We introduce a novel technique, which generates colloids made of picoliter water drops in oil inside a microfluidic chip . In the colloidal system, different states of water-oil subdivision with controllable drop sizes and water concentration can be generated. The drop size can be varied from 50 to 500 picoliter, and the water volume concentration can be varied easily. The design and manufacturing of the polymer microfluidic chip involves one or several water-filled microliter-size chambers driven by piezoelectric actuators. By sending programmable electrical signals to the actuator, water drops are dispersed on-demand from a chamber through a nozzle to a main transport channel that is filled with hexadecane. The colloids formation process is characterized with respect to the electrical pulse shapes. The use of surfactants is shown to modify the stability of colloidal system.

Extended Abstract Status: Not Uploaded