Brian Benchoff developed a 3d printable DIY parabolic reflector WiFi antenna for a very popular ESP8266 module. The reflector is s a 19-inch diameter dish, with an F/D ratio of 0.5 and took some 10 hours to print.
It is covered with thick adhesive backed aluminum foil. The real "duct tape".
It has a gain of some 16 to 17 dBi.
Recently, I was asked to come up with a futuristic, space-ey prop for an upcoming video for the 2017 Hackaday Prize. My custom-built, easily transportable parabolic antenna immediately sprang to mind. The idea of a three-meter diameter parabolic dish was rejected for something that isn't insane, but I did go so far as to do a few more calculations, open up a CAD program and start work on the actual design. As a test, I decided to 3D print a small model of this dish. In creating this model, I inadvertently created the perfect WiFi antenna for an ESP8266 module using nothing but 3D printed parts, a bit of epoxy, and duct tape.
Source article posted on Hackaday with in-depth description and the entire process documented:
Here is the project page with all the files: