A Self-Healing, Stretchable Electronic Skin

December 4, 2019 by Sharon Lin 4 Comments

In a report published by Science Advances, a research team from the United States and Korea revealed a strain-sensitive, stretchable, and autonomous self-healing semiconductor film. In other words, they’ve created an electronic skin that’s capable of self-regulation. Time to cue the ending track from Ex Machina? Not quite.

Apart from the inevitable long timeline it will take to see the material in production, there are still challenges to improve sensing for active semiconductors. The methods used by the team – notably using a dynamically cross-linked blend of polymer semiconductor and self-healing elastomer – have created a film with a gauge factor of 5.75×10^5 at full strain. At room temperature, even with fracture strains, the material demonstrated self healing.

The technique mimics the self healing properties of human skin, accelerating the development of biomedical devices and soft robots. While active-matrix transistor array-based sensors can provide signals that reduce crosstalk between individual pixels in electronic skin, embedding these rigid sensors and transistors into stretchable systems causes mechanical mismatch between rigid and soft components. A strain-sensing transistor simplifies the process of fabrication, while also improving mechanical conformability and the lifetime of the electronic skin.

The synthetic skin was also shown to operate within a medically safe voltage and to be waterproof, which will prevent malfunctions when placed in contact with ionic human sweat.

[Thanks Qes for the tip!]

The Story Of A Secret Underground Parisian Society

December 4, 2019 by Sharon Lin 28 Comments

Deep in the heart of Paris, a series of underground tunnels snakes across the city. They cross into unkept public spaces from centuries ago that have since vanished from collective memory – abandoned basements, catacombs, and subways hundreds of miles apart.

Only a few groups still traverse these subterranean streets. One that came into public view a few years ago, Les UX (Urban eXperiment), has since claimed several refurbished developments, including restoring the long neglected Pantheon clock and building an underground cinema, complete with a bar and restaurant.

While the streets of Paris are tame during the day, at night is when Les UX really comes alive. A typical night might involve hiding in the shadows away from potential authorities roaming the streets, descending into the tunnels through a grate in the road, and carrying materials to an agreed upon drop off location. Other nights might involve wedging and climbing over pipes and ladders, following the routes into the basements of buildings left unguarded.
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Making Your Own Caving Headlamp

December 2, 2019 by Sharon Lin 15 Comments

An important distinction between equipment used for caving, climbing, biking, and other outdoor activities is the level of stress that’s generally applied. For instance, while climbing helmets are built to withstand the impact of sharp rocks, they’re not made to protect a biker’s head from suddenly hitting the ground. Likewise, while camping headlamps may be able to survive a light rainfall, they’re probably not made to shine at the 800 lumens after being submerged underwater.

[LukeM] built himself a caving headlight, after being “fed up with what was available on the market”. While his project is a bit older, it’s still pretty helpful for any newer hobbyists looking to try their hand at building a custom headlamp. Many cavers have to carry around a few primary – one main light for general visibility and a secondary light for focusing on specific objects. These are typically worn on the helmet, attached somehow to prevent the light source from falling off mid-climb. From tricky operations, varying distances, cost, and ease of battery replacement, there are a number of reasons why a caver might want to build their own customizable head lamp.

The result is rugged, waterproof, reliable, bright enough to supplement flashes in caving photos and also dim enough for general use (30-700 lumens). It has options for wide and narrow beams, displays a neutral to warm color, and is relatively upgradeable without too much trouble. At the same time, it’s also fairly compact, with all of the components packed inside of a short section of 3″x2″ aluminum tubing, protected at the back and front by aluminum and acrylic backings. The LEDs used are four Cree XP-E R2 bin LEDs and a hipFlex driver from TaskLED with programmable settings for max output, thermal protection temperature, warning voltage, and lighting modes. I’m personally already smitten with the level of customizability of this build.

On top of all of that, it’s been cave tested and approved!

An Efficient Homemade Wood Furnace

November 30, 2019 by Sharon Lin 17 Comments

For poor [workshop from scratch], winter brings the joy of a cold workshop. Since the building is structurally made from tin, warming up the room is difficult.

Naturally, the solution was to construct a homemade wood furnace. The build starts off with an angle grinder being taken to a compressed air tank. After sawing off the top and sanding down the edges, the builder slices out an opening and welds together some rods into a stand for the center. He then proceeds to weld some external frames for the furnace, as well as a chimney stack, some nifty covers joined by hinges, and a fan/temperature regulator to keep the fire going.

Most of the pieces seem to come from scrap metal lying around the workshop, although the degree to which the entire project comes together is quite smooth. Some filter and spray paint do the trick for cleaning up the furnace and making it look less scrappy. The last step? A stack of wooden logs and a blow torch to start the fun. Outside of the furnace, an LCD screen keeps track of the temperature, giving some feedback and control.

The result is perhaps a too effective at warming up the workshop, but the problem sure is solved!

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Building Your Own Tensegrity Structure

November 29, 2019 by Sharon Lin 37 Comments

It seems that tensegrity structures are trending online, possibly due to the seemingly impossible nature of their construction. The strings appear to levitate without any sound reason, but if you bend them just the right way they’ll succumb to gravity.

The clue is in the name. Tensegrity is a pormanteau of “tension” and “integrity”. It’s easiest to understand if you have a model in your hand — cut the strings and the structure falls apart. We’re used to thinking of integrity in terms of compression. Most man-made structures rely on this concept of engineering, from the Empire State Building to the foundation of apartment building.

Tensegrity allows strain to be distributed across a structure. While buildings built from continuous compression may not show this property, more elastic structures like our bodies do. These structures can be built on top of smaller units that continuously distribute strain. Additionally, these structures can be contracted and retracted in ways that “compressionegrities” simply can’t exhibit.

How about collapsing the structure? This occurs at the weakest point. Wherever the load has the greatest strain on a structure is where it will likely snap, a property demonstrable in bridges, domes, and even our bodies.

Fascinated? Fortunately, it’s not too difficult to create your own structures.

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Your WiFi Signals Are Revealing Your Location

November 28, 2019 by Sharon Lin 43 Comments

The home may be the hearth, but it’s not going to be a place of safety for too long.

With the abundance of connected devices making their ways into our homes, increasing levels of data may allow for more accurate methods for remote surveillance. By measuring the strength of ambient signals emitted from devices, a site can be remotely monitored for movement. That is to say, WiFi signals may soon pose a physical security vulnerability.

In a study from the University of Chicago and the University of California, Santa Barbara, researchers built on earlier studies where they could use similar techniques to “see through walls” to demonstrate a proof-of-concept for passive listening. Attackers don’t need to transmit signals or break encryptions to gain access to a victim’s location – they just need to listen to the ambient signals coming from connected devices, making it more difficult to track bad actors down.

Typically, connected devices communicate to an access point such as a router rather than directly with the Internet. A person walking near a device can subtly change the signal propagated to the access point, which is picked up by a receiver sniffing the signal. Most building materials do not block WiFi signals from propagating, allowing receivers to be placed inconspicuously in different rooms from the access point.

WiFi sniffers are relatively inexpensive, with models running for less than $20. They’re also small enough to hide in unsuspecting locations – inside backpacks, inside a box – and emit no signal that could be detected by a target. The researchers proposed some methods for safeguarding against the vulnerability: insulating buildings against WiFi leakage (while ensuring that desirable signals, i.e. signals from cell tower are still able to enter) or having access points emit a “cover signal” that mixes signals from connected devices to make it harder to sniff for motion.

While we may not be seeing buildings surrounded by Faraday cages anytime soon, there’s only going to be more attack surfaces to worry about as our devices continue to become connected.

[Thanks to Qes for the tip!]