A 3-D printer includes development stations that electrostatically transfer first and second materials to an intermediate transfer surface. The development stations can each include a photoreceptor supplying the materials to the intermediate transfer surface, and a boosted developer roll supplying the materials to the photoreceptor. The boosted developer roll comprises an outer roll rotating in a first rotational direction to move with movement of the photoreceptor, and a magnetic roll within the outer roll rotating in a second rotational direction opposite the first rotational direction. The magnetic roll comprises alternating permanent magnets. The intermediate transfer surface transfers a layer of the materials to a platen each time the platen contacts the intermediate transfer surface to successively form a freestanding stack of layers on the platen. A bonding station is positioned to apply light and/or heat to the freestanding stack to bond the layers to one another.