Roessler, C.G. et al. Structure 24, 631–640 (2016).

A continuing challenge in utilizing X-ray free-electron lasers (XFELs) to perform serial femtosecond crystallography (SFX) is synching sample delivery with the ultrashort X-ray pulses. Most sample-delivery devices rely on either liquid jets or gel-based extruders to stream a slurry of microcrystals into the path of the XFEL beam, but much sample is wasted between femtosecond X-ray pulses with such devices. Roessler et al. introduce two microcrystal-delivery systems that are based on sound—in particular, on acoustic droplet-ejection technology. With these flexible, computer-controlled tools, the delivery of microcrystal-containing droplets to the XFEL beam can be synchronized with the pulse scheme, ensuring less sample waste and more efficient data collection. The developments should be particularly useful for collecting X-ray diffraction data for protein samples that are hard to produce and/or crystallize.