Formation of steady compound cone-jet modes and multilayered droplets in a tri-axial capillary flow focusing device

A novel method for forming steady cone-jet modes and multilayered droplets is developed based on capillary flow focusing geometry using tri-axial needles. The needles manufactured by a laser beam welding process can be readily cleaned, assembled and aligned. A tri-axial capillary flow focusing (TCFF) device is assembled in order to focus a combination of different liquids in the core of a high-speed gas stream co-flowing through a small orifice. The effects of main control process parameters on the characteristics of compound cone-jet mode are studied. Under appropriate working conditions, steady cone-jet configurations with three layers of liquids are obtained, resulting in multilayered droplets with outer shell, middle layer and inner core. The process can also produce monodisperse droplets at smaller scales by releasing the outer shell and the middle liquid. The new design of tri-axial needles and TCFF devices enables reliable encapsulation of multiple components in one shell for potential applications in multimodal imaging, drug delivery, material processing and biomedicine.