Massive nanophotonic trapping and alignment of rod-shaped bacteria for parallel single-cell studies

The emerging single-cell technologies call for novel biological tools that can manipulate target cells in a massive and spatially-arranged manner. Here we report a nanophotonic platform, named WANTS (Waveguide-pair Array-based Nanophotonic Trapping System), for massive trapping and alignment of rod-shaped bacteria. This platform leverages silicon waveguide-pair arrays to engineer an optical lattice pattern and the accompanying optical force field. The rod-shaped bacteria inside the field are trapped and aligned by three motions: the out-of-plane rotation, the in-plane rotation, and the translational motion. Massive shigella are arranged into a closely-seated distribution at a trapping rate of ∼12 shigella/min. As a demonstration, we utilize the platform to investigate the bacterial biophysical property and find that the measured bacterial lengths are 23.65% more accurate than the results measured with free solutions. Subsequently, we study the bacterial viability in situ and find that shigella present high heterogeneity in response to chemical stimuli. The WANTS holds significant promise to integrate with lab-on-a-chip technologies and yield a compact and robust platform for practical biological studies at the single-cell level.