MIT Technology Review
: Many attempts have been made to design a desktop printer that can create electrical circuits by aiming droplets of charged ink onto a variety of materials ranging from plastic to paper to cloth. Until now, those efforts have been hindered by inks that have low or hard-to-control conductivity or that need to be heated to extreme temperatures, which limits the kinds of material they can be printed on. Now, a team led by Jing Liu of the Technical Institute of Physics and Chemistry in Beijing has come up with a simple inkjet printer that creates usable circuits on many different surfaces. They have tested their new liquid-metal ink—an alloy of gallium and indium—on paper, plastic, glass, rubber, cotton cloth, and even a leaf. The ink, which is liquid at room temperature, rapidly oxidizes as it is sprayed onto a surface. That property allows it to bond with most materials. And because only the outside layer of the ink oxidizes, the liquid-metal interior maintains the high conductivity of the alloy. The technique is inexpensive and uncomplicated and could potentially be commercialized very quickly.