Paper

OXYGEN-PROMOTED CATALYST SINTERING INFLUENCES NUMBER DENSITY, ALIGNMENT, AND WALL NUMBER OF VERTICALLY ALIGNED CARBON NANOTUBES

Wenbo Shi, Jinjing Li, Erik S. Polsen, C. Ryan Oliver, Yikun Zhao, Eric R. Meshot, Michael Barclay, D. Howard Fairbrother, A. John Hart and Desiree L. Plata.  Oxygen-promoted catalyst sintering influences number density, alignment, and wall number of vertically aligned carbon nanotubes. (2017) Nanoscale 2017, 9, 5222-5233. [DOI: 10.1039/C6NR09802A]

A lack of synthetic control and reproducibility during vertically aligned carbon nanotube (CNT) synthesis has stifled many promising applications of organic nanomaterials. Oxygen-containing species are particularly precarious in that they have both beneficial and deleterious effects and are notoriously difficult to control. Here, we demonstrated diatomic oxygen’s ability, independent of water, to tune oxide-supported […]

CONFORMAL ROBOTIC STEREOLITHOGRAPHY

Adam G. Stevens*, C. Ryan Oliver*, Matthieu Kirchmeyer, Jieyuan Wu, Lillian Chin, Erik S. Polsen, Chad Archer, Casey Boyle, Jenna Garber, A. John Hart. Conformal Robotic Stereolithography. (2016) 3D PRINTING AND ADDITIVE MANUFACTURING 2016. [DOI: 10.1089/3dp.2016.0042]

Additive manufacturing by layerwise photopolymerization, commonly called stereolithography (SLA), is attractive due to its high resolution and diversity of materials chemistry. However, traditional SLA methods are restricted to planar substrates and planar layers that are perpendicular to a single-axis build direction. Here, we present a robotic system that is capable of maskless layerwise photopolymerization on curved surfaces, enabling production of large-area conformal patterns and the construction of […]

HIGH-FIDELITY REPLICA MOLDING OF GLASSY LIQUID CRYSTALLINE POLYMER MICROSTRUCTURES

Hangbo Zhao, Jeong Jae Wie, Davor Copic, C. Ryan Oliver, Alvin Orbaek White, Sanha Kim, A. John Hart.  Scalable high-fidelity fabrication of glassy liquid crystalline polymer microstructures by replica molding. (2015) ACS Applied Materials and Interfaces 2016.  [DOI: 10.1021/acsami.6b00785]

Liquid crystalline polymers have recently been engineered to exhibit complex macroscopic shape adaptivity, including optically- and thermally- driven bending, self-sustaining oscillation, torsional motion, and three dimensional folding. Miniaturization of these novel materials is of great interest for both fundamental study of processing conditions and for the development of shape-changing microdevices. Here, we present a scalable method for high-fidelity replica molding of glassy […]

ON-DEMAND ISOLATION AND MANIPULATION OF C. ELEGANS BY IN VITRO MASKLESS PHOTOPATTERNING.

C.R. Oliver, E. Gourgou, D. Bazopoulou, N. Chronis, A. John Hart. On-demand isolation and manipulation of C. elegans by in vitro maskless photopatterning. PLOS One 2016. doi: 10.1371/journal.pone.0145935

Caenorhabditis elegans (C. elegans) is a model organism for understanding aging and studying animal behavior. Microfluidic assay techniques have brought widespread advances in C.elegans research; however, traditional microfluidic assays such as those based on soft lithography require time-consuming design and fabrication cycles and offer limited flexibility in changing the geometric environment during experimentation. We present a technique for maskless photopatterning of a biocompatible hydrogel on an NGM (Agar) substrate, enabling dynamic manipulation of […]

A CELLULAR MANUFACTURING PROCESS FOR A FULL-SCALE BIODIESEL MICROREACTOR

Richard E. Billo, C. Ryan Oliver, Rachaneewan Charoenwat, Brian H. Dennis, Paul A. Wilsone, John W. Priest, Heather Beardsley.  A cellular manufacturing process for a full-scale biodiesel microreactor.  J. Manuf Syst. In Press. Available online 8/7/2014.  http://dx.doi.org/10.1016/j.jmsy.2014.07.004]

A cellular manufacturing process was developed for fabrication and assembly of a full-scale biodiesel microreactor capable of producing biodiesel fuel at the rate of 2.47 L/min and at a capacity of over 1.2 million liters of fuel per year. The scale-up of themicroreactor was done through fabrication of over 14,000 individual microchannel laminae, and assembly of these laminae into a hierarchical system of modules and manifolds, thus duplicating many times over […]

ROBOFURNACE: A SEMI-AUTOMATED LABORATORY CVD SYSTEM FOR HIGH-THROUGHPUT NANOMATERIAL SYNTHESIS AND PROCESS DISCOVERY

C.R. Oliver, W. Westrick, J. Koehler, A. Brieland-Shoultz, I. Anagnostopoulos-Politis, T. Cruz-Gonazalez, A.J. Hart. Robofurnace: A semi-automated laboratory CVD system for high-throughput nanomaterial synthesis and  process discovery. Review of Scientific Instruments. 84(11):115105, 2013. [http://dx.doi.org/10.1063/1.4826275]

Laboratory research and development on new materials, such as nanostructured thin films, often utilizes manual equipment such as tube furnaces due to its relatively low cost and ease of setup. However, these systems can be prone to inconsistent outcomes due to variations in standard operating procedures and limitations in performance such as heating and cooling rates restrict the parameter space that can be explored. Perhaps more importantly, maximization of research throughput […]

A STATISTICAL ANALYSIS OF VARIATION IN LABORATORY GROWTH OF CARBON NANOTUBE FORESTS AND RECOMMENDATIONS FOR IMPROVEMENT OF PROCESS CONSISTENCY

C.R. Oliver, E.S. Polsen, E.R. Meshot, S. Tawfick, S.J. Park, M. Bedewy, A.J. Hart. A statistical analysis of variation in laboratory growth of carbon nanotube forests and recommendations for improvement of process consistency. ACS Nano 7(4):3565–3580, 2013. [http://dx.doi.org/10.1021/nn400507y]

While many promising applications have been demonstrated for vertically aligned carbon nanotube (CNT) forests, lack of consistency in results (e.g., CNT quality, height, and density) continues to hinder knowledge transfer and commercialization. For example, it is well known that CNT growth can be influenced by small concentrations of water vapor, carbon deposits on the reactor wall, and experiment-to-experiment variations in pressure within the reaction chamber. However, […]

SYNTHESIS OF TALL CARPETS OF VERTICALLY ALIGNED CNTS VIA IN SITU GENERATION OF WATER VAPOR BY PREHEATING OF ADDED OXYGEN

G.D. Nessim, A. Al-Obeidi, H. Grisaru, E.S. Polsen, C.R. Oliver, T. Zimrin, A.J. Hart, D. Aurbach, C.V. Thompson. Synthesis of tall carpets of vertically aligned carbon nanotubes via in situ generation of water vapor by preheating of added oxygen. Carbon 50:4002-4009, 2012. [http://dx.doi.org/10.1016/j.carbon.2012.04.043]

Dense millimeter-tall carpets of vertically aligned carbon nanotubes (VACNTs) were grown using thermal chemical vapor deposition (CVD) from ethylene and hydrogen gases with two or three independently controlled hot zones while introducing controlled ?ows of oxygen. Through preheating, oxygen and hydrogen reacted through a multi-step reaction toform water, enabling the growth of tall CNT carpets. This process showed a large tolerance […]

ENGINEERING OF MICRO- AND NANOSTRUCTURED SURFACES WITH ANISOTROPIC GEOMETRIES AND PROPERTIES

S. Tawfick, M. De Volder, D. Copic, S. Park, E.S. Polsen, C.R. Oliver, M.J. Roberts, A.J. Hart. Engineering of micro- and nanostructured surfaces with anisotropic geometries and properties. Advanced Materials. [http://dx.doi.org/10.1002/adma.201103796]

Widespread approaches to fabricate surfaces with robust micro- and nanostructured topographies have been stimulated by opportunities to enhance interface performance by combining physical and chemical effects. In particular, arrays of asymmetric surface features, such as arrays of grooves, inclined pillars, and helical protrusions, have been shown to impart unique anisotropy in properties including wetting, adhesion, thermal and/or electrical conductivity, optical activity, and capability to direct cell growth. These properties are of wide […]