Wet sample confinement by superhydrophobic patterned surfaces for combined X-ray fluorescence and X-ray phase contrast imaging

In this work we propose a wet sample handling technique which enables the simultaneous collection of X-ray fluorescence (XRF) spectra and X-ray phase contrast imaging (XPCI) using a few microliters drop confined on a superhydrophobic surface. To this purpose, we fabricated and tested a superhydrophobic patterned surface entailing an hydrophilic region which leads to pinning of the drop, enabling X-ray beam effortless alignment and measuring in liquid phase. Our technique allows to acquire capillary-free XRF spectra, resulting in a significant fluorescence detection gain, which is particularly interesting for light elements. Simultaneous XPCI provides sample geometry assuring a fine control of the experimental conditions and allowing real time monitoring of the drop during measurements. As an additional advantage – after solvent evaporation – the solute is deposited on a precise spot, greatly increasing its concentration allowing further measurements, such as X-ray microanalysis and X-ray diffraction. These results could have potential applications in the study of blood proteins, such as ferritin and low density lipoprotein, which are usually available in very limited quantity.