George M. Whitesides

Bio: George M. Whitesides is an academic researcher from Harvard University. The author has contributed to research in topics: Monolayer & 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.

Muscular Thin Films for Building Actuators and Powering Devices

Abstract: We demonstrate the assembly of biohybrid materials from engineered tissues and synthetic polymer thin films. The constructs were built by culturing neonatal rat ventricular cardiomyocytes on polydimethylsiloxane thin films micropatterned with extracellular matrix proteins to promote spatially ordered, two-dimensional myogenesis. The constructs, termed muscular thin films, adopted functional, three-dimensional conformations when released from a thermally sensitive polymer substrate and were designed to perform biomimetic tasks by varying tissue architecture, thin-film shape, and electrical-pacing protocol. These centimeter-scale constructs perform functions as diverse as gripping, pumping, walking, and swimming with fine spatial and temporal control and generating specific forces as high as 4 millinewtons per square millimeter.

Formation of monodisperse bubbles in a microfluidic flow-focusing device

Abstract: This letter describes a method for generating monodisperse gaseous bubbles in a microfluidic flow-focusing device. The bubbles can be obtained in a range of diameters from 10 to 1000μm. The volume Vb of the bubbles scales with the flow rate q and the viscosity μ of the liquid, and the pressure p of the gas stream as Vb∝p∕qμ. This method allows simultaneous, independent control of the size of the individual bubbles and volume fraction of the dispersed phase. Under appropriate conditions, bubbles self-assemble into highly ordered, flowing lattices. Structures of these lattices can be adjusted dynamically by changing the flow parameters.

Formation of Monolayers by the Coadsorption of Thiols on Gold: Variation in the Length of the Alkyl Chain

Abstract: when X = Y = oH' the pure monolayers a." *eti"d by water, but the mixed monolayers are less hydrophilic because nonpolar polymethylenecha insareexposedatt hesurface. whinX =cHr, Y = oH (n=2L,m= ll),averysharptr ansitionoccurs from a monolayer composed largely of the longer, methyl-terminated component to the shorter, hydroxyl-terminated component as the mole fraction of HS(CHz) r roH in-the adsorption solution is increased. From solutions .ontuining two thiols, adsorption of the thiol with the longer chain is preferred. Tiris preference is greater when the monolayers are adsorbed from ethanol than from isooctane' The mixed monolayers do not uit ", ideal two-dimensional solutions. T-he adsorption isotherms suggest a positive excess free energy of mixing of the two components in the monolayer. The compositions of the monolayers appear to be determined largely by thermodynamics, although in some cases there is also a kinetic contribution. The two components in the mixed monolayers do not phase-segregate into macroscopic islands (greater than a few tens of angstroms across) but are probably not randomly dispersed within the monolayer, ThL wettability of mixed, methyl-terminatea can be partially rationalized by the geometric m€an approximition, but a full description probably requires inclusion of the entropy of mixing at the monolayer-liquid interface. The hysteresis in the contact angle on these monolayers cannot be explained by theories of wetting based on macroscopic heterogeneity. Contact angles ur? -o.. sensitive than optical ellipsometry or X-ray photoelectron spectroscopy to certain types of changes in the coriposition and structure of these monolayers.

Flexible Methods for Microfluidics

Abstract: Devices for handling nanoliter quantities of fluids are creating new fabrication challenges and finding new applications in biology, chemistry, and materials science.

Self-assembled monolayers and multilayers of conjugated thiols, α,ω-dithiols, and thioacetyl-containing adsorbates. Understanding attachments between potential molecular wires and gold surfaces

Abstract: This paper describes tudies of the formation of self-assembled monolayers (SAMs) and multilayers on gold surfaces of rigid-rod conjugated oligomers that have thiol, cr,a.r-dithiol, thioacetyl, or cqor{'ithioacetyl end groups' The SAMs were analyzed usingillipsom-etry, X-ray photoelectron spectroscopy Q(PS), and infrared extemal reflectance spec6oscopy. The thiol moieties usually dominate adsorption on the gold sites; interactions with the conjugated z-systems are weaker. Rigid rod cr,al-dithiols form *r"*bli"r in which one thiol gouP binds to the surface while the second thiol moiety projects upward at the exposed surface of the SAlvl. ln sinr deprotection of the thiol moieties by deacylation of thioacetyl groups using NFlaOFtpermits formation of SAMs without having to isolate the oxidatively unstable free thiols. Moreover, directidsorption, without exogenous base, of the thioacetyl-terminated oligomers can be accomplished to generate gold surface-bound thiolates. However, in the non-base-promoted adsorptions, higher concentrations of the thioaietyl groups, relative to that of thiol groups, are required to achieve monolayer coverage in a given interval. A thiol-teinninated phenylene-ethynylene system was shown to have a tilt angle of the long molecular axis of <20o from the normal to the substrate surface. These aromatic o-ro-dithiol-derived monolayers provide the basis for studies leading to the design of molecular wires capable of bridging proximate

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.