3D Printing Metal in Mid Air

Published only 3 days before our article on how it is high time for direct metal 3D printers, the folks at Harvard have mastered 3D metal printing in midair with no support (as well as time travel apparently). Because it hardens so quickly, support isn’t necessary, and curves, sharp angles, and sophisticated shapes are possible.

The material is silver nanoparticles extruded out of a nozzle, and shortly after leaving it is blasted with a carefully programmed laser that solidifies the material. The trick is that the laser can’t focus on the tip of the nozzle¬†or else heat transfer would solidify the ink inside the nozzle and clog it. In the video you can see the flash from the laser following slightly behind. The extrusion diameter is thinner than a hair, so don’t expect to be building large structures with this yet.

If you want big metal 3D printing, you should probably stick to the welders attached to robotic arms.

Thanks [Steve] for the tip

41 thoughts on “3D Printing Metal in Mid Air

    1. I’m more interested in when we can print ships, Build space ships in space instead of launching them from the surface. 3dprint a purpose built probe on the ISS and shoot it out from orbit rather than having to build it on the surface and launch it you can just pad out extra space in each resupply pod with metal printing ink, no probes to build this month, print a new module for the ISS

      1. I dunno, isn’t it mostly the weight that matters, when you’re launching into space? So if you’re going to send up mass, you may as well send up mass in the form of something high-tech, from Earth’s advanced factories, rather than trying to replicate the Earth’s production capacity in a little box with a laser.

        3D printing might be suitable on the Moon, or somewhere where you have lots of matter and metal, and need the ability to produce lots of different tools quickly, without setting up the preceding factories to produce the factories you need.

        1. Actually, this is more likely a technology you’d put in a probe to send out to the asteroid belt to build you more probes. Which can then snag a suitably large ice chunk, drop into a solar slingshot and off you go probe and fuel to meet our future Galactic Overlords

        2. Actually, this is more likely to be technology you want to put in a probe that you send to the asteroid belt. To build you more probes that then snag a suitable chunk of ice, drop into a solar slingshot, and mosey on off, probe and fuel, at a decent velocity to meet our future Galactic Overlords :)

  1. I wouldn’t think this would be limited to just silver. Each different material used would probably require a different nozzle-laser distance. Thermoresins should work as well.
    Brilliant. I couldn’t find any mention of which laser was used.

    1. Something with good beam quality in the near IR range. The purple spot is characteristic of an NIR beam viewed by a color CCD. I’d guess a single mode Nd:YAG in the 10 watt ballpark.

    2. It’s an 808nm laser diode bar stack in a fiber coupled package. The delivery fiber is a 200um core (multi-mode) 0.22NA fiber with SMA connector on the end. The output of the fiber is collimated and then focused to a 100um spot size. Beam quality is adequate for this application. A single mode source is not required or wanted in this application. A uniform “top hat” power distribution is preferred over a Gaussian distribution. The laser diode is pulsed to give 1ms (FWHM) pulse widths at repetition rates of 100Hz, 20Hz, or 5Hz at and average power of up to 5W giving a maximum peak power of 1000W (at 5Hz).

      1. I always get a good chuckle out of seeing “0.1mm” (not something imperceptibly small at all) written as “100um” (Ooooooh!); it makes things sound at least three orders of magnitude smaller than they actually are. And yes, that includes 3D-printer specs (oh, especially 3D-printer specs…). It does sound like a cool setup though.

      1. this is also powder based, except the powder is finer, thus more expensive.
        as for the mechanical parts of the printer, they are all fairly trivial compared to the laser one has to use to sinter or melt the material.

        1. I’m waiting for a dust suspended in movinginert gas, with a 3D laser scanner to print as particles brush against the sides of the part.
          Maybe even print with loads of laser projected images that create a hologramatic template. When the dust density is high enough to fuse at the rate of movement but low enough that the laser can still hit particles in the centre with enough energy. A couple of quick blasts [really high power laser] and an air cushion catches the part, printed in less than a second.

      1. i cant, but i can show you sls machines that can make 3d wires in the same shape, just shake the excess substrate away and there you go, the methods of fusing and what is fused is essentially the same.

        my point however wasn’t that this wouldn’t or couldn’t be useful, only that it isn’t exactly revolutionary so the hyperbole hackaday has shown around metal printing is completely unfounded, we have had practical metal printing for quite a while, nothing wrong with new methods but essentially the only way this differs from SLS/SLM(their difference being the method of bonding primarily) is how and where the powder is applied, instead of a z layered bed one has a freeform needle, that needle still suffers the same mechanical imprecision as the bed does so i really cant see the big revolution, even if it is extremely useful and practical for a given purpose.

        1. That it doesn’t have a huge powder-basin makes it a pretty dramatic improvement in the tech. With this, wires could be printed at the same time as a plastic structure. This is something that people have been striving to reach for a while now and something that the older style SLS systems explicitly cannot do.

    1. That is entirely incorrect. This is an interesting variant of the direct-write electronics printers that the 3d printing industry has been working on. This uses silver nanoparticles in solution. Normally, they heat the chamber and wait between layers for the solvent to evaporate. The innovation here is that they can tightly and quickly evaporate the solvent out as it prints, in midair. The laser isn’t necessary to sintered the nanoparticles, since in their original version the nanoparticles self winter at room temperature anyway.

  2. Super confusing, this looks like its completely floating, especially since HaD said printing in midair. It can take a while to realise that its actually just a super reflective base surface, and that there’s only one orange thing.

  3. Silver? So, here’s our ultimate solution for DIY PCBs! (I mean, assuming that cost isn’t a factor.) Think of the LED sculptures you could create–to hell with cubes, let’s get crazy!

      1. There once was a man from Bel Air
        Who had metal suspended in air
        Although Carl would wince,
        You should see the “Fresh Prints”,
        made of silver as thick as a hair.

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