Discipline: Technology and Engineering
Subcategory: Electrical Engineering
Stephanie Wilcox - Texas A&M University
Co-Author(s): Hyun Soo Kim and Arum Han, Texas A&M University
Biofuels from microalgae are considered a promising source of renewable and carbon-neutral energy. However, the current cost of microalgal biofuels is higher than that of fossil fuels, and in order to establish microalgae-based biofuel as an economically viable alternative, improvements must be made. One such effort is the optimization of microalgal growth and lipid production through the manipulation of environmental stresses. Such stresses include nutrients, temperature, and pH. In this study, the impact of temperature on microalgal growth rates and lipid production has been investigated using a droplet microfluidics-based platform. Droplet microfluidics enable single-cell encapsulation, manipulation, and fast analysis of numerous droplets. The platform presented here is composed of two functional parts; a top microalgal culture/analysis layer and a bottom temperature control layer. Within the top layer, droplets containing a single microalgal cell are generated and then loaded into a serpentine chamber where they are cultured under various temperatures depending on their channel location. To linearize the temperature gradient created by the bottom layer, heat transfer models were simulated in Comsol Multiphysics to determine optimum locations and temperatures of Peltier chips. Utilizing these values, Peltier chips were then attached directly to a glass substrate on the bottom of the culture/analysis layer. A LabVIEW program utilizing a PID mechanism to minimize fluctuation was then implemented to control the Peltier chips. During the culturing period, microscopic images of the droplets are taken daily for analysis of cell growth. From the Comsol simulation results and confirmed tests, two Peltier chips, sizes 48 x 48 mm2 and 30 x 5 mm2, positioned 10mm apart were utilized to obtain linear temperature distribution from 21°C (room temperature) to 40°C across the microfluidic serpentine channel (22 x 60 mm2). Deviation from target temperature was also reduced by approximately 4 times due to PID implementation, and accuracy was improved significantly. The developed platform was characterized by conducting a preliminary culture experiment with Chlamydomonas reinhardtii. C. reinhardtii cells were encapsulated in 240 um droplets and cultured for 7 days at room temperature. 6 ~ 8 hours of doubling time was observed, which is in agreement with previously reported studies. Currently, the platform is being utilized to characterize the growth profiles of C. reinhardtii cells under the linear gradient of temperature, and the optimized temperature for cell growth will be identified.
References: Kim, Hyun Soo, Adrian R. Guzman, et al.. ‘A Droplet Microfluidics Platform for Rapid Microalgal Growth and Oil Production Analysis.’ Biotechnol. Bioeng. Biotechnology and Bioengineering (2016): n. pag.Web. Georgianna, D. Ryan, and Stephen P. Mayfield. ‘Exploiting Diversity and Synthetic Biology for the Production of Algal Biofuels.’ Nature 488.7411 (2012): 329-35. Web.
Funder Acknowledgement(s): This study was supported by a grant from NSF/EFRI-REM awarded to A. Han.
Faculty Advisor: Arum Han, firstname.lastname@example.org
Role: This experiment was conducted by me under the direction and instruction of Dr. Kim and Dr. Han. Dr. Kim aided in the design of the microfluidic devices, as well as the creation of the master device used during the experiments.