Assistant Professor of Chemical and Biomolecular Engineering
<strong>Spring 2016</strong>: CHEE 3321, Analytical Methods.
<strong>Fall 2015</strong>: CHEE 6333, Transport Processes.
Spring 2015: CHEE 3321, Analytical Methods.
Fall 2014: CHEE 6333, Transport Processes.
Spring 2014: CHEE 3363, Fluid Mechanics for Chemical Engineers.
Fall 2013: CHEE 6333, Transport Processes.
Spring 2013: CHEE 3363, Fluid Mechanics for Chemical Engineers.
Fall 2012: CHEE 6333, Transport Processes.
Fall 2012: CHEE 6327, Experimental Methods in Chemical Engineering (lecturer).
Spring 2012: CHEE 3363, Fluid Mechanics for Chemical Engineers.
Fall 2011: CHEE 6333, Transport Processes.
Fall 2011: CHEE 6327, Experimental Methods in Chemical Engineering (lecturer).
Spring 2011: CHEE 3363, Fluid Mechanics for Chemical Engineers.
Fall 2010: CHEE 6327, Experimental Methods in Chemical Engineering (lecturer).
Spring 2010: CHEE 3363, Fluid Mechanics for Chemical Engineers.
We are broadly interested in the interaction between complex fluids (polymers, colloids, nanoparticles, bacteria, protozoa, cells) and the surfaces that confine or support them. These interactions appear ubiquitously in applications in petroleum engineering (drilling media, microbial corrosion), environmental engineering (biofouling, bioremediation), materials engineering (rapid prototyping, direct-write assembly), and biodefense (diagnostics, biodetection). Moreover, this broad class of problems is scientifically fascinating: both the chemical and mechanical properties of surfaces can influence the adhesion, diffusion, motility, and phase behavior of complex fluids. Our current research thrusts include:
Flow and Transport of Complex Fluids in Confinement
Processes involving the flow of complex fluids in confined geometries appear prominently in technological, environmental, and physiological settings. Confinement effects strongly influence multiphase transport properties, and are thus relevant for technological applications involving porous media, such as gel electrophoresis and chromatography, and critical resource applications, such as water remediation and oil extraction from nonconventional sources. Despite their ubiquity, the science underlying these processes remains poorly understood. We use confocal and light microscopy to directly image the flow of complex fluids in microchannels. By quantifying the flow behavior in a variety of controlled microscale geometries using high-throughput tracking algorithms, we will identify the effects of confinement on the flow properties of complex fluids and inspire new designs for manipulating these materials on the microscale. Currently, we are investigating the effects of confinement on the structure, dynamics, and phase behavior of quiescent and flowing model colloid-polymer mixtures (in part with Jeremy Palmer), and the transport properties of nanoparticles in microfabricated post arrays and polymer solutions (with Ramanan Krishnamoorti).
Near-Surface Motility of Microorganisms
Over 99% of bacteria live in bacterial biofilms, which are surface-associated communities surrounded by a protective extracellular matrix that increases the resistance of bacteria to environmental and host stresses. These stress-resistant biofilms thus cause significant problems both in human health and in industrial processes. Preventing their formation requires understanding how bacteria adapt their motility mechanisms near surfaces. We directly image the motion of bacteria and other microorganisms near engineered surfaces with confocal and light microscopy. By translating microscopy images into a searchable database of trajectories, we will elucidate the effects of surface properties on microbial motility and inspire new strategies to create antifouling materials. Currently, we are quantifying the near-surface motility mechanisms of model bacteria on engineered surfaces, and applying insights gained from these studies to understand how bacteria respond to self-cleaning surfaces (with Megan Robertson) and identifying appendage-driven attachment mechanisms (in part with Patrick Cirino).
Biomedical Applications: Lateral Flow Assays and Protein Crystallization
We apply the fundamental scientific principles identified in other studies to address critical needs in public health. With Richard Willson, we are applying our insights into nanoparticle transport in porous media to design sensitive, specific, inexpensive, and portable diagnostics based on lateral flow immunoassays (the format used in the common pregnancy test). Our assays employ engineered viral nanoparticles, M13 bacteriophage, as reporters and exhibit sensitivities that are up to one-hundred times greater than conventional gold-nanoparticle-based assays. With Peter Vekilov, we apply our high-throughput imaging methods to study dense liquid protein clusters, which are precursors in which protein crystals subsequently nucleate. Understanding the mechanisms that lead to crystallization in biological settings can help to prevent or treat pathologies, including sickle-cell anemia, gout, and amyloid fibers, that are driven by protein crystallization.
- Postdoctoral research associates: Jack Jacob, Yuly Andrea Jaimes-Lizcano
- Graduate students: Michael Byington, Narendra Dewangan, Jinsu Kim, Ryan McLay, Nayoung Park, Ryan Poling-Skutvik, Ryan Roberts, Mohammad Safari, Sumedha Sharma, Maxwell Smith, Vivek Yadav
- Undergraduate students: Tara Mars
Awards & Honors:
Member: American Physical Society, American Chemical Society, American Institute of Chemical Engineers, and the Society of Rheology.
Journal reviewer: Advanced Materials, Biophysical Journal, European Journal of Physics E, Integrative Biology, Langmuir, Journal of Rheology, Measurement Science and Technology, Nanotechnology, Nature Communications, PLoS One, PNAS, RSC Advances, Soft Matter.
Proposal reviewer: American Chemical Society Petroleum Research Fund, National Science Foundation (CBET, DMR, MPS), Leaders Opportunity Fund/Canada Foundation for Innovation, Wellcome Trust/DBT India Alliance, Center for Functional Nanomaterials (Brookhaven National Laboratory), Research Grant Council of Hong Kong.
Journal Papers / Refereed Journal Publications
F. Babayekhorasani, D. E. Dunstan, R. Krishnamoorti, and J. C. Conrad,
“Nanoparticle dispersion in disordered porous media with and without polymer additives.” Soft Matter 12, 5676–5683 [DOI], 2016
H. Chen, A. E. V. Hagström, J. Kim, G. Garvey, A. Paterson, F. Ruiz-Ruiz, B. Raja, U. Strych, M. Rito-Palomares, K. Kourentzi, J. C. Conrad, R. L. Atmar, and R. C. Wilson,
“Flotation immunoassay: masking the signal from free reporters in sandwich immunoassays.” Sci. Rep. 2, 24297 [DOI], 2016
L. Ni, S. Yang, R. Zhang, Z. Jin, H. Chen, J. C. Conrad, and F. Jin,
“Bacteria differently deploy type-IV pili on surfaces to adapt to nutrient availability.” npj Biofilms Microbiomes 2, 15029 [DOI], 2016
M. C. Byington, M. S. Safari, J. C. Conrad, and P. G. Vekilov,
“Protein conformational flexibility enables the formation of dense liquid clusters: tests using solution shear.” J. Phys. Chem. Lett. 7, 2339–2345 [DOI], 2016
R. Pandey and J. C. Conrad,
“Gelation in mixtures of polymers and bidisperse colloids.” Phys. Rev. E 93, 012610 [DOI], 2016
S. Sharma*, Y. A. Jaimes-Lizcano*, R. B. McLay, P. C. Cirino, and J. C. Conrad,
“Sub-nanometric roughness affects deposition and mobile adhesion of Escherichia coli on silanized glass surfaces.” Langmuir 32, 5422–5433 [DOI], 2016
V. Yadav, A. V. Harkin, M. L. Robertson, and J. C. Conrad,
“Hysteretic memory in pH-response of water contact angle on poly(acrylic acid) brushes.” Soft Matter 12, 3589–3599 [DOI], 2016
J. D. C. Jacob, K. He, S. T. Retterer, R. Krishnamoorti, and J. C. Conrad,
“Diffusive dynamics of nanoparticles in ultra-confined media.” Soft Matter 11, 7515–7524 [DOI], 2015
J. Kim, M. Adhikari, S. Dhamane, A. E. V. Hagström, K. Kourentzi, U. Strych, R. C. Willson, and J. C. Conrad,
“Detection of viruses by counting single fluorescent genetically biotinylated reporter immunophage using a lateral flow assay.” ACS Appl. Mater. Interfaces 7, 2891–2898 [DOI], 2015
M. Adhikari, U. Strych, J. Kim, H. Goux, S. Dhamane, M.-V. Poongavanam, A. E. V. Hagström, K. Kourentzi, J. C. Conrad, and R. C. Willson,
“Aptamer-phage reporters for ultrasensitive lateral flow assays.” Anal. Chem. 87, 11660–11665 [DOI], 2015
M. S. Safari, M. A. Vorontsova, R. Poling-Skutvik, P. G. Vekilov, and J. C. Conrad,
“Differential dynamic microscopy of weakly scattering and polydisperse protein-rich clusters.” Phys. Rev. E 92, 042712 [DOI], 2015
R. Poling-Skutvik, R. Krishnamoorti, and J. C. Conrad,
“Size-dependent dynamics of nanoparticles in unentangled solutions of polyelectrolytes.” ACS Macro Lett. 4, 1169–1173 [DOI], 2015
S. He, Y. Jiang, J. C. Conrad, and G. Qin,
“Molecular simulation of natural gas transport and storage in shale rocks with heterogeneous nano-pore structures.” J. Petrol. Sci. Eng. 133, 401–409 [DOI], 2015
F. Babaye Khorasani, R. Poling-Skutvik, R. Krishnamoorti, and J. C. Conrad,
“Mobility of nanoparticles in semidilute polyelectrolyte solutions.” Macromolecules 47, 5328–5333 [DOI], 2014
K. He, S. T. Retterer, B. R. Srijanto, J. C. Conrad, and R. Krishnamoorti,
“Transport and dispersion of nanoparticles in periodic nanopost arrays.” ACS Nano 8, 4221–4227 [DOI], 2014
R. Pandey, M. Spannuth, and J. C. Conrad,
“Confocal imaging of confined quiescent and flowing colloid-polymer mixtures.” J. Vis. Exp. e51461 [DOI], 2014
S. Sharma and J. C. Conrad,
“Attachment from flow of Escherichia coli bacteria onto silanized glass substrates.” Langmuir 30, 11147–11155 [DOI], 2014
K. He, F. Babaye Khorasani, S. T. Retterer, D. K. Thomas, J. C. Conrad, and R. Krishnamoorti,
“Diffusive dynamics of nanoparticles in arrays of nanoposts.” ACS Nano 7, 5122–5130 [DOI], 2013
R. Pandey and J. C. Conrad,
“Dynamics of confined depletion mixtures of polymers and bidispersed colloids.” Soft Matter 9, 10617–10626 [DOI], 2013
S. P. George, H. Chen, J. C. Conrad, and S. Khurana,
“Regulation of directional cell migration by membrane-induced actin bundling.” J. Cell. Sci. 126, 312–326 [DOI], 2013
J. C. Conrad,
“Physics of bacterial near-surface motility using flagella and type IV pili: implications for biofilm formation.” Res. Microbiol. 163, 619–629 [DOI], 2012
J. C. Conrad,
“Quantifying collective behavior in mammalian cells.” Proc. Natl. Acad. Sci. USA 109, 7591–7592 [DOI], 2012
K. He, M. Spannuth, J. C. Conrad, and R. Krishnamoorti,
“Diffusive dynamics of nanoparticles in aqueous dispersions.” Soft Matter 8, 11933–11938 [DOI], 2012
M. Spannuth and J. C. Conrad,
“Confinement-induced solidification of colloid-polymer depletion mixtures.” Phys. Rev. Lett. 109, 028301 [DOI], 2012
R. F. Shepherd, J. C. Conrad, T. Sabuwala, G. G. Gioia, and J. A. Lewis,
“Structural evolution of cuboidal granular media.” Soft Matter 8, 4795–4801 [DOI], 2012
R. Pandey and J. C. Conrad,
“Effects of attraction strength on microchannel flow of colloid-polymer depletion mixtures.” Soft Matter 8, 10695-10703 [DOI], 2012
F. Jin*, J. C. Conrad*, M. L. Gibiansky, and G. C. L. Wong (*Equal contribution),
“Bacteria use type-IV pili to slingshot on surfaces.” Proc. Natl. Acad. Sci. USA 108, 12617–12622 [DOI], 2011
J. C. Conrad*, M. L. Gibiansky*, F. Jin, V. D. Gordon, D. A. Motto, M. A. Mathewson, W. G. Stopka, D. C. Zelasko, J. D. Shrout, and G. C. L. Wong (*Equal contribution),
“Flagella and pili-mediated near-surface single-cell motility mechanisms in P. aeruginosa.” Biophys. J.100, 1608–1616 [DOI], 2011
J. C. Conrad, S. R. Ferreira, J. Yoshikawa, R. F. Shepherd, B. Y. Ahn, and J. A. Lewis,
“Designing colloidal suspensions for directed materials assembly.” Curr. Opin. Colloid Interface Sci., 16, 71–79 [DOI], 2011
J. C. Conrad and J. A. Lewis,
“Structural evolution of colloidal gels during constricted microchannel flow.” Langmuir 26, 6102–6107 [DOI], 2010
J. C. Conrad, H. M. Wyss, S. Manley, V. Trappe, K. Miyazaki, L. J. Kaufman, A. B. Schofield, D. R. Reichman, and D. A. Weitz,
“Arrested fluid-fluid phase separation in depletion systems: implications of the characteristic length on gel formation and rheology.” J. Rheol. 54, 412–438 [DOI], 2010
M. L. Gibiansky*, J. C. Conrad*, F. Jin, V. D. Gordon, D. A. Motto, M. A. Mathewson, W. G. Stopka, D. C. Zelasko, J. D. Shrout, and G. C. L. Wong (*Equal contribution),
“Bacteria use type IV pili to walk upright and detach from surfaces.” Science 330, 197 [DOI], 2010
D. J. Harris, J. C. Conrad, and J. A. Lewis,
“Evaporative lithographic patterning of binary colloidal films.” Phil. Trans. R. Soc. A. 367, 5157–5165 [DOI], 2009
J.C. Conrad and J.A. Lewis,
“Structure of colloidal gels in microchannels.” Langmuir 24, 7628–7635 [DOI], 2008
D.J. Harris, H. Hu, J.C. Conrad, and J.A. Lewis,
“Patterning colloidal films via evaporative lithography.” Phys. Rev. Lett. 98, 148301 [DOI], 2007
J.C. Conrad, P.P. Dhillon, E.R. Weeks, D.R. Reichman, and D.A. Weitz,
“Contribution of slow clusters to the bulk elasticity near the colloidal glass transition.” Phys. Rev. Lett. 97, 265701 [DOI], 2006
P.J. Lu, J.C. Conrad, H.M. Wyss, A.B. Schofield, and D.A. Weitz,
“Fluid of clusters in attractive colloids.” Phys. Rev. Lett. 96, 028306 [DOI], 2006
R.F. Shepherd, J.C. Conrad, S.K. Rhodes, D.R. Link, M. Marquez, D.A. Weitz, and J.A. Lewis,
“Microfluidic assembly of homogeneous and Janus colloid-filled hydrogel granules.”Langmuir 22, 8618–8622 [DOI], 2006
J.C. Conrad, F.W. Starr, and D.A. Weitz,
“Weak correlations between local density and dynamics in liquids near the glass transition.” J. Phys. Chem. B 109, 21235–21240 [DOI], 2005
S. Manley, H.M. Wyss, K. Miyazaki, J.C. Conrad, V. Trappe, L.J. Kaufman, D. R. Reichman, and D. A. Weitz,
“Dynamic arrest in spinodal decomposition as a route to gelation.” Phys. Rev. Lett. 95, 238302 [DOI], 2005