The lead-acid rechargeable battery is a not-quite-modern marvel. Super reliable and easy to use, charging it is just a matter of applying a fixed voltage to it and waiting a while; eventually the battery is charged and stays topped off, and that’s it. Their ease is countered by their size, weight, energy density, and toxic materials.
The lithium battery is the new hotness, but their high energy density means a pretty small package that can get very angry and dangerous when mishandled. Academics have been searching for safer batteries, better charge management systems, and longer lasting battery formulations that can be recharged thousands of times, and a recent publication is generating a lot of excitement about it.
Consider the requirements for a battery cell in an electric car:
High energy density (Lots of power stored in a small size)
Quick charge ability
High discharge ability
MANY recharge cycles
Lithium ion batteries are the best option we have right now, but there are a variety of Li-ion chemistries, and depending on the expected use and balancing and charging, different chemistries can be optimized for different performance characteristics. There’s no perfect battery yet, and conflicting requirements mean that the battery market will likely always have some options.
The research was published in Advanced Functional Materials on September 25, 2019. The potential use cases for this type of biofuel cell within the wearables space include medical and athletic monitoring. By using biofuels present in human fluids, the devices can rely on an efficient energy source that easily integrated with the human body.
Scientists have developed a flexible conductive material made up of carbon nanotubes, cross-linked polymers, and enzymes connected to each and printed through screen-printing. This type of composite is known as a buckypaper, and uses the carbon nanotubes as the electrode material.
The lactate oxidase works as the anode and the bilirubin oxidase (from the yellowish compound found in blood) as the cathode. Given the theoretical high power density of lactate, this technology has the potential to produce even more power than its current power generation of 450 µW.
The cell follows deformations in the skin and produces electrical energy through oxygen reduction and oxidation of the lactate in perspiration. A boost converter is used to increase the voltage to continuously power an LED. The biofuel cells currently delivered 0.74V of open circuit voltage. As measurements for power generation had to be taken with the biofuel cell against human skin, the device has shown to be productive even when stretched and compressed.
At the moment, the biggest cost for production is the price of the enzymes that transform the compounds in sweat. Beyond cost considerations, the researchers also need to look at ways to increase the voltage in order to power larger portable devices.
This is one of those stories that shows that you never know from where inspiration is going to come. [Chinna Devarapu] learned that as a result of playing around with cheap fitness bands, specifically an ID107HR. A community has built up around hacking these bands; we featured a similar band that was turned into an EEG. With some help, [Chinna] was able to reflash the microcontroller and program it in the Arduino IDE, and began looking for a mission for the sensor-laden platform.
He settled on building a continuous optical densitometer for his biology colleagues. Bacterial cultures become increasingly turbid as the grow, and measuring the optical density (OD) of a culture is a common way to monitor its growth phase. This is usually done by sucking up a bit of the culture to measure, but [Chinna] and his team were able to use the hacked fitness band’s heartrate sensor to measure the OD on the fly. The tracker fits in a 3D-printed holder where an LED can shine through the growing culture; the sensor’s photodiode measures the amount of light getting through and the raw data is available via the tracker’s Bluetooth. The whole thing can be built for less than $20, and the plans have been completely open-sourced.
We really like the idea of turning these fitness bands into something completely different. With the capabilities these things pack into such a cheap and compact package, they should start turning up in more and more projects.
Welcome to the world of cryogenic treatment. Unlike quenching, where a hot metal is quickly cooled to create a hard crystal structure in the metal, cryogenic treatment is done by cooling the metal off slowly, and then raising it back up to room temperature slowly as well. The two processes are related in that they both achieve a certain amount of crystal structure formation, but the extreme cold helps create even more of the structure than simply tempering and quenching it does. The crystal structure wears out much less quickly than untreated steel, therefore the bits last much longer.
[Applied Science] goes deep into the theory behind these temperature treatments on the steel, and the results speak for themselves. With the liquid nitrogen treatments the bits were easily able to drill double the number of holes on average. The experiment was single-blind too, so the subjectivity of the experimenter was limited. There’s plenty to learn about heat-treated metals as well, even if you don’t have a liquid nitrogen generator at home.
The sheets of temperature sensitive liquid crystals are a bit like flattened out Mood Rings; they starts out black, but as heat is applied, their color cycles through vibrant reds, greens, and blues. The sheets are perhaps best known as the sort of vaguely scientific toys you might see in a museum gift shop, but here [Moritz] has put their unique properties to practical use.
To achieve the effect, he first cut each segment out of copper. The crystal sheets were applied to the segments, thanks to their handy self-stick backing, and the excess was carefully trimmed away. Each segment was then mounted to a TES1-12704 Peltier module by way of thermally conductive epoxy. TB6612FNG motor controllers and a bevy of Arduino Nano’s are used to control the Peltier modules, raising and lowering their temperature as necessary to get the desired effect.
You can see the final result in the video after the break. It’s easily one of the most attractive variations on the classic seven-segment display we’ve ever seen. In fact, we’d go as far as to say it could pass for an art installation. The idea of a device that shows the current temperature by heating itself up certainly has a thoughtful aspect to it.
We’re always on the lookout for unexpected budget builds here at Hackaday, and stumbling across a low-cost, DIY version of an instrument that sells for tens of thousands of dollars is always a treat. And so when we saw a tip for a homebrew gas chromatograph in the tips line this morning, we jumped on it. (Video embedded below.)
For those who haven’t had the pleasure, gas chromatography is a chemical analytical method that’s capable of breaking a volatile sample up into its component parts. Like all chromatographic methods, it uses an immobile matrix to differentially retard the flow of a mobile phase containing the sample under study, such that measurement of the transit time through the system can be made and information about the physical properties of the sample inferred.
The gas chromatograph that [Chromatogiraffery] built uses a long stainless steel tube filled with finely ground bentonite clay, commonly known as kitty litter, as the immobile phase. A volatile sample is injected along with an inert carrier gas – helium from a party balloon tank, in this case – and transported along the kitty litter column by gas pressure. The sample interacts with the column as it moves along, with larger species held back while smaller ones speed along. Detection is performed with thermal conductivity cells that use old incandescent pilot lamps that have been cracked open to expose their filaments to the stream of gas; using a Wheatstone bridge and a differential amp, thermal differences between the pure carrier gas and the eluate from the column are read and plotted by an Arduino.
The homebrew GC works surprisingly well, and we can’t wait for [Chromatogiraffery] to put out more details of his build.
Rechargeable batteries are a technology that has been with us for well over a century, and which is undergoing a huge quantity of research into improved energy density for both mobile and alternative energy projects. But the commonly used chemistries all come with their own hazards, be they chemical contamination, fire risk, or even cost due to finite resources. A HardwareX paper from a team at the University of Idaho attempts to address some of those concerns, with an open-source rechargeable battery featuring electrode chemistry involving iron on both of its sides. This has the promise of a much cheaper construction without the poisonous heavy metal of a lead-acid cell or the expense and fire hazard of a lithium one.
The chemistry of this cell is split into two by an ion-exchange membrane, iron (II) chloride is the electrolyte on the anode side where iron is oxidised to iron 2+ ions, and Iron (III) chloride on the cathode where iron is reduced to iron hydroxide. The result is a cell with a low potential of only abut 0.6V, but at a claimed material cost of only $0.10 per kWh Wh of stored energy. The cells will never compete on storage capacity or weight, but this cost makes them attractive for fixed installations.
It’s encouraging to see open-source projects coming through from HardwareX, we noted its launch back in 2016.