2. 3D Printing.
One of the oldest sciences in the world is metallurgy. Think about it - metallurgy brought us from the Stone Age to the Bronze Age to the Iron Age. That's all about working with materials. As a Mechanical Engineering student, you're required to take at least a couple courses just about the crystalline structure of steel. Martensitic, Austenitic, Ferritic - it's not just what you put in it, it's how hot you cook it, how long you cook it, how quickly you cool it, how you work it, how you temper it. That's steel, the stupid, inelegant material that technophiles eschew, the fundamental basis of the 19th, 20th and 21st centuries.
Every other material has its own tweaks. Wood. Wool. Polyester. Leather. Go into the kitchen and open a drawer at random. Grab something. What is it? How was it made? If you had to replace it, what would you replace it with?
I have an engineering degree. I can answer that question for nearly everything in my house. I learned to solder at 11, learned to run a metalworking lathe at 14, learned to weld at 16, and was teaching AutoCAD by 17. I wrote my first STL file in 1998, a good ten years before any of you had ever heard of "3D printing." We used it for its intended purpose - rapid prototyping. 3D printing is a cool thing to do when you need to lay hands on something but not put any stress on it.
Go back to the kitchen. Find something utterly homogenous and plastic. It might be a jar lid. It might be a funnel. It might be a spoon. It might be a pancake turner.
Now imagine everything in your house made out of that.
The Great White Hope of 3D Printing is, of course, multi-material deposition. We'll reach the point, the acolytes will say, where our apparatus can print metal within plastic within glass. We'll sinter it with lasers and cure it in autoclaves and it'll be every bit as awesome as something manufactured through conventional methods.
Sure. I have no doubt about that. But look at the economics - a kilo of ABS filament is $36.50 on Amazon. Bulk ABS is $4.50 a pound on eBay. There's nearly a factor of 4 just in prepping the material for 3D printing. That's retail - five shite kitchen utensils are $2.99 retail at Ikea. They weigh a fifth of a kilo - your materials cost is more than double what Ikea can sell them for and make a profit.
And if you wanted a pancake turner, you wouldn't make it out of thermoplastic ABS anyway. That shit's all melty when it gets hot. Far better to do a bonded silicone and stainless utensil, which is two different manufacturing processes and a bonding step. You don't have to fuck around with either material - silicone injection molds like a champ and stainless can be stamped on a press so fast it's measured in Hz. Compare and contrast:
There's a part in the production process for stainless steel 3D printing during which the model is fragile and brittle. It's basically like wet sand. When you design, ask yourself this question: if I made this out of wet sand or brittle clay, could I lift the design without it breaking? If the answer is "no," then your design might break in production.
(Shapeways stainless printing requirements)
3D printing is a hell of a tool. The ability to draw something and form it out of the aether is supadope, no doubt. But the practical thing, then, is to come up with a way to injection mold it. CNC machine it. Sandcast it. Carve it. Plane it. In Pakistan they make AK-47s out of railroad scrap using near-stone-age tools. The practice is so pervasive it has its own term among gun collectors.
Your 3D-printed handgun is fucking irrelevant. Your 3D-printed everything is fucking irrelevant.
Consider the world of materials science to be the world of cooking. The world of manufacture is the world of food. 3D printing, then, is a spam-carving contest. Yes, you can make virtually any shape out of spam… but it's still spam. The vision of a 3D-printed future is the vision of a cornucopia reduced to Cheez Whiz. Yes, it's food and yes, it has its uses… but you're a fool if you think you can survive off it.