Hu, Wenchuang‏ (Walter)

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Wenchuang (Walter) Hu is an Associate Professor of Electrical Engineering. He also is the head of the Nanoscale Integration Lab. His research interests include:

  • Nanolithography, Nanofabrication of low dimensional nanostructures
  • Si NanoWire Bio-sensor for environmental monitoring and disease early diagnostics
  • Nanostructured Biomaterials for Nanomedicine and Tissue Engineering
  • Nanostructured Organic Electronics: OFETs and solar cells
  • Micro-, Nanofluidics, Nanoelectronic-Mechanical Systems


Recent Submissions

Now showing 1 - 6 of 6
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    Polystyrene-Coated Interdigitated Microelectrode Array to Detect Free Chlorine Towards IoT Applications
    (Japan Society for Analytical Chemistry, 2018-12-28) Liu, Y.; Liang, Yuchen; Xue, L.; Liu, R.; Tao, J.; Zhou, D.; Zeng, X.; Hu, Wenchuang (Walter); Liang, Yuchen; Hu, Wenchuang (Walter)
    We apply interdigitated microelectrode array (IDA) sensors for water quality monitoring. IDA sensors with an ion-sensitive coating show higher sensitivity of about 600 mV with the hypochlorite ion concentration increasing from 0 to 10 ppm more than the traditional sensing method. The response mechanism and selectivity have been studied. Several material components that affect the sensing process were explored. Coupling agents and plasticizer were introduced into the coating material to improve the coating material quality and its adhesion to the electrodes. The stability/repeatability and linearity have been significantly improved. ©2019, The Japan Society for Analytical Chemistry.
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    Room Temperature Operation of Directly Patterned Perovskite Distributed Feedback Light Source under Continuous-Wave Optical Pumping
    (Institute of Electrical and Electronics Engineers Inc.) Gharajeh, Abouzar; Haroldson, Ross; Li, Zhitong; Moon, Jiyoung; Balachandran, Balasubramaniam; Hu, Wenchuang (Walter); Zakhidov, Anvar A.; Gu, Qing; 0000 0003 5287 0481 (Zakhidov, AA); 0000-0003-3983-2229 (Zakhidov, AA); 0000-0003-3855-3690 (Gu, Q); Gharajeh, Abouzar; Haroldson, Ross; Li, Zhitong; Moon, Jiyoung; Balachandran, Balasubramaniam; Hu, Wenchuang (Walter); Zakhidov, Anvar A.; Gu, Qing
    We report the first directly patterned perovskite distributed feedback (DFB) resonator with a narrow amplified spontaneous emission (ASE) at pump powers as low as 0.1W/cm², under continuous-wave (CW) optical pumping condition at room temperature.
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    Nanoimprinted Perovskite Metasurface for Enhanced Photoluminescence
    (Optical Soc Amer, 2018-11-05) Wang, Honglei; Liu, Shih-Chia; Balachandran, Balasubramaniam; Moon, Jiyoung; Haroldson, Ross; Li, Zhitong; Ishteev, Artur; Gu, Qing; Zhou, Weidong; Zakhidov, Anvar A.; Hu, Wenchuang (Walter); 0000 0003 5287 0481 (Zakhidov, AA); 0000-0003-3983-2229 (Zakhidov, AA); Wang, Honglei; Balachandran, Balasubramaniam; Moon, Jiyoung; Haroldson, Ross; Li, Zhitong; Gu, Qing; Zakhidov, Anvar A.; Hu, Wenchuang (Walter)
    Recently, solution-processed hybrid halide perovskite has emerged as promising materials for advanced optoelectronic devices such as photovoltaics, photodetectors, light emitting diodes and lasers. In the mean time, all-dielectric metasurfaces with high-index materials have attracted attention due to their low-loss and high-efficient optical resonances. Because of its tunable by composition band gap in the visible frequencies, organolead halide perovskite could serve as a powerful platform for realizing high-index, low-loss metasurfaces. However, direct patterning of perovskite by lithography-based technique is not feasible due to material instability under moisture. Here we report novel organolead halide perovskite metasurfaces created by the cost-effective thermal nanoimprint technology. The nanoimprinted perovskite metasurface showed improved surface morphology and enhanced optical absorption properties. Significantly enhanced optical emission with an eight-fold enhancement in photoluminescence (PL) intensity was observed under room temperature. Temperature-dependent PL of perovskite nanograting metasurface was also investigated. Based on our results, we believe that thermal nanoimprint is a simple and cost-effective technique to fabricate perovskite-based metasurfaces, which could have broad impact on optoelectronic and photonic applications.
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    Bio-Inspired Nanostructures for Enhanced Light Management
    (A V S, 2018-11-05) Wang, Honglei; Liang, Yuchen; Cheng, Samantha; Li, Benjamin; Li, Andrew; Du, George; Hu, Wenchuang (Walter); Wang, Honglei; Liang, Yuchen; Hu, Wenchuang (Walter)
    The biological surface has developed functional structures during long-term evolution, which inspires the development of biomimic materials for optical and optoelectronic applications. For example, the micropapillae and nanofolding structures of rose petals could enhance light absorption and color saturation. Here, the authors report a successful replication of rose hierarchical surface structures by simple and cost-effective processes. A variety of rose structured surfaces were investigated, which confirmed the diversity of functional surface architecture. The polydimethylsiloxane (PDMS) negative replica was formed by casting PDMS solution on top of a rose petal followed by a temperature-assisted curing process. The hierarchical structure was further transferred into photoresist films by ultraviolet nanoimprint using the PDMS replica as molds. The imprinted photoresist films demonstrated uniform replications of rose microconvex cells with nanofolding details in the scale of a square centimeter. Super-hydrophobicity was demonstrated on both PDMS negative replica and photoresist positive replica. The incorporation of photoresist replica on the surface of photodetectors improved the responsivity by 35% to 42% due to enhanced light management effect. This bio-inspired transfer imprint process with PDMS provided a high-fidelity and cost-effective method to reproduce functional structures from biological surfaces. This study also demonstrated the potential of utilizing rose structures in photovoltaic and optoelectronic applications.
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    One-Step Combined-Nanolithography-And-Photolithography for a 2d Photonic Crystal TM Polarizer
    (MDPI AG) Choi, Kyung-Hak; Huh, J.; Cui, Yonghao; Trivedi, Krutarth; Hu, Walter; Ju, B. -K; Lee, Jeong-Bong
    Photonic crystals have been widely investigated since they have great potential to manipulate the flow of light in an ultra-compact-scale and enable numerous innovative applications. 2D slab photonic crystals for the telecommunication C band at around 1550 nm have multi-scale structures that are typically micron-scale waveguides and deep sub-micron-scale air hole arrays. Several steps of nanolithography and photolithography are usually used for the fabrication of multi-scale photonic crystals. In this work, we report a one-step lithography process to pattern both micron and deep sub-micron features simultaneously for the 2D slab photonic crystal using combined-nanoimprint-andphotolithography. As a demonstrator, a 2D silicon photonic crystal transverse magnetic (TM) polarizer was fabricated, and the operation was successfully demonstrated.
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    Effects of Nanostructure Geometry on Nanoimprinted Polymer Photovoltaics
    (RSC Pub, 2014-04-23) Yang, Yi; Mielczarek, Kamil; Aryal, Mukti; Zakhidov, Anvar A.; Hu, Wenchuang (Walter); 0000 0003 5287 0481 (Zakhidov, AA); 2005061514 (Hu, W); Zakhidov, Anvar A.; Hu, Wenchuang (Walter)
    We demonstrate the effects of nanostructure geometry on the nanoimprint induced poly(3-hexylthiophene-2,5-diyl) (P3HT) chain alignment and the performance of nanoimprinted photovoltaic devices. Out-of-plane and in-plane grazing incident X-ray diffraction techniques are employed to characterize the nanoimprint induced chain alignment in P3HT nanogratings with different widths, spacings and heights. We observe the dependence of the crystallite orientation on nanostructure geometry such that a larger width of P3HT nanogratings leads to more edge-on chain alignment while the increase in height gives more vertical alignment. Consequently, P3HT/6,6]-phenyl-C61-butyric-acid-methyl-ester (PCBM) solar cells with the highest density and aspect ratio P3HT nanostructures show the highest power conversion efficiency among others, which is attributed to the efficient charge separation, transport and light absorption.

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