Burns Lab

Dual-Wavelength Volumetric Stereolithography of Microfluidic Devices

Researchers: Kaylee Smith (alumna), Sanaz Habibi, Martin de Beer (alumna), Zach Pritchard (alumna)

Problem: Current microfluidic fabrication methods tend to be expensive and/or have low through-put. Additionally, they cannot accommodate on-the-fly design changes, which are critical to efficient research and development of microfluidic devices. Additive manufacturing, or 3D printing, has been applied to microfluidic fabrication to address some of the shortcomings of conventional fabrication methods. However, additively manufactured microfluidic devices may still take hours to fabricate.

Project Details: We are investigating novel methods to fabricate microfluidic devices using a dual-wavelength vat photopolymerization system, which was previously developed by our group to do rapid continuous printing. We are exploring dose modulation as a method to control the mechanical properties of the polymer and add integrated, flexible components to 3D printed microfluidic devices. We are also developing computational algorithms to improve dose control in continuous printing applications.

Relevant Literature:

• M. P. de Beer, H. L. van der Laan, M. A. Cole, R. J. Whelan, M. A. Burns, and T. F. Scott, "Rapid, continuous additive manufacturing by volumetric polymerization inhibition patterning," Science Advances, vol. 5, 2019. doi:10.1126/sciadv.aau8723.
• Z. D. Pritchard, M. P. de Beer, R. J. Whelan, T. F. Scott, and M. A. Burns, "Modeling and Correcting Cure‐Through in Continuous Stereolithographic 3D Printing," Advanced Materials Technologies, 2019. doi:10.1002/admt.201900700.
• H. L. van der Laan, M. A. Burns, and T. F. Scott, "Volumetric Photopolymerization Confinement through Dual-Wavelength Photoinitiation and Photoinhibition," ACS Macro Letters, vol. 8, 2019. doi:10.1021/acsmacrolett.9b00412.
• T. F. Scott, B. A. Kowalski, A. C. Sullivan, C. N. Bowman, R. R. McLeod, "Two-Color Single-Photon Photoinitiation and Photoinhibition for Subdiffraction Photolithography," Science, vol. 324, 2009. doi:10.1126/science.1167610

Microviscometer for Monitoring Biological Reactions

Researchers: Sarah Mena (alumna), Lavinia Li (alumna)

Problem: The viscosities of biological samples, such as DNA solutions and whole blood, change during diagnostic reactions and biological processes. Monitoring such viscosity changes can quantitatively determine the progression of biological reactions/processes and diagnose diseases.

Project Details: We are developing a number of tools for measurement of rheological properties in microfluidic devices, including concepts using beads, droplets, and channel geometry. Our asynchronous magnetic bead rotation (AMBR) microviscometer was developed to monitor DNA diagnostic reactions without the use of fluorescent labeling. The response of the AMBR microviscometer yields reproducible measurement of DNA solutions, enzymatic digestion reactions, and PCR systems at template concentrations across a 5000-fold range. We are continuing to develop our droplet-based device, in which length of aqueous droplets in oil can be used to measure viscosity; we have demonstrated the ability of this device to monitor blood coagulation. We are also currently developing a novel fabrication approach to produce channel geometries that can be used to assess red blood cell deformability.

Relevant Literature:

• Y. Li, K. R. Ward, and M. A. Burns, "Viscosity measurements using microfluidic droplet length," Analytical Chemistry, vol. 89, pp. 3996-4006, 2017. doi:10.1021/acs.analchem.6b04563.
• Y. Li, D. T. Burke, R. Kopelman, M. A. Burns, "Asynchronous magnetic bead rotation (AMBR) microviscometer for label-free DNA analysis," Biosensors, 4(1), 76-89, 2014. doi:10.3390/bios4010076

Microfluidic Flow Control for Precision Irrigation

Researcher: Zach Pritchard (alumna)

Problem: In precision irrigation, data collected from sensor networks is used to develop custom irrigation profiles for irrigation zones at resolutions down to single plants. These systems have the potential to improve efficiency of water and fertilizer use while improving crop quality and consistency by addressing the irrigation needs of individual plants due to the unique hyper-local conditions surrounding them. To realize irrigation at the single-plant resolution small, inexpensive, scalable systems must be developed for water delivery. Microfluidic technology is well-suited to meet these requirements, but irrigation systems impose a different set of constraints on microfluidic design than typical applications

Project Details: We are developing novel valve designs and fabrication methods to meet the unique requirements of irrigation applications. The valve design is built from the ideas developed in previous phase-change valves and also incorporates freely moving components which are fabricated directly into the valves. In addition, we are developing approaches for flow regulation to ensure that water is delivered at the appropriate rate. This system can be integrated with our group's water monitoring technologies to measure flow rate.

Relevant Literature:

• R. Pal, M. Yang, B. N. Johnson, D. T. Burke, and M. A. Burns, "Phase change microvalve for integrated devices," Analytical Chemistry, vol. 76, pp. 3740-3748, 2004.

Multifunctional Sensors for Real-Time Fluid Analysis

Researcher: Anna Nelson, Wen-Chi Lin (alumna)

Problem: Water is difficult to analyze since many parameters have to be considered simultaneously to make the analysis meaningful. Measuring these parameters requires equipment that is large, expensive, and difficult to integrate since each tool operates on different principles. The goal of this project is to develop a device containing essential micro-fabricated sensors, with a size no bigger than a grain of rice and a cost no more than $1 if mass produced.

Project Details: Flow rate, conductivity, pH, and ORP sensors, as well as micro-fabricated reference electrodes, have been constructed through funding provided by Masco. Micro-fabricated flow rate sensors are rarely studied at the high flow rates present in residential flow (2.0 GPM). Previous research focused on small flow rates around the level of ml or µl/min, and the only device measuring similar flow rates had a power consumption two orders of magnitude higher than our design. The conductivity sensor we designed is not influenced by flow rate and is suitable for home systems from 0 to 6000 µS/cm. Shrinking ion concentration and pH sensors requires a micro-fabricated reference electrode, which is the main challenge for current technology because it is difficult to maintain a specific ion concentration around the reference electrode. We have developed an innovative method avoiding this requirement and have gotten encouraging results for pH and ORP sensing. Most importantly, the design is simple and can be easily integrated, significantly reducing the cost and the frequency of sensor maintenance. Since Wen-Chi graduated, work on the flow rate sensor has been carried on collaboratively among the group. Anna has taken on heavy metal sensing as her main project.

Relevant Literature:

• W. C. Lin, Z. Li, and M. A. Burns, "A drinking water sensor for lead and other heavy metals," Analytical Chemistry, vol. 89, pp. 8748-8756, 2017. doi:10.1021/acs.analchem.7b00843.
• W. C. Lin, K. Brondum, C.W. Monroe, and M. A. Burns, "Multifunctional Water Sensors for pH, ORP, and Conductivity Using Only Microfabricated Platinum Electrodes," Sensors, vol. 17, p. 1665, 2017. doi:10.3390/s17071655.
• W.C. Lin, M.A. Burns, "Low-power micro-fabricated liquid flow-rate sensor," Analytical Methods, 7(9), 3981-3987, 2015. doi:10.1039/C5AY00517E.

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:

• R. Pal, M. Yang, R. Lin, B. N. Johnson, N. Srivastava, S. Z. Razzacki, et al., "An integrated microfluidic device for influenza and other genetic analyses," Lab on a Chip - Miniaturisation for Chemistry and Biology, vol. 5, pp. 1024-1032, 2005. doi:10.1039/B505994A.
• M. A. Burns, B. N. Johnson, S. N. Brahmasandra, K. Handique, J. R. Webster, M. Krishnan, et al., "An integrated nanoliter DNA analysis device," Science, vol. 282, pp. 484-487, 1998. doi:10.1126/science.282.5388.484