Contactless pick-and-place of millimetric objects using inverted near-field acoustic levitation

We model and realize an ultrasonic contactless pick-and-place device capable of picking, self-centering, self-orienting, translating, and releasing flat millimetric objects. The device is an ultrasonic Langevin transducer operating at 21 kHz that radiates into air through a tapered tip. Objects are trapped few micrometers below the tip due to the near-field acoustic levitation phenomenon. We first investigate the conditions to achieve an attractive force on the object depending on its size and the device operating frequency. Second, we use a 3D acoustic model that describes the converging forces and torque that provide the self-centering and self-orienting capabilities. Third, a more advanced Computational Fluid Dynamics model based on the Navier-Stokes equations explains the small gap between the tip and the trapped object. The contactless manipulation capabilities of the device are demonstrated by picking, transporting, and releasing a Surface Mount Device in air. The presented manipulation concept can be an interesting alternative for manipulating delicate objects such as microelectromechanical devices, silicon dies, or micro-optical devices. (AU)