Contactless 3-D assembly, electricity guiding, and liquid pipetting using airborne ultrasound

This work presents the development and application of airborne ultrasound for three novel manipulation tasks: (A) Trapping of elongated objects: We calculate the optimal acoustic fields required for the stable trapping, in both position and orientation, of elongated rigid elements. We demonstrate the full dynamic manipulation of these elements. These elements alongside beads and UV-curable glue droplets, serve as primitives to assemble three-dimensional structures. A prototype system integrating a robotic arm with a levitator demonstrates advanced manufacturing capabilities, including assembly on top of existing objects and within enclosed spaces. (B) Guidance of plasma: Here, we demonstrate that ultrasonic fields can precisely guide high-voltage plasma sparks, enabling to direct them towards specific targets or be steered around obstacles. This contactless control of plasma has potential applications in high-voltage switching and advanced material treatments. (C) Acoustic-Droplet-Ejection: We introduce a novel, non-contact method to extract and levitate droplets from the surface of a liquid pool using only airborne ultrasound. This approach overcomes the limitations of conventional droplet-on-demand technologies, which require an actuator to be immersed in or coupled to the liquid container and are often restricted to small volumes ( < 50 μL). Our method offers a flexible and automatable alternative to manual pipetting in laboratories.