A few months ago, we brought you the "You Built What?!" feature about Charles Guan's Electric Death Trap Shopping Cart Contraption. More recently, he released an excellent Instructable about making your own miniature electric hub motor.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.