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Comment by dragontamer | Hacker News Reader

> Each Flex-RV microprocessor has a 17.5 square millimeter core and roughly 12,600 logic gates. The research team found Flex-RV could run as fast as 60 kilohertz while consuming less than 6 milliwatts of power.

This is pretty bad from a power efficiency perspective. KHz speed silicon microcontrollers are closer to ~dozens of microwatts, about two decades of magnitude less power than this flex-circuit.

Furthermore, small silicon dies can be placed into flexPCBs. I'm sure a flexchip has more flexibility than a solid silicon die on a flex board but there's a question of how much flex is actually needed in products?

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Still, I recognize that a fully functional CPU on this process is a major achievement. I'm just trying to think of a commercial application, that's all.

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E-textiles, probably. There's a small, but real, niche trying to put circuitry onto/into fabrics. Traditional flex PCBs get you pretty close, but any large IC creates a limited bend radius and a stress point that will fail very quickly. Using lots and lots of tiny dice for this would technically work, but it's extremely impractical unless you're building your widget by the millions.

But yes, the potential applications are quite limited. Flexible electronics just aren't as useful as people think. I guess it just sounds really cool, like transparent LCDs.

The thin nature of flex circuits have interesting implications for capacitance / parasitic inductance. I've been told that flex circuits are far easier to pass EMC testing due to the physically closer ground/reference return path.

Of course: with the caveat that solid planes of copper are not flexible and will crack. So ground-grid are the best you can do. But physically closer / physically thinner circuits have niche advantages.

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But I'm talking about traditional silicon dies on a flexpcb.

This article is about printing some kind of flexible chip to begin with. It's cool and relatively new, but silicon + flexpcb will be the main technique for e-textiles (and other flex applications) for the near future.

Still, one more tool in the toolbox for electrical engineers. Niche as it is, it's still a tool with likely some good application somewhere.

>I've been told that flex circuits are far easier to pass EMC testing

That’s not correct. It really depends what application, industry and type of testing.

I would say generally it’s the opposite due to worse shielding properties (and worse pi), but it’s a huge oversimplification that’s extremely dependent on application and testing type

"a small, but real, niche" - is it though?

It's been an intriguing notion since the time of the dinosaurs, but what is an actual problem that it solves? I've never seen any textile electronics that delivered more than a novelty.

A lot of video game characters, especially SciFi ones, have glowing clothes of some kind with mesmerizing patterns. The easiest way to create this effect is a combination of etextiles, LEDs and maybe some fiberoptics (which are also flexible enough to be woven into clothing).

Recreating video game characters in real life is a niche. Cosplay. And there's also e-Fashion that is beyond just copying costumes from video games.

You'll still need to hide the battery box somewhere, and likely also the LEDs are inflexible, but by making more of the circuit etextile / flexible, it allows you to hide the electronics in the clothing itself, woven into the clothes and properly integrated.

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An almost fully rigid design with a few flexible parts (ex: the hinge of the Motorola Fold) is also hot and fashionable right now.

Motorola RAZR (the new foldable screen one) needs a hinge, and the electronics that are integrated into the hinge need to be as flexible as the hinge.

Adding little bits of flexibility, especially to space constrained applications like Phones, does add new useful design features above and beyond "novelty" status, IMO anyway.

This is mostly for medical applications. Wearable, maybe implantable, electronics for monitoring vital signs are a real thing that could completely change form with flexible processors.

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