A high-throughput and low-cost 3D imaging system for flowing Escherichia coli

In this paper, we present a novel design of low-cost, high-throughput hologram-based 3D imaging system towards the development of a detection system for Escherichia coli (E. coli). This focusing-free system can image food samples flowing in a transparent microchannel under illumination of RGB lasers through a pinhole, and yields their 3D structures in real-time using hologram-based reconstruction algorithms. We solve two key technical problems in order to realize the system: 1) implementation of a high-speed (200fps) imaging system for capturing full-frame holograms of cells flowing in microchannels; 2) reconstruction of 3D structure of E. coli by characterizing the holograms under low-cost incoherent light sources such as the incoherent laser diodes. Market-dominating food pathogen detection systems using the polymerase chain reaction (PCR) are very slow (10-20 hours/ml) in addition to their high costs. Moreover, they cannot detect the viable but non-culturable (VBNC) E. coli, which orchestrated the recent massive and deadly food poisoning outbreaks in Europe and North America. The estimated cost of the proposed system is less than US$11,000 and its speed is over 1,000 times faster than the existing methods.