Sometimes It’s Not The Solution

June 1, 2024 by Elliot Williams 54 Comments

Watching a video about a scratch-built ultra-precise switch for metrology last week reminded me that it’s not always the projects that are the most elegant solutions that I enjoy reading about the most. Sometimes I like reading about hackers’ projects more for the description of the problem they’re facing.

A good problem invites you to brainstorm along. In the case of [Marco Reps]’s switches, for instance, they need to be extraordinarily temperature stable, which means being made out of a single type of metal to avoid unintentional thermocouple joints. And ideally, they should be as cheap as possible. Once you see one good solution, you can’t help but think of others – just reading the comments on that article shows you how inspiring a good problem can be. I’m not worried about these issues in any of my work, but it would be cool to have to.

Similarly, this week, I really liked [Michael Prasthofer]’s deep dive into converting a normal camera into a spectrometer. His solutions were all very elegant, but what was most interesting were the various problems he faced along the way. Things that you just wouldn’t expect end up mattering, like diffraction gratings being differently sensitive across the spectrum when light comes in from different angles. You can learn a lot from other people’s problems.

So, hackers everywhere, please share your problems with us! You think that your application is “too niche” to be of general interest? Maybe it’s another example of a problem that’s unique enough to be interesting just on its own. Let’s see what your up against. A cool problem is at least as interesting as a clever solution.

Optical Tweezers Investigate Tiny Particles

April 22, 2024 by Bryan Cockfield 1 Comment

No matter how small you make a pair of tweezers, there will always be things that tweezers aren’t great at handling. Among those are various fluids, and especially aerosolized droplets, which can’t be easily picked apart and examined by a blunt tool like tweezers. For that you’ll want to reach for a specialized tool like this laser-based tool which can illuminate and manipulate tiny droplets and other particles.

[Janis]’s optical tweezers use both a 170 milliwatt laser from a DVD burner and a second, more powerful half-watt blue laser. Using these lasers a mist of fine particles, in this case glycerol, can be investigated for particle size among other physical characteristics. First, he looks for a location in a test tube where movement of the particles from convective heating the chimney effect is minimized. Once a favorable location is found, a specific particle can be trapped by the laser and will exhibit diffraction rings, or a scattering of the laser light in a specific way which can provide more information about the trapped particle.

Admittedly this is a niche tool that might not get a lot of attention outside of certain interests but for those working with proteins, individual molecules, measuring and studying cells, or, like this project, investigating colloidal particles it can be indispensable. It’s also interesting how one can be built largely from used optical drives, like this laser engraver that uses more than just the laser, or even this scanning laser microscope.

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Small, Quiet Air Compressor Puts 3D-Printed Parts To Best Use

April 11, 2024 by Dan Maloney 14 Comments

When the only tool you’ve got is a hammer, every problem starts to look like a nail. Similarly, while a 3D printer is a fantastic tool to have, it can make you think it’s possible to build all the things with printed parts. Knowing when to print ’em and when to machine ’em is important, a lesson that [Diffraction Limited] has taken to heart with this semi-printed silent air compressor.

The key to this compressor’s quiet operation is a combination of its small overall size. its relatively low output, and its strategic use of plastic components, which tend to dampen vibrations. The body of the compressor and the piston arms are the largest 3D-printed parts; the design calls for keeping printed parts in compression for longer life, while the parts of the load path in tension travel through fasteners and other non-printed parts. The piston design is interesting — rather than being attached to connecting rods via wrist pins, the machined Delrin pistons are solidly attached to the piston arms. This means they have to swivel within the cylinders, which are made from short pieces of metal tubing, with piston seals designed to move up and down in grooves on the pistons to allow air to move past them. The valve bodies atop each cylinder are salvaged from another compressor.

When powered by a NEMA23-frame BLDC motor via a belt drive, the compressor is remarkably quiet; not quite silent perhaps, but still impressively smooth, and capable of 150 PSI at low speeds. And as a bonus, the split crankcase makes it easy to open up and service, or just show off how it works. We’ve seen a variety of 3D-printed compressors, from screw-type to Wankel, but this one really takes the prize for fit and finish. Continue reading “Small, Quiet Air Compressor Puts 3D-Printed Parts To Best Use” →

Building A Cable-Driven Delta Printer

January 26, 2024 by Lewin Day 12 Comments

Most of us have played with a Cartesian-style 3D printer. Maybe you’ve even built a rigid delta. In this case, [Diffraction Limited] decided to a little further away from the norm with a cable-based delta design.

This delta design uses direct cable drives to control the end effector, with preloading rods effectively decoupling the preload from the drive force. Thus, the motors only have to provide enough power to move the end effector around without fighting the tension in the cables. The end effector is nice and light, because the motors remain stationary. With lightly-loaded motors and a lightweight effector, rapid accelerations are possible for faster printing. The video does a great job of explaining how the winch-based actuation system works to move the mechanism quickly and accurately. It’s a pleasure to watch the delta robot bouncing around at high speed as it executes a print.

The video notes that it was a successful build, though difficult to calibrate. The strings also wore out regularly. The truth of the matter is, delta printers are just more fun to watch at work than their less-controversial Cartesian cousins. Video after the break.

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The Chocolate Must Flow This Holiday Season

December 7, 2023 by Kristina Panos 8 Comments

After a long December of hand-coating chocolates for relatives last year, [Chaz] decided that enough was enough and built a chocolate enrobing machine to do the dirty work for him. As a side project, he built a rotary tumbler to chocolate-coat things like wasabi peas, which we assume are designated for [Chaz]’s enemies.

This build started with an off-the-shelf chocolate fountain for which [Chaz] designed and printed a new nozzle in PLA. He also knocked off the flutes that make it fountain on the band saw and removed the rest of the material on the lathe.

The conveying bit comes from a conveyor toaster oven that [Chaz] had lying around — he removed the conveyor and hooked it up to a motor from his collection using a slightly modified flex coupler.

With the chocolate enrober complete, [Chaz] moved on building to the rotary tumbler, which is made from two thrift store pans hammered together at the edges and connects up to the front of a KitchenAid mixer. The final verdict was that this did not work as well as the enrober, but it wasn’t a complete bust — wasabi peas (and most of the kitchen) got coated in chocolate.

While we’re not sure we’d use that PLA chocolate pump more than once, we sure would like to enrobe some things in chocolate, and this seems like a good way to get it done. Check out the build video after the break.

Chocolate is good for more than coating everything in sight. Speaking of sight, check out these chocolate optics.

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a–d, Crystal structures of the 1CzTrz-F (a,b) and 3CzTrz-F (c,d) compounds, determined by XRD. a,c, Diagrams of the two dimers of both crystallographic unit cells to show the molecular packing. b,d, Spatial arrangement of the acceptor–donor contacts in the 3D crystal structure. The triazine acceptor and the carbazole donor units are coloured orange and blue, respectively. The green features in d indicate co-crystallized chloroform molecules. (Credit: Oskar Sachnik et al., 2023)

Eliminating Charge-Carrier Trapping In Organic Semiconductors

August 13, 2023 by Maya Posch 4 Comments

For organic semiconductors like the very common organic light-emitting diode (OLED), the issue of degradation due to contaminants that act as charge traps is a major problem. During the development of OLEDs, this was very pronounced in the difference between the different colors and the bandgap which they operated in. Due to blue OLEDs especially being sensitive to these charge traps, it still is the OLED type that degrades the quickest as contaminants like oxygen affect it the strongest. Recent research published in Nature Materials from researchers at the Max Planck Institute for Polymer Research by Oskar Sachnik and colleagues (press release) may however have found a way to shield the electron-carrying parts of organic semiconductors from such contaminants.

Current density (J)–voltage (V) characteristics of electron- and hole-only devices of 3CzTrz and TPBi. (Credit: Oskar Sachnik et al., 2023)

In current organic semiconductors TPBi is used for electron transport, whereas for this research triazine (Trz, as electron acceptor) and carbozole (Cz, as donor) were used and compared with the properties of leading-edge TPBi. While a few other formulations in the study did not show remarkable results, one compound (3CzTrz) was found using X-ray diffraction (XRD) to have a structure as shown on the right in the heading image, with the carbozole (in blue) forming essentially channels along which electrons can move, while shielded from contaminants by the triazine.

Using this research it might be possible to create organic semiconductors in the future which are free of charge-traps, and both efficiency and longevity of this type of semiconductor (including OLEDs and perovskites) can be improved immensely.

No Moving Parts LiDAR

July 6, 2023 by Al Williams 29 Comments

Self-driving cars often use LiDAR — think of it as radar using light beams. One limitation of existing systems is they need some method of scanning the light source around, and that means moving parts. Researchers at the University of Washington have created a laser on a chip that uses acoustic waves to bend the laser, avoiding physically moving parts. The paper is behind a paywall, but the University has a summary poster, and you can also find an overview over on [Geekwire].

The resulting IC uses surface acoustic waves and can image objects more than 100 feet away. We would imagine this could be helpful for other applications like 3D scanning, too. The system weighs less than a conventional setup, too, so that would be valuable in drones and similar applications.

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