A lens-free imaging system for detecting particles in a sample deposited on image sensor includes a fluidic chamber for holding a sample and an image sensor for imaging the sample, wherein the image sensor has a light receiving surface and a plurality of photosensitive pixels disposed underneath the light receiving surface, and wherein the fluidic chamber formed at least in part by the light receiving surface. A method for detecting particles of interest in a sample deposited on an image sensor, through lens-free imaging using the image sensor, includes (ii) generating an image of the sample, deposited on a light receiving surface of the image sensor, by illuminating the sample, and (ii) detecting the particles of interest in the image.