microsystem is made up of a planar-gap capacitor with a microchannel located in between its plates. The temperature-dependent expansion/shrinkage of the water inside the microchannel modifies in a monotonic way the liquid level across the capacitor. The resulting change in the effective permittivity modifies the capacitance value in a temperature-dependent way. The first prototypes of the temperature microsensor were micromachined and integrated with an antenna, while the ambient temperature was remotely measured using frequency-modulated continuous-wave (FMCW) radar interrogation principles at 29.75 GHz. Preliminary measurement results demonstrated a 0.4 dBm/°C sensitivity over a 9°C temperature range (24°C-33°C).