Optical tweezers-assisted cross-correlation analysis for a non-intrusive fluid temperature measurement in microdomains

An image-based approach to predict the fluid temperature in microfluidic flow cell is presented. We apply Fourier-based cross-correlation processing to determine the lateral displacement of the optically trapped bead; therefore, both the mean square displacement (MSD) and the diffusion coefficient (D) can be obtained. On the other hand, applying the Stokes-Einstein equation, together with Faxen's law correction, the theoretical relation showed that D is proportional to (T=η), where T and η are temperature and temperature-dependent fluid viscosity, respectively. Hence, the fluid temperature can be determined by MSD-based thermometry.