  Although general purpose robotic manipulators are becoming more capable at
manipulating various objects, their ability to manipulate millimeter-scale
objects are usually very limited. On the other hand, ultrasonic levitation
devices have been shown to levitate a large range of small objects, from
polystyrene balls to living organisms. By controlling the acoustic force
fields, ultrasonic levitation devices can compensate for robot manipulator
positioning uncertainty and control the grasping force exerted on the target
object. The material agnostic nature of acoustic levitation devices and their
ability to dexterously manipulate millimeter-scale objects make them appealing
as a grasping mode for general purpose robots. In this work, we present an
ultrasonic, contact-less manipulation device that can be attached to or picked
up by any general purpose robotic arm, enabling millimeter-scale manipulation
with little to no modification to the robot itself. This device is capable of
performing the very first phase-controlled picking action on acoustically
reflective surfaces. With the manipulator placed around the target object, the
manipulator can grasp objects smaller in size than the robot's positioning
uncertainty, trap the object to resist air currents during robot movement, and
dexterously hold a small and fragile object, like a flower bud. Due to the
contact-less nature of the ultrasound-based gripper, a camera positioned to
look into the cylinder can inspect the object without occlusion, facilitating
accurate visual feature extraction.
