Real-time chemical imaging of bacterial activities can facilitate a comprehensive understanding of the dynamics of biofilm structures and functions. Synchrotron-radiation-based Fourier transform infrared (SR-FTIR) spectromicroscopy can yield high spatial resolution and label-free vibrational signatures of chemical bonds in biomolecules, but the abundance of water in biofilms has hindered SR-FTIR's sensitivity in investigating bacterial activity. We developed a simple open-channel microfluidic system that can circumvent the water-absorption barrier for chemical imaging of the developmental dynamics of bacterial biofilms with a spatial resolution of several micrometers. This system maintains a 10 microm thick laminar-flow-through biofilm system that minimizes both the imaging volume in liquid and the signal interference from geometry-induced fringing. Here we demonstrate the ability of the open-channel microfluidic platform to maintain the functionality of living cells while enabling high-quality SR-FTIR measurements. We include several applications that show how microbes in biofilms adapt to their immediate environments. The ability to directly monitor and map bacterial changes in biofilms can yield significant insight into a wide range of microbial systems, especially when coupled to more sophisticated microfluidic platforms.

Surface-Enhanced Raman spectroscopy (SERS) has been increasingly utilized as an analytical technique with significant chemical and biological applications [1][2][3][4][5][6][7]. However, production of a robust, homogeneous and large-area SERS substrate with the same ultra high sensitivity and reproducibility still remain an important issue. Here, we describe a large-area ultrahighuniformity tapered silver nanopillar array made by laser interference lithography on the entire surface of a 6-inch wafer. Also presented is the rigorous optical characterization method of the tapered nanopillar substrate to accurately quantify the Raman enhancement factor, uniformity and repeatability. An average homogeneous enhancement factor of close to 10 8 was obtained for benzenethiol adsorbed on a silver coated nanopillar substrate.

We investigate tunable plasmon resonant cavity arrays in paired parallel nanowire waveguides. Resonances are observed when the waveguide length is an odd multiple of quarter plasmon wavelengths, consistent with boundary conditions of node and antinode at the ends. Two nanowire waveguides satisfy the dispersion relation of a planar metal−dielectric−metal waveguide of equivalent width equal to the square field average weighted gap. Confinement factors over 103 are possible due to plasmon focusing in the interwire space.