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.

The adhesion energy between polymer thin films and self-assembled monolayers

Abstract: A superlayer test has been adapted for the measurement of the fracture energy between epoxy thin films and self-assembled monolayers (SAM’s) on Au/Ti/Si substrates. The “arrest” mode of analysis has been shown to provide consistent results, particularly when relatively wide lines are used to encourage lateral decohesions. The fracture energy, Γi, of the interface between the monolayer and the epoxy is varied by adjusting the ratio of COOH/CH3 terminal groups. Connections among Γi, the surface energies, and the inelastic deformations occurring in the epoxy are explored upon comparison with interface crack growth simulations.

Demonstration of waveguide couplers fabricated using microtransfer molding

Abstract: Arrays of single-mode optical waveguides, couplers, and interferometers were fabricated from a UV curable prepolymer using microtransfer molding. The coupling between the waveguides was reproducible and consistent across the array and was controlled after fabrication by additional UV exposure.

Synthesis, characterization, and thermodynamic analysis of a 1 + 1 self-assembling structure based on the cyanuric acid.cntdot.melamine lattice

Abstract: This article describes the reaction of the trivalent melamine derivative C 6 H 3 -1,3,5-[CO 2 (CH 2 ) 4 OCOC 6 H 4 -2-NH- C 3 N 3 (NH 2 )(NHCH 2 CH 2 C(CH 3 ) 3 )] 3 (homoflexM 3 , h-flexM 3 ) with the trivalent isocyanurate derivative C 6 H 3 -1,3,5-[CONHC 6 H 4 -3-N((CH 2 ) 17 CH 3 )COC 6 H 3 -2-NC(O)NHC(O)NHC(O)-5-O(CH 2 ) 17 CH 3 ] 3 (hubCA 3 ) in CHCl 3 to afford a structurally well-defined 1+1 supramolecular aggregate h-flexM 3 .hubCA 3 .This structure is held together by a network of 18 hydrogen bonds and is one of the most stable nonbiological supramolecular aggregates synthesized to date.The structure was characterized by 1 H NMR and UV spectroscopies, gel permeation chromotography ,and vapor pressure osmometry.The exchange reaction between h-flexM 3 .hubCA 3 and h-flexM' 3 (a close structural analog of h-flexM 3 ) was monitored by 1 H NMR spectroscopy.This exchange reaction appeared to occur by dissociation; the reaction was first-order in h-flexM 3 .hubCA 3 and zero-order in h-flexM' 3 .The transition-state parameters for the axchange reaction were calculated by following the exchange process at several temperatures.

Imaging profiles of light intensity in the near field: applications to phase-shift photolithography.

Abstract: We describe a method of imaging the intensity profiles of light in near-field lithographic experiments directly by using a sensitive photoresist. This technique was applied to a detailed study of the irradiance distribution in the optical near field with contact-mode photolithography carried out by use of elastomeric phase masks. The experimental patterns in the photoresist determined by scanning electron microscopy and atomic force microscopy were compared with the corresponding theoretical profiles of intensity calculated by use of a simple scalar analysis; the two correlate well. This comparison makes it possible to improve the theoretical models of irradiance distribution in the near field. Analysis of the images highlights issues in the experimental design, provides a means for the optimization of this technique, and extends its application to the successful fabrication of test structures with linewidths of ∼50 nm.

Pumping fluids in microfluidic systems using the elastic deformation of poly(dimethylsiloxane).

Abstract: This paper demonstrates a methodology for storing and pumping fluids that provide a useful capability for microfluidic devices. It uses microfluidic screw valves to isolate fluids in poly(dimethylsiloxane) (PDMS) microcompartments, in which the pressure of the liquid is stored in the elastic deformation of the walls and ceiling of the compartments. Fluids can be stored under pressure in these structures for months. When the valves are opened, the walls and ceiling push the fluid out of the compartments into microfluidic channels. The system has five useful characteristics: (i) it is made using soft lithographic techniques; (ii) it allows multiple reagents to be preloaded in devices and stored under pressure without any additional user intervention; (iii) it makes it possible to meter out fluids in devices, and to control rates of flow of fluids; (iv) it prevents the user from exposure to potentially toxic reagents; and (v) it is hand-operated and does not require additional equipment or resources.

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.