(a) GISAXS setup with a microfluidic cell. The incoming X-ray beam with incident angle αi is depicted in red. The scattered intensity, with exit angle αf and out-of-plane angle Ψ, is recorded on a two-dimensional detector. (b) An illustration of the X-ray beam transmitted through the channel walls and its footprint on the sample surface. Note that, for clarity, the incident angle and the X-ray beam are not to scale. (c) A composite image of vertical line profiles at qy = 0 for 210 consecutive measurements scanning the microfluidic channel along the y direction while gold nanoparticles attach to a poly(ethyleneimine) thin film. Regions in black correspond to the position of the specular beamstop and the inter-module gaps of the Pilatus detector. Numbers indicate the different regimes in the microfluidic experiment. (d) Horizontal line profiles for an in situ microfluidic experiment as the sum of ten consecutive measurements. For clarity, the intensity is shifted along the intensity axis, with the initially dry film at the bottom. Reprinted with permission from Santoro et al. (2014). Copyright (2014) AIP Publishing.