Bacteria detection with thin wetting  film lensless imaging.
Lensless on-chip imaging is a promising technique to count and monitor cells and micro-objects in liquid sample. In this paper we apply this technique to the observation of µL sample containing bacteria evaporated onto a microscope slide. Compared with previously reported techniques, a large improvement in signal to noise ratio is obtained due to the presence of a few μm thick wetting film creating a micro-lens on top of each bacteria. In these conditions, standard CMOS sensor are able to detect micro-objects as small as few μm, e.g. E.coli and Bacillus subtilis bacteria and 1 μm polymer beads with a large signal to noise ratio of 45 ± 10. An overall detection efficiency of 85 ± 7% and a co-localization error of σ(1D) = 1.1μm compared with reference fluorescence microscopy images are achieved. This novel technique will be used as a pre-positioning tool prior to other optical identification methods, e.g. Raman spectroscopy.
CEA, LETI, MINATEC, 17 rue des martyrs, 38054 Grenoble cedex 9, France.
C P
CP
Allier
G
G
Hiernard
V
V
Poher
J M
JM
Dinten
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