Ocean observation with opto-microfluidic devices

Abstract

The success of ocean observation relies on effective monitoring technologies with increased functionalities, minimized size, and reduced cost. In this study, opto-microfluidic devices for sensing the salinity and temperature of sea water are proposed and demonstrated, which can be prepared with ultrafast laser fabrication and two-photon polymerization techniques. By applying femtosecond lasers as a powerful tool to achieve laser microfabrication with unprecedented high precision and quality, a Mach-Zehnder interferometer (MZI) has been fabricated and integrated into a microchannel as a miniaturized opto-microfluidic system. When the temperature changes or different saline solutions are introduced to the microchannel, different phase shifts in the MZI can be induced. The sensitivities of salinity and temperature have been found to be 215.744 nm/RIU and 0.519 nm/ºC for the opto-microfluidic systems developed in this study. Considering the impact of the temperature perturbation to the phase shift, temperature calibration is proposed for a precise salinity measurement. The results demonstrate the practicability of opto-microfluidic devices for real-time salinity and temperature monitoring of sea water in harsh environment.