3,046 research outputs found
Simple and accurate analytical model of planar grids and high-impedance surfaces comprising metal strips or patches
This paper introduces simple analytical formulas for the grid impedance of
electrically dense arrays of square patches and for the surface impedance of
high-impedance surfaces based on the dense arrays of metal strips or square
patches over ground planes. Emphasis is on the oblique-incidence excitation.
The approach is based on the known analytical models for strip grids combined
with the approximate Babinet principle for planar grids located at a dielectric
interface. Analytical expressions for the surface impedance and reflection
coefficient resulting from our analysis are thoroughly verified by full-wave
simulations and compared with available data in open literature for particular
cases. The results can be used in the design of various antennas and microwave
or millimeter wave devices which use artificial impedance surfaces and
artificial magnetic conductors (reflect-array antennas, tunable phase shifters,
etc.), as well as for the derivation of accurate higher-order impedance
boundary conditions for artificial (high-) impedance surfaces. As an example,
the propagation properties of surface waves along the high-impedance surfaces
are studied.Comment: 12 pages, 10 figures, submitted to IEEE Transactions on Antennas and
Propagatio
Fabrication scheme for dense aquatic flow sensor arrays
A fabrication scheme to realize dense arrays of flexible, closed membranes with a small gap separating them from the substrate is presented. These membranes are the first step towards aquatic hair based flow sensors biomimicking fish lateral line. Electrodes are integrated underneath the membrane to avoid contact with the liquid. Arrays of membranes with a diameter of 100 μm, gap height of 3 μm, and mutual distance of 200 μm have been successfully fabricated
Guided Neuronal Growth on Arrays of Biofunctionalized GaAs/InGaAs Semiconductor Microtubes
We demonstrate embedded growth of cortical mouse neurons in dense arrays of
semiconductor microtubes. The microtubes, fabricated from a strained
GaAs/InGaAs heterostructure, guide axon growth through them and enable
electrical and optical probing of propagating action potentials. The coaxial
nature of the microtubes -- similar to myelin -- is expected to enhance the
signal transduction along the axon. We present a technique of suppressing
arsenic toxicity and prove the success of this technique by overgrowing
neuronal mouse cells.Comment: 3 pages, 4 figure
Suppression of Heating Rates in Cryogenic Surface-Electrode Ion Traps
Dense arrays of trapped ions provide one way of scaling up ion trap quantum
information processing. However, miniaturization of ion traps is currently
limited by sharply increasing motional state decoherence at sub-100 um
ion-electrode distances. We characterize heating rates in cryogenically cooled
surface-electrode traps, with characteristic sizes in 75 um to 150 um range.
Upon cooling to 6 K, the measured rates are suppressed by 7 orders of
magnitude, two orders of magnitude below previously published data of similarly
sized traps operated at room temperature. The observed noise depends strongly
on fabrication process, which suggests further improvements are possible.Comment: 4 pages, 4 figure
Spin Manipulation by Creation of Single-Molecule Radical Cations
All-trans-retinoic acid (ReA), a closed-shell organic molecule comprising
only C, H, and O atoms, is investigated on a Au(111) substrate using scanning
tunneling microscopy and spectroscopy. In dense arrays single ReA molecules are
switched to a number of states, three of which carry a localized spin as
evidenced by conductance spectroscopy in high magnetic fields. The spin of a
single molecule may be reversibly switched on and off without affecting its
neighbors. We suggest that ReA on Au is readily converted to a radical by the
abstraction of an electron.Comment: 5 pages, 3 figures, accepted for publication in Phys. Rev. Let
Technologies for trapped-ion quantum information systems
Scaling-up from prototype systems to dense arrays of ions on chip, or vast
networks of ions connected by photonic channels, will require developing
entirely new technologies that combine miniaturized ion trapping systems with
devices to capture, transmit and detect light, while refining how ions are
confined and controlled. Building a cohesive ion system from such diverse parts
involves many challenges, including navigating materials incompatibilities and
undesired coupling between elements. Here, we review our recent efforts to
create scalable ion systems incorporating unconventional materials such as
graphene and indium tin oxide, integrating devices like optical fibers and
mirrors, and exploring alternative ion loading and trapping techniques.Comment: 19 pages, 18 figure
Cooperativity in the enhanced piezoelectric response of polymer nanowires
We provide a detailed insight into piezoelectric energy generation from
arrays of polymer nanofibers. For sake of comparison, we firstly measure
individual poly(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFe)) fibers
at well-defined levels of compressive stress. Under an applied load of 2 mN,
single nanostructures generate a voltage of 0.45 mV. We show that under the
same load conditions, fibers in dense arrays exhibit a voltage output higher by
about two orders of magnitude. Numerical modelling studies demonstrate that the
enhancement of the piezoelectric response is a general phenomenon associated to
the electromechanical interaction among adjacent fibers, namely a cooperative
effect depending on specific geometrical parameters. This establishes new
design rules for next piezoelectric nano-generators and sensors.Comment: 31 pages, 11 figures, 1 tabl
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