August 13, 2013
The last few weeks of my internship through the Cal Energy Corps have been very eventful. I have been continuing my algal research in microfluidics and computational fluid dynamics as well as studying light penetration in algal reactors.
David viewing the algae cells.
My work in microfluidics has been very educational for me and has a promising outlook for the industry. Microfluidics is useful in the study of algae cultivation when monitoring the growth of algae populations and the lipid content of the cells (which are extracted from the algae to create biodiesel). Currently, the technique for determining lipid content is very time consuming and requires a large sample volume. The algae must be centrifuged and dried, and then the lipids are extracted using a hexane extraction technique. The mass of the lipids is then expressed as a percentage of the dry biomass weight. Because this process is so time consuming, it is difficult to constantly monitor the lipid content of the algae within the reactor.
Recently, a paper was published that used dielectrophoresis (DEP) to separate algae cells with 10% lipid and 45% lipid content within a petri dish. DEP forces occur when a dielectric material is placed in a non-uniform electric field. The ions within the algae cells cause the cells to behave like a dielectric material. This force can either be negative or positive depending upon the frequency of the alternating current, the cells’ contents, and the conductivity of the medium. I was able to come up with two designs that use electrodes in microchannels to characterize the lipid content of the algae. Unfortunately, I was not able to test these designs because the fabrication time for microchannels is about three months.
In addition to my microfluidics research, I also conducted an experiment to study light penetration in a bubble column reactor. As algae reproduce, the concentration of algae cells per unit volume increases. As the concentration of algae in the reactor increases, the solution becomes darker and light penetration within the reactor decreases. As light penetration decreases, the individual algae receive less light for photosynthesis, which slows overall algal growth. My experiment characterised the light availability within a bubble column reactor. To counteract the problem of light penetration, many reactors are mixed to provide the algae with more time in the lighted portion of the reactor.
David preparing microchannels.
The easiest way to optimize mixing within the reactors is using computational fluid dynamics (CFD). I was able to work with two Masters students in the Chemical Engineering department at IIT Kharagpur who helped me with the software used for CFD. In the time available, I was able to model the geometry of the reactor and built the mesh foundation for running simulations. I began to set boundary conditions and model parameters, but unfortunately there was a software issue and the work had to be stopped for a few days, at which point it was time to return home. However, once the simulations are successfully created, reactor dimensions and parameters can be varied to improve mixing, which in turn should improve algal growth. If the program is able to improve algal growth, the algae should produce more lipids, which would result in more available biodiesel.
I have now returned from IIT Kharagpur and am back in Berkeley. I have learned a lot from this experience, not only about bioenergy, but also about other cultures and educational structures. Getting to learn about Indian culture and society was very interesting. I am looking forward to talking to other students in the Cal Energy Corps and getting to see the projects that they worked on. I am very thankful to the Cal Energy Corps and the researchers and professors in Kharagpur for giving me this opportunity.
July 18, 2013
The Microfluidics Laboratory that David is working at over the summer.
The past few weeks have been very busy for me. Because of my background in mechanical engineering, I originally was tasked with redesigning the lab’s photobioreactors, used for algae production, using computation fluid dynamics (CFD). I quickly got a book that helped me begin studying CFD and how it could be applied to the design of the photobioreactors. I met with students and professors in the field of CFD to seek advice and suggestions. While talking to the students I learned that CFD is usually a graduate level course so the material was a little out of my reach. They also said that it would be quite a challenge to learn the CFD concepts and software, apply the techniques to the analysis of the reactor, and successfully redesign the reactors all within two months. So regrettably I had to end my research into that project.
My new research project involves microfluidics and algae. Microfluidics is a subset of mechanical engineering which involves the study of fluids at the microscopic level in very small microchannels. These microchannels range between 10-1000 microns in width and height. Because of the very small size the flow develops different properties than in a normal sized pipe. The flow has extremely low Reynolds numbers (which compares the effect of momentum of a fluid to the effect of viscosity), is very laminar, has a large surface area to volume ratio, and mixes only through diffusion. When this technology is incorporated with biology it allows for very unique study of cells and biological systems. My task was to learn about the techniques used in microfluidics and whether they could be applied to the various steps in the production of biofuel from algae. After proposing these techniques I will be testing at least one of them in my own experiment. I am enjoying my work because I have the opportunity to learn about both biological and mechanical engineering topics.
David visiting the Victoria Memorial with his lab mates.
I have also had the chance to explore some of India. One of the undergraduate interns from my lab, Aritra Goswami, is from Kolkata and two weekends ago I got the chance to see Kolkata with him. We took a train from the Kharagpur Station to Howrah Station. I was amazed at how efficient and inexpensive the train system is compared to the train system we have in the United States. I stayed with his family and they were very nice and welcoming. In the city Aritra he gave me a personal tour of the Victoria Memorial, the Indian Museum, the River Ganges, markets, malls, and many other places. The city was very crowded and I was exhausted from walking around all weekend but it was really interesting to get to see a large city of India.
July 2, 2013
I arrived in India on June 15th, after over 30 hours of travel. The first thing I noticed was the heat and humidity which hit me immediately as I stepped off the plane. I was met by an undergraduate student at the airport who accompanied me in the car to campus. We immediately began talking about our schools and majors, and this conversation lasted all the way to the Institute. I got settled in my room and then passed out in bed at around 6pm, and woke up at about 6am. The next day I was taken on a tour around campus to see where I was going to be eating, a market, and the labs. After seeing the campus I was excited to get started on my project.
Algae culture maintenance racks.
The next day Ganeshan Subramanian, the Ph.D. student with whom I would be working, met me at my room and took me to meet Professor Ramkrishna Sen, my supervisor. Both were very excited to meet me and very welcoming. After meeting Professor Sen Ganeshan walked me to his research lab. Along the way he started telling me about his work and how I would help the research.
Ganeshan is researching biofuel production from algae, and he focuses on the whole process, as opposed to one specific step. First, algae is grown in a reactor, harvested, and dried. The lipids, or oils, within the algae are then extracted, and finally the lipids are converted into biofuel. Ganeshan’s current research centers around flat panel photobioreactors, which are large, thin panels that allow the algae to receive the maximum amount of light. The lab also works with bubble column and airlift reactors, which are tubes that use bubbles to mix the algae so they can receive sufficient light. The main bottleneck in algae production that Ganeshan focuses on is the rate at which the algae grows in the reactors. Even though I have some reading to do on algae (my background is in mechanical engineering), I am excited to work on this project.