Bacteria detection with thin wetting 
film lensless imaging

Area of Science:

• Biophotonics
• Microscopy
• Cell Biology

Background:

• Lensless on-chip imaging offers potential for cell and micro-object monitoring in liquid samples.
• Current techniques face limitations in signal-to-noise ratio and detection sensitivity.

Purpose of the Study:

• To apply lensless on-chip imaging for observing bacteria in microliter samples.
• To improve signal-to-noise ratio and detection efficiency for micro-objects.

Main Methods:

• Evaporation of microliter samples containing bacteria onto microscope slides.
• Utilizing a wetting film to create micro-lenses on bacteria.
• Employing standard CMOS sensors for imaging.

Main Results:

• Achieved a significant improvement in signal-to-noise ratio (45 ± 10).
• Successfully detected micro-objects as small as 1 μm, including E. coli and Bacillus subtilis.
• Demonstrated high detection efficiency (85 ± 7%) and low co-localization error (1.1 μm).

Conclusions:

• The developed lensless imaging technique significantly enhances micro-object detection.
• This method provides a robust pre-positioning tool for subsequent optical identification techniques like Raman spectroscopy.