Look Ma, No Batteries!
Hackaday noticed that Waveshare Electronics is offering an assortment of E-Ink devices from a 1.54″ screen to a 7.5″ screen, which do not need a battery. Instead of storing power locally, the same NFC signal which provides the data it displays also feeds it enough power to run. E-Ink devices can pull this off because the only time it requires power is to update the screen, once something is displayed on the screen no power is required at all to maintain the image or text.
The model that Hackday picked up was 2.9″ diagonally, with a resolution of 296 x 128 pixels and cost them $25.99. The device comes with an app, as you will need to crop and dither the image or text you want to display and this offers a WYSIWYG editor to prepare your content. The app also provides the power and this could prove to be an issue depending on your phone, while NFC should work within 20cm in their case the Pixel 2 needed to be placed right up under the camera on the back of the phone to update the image.
These devices are intended for used as displays for barcode or QR code but a quick 3D print job turned it into an effective badge as well. With a small NFC transponder and a watch battery you could keep one of these devices going for years, so the question is what could it be used for?
A battery-free display is pretty nifty, but what are the intended applications? The vendor lists price tags, labels, and name badges as some of the suggested uses, so I decided to do a simple evaluation of each of those to see how well the display performed.