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. (C) 2013 Elsevier B.V. All rights reserved.