One aspect of the invention provides a method of producing a heterogeneous filament. The method includes applying pressure to a plurality of filament components to move the filament components into a common outlet channel. Another aspect of the invention provides a method of fabricating a scaffold. The method includes producing a plurality of filaments according to the methods described herein. Another aspect of the invention provides a scaffold produced according to the methods described herein. Another aspect of the invention provides a heterogeneous filament including a plurality of adjacent filament components. Another aspect of the invention provides a method of producing a droplet. The method includes: positioning a printing tip in proximity to a cross-linking liquid; applying pressure to one or more liquids to produce a droplet extending beyond outside of the printing tip; and contacting the droplet with the cross-linking liquid, thereby producing a droplet.