Preliminary scanning fluorescence detection of a minute particle running along a waveguide implemented microfluidic channel using a light switching mechanism

Abstract

It has long been thought that an optical sensor, such as a light waveguide implemented total analysis system (TAS), is one of the functional components that will be needed to realize a "ubiquitous human healthcare system" in the near future. We have already proposed the fundamental structure for a light waveguide capable of illuminating a living cell or particle running along a microfluidic channel, as well as of detecting fluorescence even from the extremely weak power of such a minute particle. In order to develop novel functions to detect the internal structure of living cells quickly, an angular scanning method that sequentially changes the direction of illumination of the minute cell or particle may be crucial. In this paper, we investigate fluorescence detection from moving particles by switching the laser power delivery path of plural light waveguides as a preliminary experiment toward this novel method. To construct an experimental system able to incorporate a switching light source mechanism cost effectively, we utilized a conventional TAS chip with plural waveguide pairs arranged in parallel, and a forced vibration mechanism on an optical fiber tip by a piezoelectric actuator. With this system, we performed an experiment to detect extremely weak fluorescence using micro particles with a fluorescent substance attached and an optical TAS chip that incorporated a microfluidic channel and three pairs of laser-power-delivering light waveguide cores. We successfully obtained clear, quasi-triangular-shaped pulses in fluorescent signals from resin particles running across the intersection under three different conditions: (1) a particle with approximately the same velocity as that of a forced-vibrated optical fiber tip of approximately 700 mm/s, (2) a particle with velocity 1 digit smaller than that of an optical fiber tip, and (3) a particle with velocity approximately 1/20 that of an optical fiber tip.