While other, more creative, techniques were common in the past, virtually all consumer electronic devices today utilize printed circuit boards (PCBs). They work very reliably, can contain many layers of traces for complex circuits, and are inexpensive to fabricate in large quantities. But that doesn’t mean PCBs are ideal for every scenario. They’re relatively pricey to produce in small numbers, which makes them less than ideal for prototyping. They also don’t usually look very attractive, so they are usually hidden. These metal leaf circuits, however, are easy to handle at home, look great, and can be applied to most objects.
This technique was demonstrated in a paper authored by researchers from Japan’s Kyoto Sangyo University, the University of Tokyo, and Shibaura Institute of Technology. It describes a method for quickly and easily producing functional electronic circuits using everyday tools and readily-available materials. All you need to replicate their process is a laser printer and some kind of conductive metal leaf. You can use this technique to produce prototype circuits on paper, or on other materials that can stand up to a fair amount of heat, such as wood.
To follow this method, you start by printing out your circuit on regular paper using a laser printer — an inkjet printer won’t work, as you need toner. Then lay very thin metal leaf over the printed circuit, and use a hot clothes iron to press the metal into the toner. The metal leaf will stick to the hot toner. Wait for it to cool, and then remove the loose metal leaf. You’ll be left with a functional metallic circuit on the paper. To put the circuit on another object, you start by ironing the paper onto that object to transfer the toner. You can then use the same process to iron on the metal leaf. After removing the loose metal leaf, you will once again be left with working circuit traces.