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Among different techniques developed for x-ray phase-contrast imaging (XPCi) coded-aperture and Talbot-Lau can potentially provide higher contrast and higher sensitivity in imaging soft and hard tissues. Absorption grating is the central component that makes these techniques different from other XPCi techniques. For hard xray imaging, compatible x-ray absorption gratings are a must so x-ray can be stopped at these absorption gratings to create the desired wave-fronts. For hard x-ray imaging or soft x-ray imaging with high-resolution detectors, the aspect-ratio of gratings feature size goes beyond 10:1 (height:width) – in other words thickness of absorbing part increases – which is technologically challenging through conventional UV lithography techniques. Although SU-8 photoresist along with x-ray lithography is an alternative to fabricate such a high-aspect ratio grating, a compatible UV lithograph-based fabrication process is more desirable as it reduces the cost and increases the throughput. In this work, we have broken down a high-aspect ratio x-ray grating design into multiple layers of lower-aspect ratio structures and employed only the conventional UV lithography. SU-8 photoresists are known for their multi-layer coating specification, which is used in this study. The new fabrication process proposed in this work results in a final high-aspect ratio x-ray absorption grating through accessible UV lithography with lower cost and scaling-up compatibility, thus every research group and industry can benefit from it. To the best of our knowledge, this is the first time a multi-layer x-ray grating design is proposed and reported. The output of this work can be used to perform large field-of-view high-energy coded-aperture x-ray phase-contrast imaging.
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