Sal

cross-posted from: https://mander.xyz/post/31227704

This weekend I did some experiments with turmeric powder. Here are some images of the results, and the description of how to create these microscopic chemical landscapes is given below.

Turmeric powder is a fantastic material to play with. The powder has a high concentration of colored and fluorescent curcuminoids and volatile turmerone oils.

When you use a polar solvent to extract these compounds, what you get is a kind of fluorescent oily resin called a turmeric 'oleoresin'.

The curcuminoids are yellow at acidic and neutral pH, but they become bright red at high pH due to keto-enol tautomerization. There is a lot of cool things you can do with the curcuminoids in terms of photo/electrochemistry.

I have been playing with very simple chemistry under the microscope, and I have noticed that you can create some cool-looking micro-landscapes. During this process you can also see different types of physico-chemical processes happening in real time.

Procedure to do this:

• Place a few grams of turmeric powder into a glass container
• Add enough isopropanol to cover the material, and a bit more
• Mix
• Wait for the solids to settle
• Collect a bit of the isopropanol liquid from the top and place on a glass coverslip
• Wait for the isopropanol to evaporate.

At this time, you can see under the microscope that golden oil droplets have been deposited, and that the surroundings are also yellow. The drops are oleoresins, which consist of curcuminoids suspended in turmerones and other oily compounds. Thin curcuminoid films might also be forming in between these droplets.

• Add a sprinkle of baking soda crystals (sodium bicarbonate) on top of the coverslip. You can blow on the coverslip if you accidentally add too much.

• Add a small drop of water, and wait a bit.

At this time you can see that the crystals are dissolving under the microscope, but the colors are not changing. The water and oils are not mixing, and so you get this film of alkaline water surrounding the oil droplets, but nothing is yet really changing.

• After waiting a few minutes, add a drop of isopropanol.

Now the isopropanol will re-dissolve the oleoresin and mix with the alkaline water. The carbonate ions are now able to react with the curcuminoids, and when they do, they go into the ketone form and instantly turn red. Under the microscope you can see quite dramatic movements of yellow and rad streaking as well as turbulent movements of the baking soda crystals.

• Wait some time for the liquids to evaporate again

• You will end up with a landscape that combines yellow resins, red resins, sodium bicarbonate crystals, and several different patterns.

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You can vary the parameters - the amount of sodium bicarbonate, the position and size of the drops, you can pre-mix the water and isopropanol, etc. Small changes can drastically affect the resulting landscape.

The SCD4x sensor from Sensirion measures CO₂, temperature, and humidity, and communicates these values via I²C.

The measurement principle for the CO2 is that of photoacoustic sensing. The fundamental principle is shown in the diagram below: shine light that the CO2 molecules absorb and use a microphone to listen to the pressure variations.

I ordered a batch of SCD41 sensors from China for various projects, including fermentation, mushroom and plant cultivation, and field monitoring.

Since I had extras, I sacrificed one for macro photography. I removed the cover with a dremel and pliers, then cleaned the internals using isopropanol.

Here is my take:

The temperature and humidity are measured by Sensirion’s SHT40, seen as the black square at the bottom right. It’s likely accessed by the internal microcontroller over an internal I²C bus.

The pink square at the top left is a MEMS IR emitter. The SCD4x datasheet doesn’t specify the emission wavelength, but 4.3 µm is standard for NDIR-based CO₂ detection. A similar emitter example is this one from Microhybrid. These emitters usually produce broadband IR, with a 4.3 µm band-pass interference filter on top. The pink hue likely comes from this filter. Filters like these are critical to target CO₂ absorption while avoiding spectral overlap with other gases. For further reading, see Infratec's application note and Delta Optical Thin Film’s technical explanation.

The gold component labeled “o119 ANC” is the MEMS microphone, used to detect pressure waves caused by gas molecules absorbing pulsed IR light—this is photoacoustic sensing. The vibration excited by 4.3 µm light occurs at ~70 THz, far beyond acoustic detection. However, the IR source is pulsed at a modulation frequency (typically 20–60 Hz, e.g. 40 Hz), and the microphone detects the resulting pressure variations at this frequency. The principle is outlined in patent US 2024/0133801 A1.

An example of a compatible MEMS microphone is Infineon’s IM72D128V01, which supports frequencies down to 20 Hz.

The final main component is the metal-shielded package. It likely contains a microcontroller responsible for:

• Driving the MEMS IR emitter with a modulated current (e.g., at 40 Hz)
• Capturing and analyzing the MEMS microphone signal to extract the amplitude of acoustic pressure oscillations (proportional to CO₂ concentration)
• Acting as an I²C master to retrieve temperature and humidity data from the SHT40
• Acting as an I²C slave to provide CO₂, temperature, and humidity data to an external controller

Here are top and bottom views of the sensor cap:

The cap has a circular gas inlet. The white material covering it is likely a hydrophobic ePTFE membrane, which allows gas exchange while blocking liquid water.

I hope someone else finds this interesting too!

EDIT: After posted this, I searched online and I found a photo from someone who went a deeper than me and did expose the microcontroller: https://www.hackteria.org/wiki/CO2_Soil_Respiration_Chamber

This is the photo borrowed from that site:

Abstract

For nearly 450 million years, mycorrhizal fungi have constructed networks to collect and trade nutrient resources with plant roots1,2. Owing to their dependence on host-derived carbon, these fungi face conflicting trade-offs in building networks that balance construction costs against geographical coverage and long-distance resource transport to and from roots3. How they navigate these design challenges is unclear4. Here, to monitor the construction of living trade networks, we built a custom-designed robot for high-throughput time-lapse imaging that could track over 500,000 fungal nodes simultaneously. We then measured around 100,000 cytoplasmic flow trajectories inside the networks. We found that mycorrhizal fungi build networks as self-regulating travelling waves—pulses of growing tips pull an expanding wave of nutrient-absorbing mycelium, the density of which is self-regulated by fusion. This design offers a solution to conflicting trade demands because relatively small carbon investments fuel fungal range expansions beyond nutrient-depletion zones, fostering exploration for plant partners and nutrients. Over time, networks maintained highly constant transport efficiencies back to roots, while simultaneously adding loops that shorten paths to potential new trade partners. Fungi further enhance transport flux by both widening hyphal tubes and driving faster flows along ‘trunk routes’ of the network5. Our findings provide evidence that symbiotic fungi control network-level structure and flows to meet trade demands, and illuminate the design principles of a symbiotic supply-chain network shaped by millions of years of natural selection.

A spy tan egg pretends to be on the same emotional wavelength as other tan eggs

These past few days I have been learning about bootloaders, kernels, assembly, and general OS stuff. In that process I stumbled upon your project of Redox OS.

I like the concept of the more modular micro-kernel architecture. Using Rust seems like the right choice if one were to start an OS from scratch today.

Very cool stuff. I'll use your project as my reference as I continue to learn. Happy to find you in Lemmy! Just wanted to stop by to give you a thumbs up 👍

I kept a Lion's mane petri dish stored in the fridge for well over a year.

I decided to make an attempt at refreshing it by transferring into fresh petri dishes. After a week I noticed some strong mycelium growth.

After inoculating a grain jar with one of the cultures, I decided to have a look under the microscope to double check, just in case.. And that's when I noticed a morphology that I had never seen before. It looked nothing like Lion's Mane. The full length of the mycelium is covered with these pegs with a sphere at the end.

After some searching, I am almost convinced that this is a Verticillium sp. - a new contaminant for me!

I then checked all of the petri dishes and they are all this same fungus. So, time to get a new fresh culture 😅

This gullfriend got an itchy eye during the photo-shoot.

Took this photo in Park Frankendael in Amsterdam a few years ago - just learned about this community and thought it would fit 😁