Microrheometer on lab-on-chip for high-speed chemistry

This work relates to the design of a MEMS-based microrheometer in the aim to measure the rheological behavior of complex fluids over a broad range of frequency (from 1 Hz to 100 kHz). Vibrating silicon microstructures has been demonstrated to be a powerful tool to overcome the experimental problems related to the characterization of small quantity of fluids in microfluidic. At the micro-scale, the vibrations of microcantilevers depend on both, the microstructure (geometry, materials) and the surrounding fluid (density, viscosity…). The fluid-microcantilever interaction results in two phenomena: an inertial phenomenon (‘mass effect’) and a dissipative phenomenon (‘loss effect’). The analytical expression of the hydrodynamic force is proposed for complex fluids. The degeneracy of the model agrees with the case of Newtonian fluids. Thus, the analysis of the frequency response of the vibrating microstructures enables to determine the mechanical properties of the surrounding fluid as functions of frequency. Microcantilevers can be used as a promising tools for microrheology and as a powerful microrheometer for the monitoring of structures evolution in polymer high-speed chemistry...