Development of on-demand sample loading of ultrasound acoustic levitators by focused acoustic radiation

The recently developed acoustic levitation diffractometer, combining the ultrasonic acoustic levitation with the highly brilliant X-ray source and the fast-frame-rate Xray image detector allows for high speed data collection for protein crystallography experiments with a containerless sample support. One of the current research goals is its application to a fully automated high throughput pipeline of protein crystallography experiments at room temperature by integrating an on-demand sample delivery mechanism directly from standard crystallization plates, that is widely used to grow protein samples. We recently proposed to use the acoustic droplet ejection for the on-demand sample delivery, wherein focused acoustic radiation pulses eject samples-in-droplet from a well of the crystallization plates. However, as the sample delivery mechanism, we need to establish the stability of the droplet ejection and the reliable capture of the ejected droplets by the acoustic levitator. In this work, we study the positional distribution of the on-demand acoustic droplet ejection from a crystallization plate and its combination with air jet pulses to assist capturing the ejected droplets by the acoustic levitator. In the proposed system, we demonstrate the on-demand droplet loading with the yield reaching approximately 90%.