  Materials synthesis in a microfluidic environment enables the flexible and
controllable production of various types of nanostructures which are of great
potential in the fields of chemistry, environmental science, bioengineering,
and medicine. Here, we demonstrate on-chip simultaneous continuous-flow
synthesis and in-situ spectrum diagnosis of zinc oxide (ZnO) nanomaterials
using a femtosecond-fabricated three-dimensional microchannel reactor
integrated with an array of optical fiber probes. The microchannel reactor
including 3D concentration gradient generators followed by 3D micromixing units
provides high-efficiency manipulation of reactants with different
concentrations as well as parallel reaction dynamics in an autonomous manner.
The integrated optical fiber probe array allows precise and parallel spectropic
detection in different microchannels with high spatial and temporal resolutions
for screening the synthetic conditions. The synthesized ZnO nanostructures can
be tailored in size, shape, and morphology by tuning the flow rates and
reactant concentrations based on the spectroscopic signals detected with the
fiber probe array.
