Optothermal interaction of active colloidal matter can
facilitate
environmental cues, which can influence the dynamics of active soft
matter systems. The optically induced thermal effect can be harnessed
to study non-equilibrium thermodynamics as well as applied to self-propel
colloids and form assemblies. In this work, we employ a defocused
laser trap to form self-evolving colloidal active matter. The optothermal
interaction of the active colloids in both focused and defocused optical
traps has been investigated to ascertain their thermophoretic behavior,
which shows a long-range attraction and a short-range repulsion between
the colloids. The optical gradient field-enabled attraction and the
short-range repulsion between the active colloids have been harnessed
to form a re-configurable dynamic assembly. Additionally, the assembly
undergoes self-evolution as a new colloid joins the structure. Further,
we show that the incident polarization state of the optical field
can be employed as a parameter to modulate the structural orientation
of the active colloids. The simple defocused optical field-enabled
assembly can serve as a model to understand the collective dynamics
of active matter systems and can be harnessed as a re-configurable
microscopic engine