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Dive into the research topics where Stuart Williams is active.

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Featured researches published by Stuart Williams.


Nano Letters | 2009

Photonic Crystal Geometry for Organic Solar Cells

Doo Hyun Ko; John R. Tumbleston; Lei Zhang; Stuart Williams; Joseph M. DeSimone; Rene Lopez; Edward T. Samulski

We report organic solar cells with a photonic crystal nanostructure embossed in the photoactive bulk heterojunction layer, a topography that exhibits a 3-fold enhancement of the absorption in specific regions of the solar spectrum in part through multiple excitation resonances. The photonic crystal geometry is fabricated using a materials-agnostic process called PRINT wherein highly ordered arrays of nanoscale features are readily made in a single processing step over wide areas (approximately 4 cm(2)) that is scalable. We show efficiency improvements of approximately 70% that result not only from greater absorption, but also from electrical enhancements. The methodology is generally applicable to organic solar cells and the experimental findings reported in our manuscript corroborate theoretical expectations.


Advanced Materials | 2008

The Patterning of Sub-500 nm Inorganic Oxide Structures†

Meredith J. Hampton; Stuart Williams; Zhilian Zhou; Janine K. Nunes; Doo Hyun Ko; Joseph L. Templeton; Edward T. Samulski; Joseph M. DeSimone

Elastomeric perfluoropolyether molds are applied to pattern arrays of sub-500 nm inorganic oxide features. This versatile soft-lithography technique can be used to pattern a wide range of materials; in this work inorganic oxides including TiO2 , SnO2 , ZnO, ITO, and BaTiO3 are patterned on a variety of substrates with different aspect ratios. An example of TiO2 posts is shown in the figure.


Nano Letters | 2010

High-Resolution PFPE-based Molding Techniques for Nanofabrication of High-Pattern Density, Sub-20 nm Features: A Fundamental Materials Approach

Stuart Williams; Scott T. Retterer; Rene Lopez; Ricardo Ruiz; Edward T. Samulski; Joseph M. DeSimone

Several perfluoropolyether (PFPE)-based elastomers for high-resolution replica molding applications are explored. The modulus of the elastomeric materials was increased through synthetic and additive approaches while maintaining relatively low surface tension values (<25 mN/m). Using large area (>4 in.(2)) master templates, we experimentally show the relationship between mold resolution and material properties such as modulus and surface tension for materials used in this study. A composite mold approach was used to form flexible molds out of stiff, high modulus materials that allow for replication of sub-20 nm post structures. Sub-100 nm line grating master templates, formed using e-beam lithography, were used to determine the experimental stability of the molding materials. It was observed that as the feature spacing decreased, high modulus PFPE tetramethacrylate (TMA) composite molds were able to effectively replicate the nanograting structures without cracking or tear-out defects that typically occur with high modulus elastomers.


Journal of drug delivery | 2012

Microfabricated Engineered Particle Systems for Respiratory Drug Delivery and Other Pharmaceutical Applications

Andres Garcia; Peter Mack; Stuart Williams; Catherine A. Fromen; Tammy W. Shen; Janet Tully; Jonathan Pillai; Philip J. Kuehl; Mary E. Napier; Joseph M. DeSimone; Benjamin W. Maynor

Particle Replication in Non-Wetting Templates (PRINT®) is a platform particle drug delivery technology that coopts the precision and nanoscale spatial resolution inherently afforded by lithographic techniques derived from the microelectronics industry to produce precisely engineered particles. We describe the utility of PRINT technology as a strategy for formulation and delivery of small molecule and biologic therapeutics, highlighting previous studies where particle size, shape, and chemistry have been used to enhance systemic particle distribution properties. In addition, we introduce the application of PRINT technology towards respiratory drug delivery, a particular interest due to the pharmaceutical need for increased control over dry powder characteristics to improve drug delivery and therapeutic indices. To this end, we have produced dry powder particles with micro- and nanoscale geometric features and composed of small molecule and protein therapeutics. Aerosols generated from these particles show attractive properties for efficient pulmonary delivery and differential respiratory deposition characteristics based on particle geometry. This work highlights the advantages of adopting proven microfabrication techniques in achieving unprecedented control over particle geometric design for drug delivery.


Accounts of Chemical Research | 2008

The pursuit of a scalable nanofabrication platform for use in material and life science applications.

Stephanie E. A. Gratton; Stuart Williams; Mary E. Napier; Patrick D. Pohlhaus; Zhilian Zhou; Kenton B. Wiles; Benjamin W. Maynor; Clifton Kwang-Fu Shen; Tove Olafsen; Edward T. Samulski; Joseph M. DeSimone


Chemistry of Materials | 2008

Nanostructured Titania-Polymer Photovoltaic Devices Made Using PFPE-Based Nanomolding Techniques

Stuart Williams; Meredith J. Hampton; Vignesh Gowrishankar; I-Kang Ding; Joseph L. Templeton; Edward T. Samulski; Joseph M. DeSimone; Michael D. McGehee


Archive | 2007

High fidelity nano-structures and arrays for photovoltaics and methods of making the same

Joseph M. DeSimone; Ginger Denison Rothrock; Zhilian Zhou; Edward T. Samulski; Meredith J. Earl; Stuart Williams


Proceedings of SPIE, the International Society for Optical Engineering | 2008

The patterning of sub-500 nm inorganic oxide and semiconducting polymeric structures

Meredith J. Hampton; Stuart Williams; Zhilian Zhou; Janine K. Nunes; Doo Hyun Ko; Joseph L. Templeton; Joseph M. DeSimone; Edward T. Samulski


Investigative Ophthalmology & Visual Science | 2014

Extended Release of Microfabricated Protein Particles from Biodegradable Hydrogel Implants for the Treatment of Age Related Macular Degeneration

Kevin P. Herlihy; Stuart Williams; Gary Owens; John Savage; Lindsay Gardner; RiLee Robeson; Benjamin W. Maynor; Tomas Navratil; Brian C. Gilger; Benjamin R. Yerxa


Investigative Ophthalmology & Visual Science | 2017

In vitro and In vivo Sustained Release of Dexamethasone from Intravitreal Implants

Janet Tully; Mari Yang; Stuart Williams; Sanjib Das; Rozemarijn S Verhoeven; RiLee Robeson; Rhett M. Schiffman; Benjamin R. Yerxa

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Edward T. Samulski

University of North Carolina at Chapel Hill

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Joseph M. DeSimone

University of North Carolina at Chapel Hill

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Meredith J. Hampton

University of North Carolina at Chapel Hill

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Zhilian Zhou

University of North Carolina at Chapel Hill

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Benjamin W. Maynor

University of North Carolina at Chapel Hill

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Doo Hyun Ko

University of North Carolina at Chapel Hill

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Joseph L. Templeton

University of North Carolina at Chapel Hill

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