Instructables user Urant decided to create a pocket-sized espresso machine that could be built using simple tools and parts from a local home-improvement store. He came up with a tiny, soldered contraption with its own tinsy winsy alcohol stove that uses a filed-down syringe to deliver a very slow drip of fuel for a boil that goes long enough to extract a single shot. It's a great design.
Design constraints are some of the most important points of any product design; they tell us what the limits are. The tighter the constraints, the more limited the design, and we have to be more creative to be able to meet them.
On this project, I set the following ones. 1- The product had to fit in the pocket of my jeans. 2- The product had to be made out with common, cheap and easily obtainable materials from any home improvement store or corner hardware store. 3- The product had to be made using simple tools that most makers would probably already have, or could easily borrow or buy cheaply. 4- The product had to be self-contained. 5- The budget was maximum 30 dollars.