Getting Some E Ink Done

A new toolkit uses off-the-shelf parts to simplify building and coding wearable devices with bendable, color ePaper displays.

Nick Bild
a month agoWearables
Bendable, color ePaper display (📷: K. Klamka et al.)

Graphical displays are capable of providing very useful, information dense interfaces to our devices. They tend to be both power hungry and inflexible, however, which limits their utility in wearable applications. In particular, this presents problems for the hardware hacker that wants to build a practical wearable device.

A potential solution to these problems has been developed by engineers at the Technische Universität Dresden in Germany. They have created a hardware and software toolkit that simplifies the process of prototyping devices with bendable, color ePaper displays.

Known for their minimal power consumption, ePaper was selected as a part of the toolkit. In particular, a 2.1" Plastic Logic Legio display with 240x146 pixel resolution, and four colors (red, blue, green, yellow) plus black and white. This display is bendable over a thirty millimeter radius, which allows it to contour to a wrist, waist, or other location on the body.

In many cases, user and environmental input is also needed, so the team included three linear soft membrane potentiometers and an accelerometer. Sensors were also added in to detect temperature, humidity, noise, and light.

For processing and wireless connectivity, an Adafruit Feather nRF52840 Sense development board was included. An electrophoretic display driver board handles writing to the ePaper display. A tiny 400 mAh LiPo battery is sufficient to power a device built with the toolkit for up to 24 hours. A customizable 3D-printed curved case was also designed to house the components in a way that conforms to the curves of the body.

As you have likely noticed, these are all off-the-shelf parts that are fairly simple to work with. The selected components also offer a lot of flexibility in the types of devices that can be built with the toolkit. To keep with this theme of simplicity, the engineers designed the system such that applications can be built within the Arduino ecosystem. They have also provided some helper classes within their framework that will handle many common tasks and get your projects off the ground faster.

To demonstrate what is possible with their methods, the team built a number of example applications. In one case, they built an activity app that tracks the wearer’s steps, and using a barometric pressure sensor, records ascents and descents. In another example, the team built a strap for an existing smartwatch which extends the display to provide a distributed, hybrid interface.

There are always trade offs in engineering, and this toolkit is no exception. While the display does sip power very slowly, that comes at the expense of a very slow refresh rate of fifteen seconds. The resolution is also on the low side, and few colors are available. With some luck, these issues may be resolved in the years to come by further advancements in ePaper technology. In any case, this looks like a simple — and highly accessible — way to make devices with bendable, color ePaper displays quickly.

Nick Bild
R&D, creativity, and building the next big thing you never knew you wanted are my specialties.
Latest articles
Sponsored articles
Related articles
Latest articles
Read more
Related articles