The display indicator on electronic ink "lives" on solar energy and never requires recharging


    One of the prototypes developed by Microsoft Research.

    Electronic paper (e-ink) is widely used in e-books. Thanks to the ultra-low power consumption, simple black-and-white “readers” work for months on a single charge. In the sun, the text is read better than on the most expensive tablet.

    Ultra low power consumption is a great advantage of electronic paper. Maybe it can be used not only for electronic readers, but also in the production of other gadgets? After all, if you connect a conventional photocell to the display, then the device generally does not need external power sources throughout the entire life cycle. When the display is equipped with Bluetooth, then generally excellent.

    In principle, these devices can be useful as a kind of information displays embedded in the environment. Such “situational” devices are really convenient in many areas. For example, as diaries and "reminders" of events, instead of the yellow Post-it stickers on the monitor or on the wall.

    A small display on the wall next to the table is always ready to show up-to-date information from the Internet - for example, to inform about the air temperature outside the window or to remind about the current balance of the savings account. It perfectly performs the function of an informer, shows important information from the server logs. For example, the number of users online or current statistics. Only often will not be able to be updated, but it is not always required.


    Another prototype

    It would seem that the technology is well-studied, mastered. Demand for such appliances definitely exists. For some reason, even in the richest Chinese stores, such devices are poorly presented or not represented at all. Why is that? Unclear.

    There is probably some kind of problem with the convenience of the interfaces. Designers can not guess the tastes of people, to develop such devices that fit best into the interior and satisfy the needs of users. To make gadgets comfortable and beautiful. To help the Chinese in solving this problem came engineers from the research unit of Microsoft Research. They did a lot of research - and published a reportwith examples of prototypes of convenient situational displays made using electronic ink technology, with photocells and Bluetooth receivers.

    According to engineers, just such a combination may present a promising opportunity for mass production. This is a small display, a photocell for extracting energy from the environment (ambient light in an office or a living room) and a Bluetooth Low Energy (BLE) communication module.

    The hardware device of such a device is shown in the photograph. Photocell with attached thin-film lithium-polymer battery (left), low resolution display on a conventional printed circuit board (center) and a plastic cover that holds the elements together (right). The cover is printed on a 3D printer.



    The pixels of Microsoft's displays are as follows.



    As tests have shown, the prototype charge is enough to do one operation (downloading content + updating the screen) every 25 minutes in artificial light or every minute in natural light.

    Perhaps these indicators can be improved if we use better photocells and more economical electronics. Modern solar cells are capable of generating up to 100 μW / cm 2 indoors and up to 100,000 μW / cm 2 in direct sunlight. Due to conversion losses, real power generation in existing devices ranges from 1 to 20 μW / cm 2 indoors to 1100 μW / cm 2outside. Microsoft engineers were not able to achieve record levels, so their prototypes give 0.7 μW / cm 2 on the table in the room and 8 μW / cm 2 , being attached to the glass. In principle, this is not so little. Some other devices with photocells generate an even smaller flow per square centimeter.

    The architecture of the prototype is shown in a block diagram, with electric current power between all modules.



    Apparently, this is the first time that the background lighting in a room is used as the only source of energy to power a computer display. Previously, photocells were used only for more narrowly functional devices. Prototypes of devices from Microsoft are still in the early stages of development, nothing is said about the prospects for commercial production.

    In addition to photons, there are many other potential sources of energy in the surrounding space. For example, the human body generates heat, electricity, and kinetic energy. In addition, these are vibrations of glass, walls and floors, the energy of radio waves (of their own and neighboring WiFi routers), sound waves, air currents, etc. All this can be collected and used in low-power electronic devices, including various types of sensors. Eternal devices without external power supply are ideal for installing hidden listening if it is not possible to mount a bug in an installed electrical appliance.

    If Microsoft's displays are cheap enough, they can really be used everywhere as interactive Post-it stickers. The demo video shows a program for communicating with “stickers” via Bluetooth from a tablet or smartphone.


    The report is published in the public domain (doi: 10.1145 / 2984511.2984513).

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