Tao Wang

University of Notre Dame, South Bend, Indiana, United States

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Publications (12)48.07 Total impact

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    ABSTRACT: We report an approach for cost-effective manufacturing of THz quasi-optical polarizers by inkjet printing of polymer-carbon nanowhisker (CNW) dispersions. The electromagnetic interference properties of coatings with fixed CNW/polymer composition and varying thickness are quantified by a frequency domain THz spectroscopy system in the range 570–630 GHz. A shielding effectiveness of ∼40 dB is attained for 70 μm-thick coatings. A prototype THz polarizer printed on Mylar film displayed transmission and absorbance that varied with polarization orientation. The degree of polarization for film thickness of ∼1 μm was 0.35. This performance can be improved by refining grid dimensions, increasing coating thickness and adopting multi-layer polarizer structures.
    Applied Physics Letters 12/2012; 101(24). · 3.79 Impact Factor
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    ABSTRACT: We studied the interaction of infrared optical traps with controlled-pore glass (CPG) beads in aqueous medium. The lateral optical trapping force and stiffness were experimentally found considerably smaller than those of their solid counterparts. The simulation using an average refractive index revealed significant losses of effective trapping efficiency, which quantitatively agreed well with experimentally fitted curves. This effect was ascribed to the reduced relative refractive index of medium-filled CPG beads with respect to the medium. Combining optical trapping with mechanical confinements, we demonstrated a microfluidic platform allowing for the synthesis of multiple DNA oligonucleotide sequences on individual beads of interest.
    Applied Physics Letters 04/2012; 100(15):153702-1537023. · 3.79 Impact Factor
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    ABSTRACT: We present synthesis and characterization of multicomponent polymer‐based nanocomposites for carbon dioxide capture and conversion into stable carbonates. Using a simple drop‐casting method, several metal oxide nanoparticles were homogeneously mixed into a polymer matrix. Our formulation is based on the combination of metal oxide nanoparticles and photocatalysts, such as titanium dioxide, silicon dioxide, magnesium oxide, copper oxide, and iron oxide. In this formulation, each metal oxide exhibits its own catalytic function of trapping carbon dioxide. In a mixture with several of these inorganic components, the nanocomposites exhibit the characteristics from each, with a potential of displaying multifunctionality. The liquid phase of the polymer‐based nanocomposite enables it to be sprayed onto any surface that could potentially lead to large‐area carbon capture. The combination of low‐cost materials, easy large‐scale applications, and multifunctionality offers huge potential of these multicomponent nanocomposites for effective CO2 capture and conversion into stable carbonates and other useful by‐products. © 2012 Society of Chemical Industry and John Wiley & Sons, Ltd
    Greenhouse Gases: Science and Technology 01/2012; 2(6). · 2.68 Impact Factor
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    ABSTRACT: Light-directed in situ synthesis of DNA microarrays using computer-controlled projection from a digital micromirror device--maskless array synthesis (MAS)--has proved to be successful at both commercial and laboratory scales. The chemical synthetic cycle in MAS is quite similar to that of conventional solid-phase synthesis of oligonucleotides, but the complexity of microarrays and unique synthesis kinetics on the glass substrate require a careful tuning of parameters and unique modifications to the synthesis cycle to obtain optimal deprotection and phosphoramidite coupling. In addition, unintended deprotection due to scattering and diffraction introduce insertion errors that contribute significantly to the overall error rate. Stepwise phosphoramidite coupling yields have been greatly improved and are now comparable to those obtained in solid phase synthesis of oligonucleotides. Extended chemical exposure in the synthesis of complex, long oligonucleotide arrays result in lower--but still high--final average yields which approach 99%. The new synthesis chemistry includes elimination of the standard oxidation until the final step, and improved coupling and light deprotection. Coupling Insertions due to stray light are the limiting factor in sequence quality for oligonucleotide synthesis for gene assembly. Diffraction and local flare are by far the largest contributors to loss of optical contrast. Maskless array synthesis is an efficient and versatile method for synthesizing high density arrays of long oligonucleotides for hybridization- and other molecular binding-based experiments. For applications requiring high sequence purity, such as gene assembly, diffraction and flare remain significant obstacles, but can be significantly reduced with straightforward experimental strategies.
    Journal of Nanobiotechnology 12/2011; 9:57. · 5.09 Impact Factor
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    ABSTRACT: This review highlights the most significant advances of the nanofabrication techniques reported over the past decade with a particular focus on the approaches tailored towards the fabrication of functional nano-devices. The review is divided into two sections: top-down and bottom-up nanofabrication. Under the classification of top-down, special attention is given to technical reports that demonstrate multi-directional patterning capabilities less than or equal to 100 nm. These include recent advances in lithographic techniques, such as optical, electron beam, soft, nanoimprint, scanning probe, and block copolymer lithography. Bottom-up nanofabrication techniques--such as, atomic layer deposition, sol-gel nanofabrication, molecular self-assembly, vapor-phase deposition and DNA-scaffolding for nanoelectronics--are also discussed. Specifically, we describe advances in the fabrication of functional nanocomposites and graphene using chemical and physical vapor deposition. Our aim is to provide a comprehensive platform for prominent nanofabrication tools and techniques in order to facilitate the development of new or hybrid nanofabrication techniques leading to novel and efficient functional nanostructured devices.
    Advances in colloid and interface science 11/2011; 170(1-2):2-27. · 5.68 Impact Factor
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    ABSTRACT: We demonstrate tunable mechanical properties of bone-inspired bionanocomposite scaffolds while maintaining the required viscoelasticity. Mechanical properties such as hardness and elastic modulus of the bionanocomposite scaffolds were controlled by varying mineral concentrations of the bioscaffold. In particular, higher calcium and oxygen contents in the bioscaffold resulted in a significant enhancement in hardness and modulus of the bionanocomposite. Moreover, the phosphorous content appeared to be a determining factor in the hardness and mechanical properties of the bionanocomposites. These results open up the possibility of designing new engineered biocompatible nanoscaffolds with desired and tunable biomimetic functions and biomechanical properties with significant potential for advanced bone tissue engineering platforms and bone substitutes.
    Applied Physics Letters 07/2011; 99(1):013702-013702-3. · 3.79 Impact Factor
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    ABSTRACT: We report design and synthesis of polymer-based large-area superhydrophobic carbon nanofiber (CNF) composite coatings for tunable electromagnetic interference shielding and attenuation in the terahertz (THz) frequency regime. Such coatings with different CNF/polymer weight ratios are characterized by a frequency domain THz spectroscopy system. A maximum THz shielding effectiveness of ∼ 32 dB was measured in the examined frequency range of 570–630 GHz. Coating attenuation level varied with CNF loading. Two-dimensional distributions of power attenuation at 600 GHz showed good spatial uniformity. The present composite coatings, in addition to their self-cleaning property, have high potential for advanced technology high-frequency applications.
    Applied Physics Letters 04/2011; 98(17):174101-174101-3. · 3.79 Impact Factor
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    ABSTRACT: An optical tweezers directed parallel DNA oligonucleotide synthesis methodology is described in which controlled pore glass (CPG) beads act as solid substrates in a two-stream microfluidic reactor. The reactor contains two parallel sets of physical confinement features that retain beads in the reagent stream for synthetic reaction but allow the beads to be optically trapped and transferred between the reagent and the inert streams for sequence programming. As a demonstration, we synthesized oligonucleotides of target sequence 25-nt, one deletion and one substitution using dimethoxytrityl (DMT) nucleoside phosphoramidite chemistry. In detecting single-nucleotide mismatches, fluorescence in situ hybridization of the bead-conjugated probes showed high specificity and signal-to-noise ratios. These preliminary results suggest further possibilities of creating a novel type of versatile, sensitive and multifunctional reconfigurable one-bead one-compound (OBOC) bead array.
    Lab on a Chip 03/2011; 11(9):1629-37. · 5.70 Impact Factor
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    ABSTRACT: We report design and synthesis of novel polymer-based nanocomposite for carbon capture and direct conversion into carbonate using a simple drop-casting method that allows uniform mixing of multiple oxide nanoparticles in a polymer matrix. Different functional properties including reactions with carbon dioxide (CO2) and entrapping, and catalytic actions of the individual oxide nanoparticles were combined for their synergistic functions to occur in a single material system that resulted in enhanced reactions with CO2 and direct conversion of CO2 into thermodynamically favored and stable carbonates. These nanocomposites can be conveniently sprayed to coat surfaces for large-area CO2 capture and storage.
    Chemical Physics Letters 01/2011; 508(4):276-280. · 2.15 Impact Factor
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    ABSTRACT: We report a simple and novel top-down method based on a drop-casting process for the controlled synthesis of all-bone-minerals biomimetic multicomponent bionanocomposites. Integration of micro- and nanoscale binary features into nanofibrous biocompatible polymer scaffold structures is successfully demonstrated. Compositional control of the constituents of the bionanocomposites resulted in uniform dispersion of hydroxyapatite nanospheres (~100-500 nm) among collagen nanofibers (~100 nm). The composites also present high calcium and oxygen contents and adequate phosphorus compositions comparable to the levels of bone tissues. Our preliminary results open up further possibilities to develop advanced tissue-engineered bionanocomposites for bone grafting.
    Biomacromolecules 10/2010; 11(10):2545-9. · 5.37 Impact Factor
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    ABSTRACT: The last decade has witnessed the development of a variety of single nanoparticle spectroscopy methods. This has facilitated unprecedented growth of knowledge and understanding of fascinating optical properties of individual metal nanoparticles. This has opened up exciting possibilities of single nanoparticles for applications in many areas including advanced photonics, biomedical imaging and sensing. The field of single nanoparticles detection and characterization is still growing. This paper reviews recent advances in single nanoparticles spectroscopy using both near-field and far-field optics. It covers spectroscopy methods for extremely small (approximately 1 nm) to relatively large nanoparticles (approximately 200 nm) and their optical properties. Different optical techniques are described. Finally, a perspective on possible practical applications of single nanoparticle spectroscopy focusing on biomedical fields is given.
    Nanoscale 09/2010; 2(9):1560-72. · 6.23 Impact Factor
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    ABSTRACT: We have developed a real-time chemical sensing methodology that integrates transmission terahertz frequency-domain spectroscopy (THz-FDS) with a quartz-based microuidic subsystem. The initial examination of isopropyl alcohol–water (IPA/water) mixtures at frequencies from 0.570 to 0.630 THz exhibited well-behaved transmission performance, showing the potential to reveal detailed spectral information that is usually absent in THz time-domain spectroscopy (THz-TDS). Linear least-squares regression plots at three selected THz frequencies, i.e. 0.580, 0.590 and 0.625 THz, suggested excellent linear signal responses over the entire IPA concentration range with detection responsivities greater than 4.6712 μV/% with R2 > 0.953. The system can potentially achieve a high detection sensitivity owning to the low THz detector noise. The real-time monitoring of sequentially injected IPA/water mixtures displayed fast response potentially approaching ~10 ns which is suitable for studying ultrafast in situ dynamic chemical and biological phenomena. The THz mapping capability of two-stream laminar flow was also demonstrated. The THz microfluidic sensing strategy represents a versatile approach to enable broadband, high spectral and spatial resolution, as well as fast responses for a wide range of chemical and biological applications including real-time, label-free monitoring, sensing and imaging.
    Sensors and Actuators B: Chemical. 184:228–234.