• Develop and apply novel solutions and techniques in characterizing the surface’s structural, chemical, electrical, magnetic and mechanical properties of ceramic, polymer, composite, and bio-materials using state-of-art techniques through which to assist developing new material solutions for future applications in bio-science products, daily consuming products and performance products.
• Ph.D. (12/2009) – Physics, minor in Materials Science & Engineering, North Carolina State University, Raleigh, NC, USA
o Thesis title: “Nanoscale studies of switching behavior of ferroelectric thin films”
o Thesis advisor: Alexei Gruverman
• B.S. (8/2003) - Plasma Physics, University of Science and Technology of China, Hefei, China
SUMMARY OF EXPERTISE AND SKILLS
• Highly self-motivated and strong knowledge in material science, physics, polymers science, mathematics and statistics, analytical techniques and experimentations. Highly sensitive in any latest advances in microscopy techniques and three more years’ experience in advising graduate students for using the state-of-art techniques from different research fields.
• More than 7 years’ experience in Scanning Probe Microscopy. Familiar with various Atomic Force Microscopy (AFM) systems such as MFP-3D (Asylum Research), M5 (Park Scientific), CPR & Multimode (Bruker) and homemade AFM system. Rich operation experience in air and liquid environment. Capable of modifying standard AFM system for measuring materials surface electrical, magnetic and mechanical properties such as Electrical Force Microscopy (EFM), Kelvin Probe Microscopy (KPM), Piezoresponse Force Microscopy (PFM), Conductive AFM, Magnetic Force Microscopy (MFM) and Friction Force Microscopy (FFM) etc.
• Rich experience in single-molecule fluorescent optical microscope techniques such as Total Internal Reflection Fluorescence Microscope (TIRF) and the related surface modification techniques for biological immobilization.
• Rich experience in other Microscopy techniques such as Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM).
• Various analytical techniques such as HPLC, FTIR; Various surface characterization techniques such as XPS, QCM, ellipsometry and material growth technique such as PVD (physical vapor deposition: Thermal and Electron beam).
• Electronic Devices:
• Tektronix oscilloscope, Keithley voltage unit, and various Lock-in Amplifiers, Crystal laser system, Olympus Optical microscope system and different function generators.
• Windows R operation system and Microsoft R Office package.
• Data processing software: Igor (MFP-3D), Matlab, Labview, Mathematics, Origin, WSxM, SPIP, IP2.1, Photoshop and KaleidaGraph, Nanomanipulator etc.
• SPICE (Simulation Program with Integrated Circuit Emphasis) for IC design.
• Lab Operation:
• Build a new scanning probe research lab at the University of Nebraska-Lincoln and train graduate students with various backgrounds.
• Experienced cleanroom user of Shared Materials Instrumentation Facility (SMIF) at Duke University.
• Collaboration with various research groups such as the Colloids and Interfaces Group at NC State University and the Nanomechanics Laboratory at Duke University.
• In charge of one set of simultaneous AFM (MFP-3D) and Fluorescent Microscopy system (Olympus IX71) in Prof. Erie’s lab in the chemistry department of University of North Carolina at Chapel Hill.
• 09/2010 ~ Present : Postdoctoral Associate, Dorothy Erie’s lab (Biochemistry group), University of North Carolina at Chapel Hill and Hong’s Lab (Bio-Physics group) at NC State University
• Work with Professor Dorothy M. Erie and Hong Wang to study DNA-Protein interaction, DNA mismatch repair mechanism and bio-materials’ electrical properties in the application of bio-devices by using combined techniques of atomic force microscope (PFM and EFM) and fluorescent microscope techniques (TIRF and FRET). By using the biotin-streptavidin system we can fix the DNA on treated surface and directly observe the proteins’ binding behaviors on DNA dynamically. By combining with AFM, we have also successively recognized the DNA-Proteins complex with nanometer resolution and at the same time been able to identify different binding types of proteins. In the meanwhile, we have developed a novel microscopy technique (Dural Resonance Frequency Enhanced Electrical Force Microscopy) to identify various biomolecule’s surface potential signals and been able to directly observe the DNA path inside the bound proteins and this technique can also be used to detect any other materials’ weak surface potential signals with sensitivity of 2 electrons/nm^2.
• 09/2009 ~07/2010: Postdoctoral Associate, Responsive Materials Chemistry Group, Duke University
• Work with Professor Stephen Craig to study mechanical force induced chemical ring-open reaction using a self-built AFM system. We are able to directly observe the behaviors of molecules under stretching or torsion. This will advance the fundamental understanding of how mechanical force level. It is the first time a high stretching force (~1.2 nN) curve was observed for a single polymer chain influences chemical reactivity and the design ability for new stress-responsive materials (e.g., gem-Br2-cyclopropane) and the self-healing polymers that strengthen or repair automatically at the molecular.
• 09/2004~09/2009: Graduate Student, Surface Science Lab, North Carolina State University
• Conducted research in ferroelectric thin films and ferroelectric random access memory (FeRAM provided by Fuji Inc.) using Piezoresponse Force Microscope (PFM) modified from commercial AFM systems. A new found theory and approach were therefore developed for future FeRAM fabrication and design for higher capacity which can lead more cost efficient during the future manufacture.
• Investigated the switching of resistance in ferroelectric tunnel junctions (caused by polarization reversal) in ultra-thin (1nm~10nm thickness) BaTiO3 films which has direct applications in the next generation of high density memory devices. We have published solid experimental data for its feasibility and provide constructive suggestions for further development in the memory application.
• Performed electric and mechanic measurements of collagen fibrils and piezoelectric polymers (PVDF) in micro-scale and nanoscale which could give more direct results for the bio-function of collagen.
• 07/2007-08/2007: Visiting Scholar, University of Aveiro, Portugal
• Led research of ferroelectric copolymers using PFM technique. Helped the local research group to set up a PFM system and corresponding data analyses.
• 09/2002~09/2004: Senior Undergraduate Student, CAS Key Laboratory of Basic Plasma Physics, University of Science & Technology of China
• Designed and developed a home-build plasmas device in order to generate a large area and homogenous plasma field in high pressure condition and studied its impact on the modification of materials’ surface properties.
• D. Wu, D. Erie, “Seeing DNA Through Proteins” Nature Method (Drafting and will submit this month, 2012)
• P. Sharma, D. Wu, S. Poddar, T. J. Reece, S. Ducharme and A. Gruverman, “Orientational Imaging in Polar Polymers by Piezoresponse Force Microscopy” J. of Appl. Phys. Vol. 110, 5, 2011
• D. Wu, J. M. Lenhardt, A. L. Black, B. B. Akhremitchev, and S. L. Craig, “Molecular Stress Relief through a Force-Induced Irreversible Extension in Polymer Contour Length” JACS, 132, 15936 (2010)
JACS Journal Cover at Volume 132, Number 50, December 22, 2010
• D. Wu, I. Vrejoiu, M. Alexe, and A. Gruverman “Anisotropy of domain growth in epitaxial ferroelectric capacitors” Appl. Phys. Lett. 96, 112903 (2010)
• X. Liu, D. Wu, S. Turgman-Cohen, J. Genzer, T. W. Theyson, and O. J. Rojas “Adsorption of a nonionic symmetric tri-block copolymer on surfaces with different Hydrophobicity” Langmuir, 26(12), 9565–9574 (2010)
• X. Liu, J. Song, D. Wu, J. Genzer, T. Theyson, and O. J. Rojas, “Surface and Friction Behavior of a Silicone Surfactant Adsorbed on Model Textiles Substrates” Ind. Eng. Chem. Res. 49, 8550–8557 (2010)
• C. Harnagea, M. Vallières, C. P. Pfeffer, D. Wu, B. R. Olsen, A. Pignolet, F. Légaré, A. Gruverman “Two-dimensional nanoscale structural and functional imaging in individual collagen type-I fibrils” J. Biophys., 98, 3070–3077 (2010)
• D. Wu, I. Kunishima, S. Roberts, and A. Gruverman “Spatial variations in local switching parameters of ferroelectric random access memory capacitors” Appl. Phys. Lett. 95, 092901 (2009)
• A. Gruverman, D. Wu, H. Lu, Y. Wang, H. W. Jang, C.M. Folkman, M. Ye. Zhuravlev, D. Felker, M. Rzchowski, C.-B. Eom and E. Y. Tsymbal “Tunneling electroresistance effect in ferroelectric tunnel junctions at the nanoscale” Nano Lett. 9 (10), 3539 (2009)
• P. Sharma, T. J. Reece, D. Wu, V. M. Fridkin, S. Ducharme and A. Gruverman “Nanoscale Domain Patterns in Ultrathin Polymer Ferroelectric Films” J. Phys: Cond. Matt. 21, 485902 (2009)
• A. Gruverman, D. Wu, and J. F. Scott “Piezoresponse Force Microscopy Studies of Switching Behavior of Ferroelectric Capacitors on a 100-ns Time Scale” Phys. Rev. Lett. 100, 097601 (2008)
• A. Gruverman, D. Wu, H-J Fan, I. Vrejoiu, M. Alexe, R. J. Harrison and J. F. Scott “Vortex ferroelectric domains” J. Phys.: Condens. Matter 20 342201 (5pp) (2008)
• J. F. Scott, A. Gruverman, D. Wu, I Vrejoiu and M Alexe “Nano-domain faceting in ferroelectrics” J. Phys.: Condens. Matter 20 425222 (5pp) (2008)
• A. Wu, P. M. Vilarinho, D. Wu, and A. Gruverman “Abnormal domain switching in Pb(Zr,Ti)O3 thin film capacitors” Appl. Phys. Lett. 93, 262906 (2008)
• A. Gruverman, D. Wu, B.J. Rodriguez, S.V. Kalinin, S. Habelitz, “High-resolution imaging of proteins in human teeth by scanning probe microscopy” Biochem. Biophys. Res. Comm. 352, 142–146 (2007)
• President, Chinese Student Association in Raleigh, NC (2005-2006).
• President, Badminton Club in North Carolina State University (2006-2007).
• Patent application been submitted Nov. 2011
Title: “Dural Resonance Frequency Enhanced Electrical Force Microscopy or DREfEfM Imaging Method”