Our multidisciplinary research focuses on nano-micro-macro scale devices for biomedical applications. We develop and deploy innovative functional materials, devices, and systems to enable next-generation medical diagnosis and life science research. Current projects performed to achieve these overarching goals are listed below.
I. Solid-State Nanopores: Physics, Fabrication, and Applications
Solid-state nanopores have been extensively studied in the past decade due to their mechanical robustness, tunable size, thermal robustness, and integration potential. The solid-state nanopore family includes membrane materials such as SiNx, graphene, glass nanopores (nanopipette), and polymer nanopores. We study solid-state nanopores with the aim to understand the device physics, to explore viable fabrication and integration methods, and to develop single molecule sensing applications.
- Z. Tang, G. Choi, R. Nouri, and W. Guan. Loop-Mediated Isothermal Amplification-Coupled Glass Nanopore Counting Towards Sensitive and Specific Nucleic Acid Testing. Nano Letters, 19, 7927 (2019).
- R. Nouri, Z. Tang, and W. Guan. Calibration-Free Nanopore Digital Counting of Single Molecules. Analytical Chemistry, 91, 11178 (2019).
- R. Nouri, Z. Tang, and W. Guan. Quantitative Analysis of Factors Affecting the Event Rate in Glass Nanopore Sensors, ACS Sensors, 4, 3007 (2019).
- K. Roshan, Z. Tang, and W. Guan. High fidelity moving Z-Score based controlled breakdown fabrication of solid-state nanopore. Nanotechnology, 30, 095502 (2019).
II. Point-of-care nucleic acid testing (NAT)
Nucleic acid testing (NAT) is currently the most sensitive method available for identifying infectious pathogens. Nevertheless, NAT-based diagnosis developed to date mostly require sophisticated infrastructures, reagents, and skilled technicians. While readily available in reference laboratories, NATs such as PCR remains inaccessible in resource-limited settings. Although extensive efforts have been undertaken towards point-of-care (POC) molecular diagnosis, a fully validated “sample-in-answer-out” NAT system has not developed due to significant challenges of portability, sample preparation, and throughput. In response to this urgent need, we aim to develop low-cost field-deployable field-deployable NAT devices and systems, especially for infectious disease in resource-limiting areas. These NAT devices could be loaded with easily-obtainable raw samples such as finger-prick blood, making diagnostic testing faster and easier for identifying pathogens like Malaria, Zika, and HIV.
- G. Choi, T. Prince, J. Miao, L. Cui, and W. Guan. Sample-to-answer palm-sized nucleic acid testing device towards low-cost malaria mass screening. Biosensors and Bioelectronics, 115, 83 (2018).
- G. Choi, D. Song, S. Shrestha, J. Miao, L. Cui and W. Guan. A field-deployable mobile molecular diagnostic system for malaria at the point of need. Lab Chip, 16, 4341 (2016).
Nanopores and nanochannels offer unique platforms to explore new physical and chemical phenomena appearing for molecules confined in or transported through these structures. New transport behavior and biosensing functionalities can be developed by taking advantage of these unique phenomena occurring at these scales.
- X. Li, W. Guan, B. Weiner, and M. A. Reed. Direct Observation of Charge Inversion in Divalent Nanofluidic Devices. Nano Letters, 15, 5046 (2015).
- W. Guan, and M. A. Reed. Electric Field Modulation of the Membrane Potential in Solid-State Ion Channels. Nano Letters, 12, 6441 (2012).
- W. Guan, R. Fan, and M. A. Reed. Field-effect reconfigurable ionic diode. Nature Communications, 2, 506 (2011).
We develop technologies to precisely control, manipulate fluids that are geometrically constrained to a small scale (from μL to fL). It involves multidisciplinary fields across engineering, physics, chemistry, and nanotechnology. It has practical applications in the design of systems that process low volumes of fluids to achieve multiplexing, automation, and high-throughput screening.
- G. Choi, R. Nouri, L. Zarzar, and W. Guan. Microfluidic Deformability-Activated Sorting of Single Particles. Microsystems and Nanoengineering, 6, 11 (2020).
- G. Choi, E. Murphy, and W. Guan. Microfluidic Time-Division Multiplexing Accessing Resistive Pulse Sensor for Particle Analysis. ACS Sensors, 4, 1957 (2019).
- X. Yang, Z.Chen, J. Miao, L. Cui, and W. Guan. High-throughput and label-free parasitemia quantification and stage differentiation for malaria-infected red blood cells. Biosensors and Bioelectronics, 98, 408 (2017).
- W. Guan, L. Chen, T. D. Rane, T.-H. Wang. Droplet Digital Enzyme-Linked Oligonucleotide Hybridization Assay for Absolute RNA Quantification. Scientific Reports, 5, 13795 (2015)