Christopher K. Ober

Bio: Christopher K. Ober is an academic researcher from Cornell University. The author has contributed to research in topics: Resist & Polymer. The author has an hindex of 80, co-authored 631 publications receiving 29517 citations. Previous affiliations of Christopher K. Ober include University of Massachusetts Amherst & University of Waterloo.

Emerging applications of stimuli-responsive polymer materials

Abstract: Responsive polymer materials can adapt to surrounding environments, regulate transport of ions and molecules, change wettability and adhesion of different species on external stimuli, or convert chemical and biochemical signals into optical, electrical, thermal and mechanical signals, and vice versa. These materials are playing an increasingly important part in a diverse range of applications, such as drug delivery, diagnostics, tissue engineering and 'smart' optical systems, as well as biosensors, microelectromechanical systems, coatings and textiles. We review recent advances and challenges in the developments towards applications of stimuli-responsive polymeric materials that are self-assembled from nanostructured building blocks. We also provide a critical outline of emerging developments.

Nanocomposite Materials for Optical Applications

Abstract: A substantial amount of work has been carried out in the area of nanocomposite materials for optical applications. Composites are typically constructed by embedding an optically functional phase into a processable, transparent matrix material. By doing so, the optical properties can be utilized in more technologically important forms such as films and fibers. This review covers many areas of optical composite research to date. Composites with second- and third-order nonlinearities and laser amplification properties are discussed with examples from the recent literature. Other composites, including transparent magnets, may be made using similar structures. The principles used to construct these composites may have important technological applications soon and are therefore summarized in this review.

An efficient two-photon-generated photoacid applied to positive-tone 3D microfabrication

Abstract: A two-photon-activatable photoacid generator, based on a bis[(diarylamino) styryl]benzene core with covalently attached sulfonium moieties, has been synthesized. The photoacid generator has both a large two-photon absorption cross section (delta = 690 x 10(-50) centimeter(4) second per photon) and a high quantum yield for the photochemical generation of acid (phiH+ = 0.5). Under near-infrared laser irradiation, the molecule produces acid after two-photon excitation and initiates the polymerization of epoxides at an incident intensity that is one to two orders of magnitude lower than that needed for conventional ultraviolet-sensitive initiators. This photoacid generator was used in conjunction with a positive-tone chemically amplified resist for the fabrication of a three-dimensional (3D) microchannel structure.

Advances in polymers for anti-biofouling surfaces

Abstract: Self-assembling polymers and nanostructured polymer thin films are being actively explored as advanced coatings for marine and biomedical applications This review highlights recent advances in the design and synthesis of polymers that can resist fouling by biomolecules, cells and organisms Current understanding of the mechanisms of anti-biofouling activity is also discussed

Competing Interactions and Levels of Ordering in Self-Organizing Polymeric Materials

Abstract: The sophisticated use of self-organizing materials, which include liquid crystals, block copolymers, hydrogen- and π-bonded complexes, and many natural polymers, may hold the key to developing new structures and devices in many advanced technology industries. Synthetic materials are usually designed with only one structure-forming process in mind. However, combination of both complementary and antagonistic interactions in macromolecular systems can create order in materials over many length scales. Here polymer materials that make use of competing molecular interactions are summarized, and the prospects for the further development of such materials through both synthetic and processing pathways are highlighted.

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Biosensing with plasmonic nanosensors

Abstract: Recent developments have greatly improved the sensitivity of optical sensors based on metal nanoparticle arrays and single nanoparticles. We introduce the localized surface plasmon resonance (LSPR) sensor and describe how its exquisite sensitivity to size, shape and environment can be harnessed to detect molecular binding events and changes in molecular conformation. We then describe recent progress in three areas representing the most significant challenges: pushing sensitivity towards the single-molecule detection limit, combining LSPR with complementary molecular identification techniques such as surface-enhanced Raman spectroscopy, and practical development of sensors and instrumentation for routine use and high-throughput detection. This review highlights several exceptionally promising research directions and discusses how diverse applications of plasmonic nanoparticles can be integrated in the near future.

Emerging applications of stimuli-responsive polymer materials

Abstract: Responsive polymer materials can adapt to surrounding environments, regulate transport of ions and molecules, change wettability and adhesion of different species on external stimuli, or convert chemical and biochemical signals into optical, electrical, thermal and mechanical signals, and vice versa. These materials are playing an increasingly important part in a diverse range of applications, such as drug delivery, diagnostics, tissue engineering and 'smart' optical systems, as well as biosensors, microelectromechanical systems, coatings and textiles. We review recent advances and challenges in the developments towards applications of stimuli-responsive polymeric materials that are self-assembled from nanostructured building blocks. We also provide a critical outline of emerging developments.