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Search Publications by

Lei Chen (Fed)

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Displaying 1 - 25 of 37

Short-time dental resin biostability and kinetics of enzymatic degradation

May 9, 2018
Xiaohong Wang, Sheng Song, Lei Chen, Christopher M. Stafford, Jirun Sun
Resin biostability is an important concern regarding the durability of methacrylate-based dental resin restorations. Current resin biostability evaluation methods take considerable time, from weeks to months, and provide no short-time kinetics of resin

Deep Silicon Etching for X-Ray Diffraction Devices Fabrication

September 28, 2017
Houxun Miao, Mona Mirzaeimoghri, Lei Chen, Han Wen
We report deep reactive ion etching of silicon gratings via cryogenic and Bosch processes. An aspect ratio of > 50 is achieved for 400 nm period gratings with both processes.

Graphene microcapsule arrays for combinatorial electron microscopy and spectroscopy in liquids

April 27, 2017
Alexander Yulaev, Hongxuan Guo, Evgheni Strelcov, Lei Chen, Ivan Vlasssiouk, Andrei A. Kolmakov
An atomic-scale thickness, molecular impermeability, low atomic number, and mechanical strength make graphene an ideal electron transparent membrane for scanning electron microscopy and spectroscopy in liquids. Here, we present a novel sample platform made

Cryogenic Etching of High Aspect Ratio 400 nm Pitch Silicon Gratings

July 29, 2016
Houxun Miao, Lei Chen, Mona Mirzaeimoghri, Richard Kasica, Han Wen
The cryogenic process and Bosch process are two widely used processes for reactive ion etching of high aspect ratio silicon structures. This paper focuses on the cryogenic deep etching of 400.0 nm pitch silicon gratings. By creating a metal hard mask on

A universal Moire effect and application in x-Ray phase-contrast imaging

April 25, 2016
Houxun Miao, Alireza Panna, Andrew A. Gomella, Eric E. Bennett, sami Znati, Lei Chen, Han Wen
A moiré pattern is created by superimposing two black-and-white or gray-scale patterns of regular geometry, such as two sets of evenly spaced lines. We observed an analogous effect between two transparent phase masks in a light beam which occurs at a

Multifocus microscopy with precise color multi-phase diffractive optics applied in functional neuronal imaging

March 1, 2016
Sara Abrahamsson, Robert Ilic, Jan Wisniewski, Brian Mehl, Liya Yu, Lei Chen, Marcelo I. Davanco, Laura Oudjedi, Jean Bernard Fiche, Bassam Hajj, Xin Jin, Joan Pulupa, Christine Cho, Mustafa Mir, Mohamed El Beheiry, Xavier Darzacq, Marcelo Nollmann, Maxime Dahan, Carl Wu, Timothee Lionnett, James Alexander Liddle, Cornelia Bargmann
Multifocus microscopy (MFM) allows high-resolution instantaneous three-dimensional (3D) imaging and has been applied to study biological specimens ranging from single molecules inside cell nuclei to entire embryos. In any live microscopy application

Electrodeposition of gold to conformally fill high-aspect-ratio nanometric silicon grating trenches: a comparison of pulsed and direct current protocols

October 1, 2015
sami Znati, N Chedid, Houxun Miao, Lei Chen, Han Wen, Eric E. Bennett
Filling high-aspect-ratio trenches with gold is a frequent requirement in the fabrication of X-ray optics as well as micro-electronic components and other fabrication processes. Conformal electrodeposition of gold in sub-micron-width silicon trenches with

Rolled-Up Nanoporous Membranes by Nanoimprint Lithography and Strain Engineering

April 7, 2015
Jaehyun Park, ChangKyu Yoon, Qianru Jin, Lei Chen, David . Gracias
It is extremely challenging to enable nanoscale patterning in three dimensional (3D) curved geometries using conventional nanolithographic approaches. In this paper, we describe a highly parallel approach that combines nanoimprint lithography (NIL) and

Nanoparticle size determination using optical microscopes

October 27, 2014
Ravikiran Attota, Richard J. Kasica, Premsagar P. Kavuri, Hyeong G. Kang, Lei Chen
We present a simple method for size determination of nanoparticles using conventional optical microscopes. The method, called through-focus scanning optical microscopy (TSOM), makes use of the four-dimensional optical information collected at different

Scanning Ion Microscopy with Low Energy Lithium Ions

July 1, 2014
Kevin A. Twedt, Lei Chen, Jabez J. McClelland
Using an ion source based on photoionization of laser-cooled lithium atoms, we have developed a scanning ion microscope with probe sizes of a few tens of nanometers and beam energies from 500 eV to 5 keV. These beam energies are much lower than the typical

Fabrication of 200 nm Period Hard X-Ray Phase Gratings

June 11, 2014
Houxun Miao, Andrew A. Gomella, Nicholas Chedid, Lei Chen, Han Wen
Far field x-ray grating interferometry achieves extraordinary phase sensitivity in imaging weakly absorbing samples, provided that the grating period is within the transverse coherence length of the x-ray source. Here we describe a cost-efficient process

Motionless phase stepping in X-ray phase contrast imaging with a compact source

November 26, 2013
Houxun Miao, Lei Chen, Eric Bennett, Nick Adamo, Andrew A. Gomella, Alexa D. Luca, Ajay Patel, Nicole Y. Morgan, Han Wen
X-ray phase-contrast imaging offers a new way to look into the internal structures of objects. At hard x-ray energies the phase shift in some materials is many times the attenuation of intensity, promising greater image details with less radiation. Grating

Probing coherence in microcavity frequency combs via optical pulse shaping

August 29, 2012
Fahmida Ferdous, Houxun H. Miao, Pei-Hsun Wang, Daniel E. Leaird, Kartik Srinivasan, Lei Chen, Vladimir Aksyuk, Andrew M. Weiner
Recent investigations of microcavity frequency combs based on cascaded four-wave mixing have revealed a link between the evolution of the optical spectrum and the observed temporal coherence. Here we study a silicon nitride microresonator for which the

Spectral Line-by-Line Pulse Shaping of On-Chip Microresonator Frequency Combs

December 1, 2011
Fahmida Ferdous, Houxun H. Miao, Daniel E. Leaird, Kartik Srinivasan, Jian Wang, Lei Chen, Leo T. Varghese, Andrew M. Weiner
We report, for the first time to the best of our knowledge, spectral phase characterization and line-by-line pulse shaping of an optical frequency comb generated by nonlinear wave mixing in a micro-ring resonator. The comb is compressed to a train of near

Effect of Alternating Ar and SF6/C4F8 Gas Flow in Si Nano-Structure Plasma Etching

August 1, 2011
Lei Chen, Vincent K. Luciani, Houxun H. Miao
Si is very reactive to normal plasma etchants such as fluorine based chemicals and the reactions are inherently isotropic. To fabricate small and/or high aspect ratio nanoscale structures in Si, anisotropic profile is necessary. SF6 combined with C4F8 has