Speckle fields for controlling and analysis of microscopic collective motion

The advancement of light-based structures has opened up new possibilities for controlling collective motion in various fields of study. In this paper, we show that speckle patterns (SPs), on the one hand, can be employed for smart collective manipulation of microscopic objects such as a bacterial bath. On the other hand, the analysis of SPs generated by the laser scattering from the sample can be used to detect and measure their statistical parameters. The SPs can be designed to apply different manipulation tasks on dynamic micro-objects, such as confinement, transport, and re-assembly. Simultaneously, the acquisition of sequences of SPs from such samples provides a remote, non-contact, non-invasive, and rapid methodology for phenomenological detection and measurement. We validate the integrated method by applying it on <i>E. coli</i> bacteria as a representative of the important class of active matter. Application of the methodology on light-sensitive and functional materials, without necessitating the identification and tracking of individual microscopic features, may introduce further opportunities.