Darkfield microscopy is an extremely sensitive imaging and sensing modality due to its very low
background. Metal nanoparticles as small as 20nm can been detected by darkfield imaging setups.
However, traditional darkfield microscopes are bulky and require special illumination condensers,
which limits their application in point-of-care biosensing. In this paper, we present a miniaturized
darkfield microscope based on liquid metallic on-chip condensers and imaging lenses. This microscope
is fully compatible with PDMS microfluidics and can be attached to a smartphone camera to build a
complete handheld biosensing system with very high sensitivity and low cost.