Enzymes are proteins that catalyze chemical reactions in cells — that’s all they do, and without them complex life could not exist. Quick, reliable enzyme action is a matter of life and death, yet in many cases an enzyme and its multiple substrate molecules are simply free-floating in the main compartment of the cell. Rather than forcing the appropriate molecules to interact, the cell simply tailors them to one another, floods the area with copies, and waits. Using highly specific attachment points, the cell can tailor proteins to only grab on to the exact right structure on the intended target, meaning that with enough random movement the right bits will eventually collide and stay connected.
This method of assembly never made sense for human use, back when we were primarily building things like rocking chairs and steam engines, things made from parts we can pick up and fasten together easily enough — but as we start to build more objects at the nano-scale, or on the surface of a complex device, or in the air, or in space, the cell might have some important lessons to offer.
At least that’s the idea behind a wide swathe of new research into the area of self-assembly, and the possibility of using one of life’s methods of construction to surmount some of the biggest issues in science today. One of the main projects has been Aerial Assemblies, which saw helium balloons autonomously self-assemble into complex 3D structures with minimal input from researchers.
That’s cool, and useful if you need to create arrays of sensors or other small tech-bits far up in the sky, but I think the video below does a much better job of illustrating the concept. Using water as the method of introducing random movement, the rig assembles a chair out of nothing but parts with attachment points and some noisy disturbances in the water.
Note how, once there’s a single point of attachment, further points of attachment are held physically close to their targets and tend to get snapped in quickly; this is how biological assembly happens as well, with the first few steps taking up the vast majority of the total reaction time.
This method has huge advantages — primarily, that all we have to do is properly design the attachment points on each piece, mix, and we’re done. It also has huge downsides — for instance, without thousands of copies to speed the process we will usually need hundreds or thousands of copies of each piece for the process to finish quickly enough to be worthwhile. Still, there are all manner of jobs that would be impossible to create with micro-tweezers or even a 3D printer.
When former Google X bigwig Babak Parviz wanted to put the micro-scale components of an LED display into a contact lens, the only choice was to cut uniquely shaped attachment sites into the lens then pass a liquid saturated with the micro-component over the lens; eventually, by chance, the attachment point of each type of component happened to fall into its accompanying site on the lens, stick, and hang on against the liquid flow.
In the video below, we see a higher resolution (more pieces) version of the same idea.
One aspect of this is that since the input energy can be random or functionally so, it can come from virtually any source. Ground tremors, weather, oceanographic movement, or anything else that could be used as the source of input kinetic energy for this. Now, realistically, scientists won’t be lugging their experiments out to the beach to save on power, and will simply use an electric motor to create their perturbations. But for industry, if drilling down to harness seismic movement could cut a certain factory’s power bills by two thirds, then that’s just what they’re going to do.
Here’s a crude drawing of the lock and key mechanism. You need a lot of molecules to make this collision happen very often.
When you add to this model’s simple persistence a polypeptide’s ability to create sequence-specific locks and keys, this method can assemble structures as complex as proteins themselves — not arrays of multiple proteins, but the folded strings of amino acids that come together in such mind-bending ways that the world’s largest distributed computing networks can’t figure them out. That is the level of complexity life can achieve with simple rules and unconscious physical forces, and it’s very possible we may have to mimic its strategy if we want to match life’s ability’s at the molecular scale.