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Abstract

Serial femtosecond crystallography is a new method for protein structure determination utilizing intense and destructive X-ray pulses generated by free-electron lasers. The approach requires the means to deliver hydrated protein crystals to a focused X-ray beam and replenish them at the repetition rate of the pulses. A liquid-jet sample delivery system where a gas dynamic virtual nozzle is printed directly on a silicon-glass microfluidic chip using a 2-photon-polymerization 3D printing process is implemented. This allows for rapid prototyping and high-precision production of nozzles to suit the characteristics of a particular sample and opens up the possibility for high-throughput and versatile sample delivery systems that can integrate microfluidic components for sample detection, characterisation, or control. With the hybrid system described here, stable liquid jets with diameters between 1.5 mu m at liquid flow rate of 1.5 mu l/min and more than 20 mu m at liquid flow rate of 100 mu l/min under atmospheric and vacuum conditions are generated. The combination of 2D lithography with direct 3D printing may streamline the integration of free-form-features and also facilitate scale-up production of such integrated microfluidic devices that may be useful in many other applications such as flow cytometry and optofluidics. (C) 2019 Author(s).