A systematic comparison of Kapton-based HARE chips for fixed-target serial crystallography

Fixed targets are a versatile sample delivery method for serial crystallography experiments and a favorable choice regarding sample efficiency. The hit-and-return (HARE) chips utilize pyramidal-shaped features to pre-position crystals in a regular pattern. Typically, these micron-sized features are chemically etched into single-crystal silicon wafers providing a rigid sample mount with minimal background. As polymer chips are emerging as an alternative, here we report the production of HARE chips identical to silicon with pyramidal-shaped features and micron accuracy by laser ablating Kapton foils. We systematically compare the serial crystallography experiments of five different proteins using both Kapton and silicon HARE chips. Comparing these 15 structures, Kapton HARE chips yield data quality that is comparable to the silicon chips. Therefore, we propose that Kapton is a viable and cost-effective alternative support material.