An example readout from an interference reflectance imaging sensor (SP-IRIS) when the substrate is dry (left, 0.8 NA) or when the substrate is mounted in a microfluidic chamber and immersed in water (right, 0.9 NA). Individual vesicular stomatitis virions are detected as small (about 1–3%) diffraction-limited modulations to a reflected reference field. Small fluctuations in the intensity of the reflected reference field are visible in both images. Displayed regions are about 8×8 microns. Adapted from  (Reprinted with permission from , Copyright 2016 American Chemical Society).