Spiders Are Somehow Hacking Fireflies To Lure More Victims

September 2, 2024 by Donald Papp 27 Comments

What happens when an unfortunate bug ends up in a spider’s web? It gets bitten and wrapped in silk, and becomes a meal. But if the web belongs to an orb-weaver and the bug is a male firefly, it seems the trapped firefly — once bitten — ends up imitating a female’s flash pattern and luring other males to their doom.

Fireflies communicate with flash patterns (something you can experiment with yourself using nothing more than a green LED) and males looking to mate will fly around flashing a multi-pulse pattern with their two light-emitting lanterns. Females will tend to remain in one place and flash single-pulse patterns on their one lantern.

When a male spots a female, they swoop in to mate. Spiders have somehow figured out a way to actively take advantage of this, not just inserting themselves into the process but actively and masterfully manipulating male fireflies, causing them to behave in a way they would normally never do. All with the purpose of subverting firefly behavior for their own benefit.

It all started with an observation that almost all fireflies in webs were male, and careful investigation revealed it’s not just some odd coincidence. When spiders are not present, the male fireflies don’t act any differently. When a spider is present and detects a male firefly, the spider wraps and bites the firefly differently than other insects. It’s unknown exactly what happens, but this somehow results in the male firefly imitating a female’s flash patterns. Males see this and swoop in to mate, but with a rather different outcome than expected.

The research paper contains added details but it’s clear that there is more going on in this process than meets the eye. Spiders are already fascinating creatures (we’ve seen an amazing eye-tracking experiment on jumping spiders) and it’s remarkable to see this sort of bio-hacking going on under our very noses.

The Strangest Way To Stick PLA To Glass? With A Laser And A Bit Of Foil

September 2, 2024 by Donald Papp 7 Comments

Ever needed a strong yet adhesive-free way to really stick PLA to glass? Neither have we, but nevertheless there’s a way to use aluminum foil and an IR fiber laser to get a solid bond with a little laser welding between the dissimilar materials.

A piece of sacrificial aluminum foil bonds the PLA to glass with a form of laser welding, with precise control and very little heat to dissipate.

It turns out that aluminum can be joined to glass by using a pulsed laser process, and PLA can be joined to aluminum with a continuous wave laser process. Researchers put them together, and managed to reliably do both at once with a single industrial laser.

By putting a sacrificial sheet of thin aluminum foil between 3D printed PLA and glass, then sending the laser through the glass into the aluminum, researchers were able to bond it all together in an adhesive-free manner with precise control, and very little heat to dissipate. No surface treatment of any kind required. The bond is at least as strong as any adhesive-based solution, so there’s no compromising on strength.

When it comes to fabrication, having to apply and manage adhesives is one of the least-preferable options for sticking two things together, so there’s value in the idea of something like this.

Still, it’s certainly a niche application and we’ll likely stick to good old superglue, but we honestly didn’t know laser welding could bond aluminum to glass or to PLA, let along both at once like this.

Ultra-Black Material, Sustainably Made From Wood

September 2, 2024 by Donald Papp 40 Comments

Researchers at the University of British Columbia leveraged an unusual discovery into ultra-black material made from wood. The deep, dark black is not the result of any sort of dye or surface coating; it’s structural change to the wood itself that causes it to swallow up at least 99% of incoming light.

One of a number of prototypes for watch faces and jewelry.

The discovery was partially accidental, as researchers happened upon it while looking at using high-energy plasma etching to machine the surface of wood in order to improve it’s water resistance. In the process of doing so, they discovered that with the right process applied to the right thickness and orientation of wood grain, the plasma treatment resulted in a surprisingly dark end result. Fresh from the plasma chamber, a wood sample has a thin coating of white powder that, once removed, reveals an ultra-black surface.

The resulting material has been dubbed Nxylon (the name comes from mashing together Nyx, the Greek goddess of darkness, with xylon the Greek word for wood) and has been prototyped into watch faces and jewelry. It’s made from natural materials, the treatment doesn’t create or involve nasty waste, and it’s an economical process. For more information, check out UBC’s press release.

You have probably heard about Vantablack (and how you can’t buy any) and artist Stuart Semple’s ongoing efforts at making ever-darker and accessible black paint. Blacker than black has applications in optical instruments and is a compelling thing in the art world. It’s also very unusual to see an ultra-black anything that isn’t the result of a pigment or surface coating.

Symmetrical Gear Spins One-Way, Harvesting Surrounding Chaos

August 30, 2024 by Donald Papp 12 Comments

Here’s a novel ratchet mechanism developed by researchers that demonstrates how a single object — in this case a gear shaped like a six-pointed star — can rectify the disordered energy of its environment into one-way motion.

5x speed video of gear in agitated water bath.

The Feynman–Smoluchowski ratchet has alternating surface treatments on the sides of its points, accomplished by applying a thin film layer to create alternating smooth/rough faces. This difference in surface wettability is used to turn agitation of surrounding water into a ratcheting action, or one-way spin.

This kind of mechanism is known as an active Brownian ratchet, but unlike other designs, this one doesn’t depend on the gear having asymmetrical geometry. Instead of an asymmetry in shape, there’s an asymmetry in the gear tooth surface treatments. You may be familiar with the terms hydrophobic and hydrophilic, which come down to a difference in surface wettability. The gear’s teeth having one side of each is what rectifies the chaotic agitation of the surrounding water into a one-way spin. Scaled down far enough, these could conceivably act as energy-harvesting micromotors.

Want more detail? The published paper is here, and if you think you might want to play with this idea yourself there are a few different ways to modify the surface wettability of an object. High voltage discharge (for example from a Tesla coil) can alter surface wettability, and there are off-the-shelf hydrophobic coatings we’ve seen used in art. We’ve even seen an unusual clock that relied on the effect.

Demonstrating The Photoelectric Effect Using Neon Lamps

August 28, 2024 by Dave Rowntree 30 Comments

Neon lamps are fun to play with. These old-school indicators were once heavily utilized in many types of equipment for indication purposes but now seem largely relegated to mains voltage indication duties. Here’s a fun video by [Ashish Derhgawen], discussing the photoelectric effect of neon lamps with some simple demonstrations.

[Ashish] demonstrates the well-known photoelectric effect by triggering a sub-biased neon lamp with visible light from an LED. Neon bulbs work on the principle of voltage-induced ionization, creating a visible glowing plasma. If the applied voltage is high enough, around 60 to 80 V, electrons get knocked off the neutral neon atoms. The now free electrons, roaming around highly energized, will eventually come across a neon ion (missing an electron) and recombine to make it neutral again.

The results are a lower total energy state, and the difference in energy is resolved by the emission of a photon of light, which, in the case of neon, is a dull reddish-orange. Nothing unusual there. However, nothing will happen if the applied voltage bias is just below this device-specific threshold. There’s not enough energy to strip electrons.

Apply an external light source, and this threshold can be exceeded. The photons from the LED are just energetic enough to strip a small number of electrons from the surface of the electrodes, and this causes a cascade, or avalanche effect, lighting up the plasma and turning on the neon lamp. ~~Take away the external light source, and it dies down and goes dark.~~

Continue reading “Demonstrating The Photoelectric Effect Using Neon Lamps” →

Setup of a small lightbulb passing light through a thin film

Experimenting With Interference On Thin Layers

August 26, 2024 by Heidi Ulrich No comments

[Stoppi] has taken on a fascinating project involving the interference of thin layers, a phenomenon often observed in everyday life but rarely explored in such depth. This project delves into the principles of interference, particularly focusing on how light waves interact with very thin films, like those seen in soap bubbles or oil slicks. The post is in German, but you can easily translate it using online tools.

Interference occurs when waves overlap, either reinforcing each other (constructive interference) or canceling each other out (destructive interference). In this project, [Stoppi] specifically examines how light behaves when passing through thin layers of air trapped between semi-transparent mirrors. When light waves reflect off these mirrors, the difference in path length leads to interference patterns that depend on the layer’s thickness and the wavelength of the light.

To visualize this, [Stoppi] used an interferometer made from semi-transparent mirrors and illuminated it with a bulb to ensure a continuous spectrum of light. By analyzing the transmitted light spectrum with a homemade spectrometer, he observed clear peaks corresponding to specific wavelengths that could pass through the interferometer. These experimental results align well with theoretical predictions, confirming the effectiveness of the setup.

If you like pretty patterns, soap bubbles are definitely good for several experiments. Don’t forget: pictures or it didn’t happen.

Continue reading “Experimenting With Interference On Thin Layers” →

Intuitive Explanation Of Arithmetic, Geometric & Harmonic Mean

August 24, 2024 by Maya Posch 8 Comments

The simple definition of a mean is that of a numeric quantity which represents the center of a collection of numbers. Here the trick lies in defining the exact type of numeric collection, as beyond the arithmetic mean (AM for short, the sum of all values divided by their number) there are many more, with the other two classical Pythagorean means being the geometric mean (GM) and harmonic mean (HM).

The question that many start off with, is what the GM and AM are and why you’d want to use them, which is why [W.D.] wrote a blog post on that topic that they figure should be somewhat intuitive relative to digging through search results, or consulting the Wikipedia entries.

Compared to the AM, the GM uses the product of the values rather than the sum, which makes it a good fit for e.g. changes in a percentage data set. One thing that [W.D] argues for is to use logarithms to grasp the GM, as this makes it more obvious and closer to taking the AM. Finally, the HM is useful for something like the average speed across multiple trips, and is perhaps the easiest to grasp.

Ultimately, the Pythagorean means and their non-Pythagorean brethren are useful for things like data analysis and statistics, where using the right mean can reveal interesting data, much like how other types using something like the median can make a lot more sense. The latter obviously mostly in the hazy field of statistics.

No matter what approach works for you to make these concepts ‘click’, they’re all very useful things to comprehend, as much of every day life revolves around them, including concepts like ‘mean time to failure’ for parts.

Top image: Cycles of sunspots for the last 400 years as an example data set to apply statistical interpretations to. (Credit: Robert A. Rohde, CC BY-SA 3.0)