Team:BIOTEC Dresden/Methods Vesicles

Vesicles - Methods

Setup of the microfluidic system

The microfluidic system consists of a flow chamber consisting of Polydimethylsiloxane (PDMS), a pump system that controls the flow rates of the various liquids into the chamber. Droplets are created within a defined space in the chamber and are propagated along a grid that allows containment and imaging. Two types of chambers have been used, differing in the geometry of the space where droplets were produced. One featured T-junction, and the other a V-junction (see Fig).

Production of flow chambers:

• mix PDMS and curing agent in 10:1 ratio
• degas and pour on wafer with etched microstructures
• polymerize on heat plate at 150 ºC for 30 min
• add unpolymerized PDMS mixture to points on microstructure where microtube inlets are to be pierced
• polymerize on heat plate at 150 ºC for 30 minutes
• remove polymerized PDMS from wafer, cut to fit onto glass cover slide (24 x 60 mm), and use clean needles (0.8 mm) or laser cutter to pierce tube inlets
• ionize PDMS and glass slide in plasma chamber for 30 sec to make it reactive
• align PDMS on glass slide and seal
• seal irreversibly by heating on plate at 60ºC for 6 hours

The pumping system (ceDOSYS SP-4) allows control of syringes filled with aqueous material and surfactant treated with mineral oil, respectively. The syringes access the chamber via the tubing inlets. Two inlets are used to pump in material in the aqueous phase; the remaining one is used for the oil phase. The flow rates of the syringes are controlled via a ceDOSYS user interface software.

Control via pump system:

• syringes are loaded with the required materials (1 ml) and fixed into holders
• use flow rate on ceDOSYS interface to flood the chamber first with oil phase
• gradually introduce aqueous phase and modify rates of both phases until the shear stress breaks the aqueous phase into droplets at the T- or V- junctions in the respective chambers