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A new class of tiny, self-propelled robots that can zip through liquid at speed (colorado.edu)
244 points by giuliomagnifico on May 31, 2023 | hide | past | favorite | 93 comments



"The team makes its microrobots out of materials called biocompatible polymers using a technology similar to 3D printing. The machines look a bit like small rockets and come complete with three tiny fins. They also include a little something extra: Each of the robots carries a small bubble of trapped air, similar to what happens when you dunk a glass upside-down in water. If you expose the machines to an acoustic field, like the kind used in ultrasound, the bubbles will begin to vibrate wildly, pushing water away and shooting the robots forward."

Incredible! So they're driven from outside the body and are just a delivery mechanism without electronics?


Air bubbles in the blood are lethal. Is that not a problem? Do the machines need to be reclaimed after they do their thing?


It only takes 2-3 cubic centimeters of air in the blood to kill someone but this is several orders of magnitude smaller.

These things are 0.02mm ( 0.0008 inches) wide, ~1/100 millionth of a cubic centimeter, individual bubbles or even fairly large numbers of bubbles of that size aren’t a significant issue.


Air bubbles are typically not lethal until over 150cc of air. That's a massive amount, that will not be reached by those machines.


Can you double check that amount? That is a considerable volume of air, about 3 golf balls. I don’t understand how anyone could ever end up with that much air inside their body without a hand pump or an air compressor.

Also another comment next to yours said 2-3cc.


Dr. Google leads me to believe there may be a distinction between air in arteries, and air in veins. The former may be lethal at around 5cc, but the latter may be considerably more tolerant.


I remember learning about this in EMT training. That a tiny air bubble in an IV line is lethal is a popular myth. Actually apparently IV lines have air in them all the time, the body is not that fragile


completely anecdotal experience but I had surgery recently and commented on the air in the anesthesia line and the anesthesiologist commented that it only happens in the movies, source: guy who lived


"alright, he's out, now fix that bubble!"


I’ve seen hundreds of bubbles go into the same person over the course of a couple years of infusions and no issues.


Let say one of those rockets dropped its air bubble somehow. How does the body get rid of it? Or does it?


If your question is about the air: It does! The blood carries a ton of cells that can pick up air components. Red blood cells (more specifically, their hemoglobin) bind to the O2 and CO2. Your vessels also feed into your body's plasma, which can act as a circulating reservoir for yet-to-be-collected CO2.

The major component in atmospheric air, nitrogen (N2), is already abundant in the blood too, so it isn't an issue. If I remember correctly, our bodies are generally in equilibrium with the outside air in terms of N2 partial pressure.

Admittedly, a small air bubble in the blood bypasses a lot of the specialized membranes our alveoli use to make their gas exchange, but blood itself can manage a bit of air just fine.

If you're asking about the nanorobot, however: The article says it's not yet biodegradable to the degree they want to make it.


Keep in mind that dissolved oxigen in blood is negligible in comparison to oxygen bound to hemoglobin.

In addition, a bubble shows surface tension. This is exactly the problem of divers who surface too fast: the excess of air dissolved in the blood due to higher pressure aggregates into bubbles.

EDIT: By excess of air I mean Nitrogen. We don't have proteins to bind gaseous Nitrogen.


Gas perfusion into the surrounding tissues and liquids, probably


I think the air will escape through the lungs eventually.


Not all blood is the same.

This only applies to veinous blood.

You do not want arterial blood to be messed with generally at all, as far as I understand.


> Do the machines need to be reclaimed after they do their thing

There are mechanisms to expel so called "foreign bodies", through the details are important (how long until they are detected, ...)


Does that mean eventually antibodies could be produced that match these machines?


My understanding is that these machines are made to not interact with the immune system, since that could cause massive problems - I imagine they expect them to disintegrate in inert pieces that the body can treat as normal waste, like dead cells and the like.


I don't think antibodies can bind to simple materials like these robots seem to be made of.


The article said they currently aren’t biodegradable. I assume they eventually kill the mice.


Not unless they reach escape velocity, although that might not end well for the mouse either.


Depends if kidneys filter them or not…


What happens if you go into an MRI machine with these bitches inside you?


Is self propelled the right wording when you blast a loose propellor with ultrasonic waves? If so I have created a large variety of self propelled robots in my ultrasonic cleaning machine.


Wait until that propeller has controllable pitch and direction, commanded by the on board chip. 20 um x20 um is enough area, in a 2nm process, to accommodate roughly 100,000 transistors. That's about 5x the Apollo guidance computer.

So you would supply bulk ultrasound energy to the organ or area you are treating, and these tiny machines would start to have complex interactions, communicate and locate themselves relative to one another, and coordinate to attack the tumor, deliver the drug, destroy amyloid plaque etc.


20um x 20um is still a bit impractical -- it gets close to the practical limits of wafer dicing, and you need support circuitry. That said, we've made useful payloads in as little as 100um x 100um; here's an example of our (published) work in 200um x 200um:

A 200µm x 200µm x 100µm, 63nW, 2.4GHz Injectable Fully-Monolithic Wireless Bio-Sensing System

http://www.travisdeyle.com/publications/pdf/2017_rfic_implan...


That's starting to sound like an RFID device, but with sound instead of radio waves. In this framework I guess the propeller-thing is analogous to a Crookes radiometer.[0] I wonder what would be the Great Seal Bug[1]?

[0]: https://en.wikipedia.org/wiki/Crookes_radiometer [1]: https://en.wikipedia.org/wiki/The_Thing_(listening_device)


But did they look like tiny-ass boat propellers? See, not nearly as cool.


No it's not. It's an external force propelling it. Clickbait article and headline. It's literally a piece of plastic that they move with noise. It's neither self propelling or a robot.

This kind of stuff has also already been done with magnetic fields.


Not bad, but call me when it's a submarine with Raquel Welch on board.

https://www.youtube.com/watch?v=AmNTFlRASYY (Fantastic Voyage, 1966)


Or its spiritual successor with Dennis Quaid on board, Innerspace (1987).


Was just about to say. Some alternate bloodstream footage:

https://youtu.be/qGOGNixTic4?t=18


Or the dramatic medical documentary 'Hole in my Heart' by Alphabeat:

https://www.youtube.com/watch?v=5FFpfF2AZzY


Haha I hadn't seen that for decades. Those special effects look like something a kid could do today.

Do you remember whether in the movie they explained why they can see outside the ship?


It's been ages since I watched it too.

I don't remember if they tried to explain any of the "science" - rather doubt it. Maybe blood is clear between the red blood cells? Guess they had good lights on the sub too.

Flesh Gordon (campy porn version of Flash Gordon) is another recommended movie with similarly awful special effects !


From a quick google, healthy plasma is light yellow and translucent. At the tiny distance our miniature heroes were looking through, it'd probably be close enough to transparent.

The original book by Isaac Asimov probably had pretty accurate biology. Don't know how much the movie changed it.


Fantastic reference, that I had not come across. For me, Outer limits - The New Breed (s01e17), came to my mind.


We already have tiny robots that can crawl through our body and remove damaged cells, including cancerous cells... our immune cells. Some immune cells can even crawl between other cells in solid organs, known as tissue infiltrating lymphocytes. The future may lie in engineering these already existing tools to be better. This is essentially the promise of new technologies like CAR T cell therapies, where immune cells are engineered to help control cancer.


I feel like the singularity will be achieved by ultra-rich pursuing longevity science and essentially making themselves human-machine organisms comprised of nano-bots and a brain until all is replaced with always upgradeable materials to ensure longest longevity.


Hold your horses. Calling these devices "bots" is a bit of a stretch:

> The team makes its microrobots out of materials called biocompatible polymers using a technology similar to 3D printing. The machines look a bit like small rockets and come complete with three tiny fins. They also include a little something extra: Each of the robots carries a small bubble of trapped air, similar to what happens when you dunk a glass upside-down in water. If you expose the machines to an acoustic field, like the kind used in ultrasound, the bubbles will begin to vibrate wildly, pushing water away and shooting the robots forward.

So it's essentially a small device that can be pushed around by an external field rather than an actual autonomous robot.

But a tiny bot sure sounds more exciting than "remote-controllable dust".


Who said autonomous?

A robotic arm in a factory is also "a device that can be pushed around by an external field"


> I feel like the singularity will be achieved by ultra-rich

It will trickle down though right like a rising tide lifts all boats


More like a rising tide floods the streets and causes billions in property damage.


"trickle down like a rising tide" is the greatest mixed metaphor I have ever heard.


You guys are pretty optimistic, and I admire you for it. I want to be like you.

My first thought went to assassin nanytes that could be delivered in target's tea, target's swimming pool or spa, target's shower or bath, or even the rain if you're clever enough about it. They have to work out locomotion, but I'm sure they've got some bright people working on that already in most of the world's intelligence services. These kinds of devices would have the benefit of deniability, rendering attribution virtually impossible. And their delivery would involve far less risk and danger. Pretty sure we can all envision a multi modal version 20 years from now, making delivery trivial and zero risk.

I hope you guys are right though, and we use it as a medicine rather than a weapon. My gut just tells me we'll develop it as both, and the weapon will be far more effective.


No one needs these nanobots to kill - see: https://en.m.wikipedia.org/wiki/Poisoning_of_Alexander_Litvi...


If someone wants you dead they can just shoot you.


Except if there is any sign of inflation, then you can go to hell.


When we get to true nanoscale bots or even the size that can traverse all vascular systems of all size, carry drug payloads with targeted delivery and perform micro surgery, being self powered and able to communicate. I think I'll celebrate but we're far far away from that reality.

Last I checked, we have nano medicine with targeted delivery with limited success. I think some of these made it to market.


Anyone know what is the smallest man-made powered device capable of mechanical movement?

I assume we can make mm-scale things. Considering that this 20um item is in the news and isn't powered, maybe mm scale is where the current limit is?


I've designed a device that utilizes mechanical force to transmit information that was around 5nm in diameter. It was based on the human Notch receptor. It's a few hundred amino acids in length, folded to produce a protein that senses force transmission, is cleaved upon unfolding, and releases a transcription factor the nucleus of a cell.

I kind of find the distinction of 'robots' vs cells funny, as once you get down to the (sub)nanometer level one's intuition should flip: organic material acts stiffer and more lego-like than metals - which act more like unreliable putties. A "device" that becomes small enough is much more likely to be made of organic molecules than metallic molecules - cells ARE those futuristic robots...

The kinesin motor proteins are pretty cool too [1], but those are naturally occurring machines that I suspect we'll be imitating for a long time.

[1] https://www.youtube.com/watch?v=y-uuk4Pr2i8


It turns out the real nanotechnology was the life we found along the way.

More seriously, I think that biology is better described and studied as applied nanotechnology. These are nano-scale, complex mechanical systems that are capable of manipulating their environment in an autonomous fashion. They're the science fiction nanobots we've been looking for all along!


MEMS can have elements as small as 1um. Molecular robotics operates at much smaller scales. But generally, the line between what is mechanical and what isn't becomes the blurrier the smaller the scale is.


If you mean smallest robot with an onboard power supply and control, mm is the best we can do. The problem is that the power conversion electronics are too large. Electromagnets don't work well as you scale down. So you need piezoelectric/electrostatic actuators which need high voltage. Converting low battery voltage up is difficult without electrical transformers.


People made devices where a single atom can be moved at will.

But they are fixed.


And the smallest that fly for 1h under command?


so nobody read Diamond Age by Neil Stephenson?

Basically, nanotec bots that spin around on command are put into the bodies of people, so they can be made to spin around and dissolve them from the inside out.


That's not the only thing they do! They also could fire muscle fibers perpetually so people who wantef to could get huge without intentionally working out, at the cost of looking twitchy all the time.

I loved that book.


Wouldn't that still make you sore and tired all the time?

Neat concept, though


There was an Intellivision game called Microsurgeon, later ported to the TI-99/4A, that saw you controlling a tiny probe swimming through a patient... you had to zap the viruses and bacteria with appropriate treatments while navigating the patient's body.

It's cool to see reality approaching such high-concept stuff.


micro-effectors; nano effectors; but not independent bots.


Maybe we could spend more time figuring out what actually causes painful bladder syndrome and fix that instead of taking our cues for shiny new (headline grabbing) tech from science fiction as a higher priority than actual health.


> Maybe we could spend more time figuring out what actually causes painful bladder syndrome

Yeah, I guess we could also do that for cancer! Then we wouldn't need to invest so much resources making treatments for it....

Jokes aside, I don't know anything about painful bladder syndrome, but much like other illnesses, a cure is often much harder to develop. In the meantime, what we can do is develop treatments.

Plus, as the article hints at, there are so many other applications for it. When I read it, I read the current tests as a proof of concept. The sky is the limit with simple treatments that currently require surgeries or other invasive procedures that could be addressed here. An optimistic moonshot is teaching them to attack tumors.

All and all, if you couldn't tell, I'm really bullish on this tech.


I don't think this is anything to joke about.



Can we call them robots when there is no mechanics working inside them?


If you are part of the marketing team, yes.


What are the use cases for this though? Such a small thing cannot carry anything or pack enough of a punch to cause any impact either


Next they will fly and cut your hear, in their most civil application.

Post Scriptum: I apologise if for some reason the above joke is found out of order.


Nanomachines, son!


I wonder how much damage those propeller fins can do to vascular tissue, especially capillaries, and at what density.


how to they steer? or more broadly navigate? if I dumped a bunch of self-powered boat propellers in a swimming pool, would anything aside from brownian diffusion and uncontrolled collisions happen?


As long as they can not swim up against a stream of urination.


> swim up against a stream of urination

As per findings by the Mythbusters some number of years ago, the stream of pee is not unbroken.

> The Mythbusters tested the myth that you could be electrocuted by peeing on the 3rd rail. The myth was 'busted' as the stream would be broken up due to distance and there wouldn't be a continuous path for the electrical current to follow.

https://science.slashdot.org/story/10/03/02/1536218/mythbust...


Against an ordinary 3rd rail, yes - these tend to be below 1500V DC per Wikipedia [1] and the German systems I know of all are at 750V nominal voltage, with only Hamburg's S-Bahn operating at 1200V.

Against an overhead line, say if you're urinating from a bridge? That's 15-25 kV if it's rail. I would not dare risk my chances there - and most bridges I know have "piss shields" or generally raised walls to prevent people from trying.

[1] https://de.wikipedia.org/wiki/Stromschiene#Nennspannungen_be...


Not suggesting anyone try peeing on anything that has current flowing through it :P

Was just bringing it up because the stream would need to be unbroken in order for the nanobots to swim up it.


Less than a handful of years ago some kid died doing that around here.


You can definitely get a shock if you stand not miles away from a electric fence and pee at it. I've personally observed this, to much dismay.

Not sure how peeing specifically on a "3rd rail" is relevant. The distance seems more relevant, as the further away your pee-droplets reach, the further away they'll move from each other. But stand close enough and the stream will be unbroken.


Yes, distance is important of course.

The distance they tested is still pretty close.

Only when the test dummy was abnormally near was the circuit closed.

https://www.dailymotion.com/video/x3pidli

So therefore, in normal circumstances you should be safe from nanobots swimming up your pee hole.


> specifically on a "3rd rail" is relevant

"Third rail" means the rail that is electrified (it is often literally the third rail as well): https://en.wikipedia.org/wiki/Third_rail


Yeah, but it's a lot funnier to stand "miles away from an electric fence and pee at it" since it establishes masculine dominance and indicates an incredible level of skill, not to mention unbelievable "pee pressure". Definitely Paul Bunyan-esque!

Why do I get the impression we have a lot of non-native English posters here today?!


"3rd rail" probably because it's a half joke/half warning about the subways in NYC being electrified on the 3rd rail and not to be a jerk and piss in public.


Long time ago, I've seen a dog electrocuted while peeing at a sliding security gate motor.


If you're a man who pees that slowly, you should see a urologist. You may have an enlarged prostate.

OTOH, if they can be used to seek and destroy in-motion kidney stones, the inventors could become billionaires.


10 years away for mainstream use I’ll bet.


microplastics in the bloodstream, what could possibly go wrong ?


Remotely controlled particles (machines?) in the bloodstream. What could possibly go wrong?


Borg incoming.


blood clots, anyone ?


Wouldn't something like this actually be great at breaking up clots?


If possible they should make these robots out of material that dissolves over a period of time.


Well, maybe it can clean them while doing analytics. Those are really the only two use-cases so far. Not like it can repair tears or improve artery/vein wall quality.




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