| Microfluidics, as a new interdisciplinary field, holds the promise to offer better solutions for analytical chemistry, bioscience, and material science etc. However, microfluidics is still in its infancy and there remain many challenges in the field. On-chip extraction of physical and chemical information from the extremely small volume in a microfluidic channel and finding "killer" applications are two of challenges in microfluidic field. This PhD thesis focuses on these two problems. There are six projects in the thesis, which can be classified into two parts.;In the first part, we integrate several traditional analytical techniques on chips. We measure the temperature on-chip and rates of flow using highly fluorescent ZnO quantum dots-poly(dimethylsiloxane) nanocomposite and electrochemical methods, respectively; we also analyze ions or organic molecules in microchannels using a micro-electrochemical station, on-chip capillary electrophoresis combined with fluorescence microscopy, and surface enhanced micro-Raman spectrometry. With these sensing, imaging, and detection methods, we expect to perform experiments with better control and higher sensitivity for chemical analysis on chips, compared to traditional analysis in bench mode.;In the second part, we explore the application of microfluidics in material science. We screen the optimized experimental conditions for the synthesis of nanomaterials on-chip. The key component of our approach is an array of reactors containing solutions with a one- or two-dimensional gradient of reagent concentration, pH value, or reaction temperature. In the proof-of-concept experiments, we quickly identified the parameters (e.g., reaction concentration and temperature) needed for the production of Au and Pd nanostructures with specific morphologies, including Au wavy nanowires, Au nanobelts, and Pd multipods that have not been observed previously in the products of conventional batch syntheses before. |
