An optofluidic imaging to measure the biophysical signature of single waterborne bacterium

In this paper, for the first time, an on-chip optofluidic imaging system is innovated to measure the biophysical signature of single waterborne bacterium, including both the refractive index and morphology (size and shape), based on immersion refractometry. The key features of the proposed optofluidic imaging platform include (1) multiple sites for single bacterium trapping, which enable parallel measurements to achieve higher throughput, and (2) chaotic micromixer, which enable efficient refractive index variation of the surrounding medium. In the experiments, the distinctive refractive index of Echerichia coli, Shigella flexneri and Vibrio cholera are measured with a high precision of 5×10 RIU. The developed optofluidic imaging system has high potential not only for building up a database of waterborne bacterium biophysical signature, but also developing single bacterium detection in treated water that is real-time, label-free and low cost.