Tungsten nanoparticles-based x-ray absorption gratings for cascaded Talbot–Lau interferometers

Absorption gratings play an indispensable role in grating-based x-ray differential phase-contrast imaging (DPCI), however, are generally challenging to fabricate. Even though several fabrication methods exist, they either involve high costs or require special equipment. In this work, we present a low-cost fabrication method for absorption gratings in order to simplify the fabrication process and lower technical threshold. In this method tungsten nanoparticles are used as the absorbing material and carried by a liquid carrier into grating microstructures pre-prepared by deep reactive ion etching (DRIE) with a depth of 150 µm and period of 42 µm. In addition, a vacuum chamber and ultrasonic cleaning machine are used in the filling process. The micrographs by SEM reveal that the filled nanoparticles are arranged densely. Besides, a comparison with the absorption gratings fabricated by micro-casting is provided to show validation of the current method. To test the performance of the fabricated gratings, a cascaded Talbot–Lau interferometer (CTLI) is constructed with one absorption grating as a periodic source and another as the analyzer. The acquired Moiré fringes, phase-contrast and dark-field images demonstrate that the proposed method produces qualified gratings for x-ray DPCI.