Wouter Scheublin was one of the designers on the Virtual Making stand at Dutch Design Week. He became interested in the mechanical possibilities that 3D printed models provide. He used the Selective Laser Sintering process and the Nylon 12 material(aka SLS, or White, Strong & Flexible as we call it at Shapeways) to print small working 3D printed cars. I do not want to be decieving here, these things are tiny, about 10cm by 10cm by 5cm. And they are not the get in and drive variety of car or the internal combustion engine type of car. But, I did not want to call them model or toy cars because this is clearly an experiment in design that goes much further than this.
You can see the working gears and the spring clearly. These mechanisms as well as the axles work as soon as the support material is removed. The mechanism is intentionally exposed so that people can see what you can design and build with 3D printing. The entire car comes out of the machine in one piece. The only exception is the rubber for the wheels which is made up of standard O rings.
When you pull the car back over the ground the wheels wind the gears that in turn wind the spring and once you let go the car zooms over the floor. You like?