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The thermodynamic Casimir force emerges from the confinement of concentration fluctuations in binary
solvents. In this research the confinement is made by colloidal singlets and doublets. As an effect these particles
form structures. In this research these structures are experimentally studied using a confocal microscope.
The structures formed depend on two variables, namely the concentration of the binary solvent and the
temperature. We studied the singlets and doublets below and above the binary solvents critical concentration and
at temperatures between Ta and Tc. Below the critical concentration we found chainlike structures, while above
the critical concentration we found square structures. At temperatures close to Tc both structures become
parallel. Below the critical concentration the structures are potentially of infinite size, while above the critical
concentration their size is strongly limited.
The observed structures can be explained quantitatively by measuring the strength of the Casimir force between
singlets. Below the critical concentration the strength of the Casimir force increases with temperature, while
above the critical concentration there is no attractive force between the singlets. This explains why below the
critical concentration the structures are of a potential infinite size, while above the critical concentration the
singlets are not subdued to the Casimir force and isolate the existing structures.