Object Rotation and Translation for Serial Planar Acoustic Microassembly

Damage-prone microscale products that need to be mass-assembled, such as surface mount devices, would benefit from being assembled in mid-air using acoustic forces. These forces can manipulate objects without contact, thereby circumventing damage. However, joining two objects together, which is a key step in assembly, is challenging to do acoustically because as the objects approach each other, the acoustic waves scattering off one object begins to greatly impact the position and orientation of the other object. Previous demonstrations of acoustic microassembly have demonstrated various techniques to overcome the acoustic scattering force, such as assembling, within a gel medium or using a robotic arm for object translation but there is still no way of achieving complex, configurable, 3-D assemblies in mid-air by purely using acoustic waves. To better maintain the object's orientation under a dominating acoustic scattering effect, we developed a new acoustic rotation algorithm called the two-segment phase gradient (TSPG) algorithm, which can rotate the object with an rms error of 12
$^{\circ }$
under open-loop control while maintaining the object's centroid with an root mean squared error (RMSE) of 0.41 mm. Next, we demonstrate an alternative technique to overcome the acoustic scattering force by using the widely used single trap algorithm to cause one object to jump toward another object at a specified position and orientation. Finally, we demonstrate how the TSPG algorithm and single trap algorithm can be used to generate complex and configurable 2-D assemblies.