Bendable Colour EPaper Display Has Touch Input Too

Wearable colour eink display in watch format showing additional internal details

The Interactive Media Lab at Dresden Technical University has been busy working on ideas for user interfaces with wearable electronics, and presents a nice project, that any of us could reproduce, to create your very own wearable colour epaper display device. They even figured out a tidy way to add touch input as well. By sticking three linear resistive touch strips, which are effectively touch potentiometers, to a backing sheet and placing the latter directly behind the Plastic Logic Legio 2.1″ flexible electrophoretic display (EPD), a rudimentary touch interface was created. It does look like it needs a fair bit of force to be applied to the display, to be detectable at the touch strips, but it should be able to take it.

The rest of the hardware is standard fayre, using an off-the-shelf board to drive the EPD, and an Adafruit Feather nRF52840 Sense board for the application and Bluetooth functionality. The casing is 3D printed (naturally) and everything can be built from items many of us have lying around. The video below shows a few possible applications, including interestingly using the display as part of the strap for another wearable. Here is also is a report on adding interactive displays to smart watches. After all, you can’t have too many displays.

Many wearables projects can be found in the HaD archives, including this dubious wearable scope, a method for weaving OLED fibres into garments. Finally, for a good introduction to wearable DIY tech, you could do worse than this Supercon talk from Sophy Wong.

8 thoughts on “Bendable Colour EPaper Display Has Touch Input Too

  1. Woof. Wrapping that case in suede like that looks horrible. I think any plain 3d printed case would look better. A custom board would bring those bevels down. In almost any other category I wouldn’t complain at a nice project like this, but wearables demand aesthetics.

  2. Did not know anybody was making ‘full’ colour e-ink, last I looked you could get a max of 3 colours black, one colour of choice and nothing. That is really cool.

    Not sure if e-ink as a wearable actually makes much sense – most of the tasks you might want you will want good update times, and the rest are probably not active very long. Seems like an efficient LCD/OLED type screen might suit better – maybe even lower power consumption overall as e-ink do take quite a bit to change to state. Still the colour e-ink display is really interesting, wonder if they make bigger ones…

    1. I would think the opposite, given the popularity of the late and great Pebble watch. Wearables are nice for at-a-glance information. I usually look at my own smartwatch to check the time, read the first few words of an incoming message to see whether it’s worth diverting my attention to, check workout stats, see which song is playing on internet radio, etc – for all of these use cases, the information is already on the screen by the time I look at it. The advantages of e-ink, however, can be extremely useful – long battery life and viewability in direct sunlight are both quite nice in a watch.

      1. Aye I like e-ink, but it seems to me as these things are always monitoring their orientation, and when you want to interact with them it takes large fractions of a second to change an e-ink display a nice bright active display that turns on only when its needed – which it knows because you are looking at it, and can instantly change to the screen you actually want to see is probably better – and may be better for battery life, as changing an e-ink screen is energy intensive, all the energy savings are that it is stable after the image is set, and in all your examples above you are looking at it for basically no time.

        E-inks stability makes it superb for e-readers where even a speed reader takes thousands of refreshes to read a page, and the backlight (if applicable) would have to be on for all of it with other techs. But for spending fractions of a second, maybe up to 2 seconds looking at it a nice bright active screen (or transflective for that semi passive backlight) seems like a clear winner to me, as in that time if you poked it to show something else it can do so and the energy costs are not that dissimilar. I’d also say that daylight readable while very possible isn’t always trivial with e-ink either, the surfaces can really catch the light and be hard to read with it – its a different problem for readability, one shared by some active screens, but it does unfortunately exist so require you to sheild the screen to tilt more to find the viewable angle same as other screen techs…

        The Pebble was great, no doubt about it, but what most people seem to be doing with their watches now would be hamstrung by the slow screen refresh – as it seems to me more people are really using them for many things now, more like it is the ‘real’ phone and the slab of smartphone in the bag/pocket comes out only when you need it’s bigger screen. (worth pointing out personally I don’t really do wearables, don’t really use my phone much either, so this is all from observing others use as ‘smart’ watches have evolved…)

  3. It seems like they should have used a flat flexible PCB under the display. I wonder if they didn’t do that because of the touch interface. Seems like they could try thicker plastic instead of jumping strait to an inflexible PCB. Anyway, it’s an interesting POC but they’ll need to make it washable (LiPo fires tend to ruin laundry) before it can be integrated into clothing.

    1. This looks like it’s very much a proof-of-concept. As the article mentions, they used an off-the-shelf board to drive the display. I wouldn’t be surprised if the other board is an off-the-shelf MCU breakout — it certainly looks like one. One might assume that the first iteration to actually include a custom PCB will have a flexible one.

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