Paper-based electronics have captivated research teams for the last several years. Teams from research institutions worldwide have designed paper electrodes, electric circuits, and origami-inspired generators, to name just a few examples. A new preprint paper, published in the journal Nano Energy, describes how researchers at Purdue University designed a durable, self-powered paper keyboard.

Paper-based electronic technology holds an allure for innovators because of its affordability, flexibility, and environmental friendliness, as well as the potential for use in a variety of industries. But most paper-based technology relies on an external power source to function. Additionally, the rough texture of paper and its susceptibility to water and other damaging substances have so far kept most paper-based solutions from moving beyond the research and development stage.

The Purdue engineers developed an inexpensive printing method that can transform any kind of paper into a touch-operated user interface. The process uses multiple inks — made of conductive nanoparticles and other components — layered onto paper coated with highly fluorinated molecules. This “omniphobic” coating repels water, dust, and oils; it also prevents each printed ink layer from smearing. The team successfully printed a functional computer keyboard and basic music player controls.

The layering process creates vertical pressure sensors on the back of the paper. When a user touches the keyboard printed on the front of the paper, the pressure sensors harvest energy from the friction of contact, eliminating the need for an external battery. The printed system includes Bluetooth technology that can pair with a computer, music player, and other devices.

The novel printing process has compatibility with large-scale printing systems, increasing the chance that the paper technology could soon be implemented to enable interactive packaging, foldable tablets, and more. Health tech solutions like self-tracking pill packages, wearables, and at-home monitoring devices may reap the benefits in the near future. And the technology has the potential to transform user interfaces across a wide range of industries.