Burns Research Group
Microfluidics at the University of Michigan
Burns Research Group
Dept of Chemical Engineering
3212 H.H. Dow Bldg
2300 Hayward Street
Ann Arbor, MI 48109-2136
Current Research Projects
There are several ongoing research projects within the Burns group. In general, each graduate student focuses on his or her specific project using microfluidic systems with chemical, biological or microfluidic applications. In addition to the projects listed here, there were a wide range of past group projects and many interesting projects available to be studied.
- Integrated Microfluidic Device for Influenza and Other Genetic Analyses
- Multiphase Droplet Bioreaction Systems
- Microfluidic Assembly Blocks
- Microrheometer for Measuring Blood Properties
- Bacterial Cultivation and Screening in Microdroplets
- Producing Colloidal Particles with Configurable Anisotropy
- Distributed Pressure Control in Microfluidics
- Acoustic Flow Control
- Thermally Mediated Pressure Regulator
Integrated Microfluidic Device for Influenza and Other Genetic Analyses
Problem: Genetic analysis can be performed on microfluidic devices by essentially miniaturizing all the individual components of a lab onto a single chip. This, in theory, could save time, reagents and perform inexpensive portable diagnostics. However, there is still a great deal to be done before this can be realized as a viable method for genetic diagnostics.
Project Details: We have designed and tested an integrated genetic analysis device. The device is designed to perform two independent serial biochemical reactions, followed by an electrophoretic separation. The key components (phase change valves, thermally isolated reaction chambers, gel electrophoresis, and pulsed drop motion) that were developed for this device are electronically addressable and simple to operate, properties that can lead to eventual autonomous operation.
Relevant Literature:
- Pal, R., Yang, M., Lin, R., Johnson, B.N., Srivastava, N., Razzacki, S.Z., Chomistek, K.J., Heldsinger, D.C., Haque, R.M., Ugaz, V.M., Thwar, P.K., Chen, Z., Alfano, K., Yim, M.B., Krishnan, M., Fuller, A.O., Larson, R.G., Burke, D.T., and Burns, M.A., "An Integrated Microfluidic Device for Influenza and Other Genetic Analyses," Lab on a Chip, 5 (10), 1024-1032 (2005).
- Burns, M. A., Johnson, B. N., et al., "An Integrated Nanoliter DNA Analysis Device," Science, 282 (5388), 484-487 (1998).
Multiphase Droplet Bioreaction Systems
Problem: Microfabrication technology has paved the way for constructing miniaturized point-of-care genetic analysis systems. However, most current microsystems have drawbacks such as evaporative loss and reagent adsorption, which are usually mitigated by adding other components or treatments, thus increasing the complexity of fabrication and operation.
Project Details: This project is focused on the development of an automated multiphase bioreaction microsystem without additional components. In this system, aqueous droplets containing the reaction solutions are encapsulated in a continuous oil phase. The thin oil film between the reaction solution and the device walls prevents dispersion, evaporation and reagent adsorption. With controllable droplet sizes, the device is capable of carrying out bioreactions of volumes ranging from picoliters to microliters. With easy manipulation of droplet coalescence and breakup, the microdevice is also aimed at the high throughput optimization of reagent compositions. The electrical capacitance/conductance change is used to detect the presence of the oil-aqueous interface in real time, and also to feedback control the pneumatic system for driving the fluid flow. This automated, valveless, multiphase methodology can be readily integrated into other microdevices such as those for high throughput screening.Project Investigator: Fang Wang
Relevant Literature:
Microfluidic Assembly Blocks
Problem: Although microfluidic systems are convenient platforms for biological assays, their use in the life sciences is still limited mainly due to the high-level fabrication expertise required for construction.
Project Details: An assembly approach for microdevice construction using prefabricated microfluidic components was developed. This approach involves prefabrication of individual microfluidic assembly blocks (MABs) in PDMS that can be readily assembled to form microfluidic systems. Non-expert users can assemble the blocks on glass slides to build their devices in minutes without any fabrication steps. In this paper, we describe the construction and assembly of the devices using the MAB methodology, and demonstrate common microfluidic applications including laminar flow development, valve control, and cell culture.Project Investigator: Minsoung Rhee
Relevant Literature:
Microrheometer for Measuring Blood Properties
Problem: The rheological properties of blood, such as viscosity and viscoelasticity, have been associated with a number of adverse cardiovascular conditions including stroke and hypertension. While devices exist to measure these properties, they are benchtop instruments that can only be used in a laboratory setting.
Project Details: A microfabricated device, which could be used by a medical practitioner as a point-of-care device to quickly and easily measure the viscoelastic properties of the patient’s blood, would therefore be a very useful tool. We have already developed microscale devices to measure the viscosity of Newtonian fluids and the parameters of the power law model. We are presently working on developing devices that would also measure the elastic properties of blood, thereby giving information about things like RBC count and deformability. We eventually plan to develop a fully automated device which will quickly measure the viscoelastic properties of a blood sample, while using only a low sample volume and having an intuitive user interface.
Relevant Literature:
- N. Srivastava, R. Davenport, M.A. Burns, A Nanoliter Viscometer for Analyzing Blood Plasma and Other Liquid Samples," Analytical Chemistry, 77(2) (2005) 383-392.
- N. Srivastava and M.A. Burns, Analysis of non-Newtonian liquids using a microfluidic capillary viscometer, Analytical Chemistry 78(5) (2006) 1690–1696.
- N. Srivastava and M.A. Burns, Electronic drop sensing in microfluidic devices: automated operation of a nanoliter viscometer, Lab On a Chip 6(6) (2006) 744–751.
Bacterial Cultivation and Screening in Microdroplets
Problem: Microbial secretion is an important process in many microbe-assisted biochemical production systems. Highly secreting microbes can be rewarded in a symbiotic system with appropriate partner cells in localized mini-environments.
Project Details: Microfluidics is one of the most attractive technologies, which have been combined with molecular biology technology. In this project, our goal is to develop high-throughput screening and engineering technologies for improving microbial secretion by combining microbial symbiosis and microfluidic devices. More specifically, we aim to design and fabricate microfuidic devices which can generate microdroplets compartmentalizing pairs of symbiotic cells and can support micro-cultivation as well as growth detection, which maximizes the effect of microbial secretion on the community growth rate. Such microfluidic devices can be applied to optimize microbial strains crucial for various biotechnology applications such as biofuel production.
Project Investigator: Jihyang Park
Producing Colloidal Particles with Configurable Anisotropy
Problem: Self-assembled products have seen interest in recent years because of their potential for applications in microelectronics, pharmacology, photonics, near-field optics and nano- technology. In order to make effective self-assembled constituents, we are developing microfluidic devices to accurately and reproducibly create colloidal particles out of smaller spherical particles. This will give us control of not only the geometric properties of the resultant particles, but also the particles' composition and spatial electronic properties.
Project Details: The current device is being developed to produce any 2D particle shape several hundred times at submicron sizes. In order to make this practical several approaches are being investigated. They look to address several fundamental problems of the system, which include the following. First, there should be an effective way to transport particles at the colloidal scale as brownian motion begins to dominate and pressure drops become extremely large. Second, fabrication of channels below 1 micron will become difficult because they require expensive technologies that are not used frequently in MEMS devices. Finally, thermal fusion of individual particle chains may become outdated as particles change size and materials.
Project Investigator: Ramsey Zeitoun
Relevant Literature:
- K. E. Sung, S. A. Vanapalli, D. Mukhija, H. A. Mckay, J. M. Millunchick, M. A. Burns, M. J. Solomon, Programmable fluidic production of microparticles with configurable anisotropy, Journal of the American Chemical Society 130 (4) (2008) 1335–1340.
- Glotzer, S. C., Solomon, M. J., Anisotropy of building blocks and their assembly into complex structures, Nature Materials 6 (8) (2007) 557–562.
Distributed Pressure Control in Microfluidics
Problem: Distributed pressure control is arguably the most important unsolved problem in the field of microfluidics. All current strategies whether electronic, displacement, or pneumatic based, are prohibitive when attempting to manage a substantial number of fluidic inputs, each requiring a dedicated control loop.
Acoustic Flow Control
Project Details: This project takes a unique approach to solving the problem of distributed pressure control utilizing principles from acoustic resonance theory and Navier-Stokes fluid mechanics. The concept is an acoustically powered pressure regulator, similar to a conventional stage reduction regulator; however, rather than operating a mechanical knob to achieve a desired output pressure, one adjusts the frequency of an acoustic input. Regulating the output pressure as such is possible due to a dramatic amplification of system pressure in the vicinity of a resonant mode. We take advantage of resonant vs. non-resonant frequencies by incorporating a fluidic diode with an actuation threshold accessible only under a resonant excitation. In addition to providing output pressures more suited for precise control of small liquid volumes, the concept is fully parallelizable in the sense that multiple pressure lines, interfaced with a microfluidic device can be independently operated with a set of tonal pumping instructions.
Project Investigator: Sean Langelier
Thermally Mediated Pressure Regulator
Project Details: A key difference between macroscale and microscale flow that can be exploited in a microfluidic device is the ratio of inertial forces to viscous forces, quantified by the Reynolds number, Re. For low viscosity fluids such as air, typical microchannel flows exhibit intermediate Re between 102 and 103 at which viscous forces are comparable to inertial forces. Sufficient perturbation of this meta-stable state modifies the balance between these two forces and can significantly alter the flow characteristics.
One of the simplest such perturbations is changing the fluid temperature, which subsequently changes the kinematic viscosity of the fluid. Our initial designs used microfabricated heating elements to control the temperature of air flowing through a microscale Venturi nozzle, allowing electronic switching between positive and negative output pressures. We aim to integrate these Venturi pressure microregulators in multiplexed arrays for distributed, electronically addressable pressure control over complex microchannel networks. We are also investigating alternative channel geometries to exploit differences in jetting characteristics determined by the relative dominance of inertial forces for directional flow steering.
Project Investigator: Dustin Chang