Ramses V. Martinez

Robotic Tentacles with Three‐Dimensional Mobility Based on Flexible Elastomers

Soft robotic tentacles that move in three dimensions upon pressurization are fabricated by composing flexible elastomers with different tensile strengths using soft lithographic molding. These actuators are able to grip complex shapes and manipulate delicate objects. Embedding functional components into these actuators (for example, a needle for delivering fluid, a video camera, and a suction cup) extends their capabilities.

Nano-chemistry and scanning probe nanolithographies.

The development of nanometer-scale lithographies is the focus of an intense research activity because progress on nanotechnology depends on the capability to fabricate, position and interconnect nanometer-scale structures. The unique imaging and manipulation properties of atomic force microscopes have prompted the emergence of several scanning probe-based nanolithographies. In this tutorial review we present the most promising probe-based nanolithographies that are based on the spatial confinement of a chemical reaction within a nanometer-size region of the sample surface. The potential of local chemical nanolithography in nanometer-scale science and technology is illustrated by describing a range of applications such as the fabrication of conjugated molecular wires, optical microlenses, complex quantum devices or tailored chemical surfaces for controlling biorecognition processes.

Separation of Nanoparticles in Aqueous Multiphase Systems through Centrifugation

This paper demonstrates the use of aqueous multiphase systems (MuPSs) as media for rate-zonal centrifugation to separate nanoparticles of different shapes and sizes. The properties of MuPSs do not change with time or during centrifugation; this stability facilitates sample collection after separation. A three-phase system demonstrates the separation of the reaction products (nanorods, nanospheres, and large particles) of a synthesis of gold nanorods, and enriches the nanorods from 48 to 99% in less than ten minutes using a benchtop centrifuge.

Patterning the Tips of Optical Fibers with Metallic Nanostructures Using Nanoskiving

Convenient and inexpensive methods to pattern the facets of optical fibers with metallic nanostructures would enable many applications. This communication reports a method to generate and transfer arrays of metallic nanostructures to the cleaved facets of optical fibers. The process relies on nanoskiving, in which an ultramicrotome, equipped with a diamond knife, sections epoxy nanostructures coated with thin metallic films and embedded in a block of epoxy. Sectioning produces arrays of nanostructures embedded in thin epoxy slabs, which can be transferred manually to the tips of optical fibers at a rate of approximately 2 min(-1), with 88% yield. Etching the epoxy matrices leaves arrays of nanostructures supported directly by the facets of the optical fibers. Examples of structures transferred include gold crescents, rings, high-aspect-ratio concentric cylinders, and gratings of parallel nanowires.

Silicon nanowire transistor with a channel width of 4 nm fabricated by atomic force microscope nanolithography

The emergence of an ultrasensitive sensor technology based on silicon nanowires requires both the fabrication of nanoscale diameter wires and the integration with microelectronic processes. Here we demonstrate an atomic force microscopy lithography that enables the reproducible fabrication of complex single-crystalline silicon nanowire field-effect transistors with a high electrical performance. The nanowires have been carved from a silicon-on-insulator wafer by a combination of local oxidation processes with a force microscope and etching steps. We have fabricated and measured the electrical properties of a silicon nanowire transistor with a channel width of 4 nm. The flexibility of the nanofabrication process is illustrated by showing the electrical performance of two nanowire circuits with different geometries. The fabrication method is compatible with standard Si CMOS processing technologies and, therefore, can be used to develop a wide range of architectures and new microelectronic devices.

Silicon nanowire circuits fabricated by AFM oxidation nanolithography

We report a top-down process for the fabrication of single-crystalline silicon nanowire circuits and devices. Local oxidation nanolithography is applied to define very narrow oxide masks on top of a silicon-on-insulator substrate. In a plasma etching, the nano-oxide mask generates a nanowire with a rectangular section. The nanowire width coincides with the lateral size of the mask. In this way, uniform and well-defined transistors with channel widths in the 10-20 nm range have been fabricated. The nanowires can be positioned with sub-100 nm lateral accuracy. The transistors exhibit an on/off current ratio of 10(5). The atomic force microscope nanolithography offers full control of the nanowires shape from straight to circular or a combination of them. It also enables the integration of several nanowires within the same circuit. The nanowire transistors have been applied to detect immunological processes.

Large-scale nanoshaping of ultrasmooth 3D crystalline metallic structures

We report a low-cost, high-throughput benchtop method that enables thin layers of metal to be shaped with nanoscale precision by generating ultrahigh-strain-rate deformations. Laser shock imprinting can create three-dimensional crystalline metallic structures as small as 10 nanometers with ultrasmooth surfaces at ambient conditions. This technique enables the successful fabrications of large-area, uniform nanopatterns with aspect ratios as high as 5 for plasmonic and sensing applications, as well as mechanically strengthened nanostructures and metal-graphene hybrid nanodevices. Smooth surface, crystalline 3D metallic nanostructures are fabricated using a laser shock imprinting technique. Laser shock imprinting for patterning metals High-fidelity, small-scale patterning is often a tradeoff between full-pattern methods that may have limited resolution or flexiblity, and serial methods that can create high-resolution patterns but only by slow processes. Furthermore, metals have limited formability at very small scales. Gao et al. developed a method to create very smooth threedimensional crystalline metallic nanoscale structures using a laser to create shockwave impulses. The shockwave creates ultrahigh-strain-rate deformations that overcome the metals normal strength and, thus, resistance to patterning. Science, this issue p. 1352

Large-scale Nanopatterning of Single Proteins used as Carriers of Magnetic Nanoparticles

However, the supramolecular organization attained from‘‘bottom-up’’approachesiseitherdifficulttoextendfromnano-tomesoscopic length scales or does not allow accurate placement ofthe desired structures on a specific region of an inhomogeneoussurface. Similarly, a variety of methods based on Coulomb-force-directed assembly of nanoparticles have been proposed.

Use of Thin Sectioning (Nanoskiving) to Fabricate Nanostructures for Electronic and Optical Applications

This Review discusses nanoskiving--a simple and inexpensive method of nanofabrication, which minimizes requirements for access to cleanrooms and associated facilities, and which makes it possible to fabricate nanostructures from materials, and of geometries, to which more familiar methods of nanofabrication are not applicable. Nanoskiving requires three steps: 1) deposition of a metallic, semiconducting, ceramic, or polymeric thin film onto an epoxy substrate; 2) embedding this film in epoxy, to form an epoxy block, with the film as an inclusion; and 3) sectioning the epoxy block into slabs with an ultramicrotome. These slabs, which can be 30 nm-10 μm thick, contain nanostructures whose lateral dimensions are equal to the thicknesses of the embedded thin films. Electronic applications of structures produced by this method include nanoelectrodes for electrochemistry, chemoresistive nanowires, and heterostructures of organic semiconductors. Optical applications include surface plasmon resonators, plasmonic waveguides, and frequency-selective surfaces.

Nanopatterning of carbonaceous structures by field-induced carbon dioxide splitting with a force microscope

We report a tip-based nanofabrication method to generate carbon nanopatterns. The process uses the field-induced transformation of carbon dioxide gas into a solid material. It requires the application of low-to-moderate voltages ∼10–40 V. The method allow us to fabricated sub-25 nm dots and it can be up scaled to pattern square centimeter areas. Photoemission spectroscopy shows that the carbon is the dominating atomic species of the fabricated structures. The formation of carbon nanostructures and oxides by atomic force microscope nanolithography expands its potential by providing patterns on the same sample with different chemical composition.