Transparent Graphene Speaker
Add that magical material known as graphene to the list of things you can make with inkjet printers alongside OLEDs, solar panels, and light-bending metamaterials. Scientists at the Seoul National University used printers and a technique known as vapor deposition to leave a thin film of the graphite-based conductor on sheets of PVDF (poly vinylidene fluoride). By sandwiching the the PVDF between graphene electrodes and applying a current from a sound source researchers were able to create a flat and transparent loudspeaker that could be integrated into windows or screens. Don't expect this low-power sound source to replace your hi-fi though -- since it relies on the distortion-prone piezoelectric effect, it probably won't sound much better than the earpiece on your cellphone.