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110 Articles

A multi-colored chair with a stainless steel frame sits on wooden legs against a grey background.

Recycled Chairs Bring The Subway To Your Living Room

November 6, 2022 by 38 Comments

Public transit seats have a rough life. Enduring a number of wear cycles that would make your sofa weep, they take a beating and have to keep looking presentable. When trains and buses are retired, where do the old seats go? A team from the MIT Hobby Shop investigated what was happening to the seats from retiring MBTA Red Line cars and recycled them into stylish chairs.

After some sleuthing and many emails, the MBTA relinquished a number of old subway seats to the team. Since the subway seats didn’t have legs, wood from old church pews was used to create bases. It took one pew end support to create each set of legs, which were cut out on a bandsaw. The old dark stain was sanded off, and the bases were finished with three coats of gel topcoat, letting the natural beauty of the old oak shine through.

We love seeing old things given new life here at Hackaday. If you want to see some more recycled furniture, check out this tire table, this upcycled jeans chair, or these best practices for making box forts.

Move Over Silicon, A New Semiconductor Is In Town

July 27, 2022 by 28 Comments

Silicon has had a long run as the king of semiconductors, and why not? It’s plentiful and works well. However, working well and working ideally are two different things. In particular, electrons flow better than holes through the material. Silicon also is a poor heat conductor as we’ve all noticed when working with high-speed or high-power electronics. Researchers at MIT, the University of Houston, and other institutions are proposing cubic boron arsenide to overcome these limitations.

According to researchers, this material is a superior semiconductor and, possibly, the best possible semiconductor. Unfortunately, the material isn’t nearly as common as silicon. Labs have created small amounts of the material and there is still a problem with fabricating uniform samples.

Early experiments show the material has very high mobility for electrons and holes along with thermal conductivity almost ten times greater than that of silicon. It also has a good bandgap, making it very attractive as a semiconductor material. In fact, only diamond and isotopically enriched cubic boron nitride have better thermal conductivity.

However, there are still unknowns about how to use the material in practical devices. Long-term stability tests are as lacking. So maybe it will wipe out silicon or maybe it won’t. Time will tell.

We are always on the lookout for the next big semiconductor material. However, we suspect this tech will be out of reach to the home semiconductor fab, at least for a little while.

Design Your Next Robot Hand In Minutes

June 23, 2022 by 1 Comment

MIT complains that designing a robot hand is time-consuming and takes a lot of iterations. They want to improve that using a unique approach by giving a modular hand tactile sensors. They claim this can reduce the design time down to minutes for many practical applications. For example, cutting paper. You can see a video about the paper below as well as read the text itself.

Each style of manipulator has an associated graph. Predefined elements let you assemble a palm and specialized fingers. You deform the fingers to match the use of the hand. Then a sensor that looks like a mitten provides feedback fo the task.

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This $4 Desalination Device Provides Drinking Water For The Whole Family

June 6, 2022 by 48 Comments

Researchers at MIT and in China have improved the old-fashioned solar still with a new inexpensive device that harnesses the sun to remove salt from water. Traditionally, these kinds of systems use a wick to draw water, but once the wick becomes fouled with salt, the device needs cleaning or other maintenance. Not exactly what you want in a survival situation. You can read the paper in Nature if you want more details.

The key to this new technique is black paint and polyurethane with 2.5-millimeter holes drilled in it. The idea is that warmer water above the insulating medium causes the salt to concentrate in the cooler water beneath the insulator allowing efficient vaporization of the water.  As the water evaporates, it causes the salt concentration at the top to rise, which then sinks due to the higher density and lower-concentration salt water rises to the top to evaporate.

Because the materials are commonplace, the team says a one-meter-square system costs about $4 to produce. A system that size could provide a family’s daily drinking water.

So far, the prototype system has worked in the lab for at least a week without accumulating salt. The next challenge is to scale it to something more practical, but due to the low cost and simplicity of the system, it seems it would be easy enough to make that happen or to reproduce the device for your own testing.

Desalination is a problem you can approach from many different angles. You can also harvest clean water from fog, something else that started at MIT.

High Temp Heat Engine Achieves 40% Efficiency

April 23, 2022 by 17 Comments

People generate lots of waste heat. It makes sense that there is a desire to convert that heat into usable energy. The problem is one of efficiency. Researchers from MIT and the National Renewable Energy Lab have announced a new heat converter that they claim has 40% efficiency. Of course, there’s a catch. The temperature range for the devices starts at 1,900 °C .

The thermophotovoltaic cells are tandem devices with two cells mated on one substrate. Each cell is multiple layers of very thin and somewhat exotic materials. So this probably isn’t something you will cobble up in your basement anytime soon unless you’re already manufacturing ICs down there. It appears that the secret is in the multiple layers including a reflective one that sends any missed photons back through the stack.

The paper is pretty dense, but there’s a Sunday-supplement summary over on the MIT site. Using heat storage leads to the ability to make heat batteries, more or less, and harness what would otherwise be waste energy.

We’ve noticed a lot of interest in drawing power from hot pipes lately. All of them techniques we’ve seen rely on some kind of exotic materials.

As Light As Plastic; As Strong As Steel

February 7, 2022 by 38 Comments

Chemical engineers at MIT have pulled off something that was once thought impossible. By polymerizing material in two different directions at once, they have created a polymer that is very strong. You can read a pre-print version of the paper over on Arxiv.

Polymers owe many of their useful properties to the fact that they make long chains. Molecules known as monomers join together in strings held together by covalent bonds. Polymer chains may be cross-linked which changes its properties, but it has long been thought that material that had chains going through the X and Y axis would have desirable properties, but making these reliably is a challenge.

Part of the problem is that it is hard to line up molecules, even large monomers. If one monomer in the chain rotates a bit, it will create a defect in the 2D structure and that defect will grow rapidly as you add more monomers. The new technique is relatively easy to do and is irreversible which is good because reversible chains tend to have undesirable characteristics like low chemical stability. Synthesis does require a few chemicals like melamine, calcium chloride, pyridine, and trimesic acid. Along with N-Methyl-2-pyrrolidone, the mixture eventually forms a gel. The team took pieces of gel and soaked it in ethanol. With some filtering, ultrasonics, centrifuging, and washing with water and acetone, the material was ready for vacuum drying and was made into a powder.

The powder is dissolved in acid and placed on a spinning silicon wafer to form a polymerized nanofilm. Other 2D films have been produced, of course, such as graphene, but polymer films may have a number of applications. In particular, in contrast to conventional polymers, sheets of this material are impermeable to gas and liquid, which could make it very useful as a coating.

According to the MIT press release, the film’s elastic modulus is about four and six times greater than that of bulletproof glass. The amount of force required to break the material is about twice that of steel. It doesn’t sound like this material will be oozing out of our 3D printers anytime soon. But maybe one day you’ll be able to get 2D super-strong resin.

For all their faults, conventional polymers changed the world as we know it. Some polymers occur naturally, and some use natural ingredients, too.

Squares of sample materials placed on the laser bed awaiting the sensing head

Smart Laser Cutter Ad-on Detects Material Optically

September 6, 2021 by 9 Comments

Come on now, admit it. You’ve done it. We’ve done it. You know — you were really sure that sheet of plastic stock you found lying around the hackerspace was acrylic right? You dialled in the settings, loaded the design, set the focus and pushed the little green ‘start’ button. Lots of black smoke, fire, and general badness ensued as you lunged for the red ‘stop’ button, before lifting the lid to work out how you’re going to clean this one up.

That was not acrylic. That was polycarbonate.

What you need is the latest gadget from MIT: SensiCut: A smart laser cutter system that detects different materials automatically.

The technique makes use of so-called ‘speckle imaging’ where a material illuminated by a laser will produce a unique pattern of reflected spots, or speckles into a camera. By training a deep neural model with a large set of samples, it was found possible to detect up to 30 types of material with 98% accuracy.

The pre-baked model runs on a Raspberry PI zero with an off-the-shelf camera all powered from a power bank. This allows the whole assembly to simply drop onto an existing laser cutter head, with no wiring needed.

Even if you’re a seasoned laser cutter user, with a well-controlled stock pile, the peace-of-mind this could give would definitely be worth the effort. A more detailed description and more videos may be found by reading the full paper. Here’s hoping they release the system as open source, one day in the not-to-distant future. If not, then, you know what to do :)

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