My current research interests concentrate on nanostructured materials and nanobiotechnology, more specifically, I am currently working on the following six different areas:

(1) Nanostructure fabrication and characterization. One dimensional nanowires or nanorods are building blocks that may provide breakthrough applications in nanoelectronics, photonics, and bioengineering, and they have thus stimulated great research interest. My research mainly focuses on the using of physical vapor deposition methods to control growth of nanostructures. Especially we are working on a so-called oblique angle deposition method, or glancing angle deposition (GLAD) method. With this technique, we can grow aligned nanostructures from metals, semiconductors, insulators, and design three dimensional nanostructures. More recently, we are interested in metallic nanorod arrays, oxide nanorods, and multilayer nanorod arrays for biosensor application, hydrogen storage materials. We have developed some very unique deposition systems that are capable fabricate a large variety of nanostructures. In the meantime, we are trying to combine GLAD with other nanofabrication techniques, such as nanoparticle fabrication, electrospinning, VLS method, e-beam lithography, interference lithography etc, to make advanced nanostructures.

(2) Liquid-nanostructure interaction. Nanostructure not only changes the surface morphology, but also alters the chemical composition of a surface. The practical consideration for this research is that if nanostructures are used as biological sensors, the fundamental interaction between the liquid and the nanostructure becomes important for sensor design. According to recent progress on understanding the wetting behavior for micrometer scale features, one can expect that well-aligned nanostructures with different size, separation, aspect ratio, and shape of different materials are the key for the basic understanding of wettability of nanostructures. In the past, we have performed some systematic studies on this area. We are interested in how those changes alter the static and dynamic wetting process, and its applications as superhydrophobic coating, as well as micro/nano-fluidic devices. New scaling relationship has already been discovered in our group.

(3) Novel nanostructures for chemical and biological sensors. Due to their extraordinary physical, chemical, mechanical and biological properties, nanostructured materials have been used as high sensitive and high performance sensor materials or devices. We are interested in incorporating low temperature nanostructures into chemical and biological sensors, such as nerve gas, explosives, toxins, viruses, and pathogens. Currently we are working on plasmonic sensors. Such as surface enhanced Raman spectroscopy (SERS) based sensor and localized surface plasmon resonance (LSPR) sensors. We found that ~1000 nm-long Ag nanorod arrays with high aspect ratios (~10:1) produce extremely high SERS enhancement factors (~1 billion times) for small molecules. We have conducted experiments to test the detection of a different viruses and virus strains via SERS, and have successfully classified them. Our results suggest that these novel SERS substrates can be used as a diagnostic tool to detect extremely low levels of virus with minute sample volume (~ micron liter), as well as provide structural and quantitative information about the virus. The assay is rapid, ultra-sensitive, and does not require virus manipulation to achieve results, within 10 second. The availability of a low cost, field-deployable fiber optic-based SERS probe would be highly desirable for many military and clinical applications. We have demonstrated that aligned nanostructures can be deposited onto cylindrical optical fibers to serve as fiber optical probes. This is a key step that will allow us to develop a portable, field-deployable, fiber optic-based SERS sensor. Furthermore, the Ag nanorod fabrication technique is fully compatible with microfabrication processes, thus makes further miniaturization through MEMS possible. In addition, we are also investigating theoretically how different topological metal nanorods could alter the plasmonic properties.

(4) New energy materials and devices. By tailoring the structural properties of nanomaterials, the thermodynamics and kinetics of hydrogen adsorption can be designed to satisfy the future hydrogen storage requirements. A fundamental understanding of hydrogen-nanostructure interactions also depends largely on the ability to fabricate nanostructures with the desired structural properties. The main hurdle to prevent exploring hydrogen storage capability of other nanostructured metal hydride is that most nanofabrication techniques cannot be applied to fabricate metal hydride nanostructures, a limitation that has resulted in a severe bottleneck for the application of nanostructures to hydrogen storage. The ability to design nanostructures freely in order to tailor their topography, structure, and composition, as well as incorporating catalyst will be one of the most important challenges for hydrogen storage applications. Here, one of our main goals is to use a novel nanofabrication technique, to design and produce metal hydride nanorods and nanowires with different topography, structure, and composition.

(5) Biomaterials for cellular engineering. With collaboration with colleagues from bioengineering, we are particularly interested in how to design micro-/nano-substrates to change the cell growth behavior, or their networking. We have four major goals: (a) To study how morphological environments affect different cell growth; (2) to control stem cell growth and differentiation using nano/micro environment; (3) to build three dimensional cell assay for drug accelerating drug discovery; and (4) to form artificial neural network and integrate it with microelectronics. So far, we investigated the possibility to use nanorod-structured substrates to guide neuronal cell growth by comparing the neurite outgrowth activity in a rat pheochromocytoma cell line (PC12) cultured on nano-structured, micro-structured and smooth substrates. We fabricated microwell structures on SU8 photoresist with conventional photolithography. SH-SY5Y neuroblastoma cells were cultured on both flat SU-8 surfaces and patterned microwell structures. With proper well dimensions and fabrication conditions, cells could grow predominantly inside the microwell structures. We have successfully extended our study to the fabrication of connected microwells with the objective of establishing a cell network, and studied the morphological effect on Stem cells.

(6) Designing Catalytic Nanomotors: Catalytic nanomotor design and fabrication is a new project recently established in our group, and is currently supported by NSF. We found that oblique angle deposition was a wonderful technique to carry out asymmetric deposition, and can be used to place catalytic layers on different segments of a nanorod. Therefore, by controlling the location of the catalytic sites, one can control the motion of the catalytic nanomotor. Current objectives for this project are, to design nanomotors with different dynamic properties; to characterize the nanomotors and their motion behaviors; and to explore the use of alternative fuel and the control of the nanomotors motion. The future work is to integrate catalytic nanomotors with smart materials for drug delivery, disease treatment, tissue repairing or smart NEMS.

Recent Publications

J.-G. Fan, and Y.-P. Zhao, “The effect of the shape of nanorod arrays on the nanocarpet effect,” Nanotechnology 19, 045713 (2008)

Y.-P. He, Z.-Y. Zhang, C. Hoffmann, and Y.-P. Zhao, “Designing Ag nanoparticles embedded MgF2 nanorod array,” Advanced Functional Materials 18, 1676-1684 (2008)

W.M. Hlaing Oo, M.D. McCluskey, Y.-P. He, and Y.-P. Zhao, "Strong Fano resonance of oxygen-hydrogen bonds on oblique angle deposited Mg nanoblades," Appl. Phys. Lett. 92, 183112 (2008)

J.-X. Fu, B. Park, G. Siragusa, L. Jones, R. Tripp, Y.-P. Zhao, and Y.-J. Cho “Au/Si hetero-nanorod-based biosensor for Salmonella detection,” Nanotechnology 19, 155502 (2008)

W. Smith, Z.-Y. Zhang, and Y.-P. Zhao, “Structural and optical characterization of WO3 nanorods/films prepared by oblique angle deposition,” J. Vac. Sci. Technol. B 25, 1875-1881 (2007)

H. Y. Chu, Y.-J. Liu, Y.-W. Huang, and Y.-P. Zhao, “A high sensitive fiber SERS probe based on silver nanorod arrays,” Optics Express 15, 12230-12239 (2007)

Z.-Y. Zhang and Y.-P. Zhao, "The optical properties of helical Ag nanostructures calculated by discrete dipole approximation method," Appl. Phys. Lett. 90, 221501 (2007)

Y. He, J.-S. Wu, and Y.-P. Zhao, "Designing catalytic nanomotors by dynamic shadowing growth," Nano Letters 7, 1369 - 1375 (2007)

J.-G. Fan and Y.-P. Zhao, “Spreading of a water droplet on a vertically aligned Si nanorod array surface,” Appl. Phys. Lett. 90, 013102 (2007)