This paper presents micro-interferometry as a measurement technique to extract temperature profiles and/ or mass transfer gradients rapidly and locally in microdevices. Interferometry quantifies the phase change between two or more coherent light beams induced by temperature and/or mass concentration. Previous work has shown that temporal noise is a limiting factor in microscale applications. This paper examines phase stepping and heterodyne phase retrieval techniques with both CCD and CMOS cameras. CMOS cameras are examined owing to the high speed at which images can be acquired which is particularly relevant to heterodyne methods. It is found that heterodyne retrieval is five times better than phase stepping being limited to 0.01 rad or k/628. This is twice the theoretical limit of k/1,000. The technique is demonstrated for mixing in a T-junction with a 500 lm square channel and compared favourably to a theoretical prediction from the literature. Further issues regarding application to temperature measurements are discussed.

No abstract

No abstract

In order to understand heat transfer processes at the microscale, detailed temperature measurements are required. This paper begins with a review of the current state-of-the art in fluid temperature measurement at the microscale. At present, fluid temperature profiles are not measured, with verification of predicted heat transfer performance being based on global measurements. The paper describes a potential full-field technique based on micro-interferometry. The accuracy of extracting temperature data from small phase difference intensity maps is discussed, with particular reference to the high levels of signal to noise as would be found in a micro-scale flow. Benchmark optical experiments quantifying the effect of noise on phase evaluation are described and the paper concludes with an outline of the achievable resolution for a given channel length and fluid.