Periodic Alignment of Binary Droplets via a Microphase Separation of a Tripolymer Solution under Tubular Confinement

Abstract

We report the spontaneous formation of a characteristic periodic pattern through the phase separation of a tripolymer solution comprising polyethylene-glycol (PEG)/dextran (DEX)/gelatin. When this tripolymer solution is introduced into a glass capillary with a PEG-coated inner surface, we observe the time-dependent growth of microphase separation. Remarkably, a self-organized, periodic alignment of DEX-and gelatin-rich microdroplets ensues, surrounded by a PEG-rich phase. This pattern demonstrates considerable stability, enduring for at least 8 h. The fundamental characteristics of the experimentally observed periodic alignment are successfully replicated via numerical simulations using a Cahn−Hilliard model underpinned by a set of simple, theoretically derived equations. We propose that this type of kinetically stabilized periodic patterning can be produced across a broad range of phase-separation systems by selecting appropriate boundary conditions such as at the surface within a narrow channel.

Marangoni Droplets of Dextran in PEG Solution and Its Motile Change Due to Coil–Globule Transition of Coexisting DNA

“…However, water did not penetrate to the back of the chamber ( x < 6 mm). The higher affinity of PEG to the glass surface than that of dextran and elongated shape of the chamber may have prevented water from entering.…”