Wasted Heat to Usable Electricity

When one energy form is turned into another, like when we convert electricity into light, the process is very rarely truly efficient. Instead, there is always some waste in the form of heat energy. For example, power plants are only around 33% efficient: only one third of the chemical energy in the coal or oil burned is turned into useable electricity.

Take an incandescent light bulb. If you've ever touched one after being on for any period of time at all, you're bound to get burnt. Just look at the IR image of an incandescent light bulb below: at the top, this particular bulb was reaching temperatures upward of 300 degrees fahrenheit!

Image Courtesy of Zaereth

Bruce E. Logan, professor of environmental engineering has devised a solution to harness low-grade heat (heat that is low to mid temperature that is not very energy dense, like exhaust from a car or power plant heat waste) and turn it into electricity. His solution involves an ammonia battery that can be regenerated using the waste heat we talked about earlier. 

Without heat, the battery could go through one cycle, similar to the way that your average AAA single-use battery operates. Typical rechargeable batteries can be regenerated by running electricity the opposite way it usually goes, forcing the reaction that is occurring in the battery to go in reverse. 

What is unique about the ammonia based battery however is that it can be regenerated back to full capacity using waste heat instead of electricity, allowing the cycle to continue once more without electrical input.

Image of the Ammonia based battery
Image Courtesy of Wulin Yang/Penn State

Right now the system isn't incredibly optimized (as you can probably tell from the photo above); right now about 29% of the chemical energy that gets stored into the battery is converted to electricity. This can be compared to around an 85% efficiency for lead-acid batteries (the type that you'd find in your car). However this efficiency will be able to be brought up significantly as they sure up all parts of the battery.

This battery could have some exciting impacts on the efficiency of energy production. Look at nuclear power plants for instance. These plants need very high temperatures in order to produce electricity, and after the heat is utilized, it is moved to those humungous cooling towers that you associate with nuclear power plants. Those aren't the things that are producing the electricity - it's for cooling the fluid! By adding these ammonia batteries to systems like these, the amount of heat that is wasted and put to the atmosphere can be reduced significantly while simultaneously increasing the amount of electricity that is produced. Seems like a win-win to me!

Image courtesy of Own Cliffe

Unfortunately I was not able to go in detail on the workings of the battery and the cool complexation reactions that allow this thing to work, but if you're interested in learning more about what exactly is happening here, a paper on the subject (that explains the process surprisingly well) can be found here.

For a Trip to the Restricted Section

The curses and charms and hexes were cool it's true, but what really caught my attention in Harry Potter was the invisibility cloak, for the simple reason that it seemed like it could conceivably exist. And now it does. Get ready to take trips to your local library in the middle of the night and have the best floating head costume ever!

Image courtesy of Warner Bros. via IMDB

Okay I may have exaggerated that a bit. Okay maybe more than a bit... But major progress is being made, and it is very exciting. Xingjie Ni, a new assistant professor of electrical engineering here at Penn State, is heading up the team of researchers working on a new cloaking device. While other attempts at this technology have utilized thing like giant tanks of water or lasers, Ni's method utilizes a thin fabric that is 1000 times thinner than a human hair to get the job done. To explain how this skin works we must first take a brief look at the way light reacts when it hits an object.

Image courtesy of J. Gabrielse

All objects on some level are bumpy. So when light comes in and hits an object, it get scattered all around at many many different angles. This can be seen in the photo above. Our brain can process all of these different waves in order to come up with the 3 dimensional shape and depth of the object. 

However, if you are able to change the way that light is bouncing off of the object, you can change the way that we see it. That is exactly what Ni is doing. By creating a surface that is covered in these little gold 'bricks' that change how the light bounces off of the object it is covering, the object is rendered undetectable and appears completely flat. Essentially by reflecting the light in a way that it would be reflected if the object were flat, the object appears flat to the human eye. An image of this process can be seen below. If the material was not covered in the little gold 'antennae,' the light would be going every which way. Instead, it has a clean outbound path.

Image courtesy of Xiang Zhang Group

Now, this technology has some serious caveats that must be accepted when looking at this technology. First, the surface must be custom made for the object that it is hiding, as the little gold blocks must be perfectly configured and aligned. Second, right now the skin-like material can only hide an object that is a few micrometers in size. But the team is looking into changing the way they are making the material in order to accommodate larger objects. 

This method of invisibility is my no means perfect, but as a first toe in the water for this particular technology, it is very promising. In the future all of the limitations can be worked out until we perfect a way to sneak into the adult fiction section of the library.

A paper published in Nature about a month ago on the topic can be found here.

All Cancer Cells Off at Exit 12!

Metastasis is one of the scariest terms one can hear in regards to cancer. It means that the cancer cells have detached from the original tumor and have started to spread through the lymph and/or blood vessels of the body to later reattach in a new location to start a new tumor. Once cancer metastasizes, it become much harder to treat.

Metastasis
Image Credit: National Cancer Institute

A new device from Tony Jun Huang's lab may help us better understand Metastasis and provide a more effective way to study the phenomenon, as well as allow doctors to better screen cancer patients  to see how they are reacting to treatment.

The device is about the size of two pennies, and allows a quicker and more efficient way to sort cancer cells from blood samples. 

The image over is a mock-up of what happens inside the device. From the top, an unsorted sample flows down to the bottom. As it goes, acoustic waves from either side push white blood cells to one side, while pushing the circulating tumor cells to the other side. This method has proven to have a successful separation rate of more than 83%. 

This method has significant improvements over existing cell separation methods. One method employs tumor-specific antibodies that bind with the cancer cells to flag them, but to use this method the right kind of antibodies must be known ahead of time, which significantly limits the effectiveness of the method. A second method is pretty much a centrifuge with can separate the cells based on size, but these devices can cost anywhere from $200,000 to $1,000,000 and reduce cell viability by up to 99%. In a lot of research, the cells need to be alive in order for anything useful to be gathered from them. 

The new device that relies on acoustics has the potential to solve all of these issues. A continuous sample can be flowed through the device, aiding in speed. The device is about the size of two pennies, a far cry smaller than a huge centrifuge type device. The small and simple size of the device also means that it is rather cheap, and could be disposable, a trait that is very important when dealing with medical tests (no one wants their blood getting mixed up with someone else's in a device that might tell them how well their treatment is going). Further, because the acoustic waves are around the same energy level as the waves used in ultrasonic imagery, they do not damage the cells, and can be used in a clinical setting.

The acoustic separation device
Image Credit: Tony Jun Huang, Penn State

"Looking for circulating tumor cells in a blood sample is like looking for a needle in a haystack," said Professor Huang, and this new cell sorter is like getting a giant electromagnet to place over the haystack in that it makes it so much easier and so much faster. The technology is going to help future research into cancer, as well as be there for doctors to use for diagnosis, prognosis, and treatment check-ups. Cancer is becoming ever-more treatable, and this device is one good step towards making it so.

If you'd like to learn more about the use of standing acoustic waves to sort microparticles, you can read this article published in the journal Lab on a Chip.

Cleaning Up Oil with Plastic

The 2010 Gulf of Mexico oil spill was the worst in US History and had huge, immediate impacts on the coastal ecosystems of the area. 3.19 million barrels of oil were spilled into the Gulf, an amount that could clearly be seen from space, like this photo taken from the ISS on May 5th, 2004 demonstrates. Cleaning up this disaster is obviously of utmost concern, but current clean up methods are inefficient in so many ways.

Deepwater Horizon Oil Spill as seen from the ISS
Image Credit: NASA

Physical barriers (floating booms) were used to try to surround the oil slick, but this method is only is successful when the water is calm and slow moving. 

Booms used in an attempt to protect barrier island during Deepwater Horizon
Image Credit: Kris Krug

Another method used was the use of dispersant, which helps the oil mix with the water instead of forming giant slicks. This is good in the short term, but just because you can't see the oil, it doesn't mean it's not there. The idea is that the smaller oil droplets will evaporate, and bacteria will slowly degrade the smaller oil droplets. However, the effectiveness of this is questionable. Dispersants can potentially enter the food chain and harm wildlife. Further, the dispersant-oil mixture with the water can be more harmful than just the oil itself!

This is where Penn State Professor Mike Chung comes into play. Chung began looking at hydrogels, the polymers in diapers that absorbs children's unfavorables. The issue with this is that it absorbs water as well as oil, and it disintigrates after it absorbs water… not super useful. Luckily we've got some pretty smart cookies here at Penn State, so Chung's lab was able to create a new material that meets all of the criteria.

It's called PetroGel™(it's trademarked and everything!), and it's wonderful. Structurally, it's a low density polyolefin (polymers produced from alkenes), which pretty much means it's a type of plastic. Functionally, the polymer can absorb 10 times its volume in crude oil in 10 minutes. In 24 hours, it can absorb 40 times its volume, and it doesn't absorb water. Even better, the material stays as a solid after absorbing the oil, making clean up a breeze. 

PetroGel absorbing diesel gas
Image Credit: Penn State

As plastic is an oil product, the gel along with the oil that it absorbs can be refined just like regular crude oil. That's 3.19 million barrels of crude oil that could have been saved and used in the Deepwater Horizon oil spill. At $46.26 per barrel at the time of writing this, that's a little under 150 million dollars. 

To top it all off, polyolefin polymers are rather inexpensive, and it is predicted that in large scale production the product could cost less than $2 per pound. PetroGel™is an economical as well as an environmental win.

PetroGel™will undergo more rigorous testing with the US Dept. of the Interior's Bureau of Safety and Environmental Enforcement starting this winter, so maybe we'll see Penn State's developments used in the next inevitable oil spill.