Researches on the field of flexible electronics have been intensified in the last years. Engineers from the University of California, Berkeley have incorporated e.g. electronic switches and sensors directly onto foldable papers that can be further used in advanced systems. Besides its low cost and wide availability, paper’s properties such as flexibility could be used as a good substrate for e.g. modern switchable circuits or even more sophisticated applications. So, for example, folding a paper in different ways could turn the electronic device on/off or switch its current working state to another. That’s why it’s being compared to origami.
One of the biggest problems researchers had to face was the incorporation of the electrodes onto papers, so they would offer sufficient conductivity for practical uses. Electrodes manufactured from metals such as silver or gold offered that, but they are expensive to use in a larger scale.
In this technology, engineers from UC Berkeley decided to use the molybdenum element as the source of the inexpensive, but viable conducting metal for the electrodes. It’s added to the gelatin solution and then binds to carbon in it. After that, the paper is being coated with that solution and dried. In the next step, a specially programmed laser beam ”draws” the defined circuits by heating the molybdenum to about 1,000 °C. That especially made gelatin solution prevents the laser beam from burning the paper. The aforementioned process allows forming conductors of molybdenum carbide. These circuits are very small – about 100 micrometers wide (the size of human hair in diameter). Non-heated parts of the paper remain non-conductive.
In the future, this new technology could be used as a modern replacement for a variety of applications, such as detectors of heavy metal contamination or monitoring of the toxins e.g. to detect dangerous lead levels in the water or in a patient’s blood.