Building nanopore-supported 2D vesicles in surfaces

M. MERCURI; GIMENEZ, ROCÍO; BELLINO, MARTÍN GONZALO; BERLI, CLAUDIO LUIS ALBERTO

Congreso; II Brazil-Argentine Microfluidics 1 Congress; 2019

Water compartmentalization in a two-dimensional (2D) configuration is a challenging and thriving field. Here, we form fluid-fluid structures called 2D vesicles in which aqueous solutions are encapsulated within small oil barriers into a mesoporous thin film that al lows them to communicate with a surrounding aqueous environment through predefined paths. The framework of these nanopore-supported 2D vesicles has exciting applications in advanced surface developments and multi-device technologies. A first simple demonstration of these 2D aqueous vesicles reported here is performed using mesoporous thin films and oil printed pore-perimeters. Crack-free mesoporous ti1tania thin films were deposited by dip-coating using a combination of sol-gel synthesis and template self-assembly on silicon substrates. On the other hand, oil perimeters were defined with PDMS stamps with arbitrary designs. For this purpose, microliter drops of oil were deposited by pipette on the relief patterned PDMS stamp until it was completely covered. Then, the oil excess was removed using an acetone-wetted paper. Following this, the stamp was positioned on top of the film and removed after 2 min, leaving the pores filled with oil in the selected location. The oil-filled region can be clearly seen because it produces a refractive index contrast in relation to the empty pore space. Then a small water droplet was placed by pipette on the mesoporous film inside an imbibed mineral oil outline. This way, the aqueous phase into the nanopores results separated from the rest of the empty mesoporous matrix. These results demonstrated that 2D water entrapment into mesoporous films could be easily achieved using oil barriers designed in arbitrary shapes. We studied the communication between inner and external aqueous solutions via 2D vesicle. When silver nitrate and sodium chloride solutions are deposited on the mesoporous film both solutions advance via capillarity through the nanoporous network and an abrupt precipitation of AgCl (silver chloride) is observed. However, with an oil barrier placed between the solutions, no precipitation is observed. So, aqueous media could be defined by designing oil-water interfaces on the mesoporous film. In this sense, we explored whether the inner solutions of a 2D vesicle can interact with the external aqueous solutions. For this purpose, we fabricated small interruptions printing the oil barriers and observed that precipitation only occurred where aqueous solutions were communicated. We then extended the 2D vesicles approach as reactors to conduct specific reactions over predefined regions with accuracy. We demonstrate this concept by selectively precipitating silver oxide and the aforementioned AgCl in isolated domains, using a core of silver nitrate for both chemical reactions and sodium hydroxide and sodium chloride as the other reactants, respectively. We then observed a particular band-precipitation re- II In summary, the fluid-fluid structures here reported provide, indeed, new approaches in 2D systems that could be important in various fields of applications such as nanofluidic devices, high-performance chemical and biological ultra-small volume-scale detection and even discover novel actuator surfaces. Artificial vesicles are attractive as a way to gain vision into biological compartmentalization and for applications in biotechnology.