Shape Lock Chain I (early prototype)

youmagine

## What It Is: This chain holds together purely due to its shape. The axles aren't prevented from sliding out due to friction, spring, magnet, or some other force but solely because of the geometry of the chain segments. Only the very last segment that ties the chain to a loop needs to introduce one single snap-together location that breaks this rule. The chain can only be opened starting at this location and can only be opened sequentially in one direction. This is "Hierarchical Locking Demo II," an improved and somewhat more useful version of "Hierarchical Locking Demo I" (http://www.thingiverse.com/thing:200203). ## How It Works & History >> Chain Link Assembly << The "CLA" subsumes 1) the main-chain-link-part, 2) the retainer-part (not the one on the side but the one in line), and 3) the optional roller part. The trick lies in the retainer part. When you add CLA(n+1) to CLA(n), the retainer part of CLA(n+1) locks the axle between CLA(n) and CLA(n-1) into place while still allowing you to insert the axle between CLA(n+1) and CLA(n). It would also be possible to fuse the retainer-part to the main-chain-link-body, preventing it from matching its rotation to the preceding main-chain-link. This would require the retainer body to fan out, which a) makes it unprintable without bad overhangs, b) makes the chain really fat and limits the chain bending angle below 90°, or c) blocks the possibility of attaching utilitarian stuff to the links (I did that fanout in three preceding failed attempts). ## Motivation: In atomically precise small-scale factories, chains can play a crucial role in transporting molecule fragments and molecular building blocks. If a diamondoid crystalline-molecule chain at the lower physical size limit is held together only by Van der Waals forces, thermal fluctuations pose a threat to breaking open the chain at any time and any point, especially in an environment with elevated temperature. The risk of accidental thermal-induced chain opening can be prevented with axle caps fused on with covalent bonds, but then the links cannot be taken apart again. This design combines resilience against opening and the freedom of recomposition in a very satisfying way. This chain is designed with the "same-size detail rule for bulk limit nanodesign" in mind, which is also good for 3D printers. ## Possible Extensions & Improvements: A related exercise would be to modify this design or create an alternate one such that multiple chains can be put together side by side in a similar shape-lock style. This would make it possible for the single weak points to be located on opposite ends of the chain, so if the first link breaks open, the chain won't come apart but instead has a good chance of closing up again. The total number of closing points held together only by weak small-area-VdW-force amounts to only two, no matter how long or wide the chain is made. Lay your fingers in between the fingers of your other hand to see roughly what I mean. Chains a few segments wide allow for stronger bigger-area-VdW-force; then the chain becomes effectively thermally unopenable below completely destructive melting temperatures. ## Instructions: Print at least eight full sets to make a somewhat interesting loop. Use two colors – this makes it easier to understand how the chain works. Note that this design is far from perfect. Before it's closed up, it's pretty wobbly. The good side of this is that you can close the loop by force, although it shouldn't be possible to connect the last link with the first. Closed up, it becomes sturdy enough that you can drop it from a table.