Suspended bimaterial microchannel resonators for thermal sensing of local heat generation in liquid

Suspended bimaterial microchannel resonator devices have been fabricated to measure the thermal behaviors of small biological molecules and individual cells in liquid. A resonant microbridge structure embeds this microfluidic channel in its interior. The fabrication process is based on the creation of buried channels in silicon-on-insulator wafers. For the bimaterial bridge structure layers of SiO₂ and SiN_x were used. This bimaterial resonant bridge with internal microfluidic channel could be employed as a very sensitive calorimeter, since the tensile stress generated by bimaterial effect in the heated bridge, produces a shift of resonant frequency. A laser beam was used to heat the center of the bridge resonator with the microchannel filled by water and the corresponding resonant frequency variations were evaluated. The measured sensitivity for the local heat at the center of the bridge is 8.6 ppm/μW in atmospheric condition.