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A step toward fully 3D-printed active electronics

(news.mit.edu)
183 points gmays | 2 comments | 21 Oct 24 01:17 UTC | HN request time: 0.001s | source
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jayyhu ◴[21 Oct 24 01:47 UTC] No.41900019[source]▶
Reading the article, it looks like so far they only have a working resettable fuse (a passive device), and only hypothesize that a transistor was possible with the copper-infused PLA filament. So no actual working active electronics.

And from the paper linked in the article[1], it seems the actual breakthrough is the discovery that copper-infused PLA filament exhibits a PTC-effect, which is noteworthy, but definitely not "3D-Printed Active Electronics" newsworthy.

[1] https://www.tandfonline.com/doi/full/10.1080/17452759.2024.2...

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IanCal ◴[21 Oct 24 06:37 UTC] No.41901266[source]▶
Hang on, can you explain why this is passive and not active?

> Harnessing the described phenomenon, we created the first semiconductor-free active electronic devices fully 3D printed via material extrusion. We demonstrate this breakthrough through the implementation of monolithically 3D-printed logic gates.

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magicalhippo ◴[21 Oct 24 07:53 UTC] No.41901725[source]▶
They've created a Polymeric Positive Temperature Coefficient (PPTC) device. As it heats up the resistance gets very high very abruptly.

While it is non-linear, diodes are also considered passive devices[2], as active is taken to mean electrical control of current flow.

In this case one could induce current control through thermal means, ie an adjacent heating element, and if you potted that in a box I guess you could argue the box is an active device. But not the PPTC itself.

[1]: https://m.littelfuse.com/~/media/electronics/technical_paper...

[2]: https://wiki.analog.com/university/courses/electronics/text/...

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1. adrian_b ◴[21 Oct 24 10:00 UTC] No.41902468{3}[source]▶
Unlike a device with positive temperature coefficient, the NTC thermistors (negative temperature coefficient) can be used by themselves as active devices that provide a negative resistance, which can be used to make amplifiers and oscillators, exactly like with any other diodes with negative resistance, e.g. tunnel diodes, IMPATT diodes, Gunn diodes, Shockley diodes, diacs and so on.

Nevertheless, I do not think that anyone has ever made amplifiers or oscillators with thermistors, because unlike the diodes where the negative resistance has electrical causes, the inertia of the heat transfer in thermistors makes the achievable upper limit for the amplified frequencies very low, typically under 1 Hz.

A device with positive temperature coefficient could be used as an amplifier or as a switch (like a relay) only together with a separate heater, as you say.

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2. notjulianjaynes ◴[21 Oct 24 15:58 UTC] No.41905497[source]▶
I have seen old organs which used solid state VCOs that also had an incandescent lightbulb near the circuit boards to help maintain a stable temperature, and had thought they must use a thermistor although I seem to be mistaken as I can't find much information about that.

I did find this however:

https://northcoastsynthesis.com/news/temperature-compensatio...