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.
You might expect that sourcing live algae would be as simple as scraping up a bit of green slime from a nearby pond, but that yields an uncertain mix of species. [Severin] wanted Chlorella algae for his experiment because its high fat content makes it suitable for biodiesel experiments, so had to source his culture from an aquatic shop.
The reactor takes the form of a spiral of transparent plastic tube surrounding a CFL lamp as a light source, all mounted on a lasercut wooden enclosure housing a pump. A separate glass jar forms a reservoir for the algal-rich water. He does not mention whether or not he adds any nutrient to the mix.
[Benjamin Havey] and [Michael Abed] built the controller as their final project in his microprocessor class. The idea is to monitor and control the mini-refrigerator so that the strain of Saccharomyces Cerevisiae yeast produce as much ethanol as possible. An MSP430 microcontroller was used. It monitors a thermister with its analog to digital converter and drives a solid state relay to switch mains power to the fridge. At 41 degrees Fahrenheit this is down below what most lager yeasts want (which is usually in the low fifties). But the nice thing about using a microcontroller is you can set a schedule with different stages if you find a program that gives the yeast the best environment but requires more than one temperature level.
Who knew all that beer making was getting you ready to produce alternative fuels?
Sometimes you don’t need a lot of horsepower to win a speed record. In a fluke of no one else competing in the alt fuel class, [John]’s biodiesel motorcycle set a new land speed record at the LTA event last summer.
[John]’s bike is a junkyard 1978 Kawasaki KZ400. The stock engine was replaced with a Chinese knock off of a Yanmar air-cooled diesel motor. The fuel is regular old vegetable oil. From the looks of the exhaust, we’re assuming [John]’s garage has a rich french fry smell to it.
Compared to highway speeds, [John]’s runs for a land speed record are a little absurd – a nice bonus when you’re the only driver in your class. The first pass of 42 mph was a little disappointing, so [John] removed the fender, tail light and brakes. After all the unnecessary weight was removed, the top speed – and new record – was 56.5 mph.
Converting a diesel car to run on french fry oil is great and a lot better for the environment than burning liquefied dinosaurs. In any event, a green motorcycle is a lot better than 2000 pounds of automobile moving less than 200 pounds of person. Check out a few of [John]’s land speed runs after the break.