Building a line following robot isn’t the most difficult of challenges, but try building one that’s less than 2cm^2. That’s what Naghi Sotoudeh achieved and it’s pretty cool.
The robot is built using two vibrating pager motors (similar to that found for the vibration function in mobile phones). Fitted to a DIY PCB are also IR sensors, a lipo battery from an old bluetooth headset and an ATiny45 used to control the motors.
The track built for the robot to follow is equally small, it could fit in the palm of your hand.
Via: Hack a Day