A material deposition system for additive manufacturing including an extruder that defines a first input passage for supplying a first material, a second input passage for supplying a second material, a chamber for combining the first and second materials to form a combined deposition material, and an extrusion port for extruding the combined deposition material. The system further includes an adjustable sleeve that is movable between a first position and a second position to vary the interaction between the first material and the second material in the chamber. For example, the adjustable sleeve may be configured to separate the first and second materials in the chamber, and can vary the point at which the materials interface with each other prior to deposition based on the sleeve position. Such a system may enable a varying degree of infiltration, encapsulation, or other interaction between the first and second materials prior to deposition.