In my book, I want to have a character who has a weapon that is actually a swarm of nanobots, and that can take on the shape of any melee weapon within a matter of seconds. I'm thinking of holding them together via powerful electro-magnets spread across the body of each nanobot. Powerful computers set within each bot could figure out how exactly to manipulate themselves into the desired shape using swarm intelligence, and assume the required structure through strategic activation and deactivation of the magnets.

I think I can solve the energy problem, using piezoelectic bodies and localized nuclear reactors, but the main problem is that electromagnets that small and powerful don't really exist.

Any alternative ways to hold them together so they can withstand the strain of combat?

Edit: I am thinking of using room temperature superconducting electromagnets to hold the bots together, since I read that fields of over 17 tesla have been achieved with them. Thoughts?


This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See the tag description for more information.

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    $\begingroup$ Your reputation suggests you are not a newbie here. You should know that it's advised to have 1 question per post, else it's too broad. $\endgroup$ – L.Dutch May 16 '18 at 17:22
  • $\begingroup$ The questions are actually extremely interconnected. If we figure out a way to give them energy, we also auto-figure out the way to disable them. Same with holding them together on impact. $\endgroup$ – Budhaditya Ghosh May 16 '18 at 17:23
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    $\begingroup$ Basically you are asking how they could work in general. That's way too broad. Consider including what you've got so far since it's implied that you figured some stuff out, e.g. how they get into some shape in the first place. Also check out the sandbox in the meta. $\endgroup$ – Raditz_35 May 16 '18 at 17:24
  • $\begingroup$ I think you should either drop hard science tag or narrow the question down a lot. Being broad and detailed at the same time is IMHO too much to expect. I'd first ask a general question on the basic concept and then ask for the hard science for details. $\endgroup$ – Ville Niemi May 16 '18 at 20:03
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    $\begingroup$ I voted to reopen this question, but frankly, why not use magnets? You say that magents that small and powerful don't really exist. Neither do nano-bots. If your nano-bots exist in your story, why not the magnets? If you're looking for a today-tech solution for a tomorrow-tech problem, you won't find it here (because if it can be had, the answerer would be running to the patent office, not posting the answer). $\endgroup$ – JBH May 17 '18 at 5:01

I'm uncomfortable putting "nano-tech" and "melee weapon" in the same sentence for the same reason I don't think nuclear fusion handguns would catch on. Its over-designing to the point of being dangerous.

That being said, saying your device works by applied magnetism could be interesting. Maybe the protagonist has a device that can fuse metal shavings into programmable shapes? That could explain the malleability without the chance of a grey goo indecent. Only downside would be turning the new shapes back into metal shavings. It would probably be easier just to throw the old shape away and make a new one from scratch.

Basically I'm talking about a tools that arranges the parts (metal shavings) and fusing them together with magnetism. Or, if you want to avoid pseudo-science of super accurate and portable electromagnets, have the character carry a suitcase-sized 3d printer. The printer could scan objects, then replicate them. All it could need is to be reloaded with materials whenever it ran out.

While this goes beyond the scope of the question, justifying this device in-universe could be interesting. No offence to martial artists or swordsmen, but long ranged armaments seems like the way of the future, so a hyper-advanced melee weapon is an odd tool to see. I can totally imagine a character custom ordering one for a specific task, but his mechanic/engineer would still look at him/her funny.

However, the ability to get custom-made tools on the fly would be fantastic if you are a mechanic. With a machine like Budhaditya described or the gizmos I talked about, you could make wrenches of any size, parts to replace any broken ones, and any kind of tool you could imagine. Then, when the character is in trouble, they could find one of these in-universe multi-tools and program it to make simple weapons.

Oh, and countering this weapon would probably best be done by shooting the character holding it with a gun or gun-adjacent object.

  • $\begingroup$ I recognize that ranged weapons are the best way, but the character in question is wearing an exoskeleton that is practically invulnerable to ranged sharp puncture wounds. A sharp cut or a large blunt force, like that from a warhammer, are required to pierce it. $\endgroup$ – Budhaditya Ghosh May 17 '18 at 8:50
  • $\begingroup$ Oh, I see! I assumed this was either in a close quarters environment or a non-profession combatant. In that case, what about the baddies using counter-magnets to pull the weapon away or freezing it with arcs of electricity? $\endgroup$ – Pinion Minion May 17 '18 at 14:26

It's all held together with technobabble and handwavium

The main reason being the fundamental concept is already technobabble, it has a defined concept in our minds as to what it is, but how to make it work is so far beyond us that you might as well let the technobabble run all the way to the heart of it.

So use magnets if you want to, or velcro, or just let them all hold hands, but at the end of the day it's better to handwave it away unless the mechanism is significant to the plot.


I don't think that magnets are the best tool for the job. Most nanotech conceptions seems to imitate physical devices like gears and machinery.

I would hold your nanotech creations together with "hooks." Each generalized part of the swarm would have specialized protrusions to allow members of the swarm to physically fit together. Think of them like nano-Legos.

Two points: First, I think that the devices you're named are larger than nanotech and more in the realm of microtech (the size of a bacteria). The normal surface properties that we think of at our size change when things get small. An interesting take on this is the book "Bug Park" where the technology involved are drones the size of insects and the difficulties in walking them around because at that scale different forces dominate.

Second, there are many current weapons which will deal blows more powerful blunt force than a war hammer. A .50 caliber machine gun packs a huge punch. An anti-material weapon would probably do this also. While melee weapons look good in movies and video games, I don't see them as being a major part of modern warfare. Our distance weapons are too powerful and too useful.


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