Are implantable, living pharmacies within reach?

Cell-based drug factories could produce therapies on demand inside patients.

Chemistries for Making Additive Nanolithography in OrmoComp Permissive for Cell Adhesion and Growth.

Two-photon lithography allows writing of arbitrary nanoarchitectures in photopolymers. This design flexibility opens almost limitless possibilities for biological studies, but the acrylate-based polymers frequently used do not allow for adhesion and growth of some types of cells. Indeed, we found that lithographically defined structures made from OrmoComp do not support E18 murine cortical neurons.

Protection from Below: Stabilizing Hydrogenated Graphene Using Graphene Underlayers.

We show that dehydrogenation of hydrogenated graphene proceeds much more slowly for bilayer systems than for single layer systems. We observe that an underlayer of either pristine or hydrogenated graphene will protect an overlayer of hydrogenated graphene against a number of chemical oxidants, thermal dehydrogenation, and degradation in an ambient environment over extended periods of time. Chemical protection depends on the ease of oxidant intercalation, with good intercalants such as Br demonstrating much higher reactivity than poor intercalants such as 1,2-dichloro-4,5-dicyanonbenzoquinone (DDQ).

Nanopatterning of GeTe phase change films via heated-probe lithography.

The crystallization of amorphous germanium telluride (GeTe) thin films is controlled with nanoscale resolution using the heat from a thermal AFM probe. The dramatic differences between the amorphous and crystalline GeTe phases yield embedded nanoscale features with strong topographic, electronic, and optical contrast. The flexibility of scanning probe lithography enables the width and depth of the features, as well as the extent of their crystallization, to be controlled by varying probe temperature and write speed.

Friction between van der Waals Solids during Lattice Directed Sliding.

Nanometer-scale crystals of the two-dimensional oxide molybdenum trioxide (MoO) were formed atop the transition metal dichalcogenides MoS and MoSe. The MoO nanocrystals are partially commensurate with the dichalcogenide substrates, being aligned only along one of the substrate's crystallographic axes. These nanocrystals can be slid only along the aligned direction and maintain their alignment with the substrate during motion.

Fluorinated Graphene Enables the Growth of Inorganic Thin Films by Chemical Bath Deposition on Otherwise Inert Substrates.

Chemically modified graphenes (CMGs) offer a means to tune a wide variety of graphene's exceptional properties. Critically, CMGs can be transferred onto a variety of substrates, thereby imparting functionalities to those substrates that would not be obtainable through conventional functionalization. One such application of CMGs is enabling and controlling the subsequent growth of inorganic thin films.

Transfer of Chemically Modified Graphene with Retention of Functionality for Surface Engineering.

Single-layer graphene chemically reduced by the Birch process delaminates from a Si/SiOx substrate when exposed to an ethanol/water mixture, enabling transfer of chemically functionalized graphene to arbitrary substrates such as metals, dielectrics, and polymers. Unlike in previous reports, the graphene retains hydrogen, methyl, and aryl functional groups during the transfer process. This enables one to functionalize the receiving substrate with the properties of the chemically modified graphene (CMG).

Direct mechanochemical cleavage of functional groups from graphene.

Mechanical stress can drive chemical reactions and is unique in that the reaction product can depend on both the magnitude and the direction of the applied force. Indeed, this directionality can drive chemical reactions impossible through conventional means. However, unlike heat- or pressure-driven reactions, mechanical stress is rarely applied isometrically, obscuring how mechanical inputs relate to the force applied to the bond.

Patterning magnetic regions in hydrogenated graphene via e-beam irradiation.

Partially hydrogenated graphene is ferromagnetic and may be patterned by electron-beam irradiation. Sequential patterning produces a patterned magnetic array. Removal of the hydrogen atoms also can convert electrically insulating fully hydrogenated graphene back into conductive graphene, enabling the writing of chemically isolated, dehydrogenated graphene nanoribbons as narrow as 100 nm.

van der Waals screening by single-layer graphene and molybdenum disulfide.

A sharp tip of atomic force microscope is employed to probe van der Waals forces of a silicon oxide substrate with adhered graphene. Experimental results obtained in the range of distances from 3 to 20 nm indicate that single-, double-, and triple-layer graphenes screen the van der Waals forces of the substrate. Fluorination of graphene, which makes it electrically insulating, lifts the screening in the single-layer graphene.

Nature inspires sensors to do more with less.

The world is filled with widely varying chemical, physical, and biological stimuli. Over millennia, organisms have refined their senses to cope with these diverse stimuli, becoming virtuosos in differentiating closely related antigens, handling extremes in concentration, resetting the spent sensing mechanisms, and processing the multiple data streams being generated. Nature successfully deals with both repeating and new stimuli, demonstrating great adaptability when confronted with the latter.

Fluorination of graphene enhances friction due to increased corrugation.

The addition of a single sheet of carbon atoms in the form of graphene can drastically alter friction between a nanoscale probe tip and a surface. Here, for the first time we show that friction can be altered over a wide range by fluorination. Specifically, the friction force between silicon atomic force microscopy tips and monolayer fluorinated graphene can range from 5-9 times higher than for graphene.

Graphene veils: A versatile surface chemistry for sensors.

Thin spun-coat films (~4 nm thick) of graphene oxide (GO) constitute a versatile surface chemistry compatible with a broad range of technologically important sensor materials. Countless publications are dedicated to the nuances of surface chemistries that have been developed for sensors, with almost every material having unique characteristics. There would be enormous value in a surface chemistry that could be applied generally with functionalization and passivation already optimized regardless of the sensor material it covered.

Chemical stability of graphene fluoride produced by exposure to XeF2.

Fluorination can alter the electronic properties of graphene and activate sites for subsequent chemistry. Here, we show that graphene fluorination depends on several variables, including XeF2 exposure and the choice of substrate. After fluorination, fluorine content declines by 50-80% over several days before stabilizing.

Nanoscale reduction of graphene fluoride via thermochemical nanolithography.

Graphene nanoribbons (GNRs) would be the ideal building blocks for all carbon electronics; however, many challenges remain in developing an appropriate nanolithography that generates high-quality ribbons in registry with other devices. Here we report direct and local fabrication of GNRs by thermochemical nanolithography, which uses a heated AFM probe to locally convert highly insulating graphene fluoride to conductive graphene. Chemically isolated GNRs as narrow as 40 nm show p-doping behavior and sheet resistances as low as 22.

Chemical gradients on graphene to drive droplet motion.

This work demonstrates the production of a well-controlled, chemical gradient on the surface of graphene. By inducing a gradient of oxygen functional groups, drops of water and dimethyl-methylphosphonate (a nerve agent simulant) are "pulled" in the direction of increasing oxygen content, while fluorine gradients "push" the droplet motion in the direction of decreasing fluorine content. The direction of motion is broadly attributed to increasing/decreasing hydrophilicity, which is correlated to high/low adhesion and binding energy.

Engineering graphene mechanical systems.

We report a method to introduce direct bonding between graphene platelets that enables the transformation of a multilayer chemically modified graphene (CMG) film from a "paper mache-like" structure into a stiff, high strength material. On the basis of chemical/defect manipulation and recrystallization, this technique allows wide-range engineering of mechanical properties (stiffness, strength, density, and built-in stress) in ultrathin CMG films. A dramatic increase in the Young's modulus (up to 800 GPa) and enhanced strength (sustainable stress ≥1 GPa) due to cross-linking, in combination with high tensile stress, produced high-performance (quality factor of 31,000 at room temperature) radio frequency nanomechanical resonators.

High-density amine-terminated monolayers formed on fluorinated CVD-grown graphene.

There has been considerable interest in chemically functionalizing graphene films to control their electronic properties, to enhance their binding to other molecules for sensing, and to strengthen their interfaces with matrices in a composite material. Most reports to date have largely focused on noncovalent methods or the use of graphene oxide. Here, we present a method to activate CVD-grown graphene sheets using fluorination followed by reaction with ethylenediamine (EDA) to form covalent bonds.

Direct-write polymer nanolithography in ultra-high vacuum.

Polymer nanostructures were directly written onto substrates in ultra-high vacuum. The polymer ink was coated onto atomic force microscope (AFM) probes that could be heated to control the ink viscosity. Then, the ink-coated probes were placed into an ultra-high vacuum (UHV) AFM and used to write polymer nanostructures on surfaces, including surfaces cleaned in UHV.

High-quality uniform dry transfer of graphene to polymers.

In this paper we demonstrate high-quality, uniform dry transfer of graphene grown by chemical vapor deposition on copper foil to polystyrene. The dry transfer exploits an azide linker molecule to establish a covalent bond to graphene and to generate greater graphene-polymer adhesion compared to that of the graphene-metal foil. Thus, this transfer approach provides a novel alternative route for graphene transfer, which allows for the metal foils to be reused.

Chemically isolated graphene nanoribbons reversibly formed in fluorographene using polymer nanowire masks.

We demonstrated the fabrication of graphene nanoribbons (GNRs) as narrow as 35 nm created using scanning probe lithography to deposit a polymer mask(1-3) and then fluorinating the sample to isolate the masked graphene from the surrounding wide band gap fluorographene. The polymer protected the GNR from atmospheric adsorbates while the adjacent fluorographene stably p-doped the GNRs which had electron mobilities of ∼2700 cm2/(V·s). Chemical isolation of the GNR enabled resetting the device to nearly pristine graphene.

Optimal method for efficiently removing extracellular nanofilaments from Shewanella oneidensis MR-1.

The identification, production, and potential electron conductivity of bacterial extracellular nanofilaments is an area of great study, specifically in Shewanella oneidensis MR-1. While some studies focus on nanofilaments attached to the cellular body, many studies require the removal of these nanofilaments for downstream applications. The removal of nanofilaments from S.