Could patterned light sort tiny particles by size without computer-assisted control?

Details

Optical hierarchical sorting has attracted significant attention in recent years. Existing approaches use either complex numerical calculations or computer-aided experimental tools. The researchers proposed a computationally simple method for hierarchical sorting that does not need computer aid.

In this theoretical analysis and numerical study, they used a focused optical vortices array (FOVA), generated by a spiral phase plate array (SPPA) and focused by a microlens array. They designed the spiral phase plates with different heights in different columns of the SPPA. This gave different columns of the FOVA different topological charges and, consequently, different particle-capture capabilities.

To achieve hierarchical sorting, the proposed setup deployed the FOVA in a microfluidic chamber containing particles of various sizes. The four columns of the FOVA formed four corresponding capture regions in the particles’ flow area. The theoretical analysis and numerical results indicated that particles in the size range of 1 to 582 nm could be sorted.

The researchers concluded that the approach provides a theoretical framework that can be readily used in experiments for optical hierarchical sorting.