WorldCat Identities

Lewis, Jennifer A.

Overview
Works: 44 works in 54 publications in 1 language and 228 library holdings
Roles: Editor, dgs
Publication Timeline
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Most widely held works by Jennifer A Lewis
Polymers in particulate systems : properties and applications( Book )

9 editions published between 2001 and 2002 in English and held by 173 WorldCat member libraries worldwide

This work covers research on the flow and structure of complex particulate suspensions, the adsorption behaviour of polymers, and the consolidation behaviour and mechanical properties of films
Direct ink writing of microvascular networks by Willie Wu( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

Nature is replete with examples of embedded microvascular systems that enable efficient fluid flow and distribution for autonomic healing, cooling, and energy harvesting. The ability to incorporate microvascular networks in functional materials systems is therefore both scientifically and technologically important. In this PhD thesis, the direct-write assembly of planar and 3D biomimetic microvascular networks within polymer and hydrogel matrices is demonstrated. In addition, the influence of network design of fluid transport efficiency is characterized. Planar microvascular networks composed of periodic lattices of uniformal microchannels and hierarchical, branching architectures are constructed by direct-write assembly of a fugitive organic ink. Several advancements are required to facilitate their patterning, including pressure valving, dual ink printing, and dynamic pressure variation to allow tunable control of ink deposition. The hydraulic conductance is measured using a high pressure flow meter as a function of network design. For a constant vascular volume and areal coverage, 2- and 4-generation branched architectures that obey Murray's Law exhibited the highest hydraulic conductivity. These experimental observations are in good agreement with predictions made by analytic models. 3D microvascular networks are fabricated by omnidirectional printing a fugitive organic ink into a photopolymerizable hydrogel matrix that is capped with fluid filler of nearly identical composition. Using this approach, 3D networks of arbitrary design can be patterned. After ink deposition is complete, the matrix and fluid filler are chemically cross-linked via UV irradiation, and the ink is removed by liquefication. Aqueous solutions composed of a triblock copolymer of polyethylene oxide (PEO)-polypropylene oxide (PPO)-PEO constitute the materials system of choice due to their thermal- and concentration-dependent phase behavior. Specifically, the fugitive ink consists of a 23 w/w% PEO-PPO-PEO (Pluronic F127) solution, while matrix (25 w/w%) and fluid filler (20 w/w%) are composed of an acrylate-modified form of the Pluronic F127 that can be subsequently photopolymerized. The ink and matrix concentrations exceed the critical micelle concentration (CMC) of 22 w/w% and thus reside in a physical gel state. At their respective concentrations, they possess an elastic plateau modulus G'> 104 Pa needed for ink filament formation, shape retention, and support during the printing process. By contrast, the fluid filler is formulated below the CMC to facilitate its flow into void spaces created as the nozzle translates through the matrix during printing. After printing is completed, photopolymerization is carried out to yield a chemically cross-linked matrix from which the fugitive ink is removed leaving behind the desired 3D microvascular network. Due to the potential application of 3D microvasularized hydrogels in tissue engineering, dye diffusion through the cured Pluronic F127-diacrylate matrix is investigated via fluorescent microscopy. Image analysis is used to extract diffusion profiles of the dye as a function of time. Extraction of the 1-D Gaussian fitting parameters is used to determine the spatial peak variance ¹̐đ2 and plotted as a function of time to determine the dye diffusivity
Microfluidic assembly and packing dynamics of colloidal granules by Robert F Shepherd( )

1 edition published in 2010 in English and held by 2 WorldCat member libraries worldwide

Granular materials composed of primary colloidal particles are of both scientific and technological importance. The creation of granular systems for fundamental studies of their packing dynamics as well as applications ranging from ceramics processing to low-cost MEMS devices requires the ability to precisely control the granule size, size distribution, shape, and composition. Many methods exist for producing colloidal granules, including fluidized granulation, high shear mixer granulation, and spray drying. However, none of these methods provide adequate control over these important parameters. In this thesis, we use microfluidic-based assembly methods to control granular size, shape, and chemical heterogeneity. We then investigate the packing dynamics of non-spherical granular media using X-ray micro-computed tomography. Monodisperse spheroidal granules composed of colloid-filled hydrogels are created in a sheath-flow microfluidic device. By exploiting the physics of laminar flow in microchannels, drops composed of silica microspheres suspended in an aqueous acrylamide monomer solution are created within a continuous oil phase. The interfacial tension between these two immiscible fluids drives a Rayleigh-mode instability that promotes drop formation. Next, the drops undergo photopolymerization to create an acrylamide hydrogel that freezes in the desired morphology and composition during assembly. To demonstrate the flexibility of this new granulation technique, we assemble both dense homogenous and Janus granules in both spherical and discoid geometries. To produce non-spherical granular media, a lithographic-based microfluidic technique known as stop-flow-lithography is employed. Specifically, colloidal granules and microcomponents in the form of microgear, triangular, discoid, cuboid, and rectangular shapes are produced by this approach. In addition, pathways are demonstrated that allow these building blocks to be transformed into both porous and dense oxide and non-oxide structures. Finally, large quantities of non-spherical colloidal granules of controlled surface roughness are created via stop-flow lithography in cube and rectangular prism geometries of varying polydispersity. Their packing behavior under static and dynamic conditions is investigated by X-ray micro-computed tomography. Their voronoi volume distribution is quantified as a function of granule shape and agitation time using image analysis techniques. These data are then fit to a probabilistic k-Gamma analytical function, which allows one to quantify an order parameter, k, for the jamming condition of low dispersity cube, rectangular prism and bimodal cube granules. We find a steadily decreasing k-value for monodisperse cubes, suggesting local cube rearrangement during consolidation; while monodisperse rectangular granules and a bimodal distribution of cube granules demonstrate a relatively consistent k-value during consolidation, suggesting the local granule configuration remains similar. In each case, the data collapse onto a single master curve, suggesting a qualitatively similar jamming condition during compaction
Manipulating soft materials to direct cell growth in multiple dimensions by Jennifer N Shepherd( )

1 edition published in 2010 in English and held by 2 WorldCat member libraries worldwide

Creating in vitro microenvironments for the study of important biological processes, examples of which include chemotaxis, haptotaxis, axonal guidance and angiogenesis, has been a relevant research focus for many years. Microfabrication techniques involving soft lithography, microfluidic devices and direct-write assembly can be used to create such microenvironments. Soft lithography techniques, which typically include microcontact printing and decal transfer, rely on elastomeric molds, stamps or flexible photomasks to create patterns on or transfer patterns to, an underlying surface; these molds or stamps themselves have also been used for study. In microfluidic devices, small fluid volumes are transported through microchannels via gravity or pressure-driven methods. Biological studies are either conducted within the gradients maintained by laminar flow through the microchannels, or on the residually patterned underlying rigid surface, created via physi-adsorption or through chemical interactions with the surface. Both soft lithography and residual substrate microfluidic patterning approaches yield planar patterned substrates. In contrast, fluidic gradients maintained in microchannels are three-dimensional in nature, but are only used for specific applications⁰́₄e.g. the study of non adherent cell types such as white blood cells. Recent studies, however, have shown that different cell types present important biological differences, in their differentiation, proliferation rates, migration and cell signaling, in two- versus three-dimensional culture systems. Thus, there has been increased interest in the development of three-dimensional fabrication techniques to create microenvironments that can better mimic those found in vivo. Direct-write assembly is an example of a three-dimensional fabrication method that enables the creation of micro-periodic structures with well defined features and an interconnected porous network, 1-100℗æm in size. Other 3D fabrication techniques include electrospinning, solvent/particulate leaching and freeze drying, however they usually yield random three-dimensional structures with an unpredictable porous structure. This thesis describes three different in vitro systems generated using three distinct microfabrication techniques, including a modified decal transfer lithography, a combination of microfluidic assembly and microcontact printing, as well as direct-write assembly, for the study of primary mammalian hippocampal neuron development, one of the most well characterized in vitro models of neurite development currently available
Direct-Write Assembly of Three-Dimensional Photonic Crystals: Conversion of Polymer Scaffolds to Silicon Hollow-Woodpile Structures( Book )

2 editions published in 2005 in English and held by 2 WorldCat member libraries worldwide

Impressive developments in silicon microfabrication are enabling new applications in photonics, microelectromechanical systems (MEMS), and biotechnology. Yet conventional Si microfabrication techniques require expensive masks and time-consuming procedures, including multiple planarization or bonding steps, to generate three-dimensional (3D) structures. In contrast, direct-write approaches, such as laser scanning and ink deposition, provide rapid, flexible routes for fabricating 3D micro-periodic structures. However, these approaches are currently limited to polymeric structures that lack the high refractive index contrast and mechanical integrity required for many applications. To take full advantage of these rapid, flexible assembly techniques, one must develop a replication (or templating) scheme that enables their structural conversion within the temperature constraints imposed by both the organic and inorganic components of the system. Here, we present a novel route for creating 3D Si hollow-woodpile structures that couples direct-write assembly of concentrated polyelectrolyte inks with a sequential silica/Si chemical vapor deposition (CVD) process. The optical properties of the 3D microperiodic woodpiles are characterized after each fabrication step. These interconnected, hollow structures may find potential application as photonic materials, low-cost MEMS, microfluidic networks for heat dissipation, and biological devices
Biomineralized 3-D Nanoparticle Assemblies with Micro-to-Nanoscale Features and Tailored Chemistries( Book )

2 editions published in 2008 in English and held by 2 WorldCat member libraries worldwide

This collaborative research project has focused on the integrated use of robust biomimetic or biological silica assembly processes with shape-preserving chemical conversion reactions to produce freestanding 3-D structures with selectable microscale morphologies, nanoscale features, and tailored, non-silica chemistries. Biomimetic 3-D silica structures have been synthesized through Direct-Write Assembly using polyamine-based inks, followed by templated conformal silicification. With proper selection of ink composition and silicification conditions, robust silica structures were formed that retained the patterned morphology after firing to 1000 C. Such 3-D biomimetic silica and biological silica (diatom frustule) structures were converted into freestanding 3-D silica-free replicas comprised of other oxides or metals through the use of gas/solid reactions. For example, these 3-D silica structures were converted into high surface area, microporous Si replicas through reaction with Mg gas (to yield MgO and Si products) and then selective MgO dissolution. Such Si replicas have, in turn, been converted into noble metal replicas through electroless deposition and selective Si dissolution. The reaction kinetics and micro/nanostructural evolution during such reactions have been examined
Functional nanostructured plasmonic materials: fabrication, simulation, imaging and sensing applications by Jimin Yao( )

1 edition published in 2010 in English and held by 2 WorldCat member libraries worldwide

Surface plasmons, due to their extreme sensitivity to changes in refractive index occurring at a metal/dielectric interface and their ability to significantly enhance electromagnetic fields near a metal, offer exciting opportunities for real-time, fully label free forms of chemical/biological detection and field-enhanced applications including surface enhanced Raman scattering (SERS), and photovoltaics. Novel classes of plasmonic crystals fabricated with precisely controlled arrays of subwavelength metal nanostructures provide a promising platform for the sensing and imaging of surface binding events with micrometer spatial resolution over large areas. Soft lithography, one family of unconventional nanofabrication methods, provides a robust, cost-effective route for generating highly uniform, functional nanostructures over large areas with molecular scale resolution. This dissertation describes the development and utility of several classes of functional, nanostructured plasmonic materials with predictable optical properties. A novel, low-cost optical sensor with atomic scale sensitivity at visible wavelength range was developed by tuning the optical response of a plasmonic crystal to visible wavelengths through optimization of the distribution and thickness of the thin metal film. Sensing and imaging of various surface binding events were studied to demonstrate their utility for label-free detection. Finite-Difference Time-Domain (FDTD) calculations were carried out to model the optical response of the system and gain insight into the physics of the system. New classes of plasmonic crystals were developed using new materials and fabrication methods, in concert with rational design of the device form factor guided by both experiment and computational electrodynamics simulations
Direct-write assembly of 3D microperiodic scaffolds for tissue engineering applications by Sara T Parker( )

1 edition published in 2010 in English and held by 2 WorldCat member libraries worldwide

Structural properties and phase behavior in colloidal suspensions by Stephen A Barr( )

1 edition published in 2010 in English and held by 2 WorldCat member libraries worldwide

In this dissertation I present my research on the effective interactions of colloidal particles induced by a smaller species, as well as the structure of colloidal particles undergoing freeze casting. In this research I have used a wide variety of computational techniques in order to understand these systems. Specifically, in Chapter 2 I study nanoparticle haloing in a system of silica microspheres and highly charged polystyrene nanoparticles. Computer simulations are employed to determine the effective microsphere⁰́₃ microsphere potential induced by the nanoparticles. From these simulations I am also able to determine the degree of nanoparticle adsorption on the microsphere surface. In Chapter 3 I investigate the depletion interaction in a system of charged microspheres and rigid rods. The effect of both rod concentration and screening length is explored. In Chapter 4 I study the effective interactions between charged colloids in the presence of multivalent counterions. The role of colloid charge is investigated and the onset of like-charged attraction is determined and compared with theoretical predictions. In order to study this system, I extended the geometric cluster algorithm to efficiently simulate systems interacting through the Coulomb potential. In Chapter 5 computer simulations are employed to elucidate the experimentally observed crystal phases of the Q and MS-2 virus particles in solution with multivalent salt and non-adsorbing polymer. Freeze casting is studied in Chapter 6. In this process colloidal particles are pushed by an advancing ice front. I use molecular dynamics simulations to study the dynamics of the colloidal particles and the resulting structures formed. iii
Development of soft lithography based non-planar and 3-D photo-patterning techniques by Audrey M Bowen( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

The fusion of soft lithography fabrication processes and optical lithography has been demonstrated in the literature. The focus of this thesis is on the adaptation of soft lithography protocols and further understanding of the materials chemistry of PDMS that allows for fabrication of soft optical lithography masks. A collection of new methods for fabrication of photolithography masks that are used in new forms of 3D patterning, such as patterning on non-planar (3D) surfaces and fabricating multi-height (3D) photoresist structures, is presented. The mask fabrication processes utilize novel approaches to soft lithography that allow for desired optical properties to be easily programmed into the masks. This body of work progresses from the simplest optics, binary modulation of intensity through optically dense mask elements, to grayscale mask elements that vary in optical density and thus allow for single step multi-intensity exposures, and finally to a stamp fabrication approach that results in features with triangular cross-sections that are then used to transfer the patterns into application enabling materials for use in a number of systems that require careful manipulation of light-matter interactions. By harnessing both the benefits of soft lithography and optical lithography, these new patterning protocols provide more efficient, lower cost, methods for achieving novel patterning in forms that prove to be extremely challenging with traditional lithographic processes
Shape and chemically anisotropic colloidal particles: A theoretical study of their structure, phase behavior, and slow dynamics by Mukta Tripathy( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

A detailed non-equilibrium state diagram of shape-anisotropic particle fluids is constructed. The effects of particle shape are explored using Naive Mode Coupling Theory (NMCT), and a single particle Non-linear Langevin Equation (NLE) theory. The dynamical behavior of non-ergodic fluids are discussed. We employ a rotationally frozen approach to NMCT in order to determine a transition to center of mass (translational) localization. Both ideal and kinetic glass transitions are found to be highly shape dependent, and uniformly increase with particle dimensionality. The glass transition volume fraction of quasi 1- and 2- dimensional particles fall monotonically with the number of sites (aspect ratio), while 3-dimensional particles display a non-monotonic dependence of glassy vitrification on the number of sites. Introducing interparticle attractions results in a far more complex state diagram. The ideal non-ergodic boundary shows a glass-fluid-gel re-entrance previously predicted for spherical particle fluids. The non-ergodic region of the state diagram presents qualitatively different dynamics in different regimes. They are qualified by the different behaviors of the NLE dynamic free energy. The caging dominated, repulsive glass regime is characterized by long localization lengths and barrier locations, dictated by repulsive hard core interactions, while the bonding dominated gel region has short localization lengths (commensurate with the attraction range), and barrier locations. There exists a small region of the state diagram which is qualified by both glassy and gel localization lengths in the dynamic free energy. A much larger (high volume fraction, and high attraction strength) region of phase space is characterized by short gel-like localization lengths, and long barrier locations. The region is called the attractive glass and represents a 2-step relaxation process whereby a particle first breaks attractive physical bonds, and then escapes its topological cage. The dynamic fragility of fluids are highly particle shape dependent. It increases with particle dimensionality and falls with aspect ratio for quasi 1- and 2- dimentional particles. An ultralocal limit analysis of the NLE theory predicts universalities in the behavior of relaxation times, and elastic moduli. The equlibrium phase diagram of chemically anisotropic Janus spheres and Janus rods are calculated employing a mean field Random Phase Approximation. The calculations for Janus rods are corroborated by the full liquid state Reference Interaction Site Model theory. The Janus particles consist of attractive and repulsive regions. Both rods and spheres display rich phase behavior. The phase diagrams of these systems display fluid, macrophase separated, attraction driven microphase separated, repulsion driven microphase separated and crystalline regimes. Macrophase separation is predicted in highly attractive low volume fraction systems. Attraction driven microphase separation is charaterized by long length scale divergences, where the ordering length scale determines the microphase ordered structures. The ordering length scale of repulsion driven microphase separation is determined by the repulsive range. At the high volume fractions, particles forgo the enthalpic considerations of attractions and repulsions to satisfy hard core constraints and maximize vibrational entropy. This results in site length scale ordering in rods, and the sphere length scale ordering in Janus spheres, i.e., crystallization. A change in the Janus balance of both rods and spheres results in quantitative changes in spinodal temperatures and the position of phase boundaries. However, a change in the block sequence of Janus rods causes qualitative changes in the type of microphase ordered state, and induces prominent features (such as the Lifshitz point) in the phase diagrams of these systems. A detailed study of the number of nearest neighbors in Janus rod systems reflect a deep connection between this local measure of structure, and the structure factor which represents the most global measure of order
Polymers as directing agents for motions of chemical and biological species by Nihan Yonet Tanyeri( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

This thesis involves descriptions of solid surface modifications with various polymeric materials which were used as a guiding agent for motion of chemical and biological species. Quasi-two dimensional poly(oligoethylene glycol) acrylate polymer brush based molecular conduits have been designed with the goal of regulating and controlling the diffusive transport of molecular, e.g. organic dyes, and ionic species, e.g. AuCl4-, and Cu2+ ions, along predefined 2-D pathways. The transport of these chemical species has been examined by both fluorescence and dark field microscopy. The polymer brushes were formed through microcontact printing of an initiator, followed by surface-initiated Atom Transfer Radical Polymerization (SI-ATRP). SI-ATRP enables both 2-D patterning with a resolution of about 1 micrometer, and control over the resultant polymer brush thickness (which was varied from 10-100 nm). A hydrophilic poly(oligoethylene glycol) acrylate brushe was selected because of its potential to dissolve a wide range of hydrophilic species. The transport of fluorescent species can be directly followed. A non-lithographic fabrication method was developed for microfluidic devices used in the diffusion studies. Singular channel microfluidic device was utilized to study the directed organic dye diffusion. The AuCl4-, and Cu2+ ion transport was studied by designing molecular devices with two microfluidic channels. We have demonstrated that the various species of interest diffuse much more rapidly along the predefined pathway than along the bare (polymer brush free) regions of the substrate, demonstrating that diffusive conduits for molecular transport can indeed be formed. The protein resistance of poly(N-isopropylacrylamide) (PNIPAM) brushes grafted from silicon wafers was investigated as a function of the chain molecular weight, grafting density, and temperature. Above the lower critical solution temperature (LCST) of 32°C, the collapse of the water swollen chains, determined by ellipsometry, depends on the grafting density and molecular weight. Ellipsometry, radio assay, and fluorescence imaging demonstrated that, below the LCST, the brushes repel protein as effectively as oligoethylene oxide terminated monolayers. Above 32°C, very low levels of protein adsorb on densely grafted brushes, and the amounts of adsorbed protein increase with decreasing brush grafting densities. Brushes that do not exhibit a collapse transition also bind protein, even though the chains remain extended above the LCST. These findings suggest possible mechanisms underlying protein interactions with end-grafted PNIPAM brushes. 3D porous materials on solid surfaces were built to mimic the corneal basement membrane so that we can monitor direction of the corneal epithelia cells behaviors as the surface topography changes. We have used colloidal crystal templating approach to build the 3D porous structures. Polystyrene (PS) colloids were crystallized in a flow cell. The crystals were filled with acrylamide precursor (including photoinitiator, crosslinker) in the oxygen free aqueous solution. After polymerization of acrylamide under UV exposure, PS colloids were dissolved in chloroform. Thus, 3D porous polyacrylamide hydrogels have been fabricated. The various pore sizes at the 3D porous surface have been obtained by using PS colloids with the colloid diameters ranging from 450 nm to 4000 nm. Human corneal epithelial cell growth, morphology change and adhesion studies have been conducted on the porous polyacrylamide scaffolds. The effect of pore size on human corneal epithelial cell function has been investigated
Unconventional structured semiconductors and their applications in optoelectronics and photovoltaics by Xiaoying Guo( )

1 edition published in 2010 in English and held by 2 WorldCat member libraries worldwide

Correction: 3D polymer objects with electronic components interconnected via conformally printed electrodes( )

1 edition published in 2018 in English and held by 1 WorldCat member library worldwide

Abstract : Correction for '3D polymer objects with electronic components interconnected via conformally printed electrodes' by Yejin Jo, et al., Nanoscale, 2017, 9, 14798–14803
Structural and plasmonic properties of gold nanocrystals by Sean Sivapalan( )

1 edition published in 2013 in English and held by 1 WorldCat member library worldwide

Structure and property evolution during film formation from binary colloidal suspensions by Carlos J Martinez( )

1 edition published in 2002 in English and held by 1 WorldCat member library worldwide

The influence of nonadsorbed polymer on the behavior of weakly flocculated suspensions by Andrea L Ogden( )

1 edition published in 1997 in English and held by 1 WorldCat member library worldwide

Nanoparticle and sol-gel inks for direct-write assembly of functional metallic and metal oxide materials by Eric Brian Duoss( )

1 edition published in 2009 in English and held by 1 WorldCat member library worldwide

The ability to pattern 1D arrays of TiO2 microwires offers precise control of filament diameter and spatial location, enabling a systematic study of microwire TiO2 gas sensors. A model gas sensor consisting of a single layer of parallel microwires is printed with the TiO2-based sol-gel ink in a well-defined, programmable pattern. The as-printed structure is heat treated in air to 600 & deg;C to form anatase TiO2. After heat treatment, the TiO2 wire diameter is measured as (628 +/- 13 nm). Gas sensing measurements on the TiO2 microwire array performed at elevated temperatures (200--300 & deg;C) indicate high sensitivity towards NO2 and CO gases, with estimated sensitivity limits in the sub-ppm range for NO2 and single ppm range for CO. Under ambient conditions, the TiO2 microwire array responds quite significantly and reversibly to low NO2 concentrations (down to 0.5 ppm). This is a highly promising result for the creation of low-power, gas sensor devices based upon direct-write assembled TiO2 microwire arrays
Aggregation effects on the rheological sedimentation and drying behavior of colloidal silica suspensions by Joe Jiyou Guo( )

1 edition published in 1998 in English and held by 1 WorldCat member library worldwide

Compositional effects on the chemorheological properties and forming behavior of aqueous alumina-poly (vinyl alcohol) gelcasting suspensions by Sherry L Morissette( )

1 edition published in 1999 in English and held by 1 WorldCat member library worldwide

 
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Audience level: 0.70 (from 0.67 for Polymers i ... to 0.95 for Direct-Wri ...)

Polymers in particulate systems : properties and applications
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Jennifer A. Lewis Professor of Materials Science and Engineering

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English (30)