Making Photovoltaic Solar Cells With A Microwave

October 19, 2026 by Maya Posch 3 Comments

Although solar panels may seem like a kind of magic, they’re really quite simple devices, in their silicon form featuring nothing but the p-type silicon wafer and an n-type layer doped with e.g. phosphorus. Because of this simplicity it’s quite possible to make your own solar cells at home using only a few basic, off-the-shelf ingredients and a kiln, which in this recent video by [Dr. Semiconductor] uses a microwave kiln and thus justifies the video’s title.

Even the silicon wafer that you start with can be easily purchased online, though you have to be careful that it’s a bare wafer, without existing etchings on it. On this you need to get a phosphorus-rich layer, which is done by creating a delicious mixture of 1 mL of tetraethyl orthosilicate (TEOS), 0.3 mL of 85 wt% phosphoric acid, 5 mL of ethanol and 0.25 mL of distilled water. After low heat boiling this for 30 minutes, it is spincoated onto the cut square of silicon wafer using a spinning platform, like a PC fan.

Next, you shove the coated silicon into the kiln and put it into the microwave to bake at a fairly low power level for half an hour. In the video it took less than 50% power of the microwave to not melt the silicon, so remember that those microwave kilns get pretty hot.

With the delightful smells of freshly baked silicon now teasing your nostrils, you can then take out the doped silicon to sand or etch off the thin layer of glass that’s formed around the new PV cell. On the clear spots you can now put a gallium-indium contact on the p-type Si side and a wad of indium on the newly doped Si-P side, which are now your contacts for the PV cell.

The full recipe along with many of the issues discussed in the video can also be found on the blog article, though the video conclusion notes that many improvements are still possible. The created PV cell in the video reaches an efficiency of about 5%, but this could be improved through changes like the use of a clean-room, adding an anti-reflection coating and improving the contact with the cell.

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The New Phobos Martian Moon Rover That Weighs In At Only 15 Grams

October 18, 2026 by Maya Posch 27 Comments

Although for many decades the planet Mars has been prodded, poked, driven upon, flown over and especially orbited by various spacecraft, landers and rovers sent over by a certain humanoid species on Earth, the two moons that orbit Mars have featured significantly more in science-fiction and video games than in scientific literature. This is now about to change when the Martian Moons eXploration (MMX) mission launches on October 19th, which will include a sample return from Phobos.

So far these two moons of Mars – Phobos and Deimos – have only received a few cursory glances by passing spacecraft, leaving many fundamental questions surrounding their formation and composition very much open. With the MMX mission this should change dramatically, with this spacecraft intended to perform detailed measurements of both moons.

In addition a rover – called Idefix – will perform a landing on Phobos for observations of its surface. This will be quite a feat as despite this lander coming in at 25 kg, on Phobos’ surface it will weigh only 15 grams due to the low gravity, or even less than the diminutive dog companion of Obelix, with potential bouncing as we have seen with previous landing attempts on such small bodies.

After launch, the MMX mission will take a year to arrive at Mars, in August of 2027, with Idefix being released in early 2029 for its hopefully soft paws-down on the surface of Phobos where it can scurry about for a while until the main MMX spacecraft lands later for its sample retrieval and return part of the mission. If everything goes well, this would mean that a sample of Phobos should be landing in Australia in 2031.

Busting The Myth That Plastics Are Chemically Inert In Water

October 17, 2026 by Maya Posch 4 Comments

One of the often made claims about plastics is that they are chemically inert under most conditions, such as when exposed to water. This long-held belief has also challenged the notion that micro- and nanoplastics (MNPs) are dangerous to organisms such as us human animals. A hitherto unknown mechanism between common plastics as investigated by [Naixin Qian] et al. and published in Nature serves to generate highly reactive hydroxyl radicals when exposed to water.

Hydroxyl radicals (HO^•) are the neutral form of the hydroxide ion (OH^–). It’s a free radical that tends to be extremely short-lived due to its reactivity, much like the singular oxygen molecule that is freed at the plastic-water interface. The energy provided for this reactivity comes from the electrostatic effect, itself highly correlated with many plastics, with the six types of microplastics used in the experiment showing varying levels of free radicals, particularly for the more hydrophobic types.

This high reactivity of free radicals is a well-known problem in cellular biology, with evolution having developed many tools over the years to deal with capturing these radicals as well as repair the (DNA) damage that they can cause. The effect of these microplastics and their generated free radicals was thus studied as well.

Of note here is that the electrostatic effect itself already serves to draw charged biomolecules to it, before the impact of free radicals is considered. By using mouse red blood cells and exposing them to polystyrene (PS) microplastics fatal damage was observed to the red blood cells.

This indicates that there are at least three possible ways in which MNPs can be harmful to organisms. It also provides another clue to how this may affect the ageing of plastics, among other implications.

Currently there is still ongoing debate on whether MNPs are truly harmful and just how prevalent they may be in e.g. our bodies. Reliably detecting them in e.g. biological tissues remains a challenge, which this new study may also be helpful with, since one of our biggest blind spots is that we lack solid knowledge of how MNPs may behave inside an organism.

Building A Flying Drone With A Single Propeller

October 17, 2026 by Maya Posch 6 Comments

Technically all that you need in order to make a drone fly is a single motor and single propeller, but realistically it becomes basically impossible to fly it at that point. In the case of helicopters you therefore need a second rotor somewhere to provide counterbalance to the first and to be able to steer.

There are of course a number of ways to make a drone fly with a single propeller, but the compromise usually is to use very large propellers, as well as other mechanisms that make for a very large drone. This wasn’t good enough for [Joshua Bird] who wanted to have a very small, single propeller drone.

Key to making it work is not only a very high RPM, but also a hinged propeller hub that manipulates the angle of the blades in such a way that both pitch and roll can be controlled if you react quickly enough. This turned out to be impossible using standard motor ESCs that do not directly measure the motor’s speed and position but rely on back EMF.

In the final prototype of the drone such details had to be measured directly, with super-fast adjustments to the motor’s speed only possible with custom controller code and a lot of trial and error. Even then the drone would often lose track of its position and crash once more. The solution there was to add an infrared beacon in the room and a sensor on the drone, to give it a fixed reference point.

You can find the project files so far on the GitHub project page, with upcoming changes to the drone design involving improvements like adding a scanner to the drone so that it can autonomously use features in its environment as fixed reference points. That way it might conceivably be able to fly outside as well, which would be quite exciting to see.

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Fairbuds 2 Teardown Shows Little Glue, Easy Battery Swap

October 16, 2026 by Maya Posch 12 Comments

In a world where wireless earbuds are increasingly seen as devices that you toss into the e-waste bin as soon as they stop working, it’s heartening to see companies take the opposite approach with their designs. In a recent teardown of the new Fairbuds 2 by [iFixit] we get a blow-by-blow report of disassembling one of these devices, getting to its rechargeable LIR1054 coin cell, as well as the very accessible PCB should you have to replace a shorted capacitor or similar issue.

Much like with the first version, the 3.6 V lithium-ion coin cell can be extracted simply by pulling on the battery door, which leverages it out of the enclosure. Despite this easy access method and no glue these earbuds are still IP54 rated, so they’re safe to wear when you’re dashing for shelter in a sudden downpour.

To get further into the device, you have to overcome the plastic clips that hold the enclosure together, along with what appears to be a few dabs of glue. Inside it you find the PCB containing the guts, including the Airoha AB1577S, Cortex-M4F-based IC that provides the Bluetooth Low Energy capabilities as well as enabling the touch control and other features.

Below the PCB is the coin cell holder, followed by the only part that saw real glue usage, namely the driver section. Presumably this is the compromise to keep things like sweat out of the device. Even so, after disassembly [iFixit] managed to reassemble the device and the earbud remained in working condition.

The case for the earbuds is even easier to disassemble, using just some bolts to unfasten. The USB-C port is soldered to the PCB which [iFixit] dinged them on, but still gave it a 10/10 on their repairability score.

Compared to Apple’s AirPods this is obviously a whole different world, although recently [iFixit] was somewhat pleased with the most recent AirPods generation being slightly more repairable, with non-destructive entry for a battery swap at least somewhat feasible.

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Disposing Of PLA And Why Composting Is Not An Option

October 16, 2026 by Maya Posch 28 Comments

The ‘biofriendly’ nature of poly(lactic acid) (PLA) filament often gets touted as one of its main advantages over alternatives like PETG, but even a modicum of research ought to inform a person that the biodegrading feature of PLA is only true for pure PLA without additives and at temperatures at or above its glass transition temperature (Tg). Thus the results of a year-long experiment by [I built a thing] shouldn’t be too surprising.

After burying said PLA in the garden like any self-respecting person does who tries to dispose of some evidence, the PLA suffered through a European winter and very hot, dry summer, before being dug up again recently for inspection and testing. Although not the first time that someone has tested this, it’s a good reminder considering just how much PLA filament is used each year.

In total three sample sets were used, one being the control, the other two buried in soil and compost respectively. A visual inspection showed no major difference, and a tensile strength test also showed no statistically significant change among all three sample sets. The experiment could have been concluded here, but instead calorimetry was used in a laboratory setting to see whether exposure to microbes as commonly found in soil does anything significant.

This isothermal microcalorimetry test was performed at the University of Basel, effectively to answer the question whether there’s anything in the PLA samples that can feed said microbes. As it turns out, the answer is a resounding ‘no’, with microbial activity within the presence of PLA dropping off even quicker presumably due to there being less volume available for nutrients.

When [I built a thing] contacted a large number of commercial biodegrading facilities in Switzerland, Germany and the USA, many would happily take PLA, but none of them would accepted 3D-printed PLA parts, which says a lot. The primary reason for this appears to be that even under industrial composting conditions it simply takes too long for these facilities to consider these to be economical to compost.

With PLA primarily degrading via hydrolysis, it needs to be exposed to the right conditions for this process to not take an eternity. You can of course use something like PHA instead, which doesn’t require this hydrolysis step to be biodegradable. Overall PLA is quite a crummy material, with it also suffering from embrittlement due to crystallization that will happily turn a spool of PLA into lots of sad fragments. This makes PETG into a very common and very attractive alternative to PLA.

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Using Optical Waveguide Arrays To Make Sheets Sense Shapes

October 15, 2026 by Maya Posch 9 Comments

Determining the shape of an object which can change dynamically is a bit of a challenge, one that especially vexes those who are really into Virtual Reality. Sensing the orientation of various limbs and appendages usually requires external sensors like cameras, or limit the focus to specific details like just the hands and fingers of the player. A more comprehensive and potentially flexible approach might be possible using optical waveguides, as demonstrated by [Qifan Yu] et al. in a recent article in Advanced Intelligent Systems.

Waveguides are structures that guide electromagnetic waves, with optical waveguides such as used here targeting EM radiation in the optical band. This can even allow for the use of cheap and plentiful optical fiber, though here custom elastomeric waveguides are manufactured. These are laid out onto the sheet in a double-sided, overlapping zig-zag pattern, which allows for easy reconstruction of the shape of said sheet based on how the wave propagation through the waveguide changes.

By characterizing the behavior of the signals through the waveguide, its shape and thus that of the sheet can be reconstructed. This was then demonstrated to be accurate by wrapping the sheet around a volunteer’s arm, elbow and hand, detecting the flexing and movement of individual joints.

Although fairly bulky in the demonstrated configuration and with an unoptimized algorithm, it’s conceivably something that can be miniaturized to the point where it can be woven into regular fabric. This could make for sensor sheets that could track the configuration of everything from robots to human bodies for something like VR purposes.