Tapping into Microbially Produced Electricity

Although I studied physics and chemistry in college, I have always held an inherent appreciation for how life works.  And now, researching microbes in action, I am continually amazed by their diverse habitats and metabolisms.  It is remarkable to think how despite the diminutive size of microbes, they are dominant members of our biosphere and play a key role in every known biogeochemical cycle.  This list includes carbon, sulfur, nitrogen, and oxygen as well as trace metals such as iron, cobalt and zinc.  I have started thinking that if there is an available compound on Earth, then microbes have found a way to use it.

What does it mean that microbes are involved in these biogeochemical cycles?  It usually implies that a microbial species has found a way to use a form of that specific element while the microbe undergoes cellular respiration.  Although respiration is complex, I tend to think of it in a simplified manner as a transport of electrons from one compound to another by a living organism.  The organism utilizes this electron transport to produce energy in order for it to stay alive and reproduce.  As humans, we take electrons from the carbon compounds we consume as food and transport those electrons to the oxygen we breathe.  Since we use oxygen, this is aerobic respiration. One can think of the food we eat as electron donors and oxygen as the electron acceptor.  Now, a fascinating aspect about microbes is that different species have evolved to use a variety of electron donors and acceptors in respiration process.  Not only is this how microbes are involved in Earth’s biogeochemical cycles, but this is why certain microbes can be found in such extreme conditions, such as hydrothermal vents which have been discussed earlier.

Since microbes can use a variety of compounds as electron acceptors, what if there was a way to harness these electrons to produce electricity?  In 1911, M.C. Potter was reported to be the first person to observe electricity production from microbes but it has only been within the past 30 years that this research has gained momentum.  In these systems, which are called microbial fuel cells, the material the microbes are using as an electron acceptor is called an electrode, more specifically an anode. By connecting the anode with a metal wire to a region with even higher electron affinity, termed a cathode, we can generate a circuit.  Oxygen is one of the best electron acceptors and typically these systems have oxygen present near the cathode and the microbes grow in an chamber without oxygen in order for electrons to flow from the anode to the cathode.

Personally, I find the mechanism for microbes to transport electrons to a solid surface fascinating as a basic science question and think that understanding this process better would shed some light on how microbes do this in nature.  Right now, there are a handful of microbes known to utilize a solid surface as an electron acceptor and I am curious about what others are out there that have not yet been identified.  What do these different species have in common?  What influences growth and thus electron generation?  How is the structure of the microbes growing on the anode as a biofilm influenced by the anode properties, such as material composition or surface patterning?  How does the internal properties within the biofilm correspond to electron generation, such as pH?  To address these questions, I perceive microbial fuel cells as a useful system to explore how microbes form biofilms on surfaces that act as an electron acceptor.

Further, as a new area of research with potentially huge contributions to be made more knowledge will improve how this mechanism is utilized in technology not only for energy production but also for organic waste removal.  An attractive aspect of this technology is that electricity generation by the microbes goes hand-in-hand with organic waste removal because the microbes use the organic compounds as their electron donors, or food.  In wastewater treatment, this would allow for the water to become purified at the same time electricity is generated.  Electricity production is still quite low with one report stating that their microbial fuel cell design could power 16 60-watt light bulbs.  There is still room for improvement in power generation and I believe that addressing the mechanistic questions about microbial electron transport to an outside electron acceptor will aid in both improving our basis for building these technologies and our understanding of how our microbes are major players in our world’s biogeochemical cycles.

 

January SITNFlash, Second Edition: 3D cinema: there’s a reason for wearing those goofy glasses

This article was contributed by Billy Lau

Do you remember wearing the red and cyan 3D eyeglasses when you were a kid? Well, 3D tech certainly has improved by leaps and bounds, and is turning into the latest fad in the entertainment industry. 3D films have matured from campy to epic, with the most recent blockbuster being James Cameron’s Avatar. The technology that makes 3D possible, known as stereoscopy, was pioneered at the turn of the 20^th century and popularized by the entertainment industry during the 1950s and onward. The biological basis of this three dimensional effect is called stereopsis (or depth perception, but we want to sound scientific), and relies on displaying slightly different images to each eye. Then, visual processing in your brain generates the sensation of depth. Stereopsis occurs naturally in everyday life, as your eyes receive a slightly different perspective of a single three-dimensional object because your eyes are in slightly different locations.

The main hurdle to perceiving depth from flat media (such as photographs or film) is that both eyes receive the same image. Because your eyes are getting the same information, the visual processing inside your brain interprets the scene as being flat. Over the past century, many techniques have been developed to overcome this problem and to generate a sense of depth in flat images. Here, we will briefly describe the science and engineering behind two of the most popular techniques and what new technologies are being developed.

 

November SITN Flash: The Skinny on Electronic Paper

This article was contributed by Lauren L. C. Marotta

As the holiday season approaches, you may be starting to consider gifts for family or friends. A good choice this year might be a product that incorporates the clever technology called “electronic paper,” known best for its use in Amazon’s Kindle, one of several electronic book readers that have recently become popular. Introduced in the U.S. in 2007 and worldwide this October, the Kindle is lighter than a typical paperback novel, but it can store 1,500 books, newspapers, or magazines at once. Its screen displays pages one at a time, and pages can be “turned” with the click of a button. Importantly, devices with electronic paper screens have much longer battery lives than those with conventional screens, and electronic paper can be viewed in bright sunlight without glare and from almost any angle, just like normal paper and unlike other types of screens. These amazing properties are fueling the development and adoptance of the technology, and they are a result of the science underlying it.

 

The 2009 Nobel Prize in Physics – The Critical Components of Today’s Communication Network

This article was contributed by Kevin Beier

Instantaneous transmission of stunning scenes from the opening ceremony of the 2008 Olympic Games in Beijing; the ability to call family from anywhere in the world, anytime; these are luxuries that have only existed in recent decades.  They depend on two key advancements: an intricate and elaborate mesh of fiber optic cables spanning the globe, and the ability to transform light into electrical signals to create digital images.  The importance of this work cannot be underestimated: without these developments, the computer you are using would likely not be able to access and display the article you are reading right now!  For the impact of these technologies on the global community, the work pioneered by Charles K. Kao, Willard S. Boyle, and George E. Smith received the 2009 Nobel Prize in physics.