Author: Aaron Beckendorf

168 Articles

Continously Extruding 3D Printed Tubes With Compressed Air

August 9, 2026 by 8 Comments

[Jan] of [Roetz 4.0] has a unique approach to multi-material 3D printing: he’s designed an extruder which takes two different materials and extrudes one as a shell around the other. This opens up some interesting possibilities, such as a conductive filament surrounded by an insulating shell; [Jan], however, didn’t have an immediate use for the process, so he moved on to a related technique: extruding plastic tubes with a compressed-air core.

The extruder he used for this was a variation on the dual-material extruder; it takes in two strands of filament, melts them, and extrudes them as a shell around the outlet of a compressed-air line, which was controlled by a high-precision pressure regulator. During testing with PLA, it seemed capable of extruding airtight tubes of filament, though it had a tendency to blow bubbles and form tubes with inconsistent diameters. The low thermal conductivity of the stainless steel extruder also proved problematic; coupled with the cooling effect of the compressed air, filament sometimes solidified inside the extruder.

[Jan] found it almost impossible to get consistent results using only pressure-based control; as the layer of molten plastic around the air gets thinner, it provides less resistance to further ballooning, leading to continuous expansion until the bubble bursts. Controlling the volume of air extruded provided much more consistent results, and in a second video, he built a peristaltic pump to do just that. He also switched to using TPU filament, which greatly improved layer adhesion. When inflated with compressed air, the finished TPU structures expanded slightly, though there were still air leaks. The results look promising, and TU Darmstadt has already carried out some research in this area.

In a separate research project, we’ve seen a similar multi-material co-extrusion approach used to print pneumatic channels. For more on the history of [Jan]’s multi-filament extruder, check out his Minuteman printer. Continue reading “Continously Extruding 3D Printed Tubes With Compressed Air” →

A man's hand is shown adjusting a black Bakelite dial on the front panel of an instrument. The instrument is contained in a wooden box, and to the left of the box, a thermocouple is inserted into the flame of an alcohol burner.

Reading A Thermocouple With Mercury And A Potentiometer

August 5, 2026 by 2 Comments

If you’ve ever thought about the nomenclature of electrical components, potentiometer stands out as a strange name, etymologically suggesting something like a voltmeter. In fact, the component took its name from a voltage-measuring instrument also named the potentiometer. [Alnwlsn] recently took a look at one such device, which was integrated into a thermometer, and the Weston cell used to calibrate it.

The potentiometer (instrument) has a galvanometer at its heart. One side of the galvanometer is connected to the center lead of a potentiometer (component) which spans a voltage source; the other side is connected to a reference voltage. The potentiometer can be adjusted until no current flows through the galvanometer, at which point both sides match the reference voltage. The reference voltage source can then be replaced with some other source, which can then be measured relative to the reference by adjusting the potentiometer until both the voltages match. The reference voltage source is a Weston cell, which uses two mercury electrodes, one amalgamated with cadmium, to produce a stable 1.018 volt reference; despite being 74 years old, this particular cell still measured at 1.017 volts.

In this case, the potentiometer was made to measure the voltage produced by a thermocouple. After calibrating the potentiometer and connecting an iron-constantan thermocouple, [Alnwlsn] tested it with ice and boiling water, and in each case it proved accurate. In a more extreme test, it captured the temperature difference between the base and the tip of an alcohol flame.

For a bit more on the history of similar devices, check out the history of Weston Electrical Instruments.

Continue reading “Reading A Thermocouple With Mercury And A Potentiometer” →

A man's hands are shown holding a broken 3D-printed hook. The hook has a loop and hook, in a number 9-shape. The hook portion has broken, exposing carbon fibers.

Strengthening 3D Prints With A Carbon-Fiber Epidermis

August 4, 2026 by 10 Comments

As strong and light as carbon fiber-epoxy composites are, the same can’t always be said of carbon-fiber reinforced 3D printer filaments. Of those that do improve over stock filament, the best performance comes from long, continuous strands, but the printers that can embed these are quite expensive. [MagicLAG], looking for a cheaper method, made something even stronger: prints reinforced with subsurface carbon-fiber cloth.

They tried a few other methods first, including pausing the print and manually embedding carbon fiber strands, ironing strands into the finished part, and ironing carbon fiber cloth into the bottom layer. For the main method, though, he printed the test part in three pieces: a core part, and two outer shell layers. Between the core and the shell is a small gap, into which carbon-fiber cloth can be epoxied. Under good conditions (not using quick-setting epoxy), this mostly preserves the outer surface and dimensional accuracy.

To test the various strengthening methods, [MagicLAG] printed hooks and tensioned them on a load cell until failure. None of the methods using single-stranded fiber showed any improvement; the fiber simply bent and let the surrounding plastic break. As a control for the epidermal cloth parts, they printed shells and cores and epoxied them together. These controls performed better than the standard parts, but not nearly as well as the carbon-fiber cloth composites. With only a few layers of cloth, these more than tripled the yield strength of the basic hook.

If you’d rather use a carbon-fiber filament, the type of plastic matters; carbon fiber makes PLA, at least, weaker. Regardless of form, some caution is called for whenever handling carbon fiber, since it seems to show some asbestos-like effects.

A plastic device sits on a desk, with a computer display and an oscilloscope behind it. A fiber-optic cable runs from the device to a laser diode source.

2026 Frikkin Lasers Challenge: Measuring Nanometer-Scale Displacements With An Optical Cavity

July 26, 2026 by 4 Comments

Optical cavities – two mirrors arranged to reflect light multiple times between them – form the basis of lasers and certain optical filters. Since any angle between the two mirrors results in light being scattered away, parallel alignment is essential, yet difficult to maintain. Nevertheless, [Timothy Giles] managed to 3D-print and align such an optical cavity, and used it to detect minute shifts in space and wavelength.

The cavity has two semi-transparent mirrors facing towards each other. One mirror is held in a 3D-printed mount, and the other is attached to the diaphragm of a speaker with a hole drilled through the center. The hole avoids the speaker coil, and allows light exiting the optical cavity through the semi-transparent mirror to appear on a paper target, which is monitored by a webcam. On the other side of the optical cavity, a laser diode coupled to a single-mode fiber shines in through the other mirror. Alignment is challenging, but the webcam makes it easier; as the mirrors tilt relative to each other, the pattern seen on the paper target changes, providing feedback for more precise adjustment.

Light reflected within the cavity can interfere constructively or destructively with incoming light, changing the brightness of the emitted beam. [Tim] used the speaker as a linear actuator to vary the cavity’s length, which, by counting the peaks in brightness, allowed him to measure the diaphragm’s displacement. This also demonstrated a laser diode’s wavelength instability: when the cavity was set to a constant length and the laser started up, the output brightness would cycle a few times. As the diode was warming up, its output wavelength was shifting, creating the same changing interference pattern.

To get a Gaussian beam distribution, [Tim] used a fiber-coupled laser; if you’d like to build one, we’ve seen a coupling mechanism built before. Most lasers are built around an internal optical cavity, but some instead use an external cavity.

2026 Hackaday Freaking Lasers Contest
An image of skyscrapers over a bay is shown, with some foliage along the bank. The sky and water are a pale blue-grey, while the foliage is pink.

Taking Tri-Camera True-Color Infrared Videos

July 25, 2026 by 30 Comments

Silicon-based CMOS camera sensors are cheap and plentiful, but they’re rarely used to their full potential: they can detect a greater range of wavelengths in the infrared spectrum than they can in the visible spectrum, but in most cameras this is blocked by an IR-cut filter. [Project 326]’s infrared camera system reverses this: it records infrared images in color while blocking out visible light.

The system uses three USB webcams, each with its IR cut filter removed and replaced with a different dichroic IR band-pass filter. One filter is centered at 750 nm, one at 850 nm, and one at 940 nm. There is no band overlap; in testing, each camera only detected an infrared flashlight tuned to its own filter wavelength. The original cameras didn’t hold the sensors in a consistent position, so [Project 326] designed new housings. Using three lenses, each with distinct aberrations, introduced some difficulties in alignment. [Project 326] originally intended to use a pair of beam-splitting prisms with only one lens, but this proved too difficult to align using 3D-printed frames.

A Raspberry Pi records a separate monochromatic stream from each camera, which can then be processed into a composite color video. The first frames need to be manually aligned, but afterwards a script can apply the alignment to the rest of the video. Finally, the channels are mapped to colors, with the precise mapping being freely changeable. There were some few unexpected issues: each camera has its own, not terribly precise, local oscillator, and they drifted apart by about one or two frames per minute. Parallax error, on the other hand, was less severe than might be expected: at close range it’s noticeable, but by a distance of 35 meters, it represents less than one pixel of distortion.

The resulting images look great, and it’s easy to forget that they’re being captured without the use of any visible light. We’ve seen a similar technique (though extending into the visible range) used to recreate the surreal effect of Aerochrome film.

A scanning-electron micrograph is shown of a cricket's body, focusing on the head, which has been sliced off just above the eyes.

Cross-Sectioning Crickets With A Femtosecond Laser

July 18, 2026 by 14 Comments

Unlike most cutting lasers, femtosecond lasers don’t vaporize materials; rather, they produce such short, intense bursts of light that the affected region is ablated without having the chance to heat its surroundings. This makes them good at cutting away material without damaging the surroundings, something [Ben Krasnow] exploited to cut cross-sections of samples while still in a scanning-electron microscope.

In this case, the samples were crickets, and before imaging they had to be prepared. First, the bodies were soaked in glutaraldehyde to cross-link the proteins and stabilize the structure. Next, a series of solvent exchanges replaced the water in the bodies with a low-surface-tension solvent; this meant that during the next step, drying, surface tension wouldn’t distort the crickets’ internal structure. Finally, the insect bodies were charred under argon, which made the bodies conductive and more absorptive to laser light.

The laser itself and the scanning galvo are mounted outside the microscope, and shine in through a transparent window. To protect the detector and electron optics from a spray of ablated carbon, a servo motor swings an aluminium shutter between these and the sample while the laser is active. This caused some mysterious problems during testing: after the first ablation run, the electron microscope’s image would contain so much noise as to be unusable, but it would improve over time. As it turned out, the shutter was painted, and the other side of the paint was getting coated with charged carbon particles. This created a small capacitor which disrupted the electron optics as it discharged. Eventually, after solving this and a few other strange problems, [Ben] was able to take several time-lapse videos of the laser gradually ablating a cricket, 30 microns at a time, revealing its inner structure.

Although scanning-electron microscopes are unfortunately shard to come by, it’s still possible to restore a secondhand microscope or, as [Ben] did, build your own. Femtosecond lasers are yet more inaccessible, though they can be used to replicate themselves.

Continue reading “Cross-Sectioning Crickets With A Femtosecond Laser” →

A person's hand is shown holding a glass flask in a dark room. An orange-red glow is emanating from the flask in a patches, forming a splash-like pattern near the base of the flask.

A Sloshing-Mercury-Powered Neon Light

July 16, 2026 by 16 Comments

In 1675, while transporting a barometer by night, the astronomer Jean Picard noticed a glow inside its glass tube, just above the mercury. As the mercury sloshed and splashed across the surface of the glass, a static electric charge had built up, which was discharging by ionizing the residual gas molecules inside the evacuated tube. [Styropyro] recreated this effect, and found that the dim glow could be made much stronger by adding some noble gas to the tube.

It starts with a simple recreation: he took a volumetric flask, attached a narrow glass stem to the mouth, added some mercury to the flask, evacuated it with a vacuum pump, and sealed off the glass stem. This produced a faint glow when shaken, but it was only really visible under very low light. When [Styropyro] brought it near a Tesla coil, however, it did glow much more brightly.

Backfilling an identical flask with neon to about 40 millitorr produced a much more spectacular result (a low pressure in the tube is necessary, but moderate pressure variations don’t significantly alter the effect). When shaken even slightly, this neon-containing flask produced a bright orange-red glow just above the surface of the mercury. Points of obstruction, such as those in a zig-zag tube, produced a brighter glow. A krypton-containing tube glowed blue, but less brightly than the neon tube.

Since this is, essentially, a triboelectric effect, other materials besides mercury should work; [Styropyro] tested several materials, and found that pieces of Teflon produced a faint glow, and copper beads a somewhat brighter glow. Unfortunately, Galinstan, the obvious replacement for mercury, wets and coats glass, preventing a charge buildup.

Without an added noble gas, the standard glow of barometric light comes from the excitation of mercury vapors, a glow which can also be seen in mercury rectifiers, and which excites the phosphors of fluorescent light bulbs.

Continue reading “A Sloshing-Mercury-Powered Neon Light” →