Spotted by Windows Latest, a patent titled "Stylus Capsule" describes a Surface Pen with a cylindrical housing that contains a removable capsule. These plastic capsules would contain multiple antennas and have a tapered end for the nib.
You can already replace the nib, or tip, on the current Surface Pen, but with this patented stylus you would be able to remove all of the electronics that are housed within the capsule. The benefit is that customers could reuse the capsule on different stylus housings without having to purchase an entirely new stylus. For example, you could finish drawing a picture on a Surface Pro device with a paintbrush stylus, then simply remove the capsule and pop it into a pencil housing when you need to write.
Microsoft also explains how the design could improve reliability and reduce costs on its end.
"The cost of manufacture and transportation of the module capsule are low since the stylus housing and other components of the stylus are not included in the capsule," the patent reads. "The assembly process for assembling the capsule inside a stylus housing is also very straightforward which leads to improved quality and reduced costs."
It's unlikely that we'll see the stylus later this year when Microsoft is scheduled to announce new Surface products, especially given that the patent was filed earlier this month. Still, a modular stylus that could potentially sell for less than the current pen is certainly something for Surface users to get excited about.