The chain is composed of individual chain links. I have designed three different types of chain links:

• Round-section chain links
• Octagonal cross-sectional chain links
• A quadrilateral cross-section and smooth-edged links
  There are X-shaped grooves in the middle of each link. These grooves not only make it easy to string the links together to form a complete chain, but also effectively prevent the links from falling off on their own. The principle is the same as the locking mechanism of traditional handcuffs.

I also made a regular-sized version suitable for the palm, as well as a small-sized version designed specifically for the fingers.
Regular-sized handcuffs are assembled using M4×35mm bolts and locking nuts; while the small-sized version uses 1.75mm-diameter consumables

In addition, I have also attached the files of Fusion 360, so that everyone can freely adjust the size and shape of the chain links according to their needs.

Due to the grooves in the middle of the chain links, their overall strength is inevitably limited. If there are higher requirements for the load-bearing performance of the chain links, after the chain links are assembled, local reinforcement welding can be carried out with a 3D pen, or the grooves can be reinforced with a rotating tool and a friction welding process.