Full field measurement at the micro-scale using micro-interferometry

Abstract

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.

Heat Transfer in Microchannels—2012 Status and Research Needs

“…Some promising emerging techniques such as MTT and interferometry should be developed for this analysis of heat transfer in gas microflows. Up to now, these techniques are successfully used for thermography in liquids microflows [22,23] and their application to gas microflows is a challenging goal. Preliminary results detailed in Ref.…”

Investigations of the unsteady diffusion process in microchannels

“…We have to mention that diffusion time scales are different on the other directions, e.g. the diffusion across the channel width has the characteristic time t d ¼W 2 /4D (Garvey et al, 2008;Hartmann and Sasso, 2007). We also remark that (1) is obtained with imposed infinite boundary conditions for the x-direction, but here the formula is used to approximate at t ¼constant (i.e.…”

“…Two liquid specimens (one enriched with the dispersed particles in small concentration) are introduced through the branches in the main channel of length L (LbW), where the diffusivity of the dispersed particles is quantified by optical measurements along the flow (which defines the z-direction). Using classical visualizations techniques (micro-PIV, Wu and Nguyen, 2005) or molecular tagging velocimetry (Garbe et al, 2008), coupled with confocal microscopy (Ismagilov et al, 2000;Kamholz et al, 1999;Tian and Wohland, 2008), NMR imaging , Raman imaging (Dambrine et al, 2009), time-resolved fluorescence imaging (Benninger et al, 2005), or micro-interferometry (Garvey et al, 2008), the concentration distribution is measured in the main channel at fixed distances downstream the junction (at different heights within the channel, if proper devices are available).…”

A review of optical interferometry techniques for VOC detection

“…For instance, the displacement sensitivity of pico-meter has been demonstrated using interferometry [43][44]. Interferometry has also been applied for highly precise measurement of temperature [45], pressure [46], gas concentrations [47], growth rate in crystallization [48], refractive index of materials [49], acoustic field [50], surface profile [51], vibration [52] and bio-sensing [53][54], for different applications.…”

“…Direct phase retrieval techniques, i.e. phase stepping interferometry and heterodyne interferometry is a good candidate for phase measurement [122]. A resolution up to λ/1000 can be achieved with heterodyne interferometry [123].…”