Wenchuang (Walter) Hu Homepage

We focus on integrating nanoscale elements of electronics, chemistry, and biology. Such nano-bio-engineering fusion may provide rare opportunities to explore new science and applications

Lithographic Nanofabrication
"Top-down" or nanolithographic fabrication based on e-beam lithography and nanoimprint lithography is applied to make single digit (2-10 nm) low-dimensional structures with size comparable to chemical synthesis, but with better controlability and uniformity. We also investigate material property, metrology, and "strange" phenomena emerged with these nanostructures.

Publications:
Krutarth Trivedi, Hyungsang Yuk, Carlo Floresca, Moon J. Kim, and Walter Hu, High performance sub-5 nm “top-down” silicon nanowire transistors, submitted.

Krutarth Trivedi, Carlo Floresca, Sangjeoung Kim, Hyunjin Kim, Deogbae Kim, Jaehyun Kim, Moon J. Kim, and Walter Hu, "Void-free filling of spin-on dielectric in 22 nm wide ultrahigh aspect ratio Si trenches," J. Vac. Sci. Technol. B, 27(6), pp. 3145-3148, 2009.PDF

K. Trivedi and W. Hu, “Nanogratings containing sub-10-nm wide trenches by dimension reduction from sloped polymer profile”, J. Vac. Sci. Technol. B. 27(6), pp. 2854-2857, 2009. PDF

L. Tao, S. Ramachandran, C. T. Nelson, M. Lin, L. J. Overzet, M. Goeckner, G. Lee, C. G. Willson, W. Wu, and W. Hu , “Durable diamond-like carbon templates for UV nanoimprint lithography,” Nanotechnology 19(10) 105302/1-105302/7, 2008. PDF

W. Hu , K. Sarveswaran , M. Lieberman, and G. H. Bernstein, “High-resolution electron beam lithography and DNA nano-patterning for molecular QCA,” IEEE Trans. Nanotechnol., 4 (3), pp. 312-316, 2005. PDF

W. Hu , G. H. Bernstein, K. Sarveswaran , and M. Lieberman, “Sub-10 nm e-beam lithography using cold development of PMMA,” J. Vac. Sci. Technol. B 22 (4), pp. 1711–1716, 2004. PDF

Si NanoWire Electronic Biosensor
Si nanowires field effect transistors (FETs) are fabricated using CMOS process on Si-on-insulator wafers. Chemical receptors are anchored on these SiNWs for label-free detection of biospecies for a wide-range of applications, e.g. disease diagnostics and enviromental monitoring. Advantages of nanoelectronic biosensor is its ultrasensitivity, real time, low cost, and small form factor.

Publications:
Ruhai Tian, Suresh Regonda, Jinming Gao, and Walter Hu, Reliable multi-Si-nanowires FETs for ultrasensitive protein detection at sub-femtomolar levels, submitted.

Suresh Regonda, Mukti Aryal, and Wenchuang (Walter) Hu, "Stability of HSQ nanolines defined by e-beam lithography for Si nanowire field effect transistors," J. Vac. Sci. Technol. B. 26(6), pp. 2247-2251, 2008. PDF

(Invited) W. Hu , F. Yoon, S. Regonda, P. Fernandes, E. M. Vogel, F. Buyukserin, X. Zhao, J. Gao, “ Lithographically Defined Si Nanowire Field Effect Transistors for Biochemical Sensing ,” IEEE International Conference on Nanotechnology (IEEE NANO 2008).

Nanoimprinted Organic Solar Cells
We use nanoimprint to create an optimal nano-morphology of vertically interdigitized and bi-continuous donor and acceptor materials for high efficiency in organic solar cells. Nanoimprint can simutaneously control the morphology and chain alignments in polymer, which is a challenge for chemical methods. We are also developing rollable nano-printing to enable low cost fab.

Publications:
Mukti Aryal, Krutarth Trivedi, Walter Hu, "Nano-confinement induced chain alignment in ordered P3HT nanostructures defined by nanoimprint lithography," ACS Nano 3(10), pp. 3085-3090 , 2009. PDF

K. Trivedi, U. S. Bhansali, B. Gnade, and W. Hu, "Fabrication of high density nanochannel
organic light emitting diodes with reduced charge spreading," Nanotechnology 20 (2009) 405204.PDF

Mukti Aryal, Fatih Buyukserin, Kamil Mielczarek, Xiao-Mei Zhao, Jinming Gao, Anvar Zakhidov, and Wenchuang (Walter) Hu, "Imprinted large-scale high density polymer nanopillars for organic solar cells", J. Vac. Sci. Technol. B. 26(6), pp. 2562–2566, 2008. PDF

Biomaterials for Nanomedicine
Combination of top-down nanoimprint lithography and bottom-up self-assembly is developed to make uniform and shape-specific polymer nanoparticles for nanomedicine applications. Molecular agents and drugs can be encapsulated in these polymer nanoparticle platforms for targetted delivery and imaging. We also develop jet roller nanoprinting tool for high-throughput particle production.

Publications:
L. Tao, X.M. Zhao, J. Gao, and W Hu , “Lithographically defined uniform worm-shaped polymeric nanoparticles,” Nanotechnology 21, 095301, doi: 10.1088/0957-4484/21/10/109802, 2010.PDF

Fatih Buyukserin, Mukti Aryal, Jinming Gao, and Walter Hu, “Fabrication of Polymeric Nanorods Using Bilayer Nanoimprint Lithography," Small, 5 (14), pp. 1632-1636, 2009.PDF.

L. Tao, A. Crouch, F. Yoon, B. Lee, H. Hillebrenner, J. Setti Guthi, J. Kim, and J. M. Gao, and W. Hu ,“Induced patterning of organic and inorganic materials by spatially discrete surface energy,” J. Vac. Sci. Tech. B. 25 (6), pp. 1993-1997, 2007. PDF

Nanostructures for Tissue Engin.
Nanoimprint is used to make nanogratings as scaffolds for tissue engineering. By elongating pillars during mold release, very high aspect ratio pillars like nano-grass are made. Gratings can guide cell alignment and elongation, while nano-grass strongly inhibits cell adhesion despite of surface chemistry. These nanoscaffolds serve as a testbed to study cell-substratrum interaction at the nanoscale.

Publications:
Adam S. Crouch, D. Miller, Kevin J. Luebke, and W. Hu, "Inhibited cell spreading on polystyrene nanopillars fabricated by nanoimprinting and in situ elongation", Nanotechnology, in press.

Adam S. Crouch, D. Miller, Kevin J. Luebke, and W. Hu, “Correlation of Anisotropic Cell Behaviors with Topographic Aspect Ratio,” Biomaterials 30, pp. 1560-1567, 2009. PDF

W. Hu , E. Yim , R. M. Reano , K. W. Leong , and S. W. Pang, “ Effects of nanoimprinted patterns in tissue-culture polystyrene on cell behavior ”, J. Vac. Sci. Technol. B. 23(6), pp. 2984-2989, 2005. PDF

Thanks to our research sponsors:
National Science Foundation