Real time wavelengths switching and flow rate measurements in an optofluidic device

Optical techniques applied to microfluidics usually bring to extremely high precision measurements and sophisticated experimental approaches [1,2]. In the recent years, several types of microfluidic flow sensors were developed. In situ real-time monitoring is always desirable and crucial for the precise control of flowing parameters in microfluidic systems and LOC applications. In this work we present a simple optofluidic device able to perform in real time a wavelength switching and flow rate measurements. The device is essentially based on a fluid-confining soft wall on which a transmission grating, working as sensor in the Bragg regime, is recorded. Any displacement from the Bragg condition due to the fluid flowing is monitored using a real time spectrometer and data concerning the wavelenghts switching and flow rate measurements analyzed using a proper developed theoretical approach. In particular the excitations an relaxations times of the system can be measured and linked to the flow rates inside the microfluidic channel. 1) C. Monat, P. D. and B.J.Eggleton, Nature Photonics 1, 106 (2007). 2) V. Lien and F. Vollmer, Lab Chip, 7, 1352 (2007).