Microsoft was recently granted a patent that could mean a Surface Pen future without batteries. The patent, first spotted by Digital Trends (via OnMSFT), was published on June 7 by the US Patent and Trademark Office and describes a housing that would provide power to the Surface Pen by harvesting and storing energy from the light emitted by your Surface's display.
The housing holds a panel of solar cells that would sit near the tip or the pen so it remains close to the screen while inking. The solar cells would be configured to absorb light through a window, transferring it to an optical diffuser that would then use the generated energy to recharge the pen.
"Due to the close proximity of the stylus to the touch screen during harvesting, the intensity of light that is collected from the electronic display is significantly higher than intensity from ambient lighting in a room or from outdoor lighting," Microsoft says. "The higher intensity light may lead to harvesting at a faster rate."
For charging while not in use, Microsoft also provided an example of a dock with an LED light inside that could charge the stylus while at rest.
It's worth keeping in mind that this is just a patent, so it's entirely possible we'll never see this idea make its way to a final product. Still, it's an interesting look at one of the ideas Microsoft is exploring for a potential future stylus. And it's not the first look at Surface Pen innovations we've seen in recent months. In February, two patent filings showed that Microsoft is experimenting with a touch-sensitive clip and a haptic feedback mechanism that could make their way into a future product.