Spatio-temporal pattern-ing of growth factors in micro-fabricated scaffolds

Material compression apparatus including a rotable auger provided with a variable pitch screw extending through a hopper for receiving material to be compressed, a material compression and shredding chamber and a material discharge chamber. The material compression and shredding chamber is provided with raised counter spirals for cooperating with the screw to shred and compress the material. A portion of the entrance shoulder to the material compression, and shredding chamber and the entrance shoulder to the material discharge chamber, are provided with predetermined angles for retarding the advancement of the material sufficiently to achieve material compression, and yet not retarding the material sufficiently to preclude advancement of the material.