  Holographic Optical Tweezers (HOT) are powerful tools that can manipulate
micro and nano-scale objects with high accuracy and precision. They are most
commonly used for biological applications, such as cellular studies, and more
recently, micro-structure assemblies. Automation has been of significant
interest in the HOT field, since human-run experiments are time-consuming and
require skilled operator(s). Automated HOTs, however, commonly use point traps,
which focus high intensity laser light at specific spots in fluid media to
attract and move micro-objects. In this paper, we develop a novel automated
system of tweezing multiple micro-objects more efficiently using multiplexed
optical traps. Multiplexed traps enable the simultaneous trapping of multiple
beads in various alternate multiplexing formations, such as annular rings and
line patterns. Our automated system is realized by augmenting the capabilities
of a commercially available HOT with real-time bead detection and tracking, and
wavefront-based path planning. We demonstrate the usefulness of the system by
assembling two different composite micro-structures, comprising 5 $\mu m$
polystyrene beads, using both annular and line shaped traps in obstacle-rich
environments.
