Microfluidic Devices for High-Throughput In Situ Serial Crystallography

Historically, the first microfluidic devices employed in structural biology were fabricated to facilitate on-chip crystallization and to perform high-throughput screening of multiple conditions in a single device with minimal sample consumption and consistent reproducibility rates. Here, we explore the various technologies and materials used to produce microfluidic sample preparation/delivery devices for data collection for protein crystals at X-ray/electron facilities. Particular emphasis is placed on the design and fabrication of fixed-target devices for in situ serial X-ray diffraction experiments on protein crystals, a rapidly growing field being steered by advances in microfluidics and microfabrication. Additionally, sample requirements along with practical considerations regarding handling, storage, and transportation are covered. Finally, an overview of moving-target devices for serial X-ray crystallography at synchrotron or X-ray free-electron laser (XFEL) sources is provided, along with the application of microfluidics for sample preparation in cryogenic electron microscopy (cryo-EM).