Carbon Quantum Dots in Your Favorite Color

Citizen scientist extraordinaire [Thought Emporium] put out a new video about colorful quantum dots which can be seen below the break. Quantum dots are a few nanometers wide and you can tell which size they are by which color they fluoresce. Their optical and electrical properties vary proportionally with size so red will behave differently than purple but we doubt they will taste like “cherry” and  “grape.” Let’s not find out. This makes sense when you realize that a diamond will turn into black powder if you pulverize it. Carbon is funny like that.

[Thought Emporium] uses the video for two purposes. The first is to demonstrate the process he uses to make different size quantum dot in his home lab. The second purpose is to implore the scientific community, in general, to take better care when publishing scientific papers. A flimsy third reason is to show that the show must go on. Partway through, all the batteries for his light were dead so he hastily soldered a connection for his benchtop power supply.

We’ve mentioned [Thought Emporium] a few times before. Another of his carbon-based experiments involved graphene creation. How about magnetic DNA extraction? [Thought Emporium] did that too. If you can’t get enough magnets, how about implanting one?

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The Hackaday Prize: Growing Your Own Soil

When a rainforest is clearcut for agricultural use, we only see the surface problems: fewer trees, destruction of plant and animal habitats, and countless other negative effects on the environment. A lurking problem, however, is that the soil is often non-ideal for farming. When the soil is exhausted, the farmers move further into the rainforest and repeat the process.

In the Amazon, however, there are pockets of man-made soil that are incredibly nutrient-dense. Figuring out how to make this soil, known as Terra Preta, on a massive scale would limit the amount of forest destruction by providing farmers a soil with more longevity which will, in turn, limit the encroachment on the rainforest. That’s the goal of this Hackaday Prize entry by [Leonardo Zuniga]: a pyrolysis chemical reactor that can make this soil by turning organic matter into a type of charcoal that can be incorporated into the soil to make Terra Preta.

As a bonus to making this nutrient-dense soil on a massive scale, this reactor also generates usable energy as a byproduct of processing organic waste, which goes several steps beyond simple soil enrichment. If successful and scalable, this project could result in more efficient farming techniques, greater yields, and, best of all, less damage to the environment and less impact on the rainforests.

How Many Inventors Does It Take To Invent A Light Bulb

Many credit the invention of the incandescent light bulb with Edison or Swan but its development actually took place over two centuries and by the time Edison and Swan got involved, the tech was down to the details. Those details, however, meant the difference between a laboratory curiosity that lasted minutes before burning out, and something that could be sold to consumers and last for months. Here then is the story of how the incandescent light bulb was invented.

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What is There to Know About Resistors?

Resistor: A passive chunk of material that resists the flow of electrical current. A terminal is connected to each end you’re done. What could be simpler?

It turns out it’s not so simple at all. Temperature, capacitance, inductance and other factors all play a part in making the resistor a rather complex component after all. Even its uses in circuits are many, but here we’ll just focus on the different types of fixed-value resistors, how they’re made, and what makes them desirable for different applications.

Let’s start with a simple one, and one of the oldest.

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Amazing Carbon Foam Doesn’t Take Much Bread

A lot of people knew the Space Shuttle had ceramic tiles to protect its nose from reentry heat. That’s mostly because the tiles fell off a lot and each one was a unique shape, so it got a lot of press coverage. However, you didn’t hear as much about the parts of the orbiter that got really hot: the forward part of the wings and the tip of the nose. For those, NASA used an exotic material called RCC or reinforced carbon-carbon. Other uses include missile nose cones and Formula One brakes. A similar material, carbon fiber-reinforced silicon carbide appears in some high-end car brakes. These materials can take high temperatures, easily.

[AvE] wanted to make some carbon foam for experiments. It does take a little bread, though. Not money, but literal bread. To create the foam, he burns bread slices in a chamber full of argon. The stuff has some amazing properties.

In the video below, you can see the foam protecting a thermocouple from a torch flame and even holding melting aluminum. Not bad for a few pieces of bread.

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Forget Stopping Bullets – Vest Warms You While Stopping Taser

carbon-ribbon-clothing

[Bruce Wayne] [Shenzhen] wanted a garment that would protect him from a jolt, while keeping him toasty in the cold weather. Well that’s not it at all, these are merely two of his projects using the same material in different ways.

We’re going to start with the infrared image on the right. This is a vest with chest and back pieces made of carbon tape totaling two meters of the material swirled on each side. Hook it to a power source and the carbon tape warms the wearer. Portability is something of an issue as each “element” takes 36 W of power (3A at 12V). Click through for advice on how to interface the tape with the power source.

Onto the main event… avoiding electrical shock when you get all up in the grill of that mall cop you’re hated for years. [Shenzhen’s] jacket is really just an ordinary long-sleeved coat. But he separated the lining at the bottom seam and used fusible material to hold the carbon tape in place. The carbon tape provides a better conductor than your skin, preventing the shock from stunning you as it was intended. This really is the thing of superheroes, or former editors who should have known better.

Paper accelerometers for pennies in the works

Cheap paper accelerometers? Put us down for a dozen to start. They’re not quite ready for mass production yet but it looks like they’re on the way.

[George Whitesides] led a team to develop the new technology that uses simple manufacturing methods to produce the sensor seen above. Graphite and silver inks were screen printed onto heavy paper. The single limb sticking out from the body of the sensor is a separate piece of paper that bends the carbon area when force is applied. This changes the carbon’s resistance which is measured using a Wheatstone bridge constructed by gluing resistors to the device.

It sounds unsophisticated compared to most of the accelerometer modules we’re used to, but if you need a sensor that detects sudden motion this sounds like the perfect part. Now who wants to be the first person to replicate this in their basement?

[Thanks Fabien]