A volumetric temperature and velocity measurement technique for microfluidics based on luminescence lifetime imaging

Abstract

A novel optical measurement technique is introduced and qualified which enables the simultaneous determination of the three-dimensional temperature field and the three components of the three-dimensional velocity field in microfluidic applications with only one camera. The temperature is obtained by evaluating the emission decay of individual luminescent polymer particles, whereas the velocity field can be calculated simultaneously from the flow-induced shift of individual particle images in time. To acquire the depth information, the well-established astigmatism particle-tracking velocimetry technique is employed. With this method, systematic errors caused by volume illumination and the reduced spatial resolution due to window averaging as in micro particle image velocimetry (µ-PIV) or laser-induced fluorescence (LIF) can be avoided. The technique can easily be optimized for the investigated temperature range and flow velocities and offers an exceptionally high spatial resolution and accuracy.