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I'm having no luck researching this topic so my terms may be wrong or my entire premise faulty. I have found a related question that might be a corollary: "Can I kill a cyborg with magnetism?"

My setting is the distant future where sentient androids exist. They are electro-mechanical with no biological parts. I am writing under the assumption they would be susceptible to electromagnetic fields (EM weapons, superconductors, etc). Under intense magnetism their bodies will seize up, but in time they often recover because their skull and "bones" shield their nervous system.

My question is about an alternate design of android that would be passive to magnetic forces, or otherwise resistant to the harmful effects. They are designed to operate within shifting magnetic fields inside a superconducting machine. My idea is that they are built on a similar skeletal frame that shields their nervous system, but their outer bodies are not susceptible to magnetism. They still function, think, and ambulate under conditions that would paralyze the normal androids.

Can an android's body be "immune" to electromagnetic forces?

And to prevent a world-breaking technology, why wouldn't all androids be made with this kind of body? What are the limits and trade-offs that make traditional electromechanical bodies "better" and these specialized bodies only suitable under specific environments?

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    $\begingroup$ There is a wikipedia page for Electromagnetic shielding. It doesn't look like there is a way to be "immune", but there is some useful info. $\endgroup$ – Frank Anderson May 31 '17 at 15:16
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So long as any electronic/electrically sensitive parts are completely enclosed in ferromagnetic material and the input and output cables from these are shielded, there shouldn't be a problem.

As regards the rest of the body, use paramagnetic material like aluminium or ceramic. Ceramics are probably better in an intense EM field, as it won't allow currents to be induced within the body.

Within a superconductor, though virtually all the field is outside the conductor. It would probably be simpler to use normal robots inside your hollow superconductor unless you have good reason not to.

The reason to not use such robots outside such applications is cost; derived not from the robot being able to resist strong EM fields, but from it having to resist very low temperatures. Superconductors operate at nearly 0K, very few materials can sustain mechanical loading cycles at that temperature--in fact, I don't think there are any at present. Normal electromechanical systems will probably not work, you'll probably need centrally heated musculature inside an insulated body.

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  • $\begingroup$ The ability to pass through the electromagnetic field to get in and out of the machine is a good-enough reason. Giving it a warm body fits fantastically with my other story themes that were off-topic. Wow! $\endgroup$ – wetcircuit May 31 '17 at 16:03
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    $\begingroup$ It also should be noted that if you perfectly shield electromagnetic radiation, you're also shielding radio frequencies. This means no cellphone, Wi-Fi, bluetooth, or RC frequencies are getting in or out. $\endgroup$ – Ranger May 31 '17 at 17:31
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Most of the technology we have for manipulating electricity at present is narrow bandgap semiconductors based on silicon. It has only been in the last couple of decades that wide bandgap semiconductors have started to become used. Wide bandgap devices (GaN, SiC, GaAs) would have a better immunity although still be vulnerable to EMP or electromagnetic effects. If the information processing and control capabilities were photonic rather than electronic, then there would be an immunity to adverse effects from electromagnetic fields. If the processing is done with photonics, and motive capabilites are electrical, then you might have a system that is only temporarily incapacitated or damaged by strong EM fields. So replace electronics with photonics, and you explain immunity easily. Or use a hybrid photonic/electronic machine that is temporarily affected. I missed part of the question the first time around.

"why wouldn't all androids be made with this kind of body?" It would be a very expensive undertaking to build the facilities required to construct these specialized androids, and it would still be a low yield process. So it would probably be a government or military "cost is not an issue" type project.

What are the limits and trade-offs that make traditional electromechanical bodies "better" and these specialized bodies only suitable under specific environments?

Any machine that has to function in a very high strength magnetic field will be subject to induction heating, if it has ferrous materials in its construction. So design has to look at tradeoffs of cost and function. Example: Assume that the nervous system is photonic, and the muscular system is based on wires made of shape memory metal. The muscles are then actuated by temperature changes. This would mean that the entire musculature would require electromagnetic shielding from superconductors. And the supeconducting effect itself fails above a certain gauss level. So there would have to be a chilled exoskeleton of ferrous metal that damped field strength enough to allow a superconductor layer to effectively shield sensitive internals. We might well imagine that such an android has a tank of liquid nitrogen on its back to feed these demanding requirements.

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Use photonic computing wiki.

Optical or photonic computing uses photons produced by lasers or diodes for computation. For decades, photons have promised to allow a higher bandwidth than the electrons used in conventional computers.

A bit more detail from the article:

The fundamental building block of modern electronic computers is the transistor. To replace electronic components with optical ones, an equivalent optical transistor is required. This is achieved using materials with a non-linear refractive index. In particular, materials exist[4] where the intensity of incoming light affects the intensity of the light transmitted through the material in a similar manner to the current response of a bipolar transistor. Such an 'optical transistor'[5][6] can be used to create optical logic gates,[6] which in turn are assembled into the higher level components of the computer's CPU. These will be nonlinear optical crystals used to manipulate light beams into controlling other light beams.

You could build the frame out of plastics, ceramics or other non-ferric materials. If you can make artificial muscle fibers that react to light, you can have a non-magnetic robot that can think and move.

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I would use a material on the android which doesn't conduct electricity. If the electricity can't get to the nervous system, then the android wouldn't be affected.

The second solution would be to use a material that dampens electromagnetic waves.

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  • $\begingroup$ So it could be as simple as their bodies are made out of an insulating material that may not be as durable as the "normal" android bodies? $\endgroup$ – wetcircuit May 31 '17 at 15:22
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    $\begingroup$ Well, for the durability factor, you could have two layers: an inner layer to shield against electromagnetic waves, and a harder outer layer to shield against everything else. $\endgroup$ – F1Krazy May 31 '17 at 15:30
  • $\begingroup$ Yes, if you used something durable like steel or lead on the inside, and but a dampening material on the outside $\endgroup$ – Synergetic May 31 '17 at 16:06
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Electromagnetic radiation is harmful to integrated circuits because it can induce current, misfiring and potentially damaging them. If a circuit is only rated for 1.5 volts and power briefly surges to say, 1,200 volts for a few milliseconds then you're probably going to find fried electronics upon inspecting the cause of the outage.

Aircraft (and for that matter, satellites, space stations, etc..) that get exposed to more radiation than we do on Earth sheild systems like this using grounded copper plating - like you'd find in any computer case. That's probably enough to sheild against 50-100 dB of EM radiation. Increase the radiation and you need to increase the shielding. You could theoretically put a computer inside a nuclear reactor if it was shielded enough - say with lead. But lead is heavy and more weight means more power needed to move.

This wouldn't be a useful feature for robots not intended to operate in that extreme environment because the extra sheilding / weight would be very energy inefficient for locomotion. If some new sheilding method that was more weight efficient was invented, then it would be easier to standardize.

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