A step toward fully 3D-printed 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...

PPTCs are just plastic and metal with no semiconductors afaik

Is this actually an MIT article?

Intended to comment on

"Show HN: HN Update – Hourly News Broadcast of Top HN Stories (hnup.date)"

at

https://news.ycombinator.com/item?id=41893524

but apparently somehow posted to

"3D-Printed Active Electronics (news.mit.edu)"

at

https://news.ycombinator.com/item?id=41893524

Just deleted the post at

"3D-Printed Active Electronics (news.mit.edu)"

and submitted the post to

"Show HN: HN Update – Hourly News Broadcast of Top HN Stories (hnup.date)"

Thanks.

> This is, to the best of our knowledge, the first report of fully 3D-printed resettable fuses.

I think unique the contribution is that the entire circuit -- active and passive -- can be made with this one single material. Normally, you need to use many different materials and chemical baths to make a circuit with active components, but using this metal-polymer mix, you can _just_ deposit the metal and you are finished.

If they passed a

large amount of electric current into the material, it would exhibit a huge spike in resistance

but would return to its original level shortly after the current flow stopped."

This is interesting -- large amounts of current being associated with increased resistance...

I have never seen or read about something like that with respect to other electronic components or systems.

It would be an interesting experiment to see if this effect could be simulated, and if so, under what conditions, in non-nanoparticle standard regular-sized electrical components...

I'm guessing (but not knowing!) that you'd you'd need a very high amount of current (like something from a car battery), but at a very low voltage, like maybe 0.1 or 0.01 volts (or less), and maybe like a very thin long wire made of some mostly-conducitive material, and then maybe something at some scale or low voltage if the experimenter was lucky...

Anyway, large current associated with increased resistance... I've never heard of that one before, except I suppose if the current heats the electrical path so much that it destroys it... which would be different for different materials, voltages, cross-section of conductors, temperatures, etc., etc.

I'd assume that wouldn't happen at the nanoscale and/or in a switching semiconductor... but perhaps I might be wrong on some level...

It didn't work out for most of it, but does show that you can do logic without transistors.

Think of these as incredibly slow negative resistance devices. Computing with them might be possible, barely. But sometimes that's all you need.

Oh so this is another scam like the MIT Food Computer. At this point I assume everything coming out of MIT is a scam until independently validated by disinterested third parties

Diy 8ghz (sampling) oscilloscope with tunneling diodes https://hackaday.io/project/167292-8-ghz-sampling-oscillosco...

My take on the Spacex is Mars habitation project is that Musk will put a bunch of edgelords on Mars, and then not really be able to follow up with adequate supply lines and the operation will be offline for a hundred years or so while the climate settles down. The people who live on Mars will then have been there alone for a century and in the 2100s we will send a follow up mission with hilarious consequences.

BTW you can tell I'm not Thunderf00t because he says that "the taxpayer" paid $3 billion. I would never use "taxpayer funding" language, I would only ever call it public money (because Treasury creates money when it spends).

And the 3D part is gimmicky. We have built electronic systems of monstrous complexity just with planar printers.

Wake me up when someone build a system that can reliably make PCBs at home, with placing components, and doesn't cost an arm and a leg, and is cheap and easy to run.

considering the low melting point of these 3d printing plastics, they probably melted the wire.

> 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.

They’re used as auto-resetting fuses in many devices.

Whether or not it is newsworthy… eh, I mean, what is MIT News? A campus newspaper? I’m pretty sure we had articles on particularly big games of capture the flag in mine.

But active electronics? That's a huge stretch. But more importantly, the economics just doesn't make sense. Components already cost fractions of a cent. Small-run PCB prototyping is like <$25 for 5 boards or so.

"A step toward..."

Maybe. But why?

I also don't see this as the final result, printers could be purpose built for this to speed up production and make size smaller

1. Scientists make minor progress as part of a multi-year effort, release a paper, paper features overly optimistic outlook to get future funding

2. Institute marketing department both hypes it up and dumbs it down a little

3. Popular science press picks it up and both hypes it up and dumbs it down a little more

4. Scientific literate readers read it and complain

TL;DR: Nothing new under the sun

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/...

Unfortunately I can’t edit my original post, so apologies for causing any confusion.

The most succinct way that I have found to express the relationship between taxation and spending is that spending at the federal level is constrained by aggregate spending this year, not tax receipts last year.

https://defector.com/neither-elon-musk-nor-anybody-else-will...

https://www.acityonmars.com/

Is a transformer an active device? Asking because current in one loop can control current in the other loop.

From there, are two copper wires an active device?

Anyone seriously attempting this should make sure they understand solid state physics, and at a minimum understand diffusion length of charge carriers and the different type of contacts: Ohmic, Schottky ( for example https://lampz.tugraz.at/~hadley/psd/lectures20/contacts.pdf )

Performance will be horrible, but in some situations constructing and inspecting the device oneself can be paramount ( bootstrapping a secure computational platform, implementing formal verifier associated to a cryptocurrency, ... )

Although I like when thunderfoot compare the archives of what musk said with what actually happened

the government can also destroy money about as easily as it creates it, too. it isn't a politically (and usually economically) desirable thing to do. when it's done, it's usually via replacing the whole currency wholesale (e.g. brazilian real).

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.

It's also not out-of-line with what credible sources observe:

https://blogs.bmj.com/bmj/2021/07/05/time-to-assume-that-hea...

I'm affiliated with MIT, and have been for the vast majority of my life, including at points in fairly senior roles. If you shut people out pointing problems, it will never get better.

There's an incredible urge to defend elite academic institutions, but it's not in the interest of those institutions. Remember your civics class (patriots criticize their government institutions).

The only way I see this fixed involves a period where MIT is viewed like a used car salesman in the public eye for at least enough years to cause enough pain to lead to reform. The endowment is big enough it'll do fine in the end. If it keeps sliding to fraud, it won't.

The power from one loop is transferred into the other, there is no control. The same for two copper wires.

"Control" means that you can determine the value of the power in some circuit by consuming less power to do this. If you have to use the same power, not less, then you are the provider of power, not someone in control, i.e. this is the difference between bosses and the workers commanded by them. The bosses do not lift heavy parcels themselves, they order to some worker to do that.

A device that apparently looks like a transformer but it is an active device is the magnetic amplifier. There are 2 differences from a transformer, the magnetic core is saturable during normal operation (any magnetic core is saturable at a high enough magnetic field, but when that happens in a transformer this means that the transformer has failed, which leads to overcurrents that would destroy the equipment unless a protection is triggered), and the second difference is that the control coil has a very high number of turns, so that a very small current can saturate the magnetic core.

In a magnetic amplifier, the output coil is inserted in an AC circuit where the power must be controlled. When the core is not saturated, the impedance of the coil is high and the output AC current is low. When the core is saturated, the impedance of the coil is low and the output AC current is high. Whether the magnetic core is saturated or not is controlled with a very small current and power on the control coil, which makes this an active device.

Magnetic amplifiers have been heavily used during WWII, especially by the Germans, who had improved them, and they continued to be used for a few decades after the end of WWII, when USA had captured the German technology, because of their very high reliability, until the transistor amplifiers have become reliable enough.

Does the building of logic gates controlling a motor not show electrical control of current flow?

[0] very loosely speaking, also I am not a doctor

You are right about the power, but the current in one loop __does__ control the current in the other loop.

I mean, yes, technically, this approach could advance to catch up with lithography. In practice? Yes we are working toward smaller feature size in additive, but we are nowhere close to micro let alone nano scale.

If the advantage is "hobbyists can do it" then I would say "hobbyists can eaglecad too"

This seems like a detour or speedbump on our existing path toward atom level logic production.

I suspect this is because the most casual analysis reveals incredible difficulties - the structures would have to be buried under a few meters of regolith to avoid constant radiation burn, and the ration of human living space to plant growing space (for food) would have to be about 1:6 I'd guess. The amount of material required to build such a structure for 100 humans? Let alone maintenance, etc.

If realistic plans were actually presented no doubt everyone would start laughing, which is why we haven't seen any mock-ups, VR models, etc.

According to your usage, the voltage on a resistor is controlled by its current, because the voltage is proportional with the current (by the resistance of the resistor), and also the current is controlled by the voltage, because the current is proportional with the voltage (by the conductance of the resistor), exactly like in a transformer the input and output currents and voltages are bound by proportionality relationships.

It is true that this meaning of "control" is encountered in speech, but in engineering and physics "control" has a precise meaning, more restricted that how you use it.

In the engineering use of "control", it is always possible to distinguish which is the controller and which is the controlled in a control relationship.

When "control" is used like you use it, the "control" relationship is bidirectional and you cannot say which is the controller and which is the controlled, e.g. between the primary loop and the secondary loop of the transformer, or between the current and the voltage through a resistor.

For "control" in the engineering sense, unidirectionality is an essential property. Real control devices have some internal feedbacks that make them not completely unidirectional, but this is considered a defect and serious efforts are done to improve the unidirectionality of the control devices. A device with total feedback like a transformer cannot be used to implement any of the known control methods, i.e. you cannot make amplifiers or oscillators or logic gates with it.

All your other solutions are hand-wavey. Sure, let’s “just live underground” as if that’s just as easy as pitching a tent. And who on Earth is surviving nine months without any food? You’re talking as if Mars is just turning right on Albuquerque.

https://www.tandfonline.com/cms/asset/5043deae-e79e-45fc-bb7...

It's always weird to see people making arguments like this on a forum titled "Hacker News"

Even at mm scale it changes the types of prints that can be done.

HN just has forgotten its hacker roots and instead gets off to unconstructively sitting back and criticizing with shallow gotchas.

I did find this however:

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

> In addition to nanolithography and nanoassembly, there is 3d printing with graphene.

And conductive aerogels, and carbon nanotube production at scale

From https://news.ycombinator.com/item?id=41210021 :

> There's already conductive graphene 3d printing filament (and far less conductive graphene). Looks like 0.8ohm*cm may be the least resistive graphene filament available: https://www.google.com/search?q=graphene+3d+printer+filament...

> Are there yet CNT or Twisted SWCNT Twisted Single-Walled Carbon Nanotube substitutes for copper wiring?

Aren't there carbon nanotube superconducting cables?

Instead of copper, there are plastic waveguides

or you know, don't print trillions to bail out failed banks.

I am able to find copper PLA for sale too, although I'm not positive it is what was used in the experiment, and it's kind of pricey (~ $100/kg).

I seriously doubt it.

It’s far easier and more effective (and economical) to have a bunch of jelly bean components around in stock.

You’re going to have a hard time 3D printing anything that can be solderable (either the 3D printer needs to work at high temperatures for DIY, or you need exotic solder that melts at low temperatures).

If you have the need to fabricate quick PCBs for prototyping, you’ll be better served by a cheap CNC machine and some copper foil blanks.

The only real promise I see is that you might, in the very long future, be able to print custom multi-purpose devices, that integrate the characteristics of non critical electronics with mechanical elements, i.e. integrating NTCs on cases or fan supports,..

Nevertheless, using "control" with this meaning in any engineering text would be a mistake, because there "control" must be used in its strict sense, to avoid confusions.

In any system there are many dependency relationships, corresponding to all the equations that are applicable to that system, but much fewer control relationships. The control relationships are quite important for the understanding of the system, so they must be identified clearly in a distinct way from other dependencies.

Etymologically, the right sense of "control" is the strict sense, because it has never been applied to a bidirectional relationship like that between the quantities connected by an equation, but it originally referred to a unidirectional relationship, between a dominant party, the controller, and a subordinate entity, the controlled, whose accounts were checked by the controller.

In proper engineering terms it is not the source of power which controls the speed of a motor, but the device that is used to vary the amount of that power. When there is no device to vary the input power, a DC motor works like a transformer, the input voltage is proportional with the output rotational speed and the input current is proportional with the output torque. The input quantities and the output quantities are dependent, so in the wide meaning of "control" you can say equally well that the input electric power is controlled by the output mechanical power or that the output mechanical power is controlled by the input electrical power. However the use of this phrases does not provide any advantage instead of just saying that you have a system of 2 equations that connect the 2 input quantities and the 2 output quantities, so given an appropriate pair of quantities the other 2 are provided by the equations. On the other hand, saying for instance that the motor speed can be controlled by the excitation current of the motor provides useful information by using the word "control", because it is implied that this method of varying the motor speed requires only a small power in comparison with the output power.

Any induced current is superimposed on top of whatever is already there on the other side. This is different from controlling the current.

For example, you couldn't block DC current passing through the secondary side regardless what you did on the primary side.

I don't see how this is fundamentally different from controlling the current through a transformer.