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TL;DR An open-source project called LightInk could put an ultra-efficient E-Ink display on your wrist.
The watch reportedly uses just ~0.5mAh per day, translating to roughly 40 days of battery life in typical use.
It is also solar powered, and aggressively optimized for “infinite” runtime under the right conditions.
E-Ink already makes a lot of sense for reading, and now someone’s making a strong case for wearing it, too. A new open-source project called LightInk is gaining attention for turning an E-Ink panel into a minimalist wrist watch, pushing battery life to an extreme that most wearables can’t offer.
At the heart of the device is an ESP32, a low-cost microcontroller known for its Wi-Fi support and ultra-low-power sleep modes. It’s paired with a small E-Ink display, similar to the panels used in compact DIY e-readers (including builds we’ve covered before). Unlike OLED or LCD screens, E-Ink only draws power when the image changes, making it an ideal fit for glanceable information like the time or basic stats.
LightInk is designed to avoid fully waking the ESP32 whenever possible, instead relying on ultra-low-power routines that execute quickly and then drop back into sleep. The result is a reported power draw of around 0.5mAh per day. With a 20mAh battery, that works out to roughly 40 days of runtime on a single charge. There’s also solar support, so under the right conditions, the device can top itself up faster than it drains. In other words, there’s potential for infinite run time.
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Despite the extreme focus on efficiency, the watch includes support for features like an LED light, vibration motor, speaker, GPS, and even LoRa communication, though the developer notes it’s a significant power draw and intended for occasional use. This is alongside more typical smartwatch features like touch controls and customizable alarms, though some elements are still in development. For now, there’s also a surprising amount of environmental data baked in, including sunrise and sunset times and moon phases.
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