All computers, with the recent exception of quantum computers, rely on switches for logic. Those switches — transistors in the case of modern computers — can either be on or off and form logic gates. Every single logical operation a computer takes is dependent on the states of those transistors. Traditionally, somewhere between thousands and billions of transistors are placed on a rigid silicon wafer to create a processor. But now a team of researchers from Tufts University have built transistors into flexible thread.
This transistor thread could, theoretically at least, be used to create wearable computers. Most wearable technology today relies on IC components, such as microcontrollers, that are embedded somewhere on the device. The general focus has been on making those as small as possible in order to make wearable devices comfortable. But imagine if your t-shirt itself could be a processor. Instead of trying to fit a rigid microcontroller somewhere on the shirt, the shirt could be packed full of transistor logic gates in order to process operations itself.
To make the thread, the team started by winding two thin, gold wires around a linen suture. Those wires act as the source and drain electrodes of a transistor. They then applied a semiconducting solution to the thread, which coats the wires and is absorbed into the linen suture. After the solution’s solvent evaporated, it left behind an even layer of semiconductors on the thread. To form the transistor’s gate electrode, they placed a dab of a material called ionogel between the source and drain wires. A third gold wire was inserted into the ionogel to create the gate electrode. For now, the transistor wires have to be wound together by hand in order to set their state and perform standard logical operations, but it could be possible to improve on that in the future.