George M. Whitesides

Bio: George M. Whitesides is an academic researcher from Harvard University. The author has contributed to research in topics: Microcontact printing & Self-assembled monolayer. The author has an hindex of 240, co-authored 1739 publications receiving 269833 citations. Previous affiliations of George M. Whitesides include University of California, Davis & University of Texas at Austin.

Micromagnetic systems and methods for microfluidics

Abstract: The invention provides systems (10) and methods of manipulating biological or chemical species (12). The species (12) may be attached to a magnetic particle (16) which is manipulated using micro-magnetic fields. In some cases, the magnetic fields are generated by current carrying wires (18) that are patterned on a substrate (14). The magnetic fields define channels (22) on the surface of the substrate (14) in which the magnetic particles (16) and attached species (12) may be transported, positioned and stored. In other cases, the magnetic fields are generated by magnetic features located within the channels (22) on the surface of the substrate (14). Thus, the systems (10) and methods can manipulate biological or chemical species (12) on a microscale (e.g., less than 5 cm). Applications of the systems (10) and methods are in, but are not limited to, the fields of biotechnology, microanalysis, and microsynthesis.

Uniform Amplification of Phage with Different Growth Characteristics in Individual Compartments Consisting of Monodisperse Droplets

Abstract: Uniform amplification of a mixture of phage clones is central to the selection of peptides and proteins presented on the coat proteins of phage (phage display).[1,2] Uniform amplification cannot be achieved when phage having different rates of growth compete with each other in a common solution. Here we describe a method for uniform amplification of individual phage clones, from a mixture of clones possessing different growth characteristics. We use a microfluidic droplet generator[3] to separate individual clones from a mixture of slowly growing (S) and rapidly growing (R) M13 filamentous phage into droplets of growth media (ca. 200 µm in diameter) containing E. coli. At sufficiently low concentrations of phage, each droplet contains one or no phage particles. Different phage cannot compete for bacterial hosts when isolated in different droplets, and the relative number of S and R clones present at the start is preserved after amplification. Because amplification of phage clones depends on the size of the droplets in which they reside, the use of droplets of uniform size is essential for the success of this process.

Templated Self‐Assembly: Formation of Folded Structures by Relaxation of Pre‐stressed, Planar Tapes

Abstract: germanium nanowires grow at an inclined angle on a non-ger-manium (111) substrate due to crystallographic mismatch. We demonstrate the feasibility of controlled synthesis of individual vertical semiconducting germanium nanowires. These nano-wires can be directly integrated into fabricated devices [1,2] to produce nanoscale vertical transistors. Other applications for individual vertical germanium nanowires or arrays of high-density germanium nanowires include terapixel infrared photodetection systems, memory devices with metal oxide/ semiconductor structures and germanium nanowires, germa-nium-based cryogenic power electronics for deep-space exploration , and monolithic germanium nanoresonators. Large-scale synthesis of functionalized germanium nanostructures may find chemotherapeutic applications in nanomedicine, as certain germanium compounds exhibit low mammalian toxicity but marked activity against certain bacteria. Other applications may include high-sensitivity functionalized biosensors or catalysts for nanoelectroplating. Germanium oxide is a photo-luminescent material with peak energies at 3.1 eV and 2.2 eV. Oxidation of the germanium nanowires can produce germa-nium oxide nanowires for photoluminescence studies and optoelectronic applications. Experimental Doped and intrinsic germanium(III) substrates were coated with poly(methyl methacrylate) (PMMA, 950 kg mol ±1 relative molecular mass, 2 wt.-% in chlorobenzene, spin-coated at 5000 rpm and 200 C, with a post-bake), exposed with an electron beam (Hitachi H-700, 600±700 lC cm ±2 , 30 kV), and developed with methyl isobutyl ketone/ isopropanol (1:3 v/v, 30 s, 23 C, 20±30 s isopropanol rinse). Gold (99.95 % metal basis) was deposited by ion-beam sputtering technology , and the resist lift-off process was performed in acetone (1±2 min, sonication, 23 C). The germanium nanowires were synthesized using the gold catalyst mediated homoepitaxial growth approach in a dual-zone tubular reaction chamber setup. The source, composed of a 1:1 weight ratio of germanium powder (Alfa Aesar, 99.999 % metal basis) and synthetic graphite powder (Alfa Aesar, 99.9995 % metal basis), was placed upstream of the substrate. The graphite additive provides enhanced surface area for the evaporation of germanium at elevated temperature and control of the germanium partial pressure at a given carrier gas flow rate and fixed source temperature. Graphite also reduces the amount of germanium oxide (native oxide on the as-purchased ger-manium powder) by carbothermal reduction. Thermodynamic considerations [3] suggest that formation of crystalline germanium carbide nanowires is highly unlikely due to the disproportionate heats of formation of gaseous carbon and germanium species, the intrinsic metastability of the Ge±C bond compared with C±C bonds, and the thermodynamic insolubility of carbon in crystalline germanium at a wide range of temperatures and …

Dissections: self-assembled aggregates that spontaneously reconfigure their structures when their environment changes.

Abstract: This Communication describes a new strategy for the design of adaptive structures based on reconfigurable mesoscale self-assembly. Several sets of millimeter-scale objects have been designed that can self-assemble into two different, regular aggregates at the interface between an aqueous solution and perfluorodecalin; the choice between the two aggregates is determined by the density of the aqueous phase.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

The Theory of Island Biogeography

Abstract: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

Large-scale pattern growth of graphene films for stretchable transparent electrodes

Abstract: Problems associated with large-scale pattern growth of graphene constitute one of the main obstacles to using this material in device applications. Recently, macroscopic-scale graphene films were prepared by two-dimensional assembly of graphene sheets chemically derived from graphite crystals and graphene oxides. However, the sheet resistance of these films was found to be much larger than theoretically expected values. Here we report the direct synthesis of large-scale graphene films using chemical vapour deposition on thin nickel layers, and present two different methods of patterning the films and transferring them to arbitrary substrates. The transferred graphene films show very low sheet resistance of approximately 280 Omega per square, with approximately 80 per cent optical transparency. At low temperatures, the monolayers transferred to silicon dioxide substrates show electron mobility greater than 3,700 cm(2) V(-1) s(-1) and exhibit the half-integer quantum Hall effect, implying that the quality of graphene grown by chemical vapour deposition is as high as mechanically cleaved graphene. Employing the outstanding mechanical properties of graphene, we also demonstrate the macroscopic use of these highly conducting and transparent electrodes in flexible, stretchable, foldable electronics.

Fuzzy Nanoassemblies: Toward Layered Polymeric Multicomposites

Abstract: Multilayer films of organic compounds on solid surfaces have been studied for more than 60 years because they allow fabrication of multicomposite molecular assemblies of tailored architecture. However, both the Langmuir-Blodgett technique and chemisorption from solution can be used only with certain classes of molecules. An alternative approach—fabrication of multilayers by consecutive adsorption of polyanions and polycations—is far more general and has been extended to other materials such as proteins or colloids. Because polymers are typically flexible molecules, the resulting superlattice architectures are somewhat fuzzy structures, but the absence of crystallinity in these films is expected to be beneficial for many potential applications.