Team:BIOTEC Dresden/Methods Vesicles

Vesicles - Methods

Setup of the microfluidic system

The microfluidic system consists of a flow chamber created out of Polymethylsiloxane (PDMS)- an organic silicon based polymer, and a pump system that controls the rates of flow 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 temporary containment and imaging.

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 and lipid material. 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 lipid phase. The rates discharge of the syringes is controlled via a ceDOSYS user interface.

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 lipid phase
• gradually introduce aqueous material and modify rates of both phases until the shear stress breaks the aqueous phase into droplets at the T-junction in the chamber