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.

Photolithography with transparent reflective photomasks

Abstract: A new type of photomask was fabricated by casting a prepolymer of a transparent, elastomeric polymer (polydimethylsiloxane, PDMS) against a Si(100) master whose surface has been patterned with V-shaped trenches or pyramidal pits using anisotropic etching. The PDMS replica, when placed in contact with a film of photoresist and illuminated, acts as a photomask. The sidewalls of the trenches and pits in the silicon master meet with the plateaus in dihedral angles of 54°; as a result, the PDMS replica selectively blocks the incident light in regions where it has sloping features by total internal reflection, and acts as a reflective contact mask for photolithography. The feasibility of this new type of photomask has been demonstrated by the fabrication of micropatterns in photoresist (and in an underlying silicon substrate) with smaller feature sizes and higher complexities than those present on the original chrome mask used in patterning the silicon master. The patterns produced using these elastomeric photo...

Deformable stamp for patterning three-dimensional surfaces

Abstract: A deformable stamp for patterning a surface. The stamp can be placed in contact with an entire 3-dimensional object, such as a rod, in a single step. The stamp can also be used to pattern the inside of a tube or rolled over a surface to form a continuous pattern. The stamp may also be used for fluidic patterning by flowing material through channels defined by raised and recessed portions in the surface of the stamp as it contacts the substrate. The stamp may be used to deposit self-assembled monolayers, biological materials, metals, polymers, ceramics, or a variety of other materials. The patterned substrates may be used in a variety of engineering and medical applications.

Design, Synthesis, and Characterization of a High-Affinity Trivalent System Derived from Vancomycin and l-Lys-d-Ala-d-Ala

Abstract: A trivalent derivative of vancomycin, tris(vancomycin carboxamide), [C6H3-1,3,5-(CONHC6H4-4-CH2NHCOV)3 (RtV3; V = vancomycin)], binds an analogous trivalent derivative of d-Ala-d-Ala, R‘tL‘3, (C6H3-1,3,5-[CONeH(Nα-Ac)-l-Lys-d-Ala-d-Ala]3) in water with a dissociation constant that is approximately 4 × 10-17 M, as estimated by HPLC using a competitive assay against Nα,e-diacetyl-l-Lys-d-Ala-d-Ala (L). This binding is one of the tightest known for low molecular weight organic species. The dissociation of RtV3·R‘tL‘3 in the presence of an excess of L could be followed by HPLC. The kinetics of dissociation are quite different from those of monovalent tight-binding systems such as avidin and biotin. In particular, the rate of dissociation of the aggregate RtV3·R‘tL‘3 is rapid in the presence of monovalent L at concentrations greater than the value of the dissociation constant for the complex of L with V; by contrast, the rate of dissociation of biotin·avidin is independent of the concentration of biotin. Two m...

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.