Flexible circuits are rapidly growing in popularity: They can be used in future cell phones with flexible screens to electronics embedded in clothing. Unfortunately, fabricating a flexible PCB is far more expensive than a standard, rigid PCB. But fear not! You can now make your own flexible PCBs at home using conductive paint. You can literally paint wires on any material, such as the flexible plastic shown above.
As a proof of concept, this circuit uses a flex sensor to control the brightness of an LED (it creates a simple voltage divider between 9V and ground). When the resistor is bent, it changes resistance, causing the LED brightness to change. Now go forth and build a flexible circuit of your own!