Techniques for preparing PNCs are provided. In one embodiment, a polymer extruding device may include a barrel configured to accommodate a composite material, a shaft rotatably disposed in the barrel, and a motor coupled to the shaft and configured to rotate the shaft, thereby moving the composite material. The polymer extruding device may further include a die including one or more injectors configured to inject nano particles into the die to cause shear stress to be exerted to the composite material, thereby forming a layer of the nano particles on a surface of the composite material.