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Comment by qaute | Hacker News Reader

> I always wondered why you needed gearing mechanisms in a micro machine. Has there ever been a practical application for gears in MEMS?

IIRC, Sandia Lab's SUMMiT V process (the source of videos like [1]) was funded in part to make mechanical latches and fail-safes for nuclear weapons, but I'm not sure what's currently in use for obvious reasons. I don't think they found many other practical applications, though experimentation led to TI's DMD chips, among other things.

Occasionally, MEMS techniques are used to make (relatively large) gears for watches.

I've also seen people try to use gears for microfluidic pumps, but I don't think any are much better than current simpler solid-state approaches.

[1] https://www.youtube.com/watch?v=GiG5czNvV4A

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Fascinating, thanks for the info. Some ideas about this:

(1) I wonder if you can make an unpickable lock with MEMS.

Say, if you get a finger print scan, or retinal scan, then the device would need a positive confirmation in order to unlock itself.

I have no idea how practical this is, but it sounds like some kind of Superman genetic authentication system, in order to unlock the information crystals.

(2) The other thing is, can the gears be used to store potential energy? Such as using the microfluidic pumps? Or a microspring?

Where maybe you can use another piezoelectric device, or solar, to provide the electricity to run the gears, in order to store potential energy during peak production hours.

Then, when you need it, you release the potential energy.

The key here might be if you can build a micro electric generator. But I don’t know if you can deposit a pair of opposing micro magnets on a MEMS unit.

But if this can work, then you would need a lot of units, in the tens of billions, in order to produce enough electricity to do something useful.

> I wonder if you can make an unpickable lock with MEMS

I'm not sure what you mean. MEMS are generally tiny and I'm not sure why you'd need a ~1mm safe? But MEMS relay switches, which mechanically connect/disconnect circuits, exist.

> The other thing is, can the gears be used to store potential energy?

Springs and fluid reservoirs aren't very energy or power dense; good batteries and capacitors are much more effective and reliable. MEMS flywheels have been built and are potentially competitive, but are also extremely tricky to build.

> The key here might be if you can build a micro electric generator.

This is doable and an area of active research (for, say, charging low-power devices when a human walks, definitely not grid-scale power). Magnets are hard to work with in MEMS, so other techniques (piezoelectricity, triboelectricity) are used. [1] is currently badly-written but mentions most important bits.

[1] https://en.wikipedia.org/wiki/Nanogenerator

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