Microchannel-assisted thermal-lens spectrometry for microchip analysis

Microchannel-assisted thermal lens spectrometry (MATLS) was developed for microchip analysis. This method utilized a photothermal effect in a very small space and rapid thermal conduction between a solid–liquid interface to produce a temperature gradient in the microchannel. In order to examine the mechanism experimentally, we constructed a detection system of laser defocus setup in which an excitation beam was not tightly focused, but it irradiated the microchannel homogeneously. The signal intensity dependence on modulation frequency of excitation and on solvent was investigated with the laser defocusing setup. The results of this investigation indicated that the mechanism of MATLS worked as expected. Since the mechanism of MATLS does not require directivity and coherence of the laser beam, other incoherent light sources can be used as excitation light for sensitive detections. Finally, we considered some future applications utilizing the mechanism.