Spectroscopic Analysis of Single Microparticles Under Solution-Flow Conditions

Abstract

Laser trapping-microanalysis techniques have high a potential to characterize single microparticles in solution [1,2]. In practice, chemical/physical characteristics of single polymer beads [3–5], droplets [6–8], capsules [9], and so forth [10] have been demonstrated on the basis of laser trapping-microanalysis techniques. It is worth emphasizing that, although the technique can certainly provide wide opportunities to analyze single microparticles among others, the methodology is essentially a “particle-resolved” mode, but not a “singleparticle” mode (Fig. 26.1). For studying the chemical/physical response of a single microparticle upon an external stimulus, untrapped particles involved in a sample solution disturb the quantitative analysis of the response. Therefore, a “unique” microparticle should be introduced to a sample solution to study the time response of the microparticle. In order to pursue such a study, we recently developed a laser trapping-microspectroscopy system combined with a fluid manifold [11]. The developed system can hold a single microparticle by laser trapping, while untrapped particles presented in the sample solution are pumped out by flushing a large enough amount of water by using a fluid manifold. In practice, we succeeded in studying the temporal profile of dye adsorption on single ion-exchange resin microparticles. We expect that such a methodology can also be applied to investigating chemical/physical responses of various single microparticles.