Sensors and actuators based on carbon nanotubes and their composites: A review

We discovered that many of the commonly studied two-dimensional monolayer transition metal dichalcogenide (TMDC) nanoscale materials are piezoelectric, unlike their bulk parent crystals. On the macroscopic scale, piezoelectricity is widely used to achieve robust electromechanical coupling in a rich variety of sensors and actuators. Remarkably, our density-functional theory calculations of the piezoelectric coefficients of monolayer BN, MoS2, MoSe2, MoTe2, WS2, WSe2, and WTe2 reveal that some of these materials exhibit stronger piezoelectric coupling than traditionally employed bulk wurtzite structures. We find that the piezoelectric coefficients span more than 1 order of magnitude, and exhibit monotonic periodic trends. The discovery of this property in many two-dimensional materials enables active sensing, actuating, and new electronic components for nanoscale devices based on the familiar piezoelectric effect.

Intrinsic Piezoelectricity in Two-Dimensional Materials

The idea of wireless power transfer (WPT) has been around since the inception of electricity. In the late 19th century, Nikola Tesla described the freedom to transfer energy between two points without the need for a physical connection to a power source as an ?all-surpassing importance to man? [1]. A truly wireless device, capable of being remotely powered, not only allows the obvious freedom of movement but also enables devices to be more compact by removing the necessity of a large battery. Applications could leverage this reduction in size and weight to increase the feasibility of concepts such as paper-thin, flexible displays [2], contact-lens-based augmented reality [3], and smart dust [4], among traditional point-to-point power transfer applications. While several methods of wireless power have been introduced since Tesla?s work, including near-field magnetic resonance and inductive coupling, laser-based optical power transmission, and far-field RF/microwave energy transmission, only RF/microwave and laser-based systems are truly long-range methods. While optical power transmission certainly has merit, its mechanisms are outside of the scope of this article and will not be discussed.

Harvesting Wireless Power: Survey of Energy-Harvester Conversion Efficiency in Far-Field, Wireless Power Transfer Systems

This paper presents a study of reception and rectification of broad-band statistically time-varying low-power-density microwave radiation. The applications are in wireless powering of industrial sensors and recycling of ambient RF energy. A 64-element dual-circularly-polarized spiral rectenna array is designed and characterized over a frequency range of 2-18 GHz with single-tone and multitone incident waves. The integrated design of the antenna and rectifier, using a combination of full-wave electromagnetic field analysis and harmonic balance nonlinear circuit analysis, eliminates matching and filtering circuits, allowing for a compact element design. The rectified dc power and efficiency is characterized as a function of dc load and dc circuit topology, RF frequency, polarization, and incidence angle for power densities between 10/sup -5/-10/sup -1/ mW/cm/sup 2/. In addition, the increase in rectenna efficiency for multitone input waves is presented.

Recycling ambient microwave energy with broad-band rectenna arrays

The present invention relates generally to sub-microelectronic circuitry, and more particularly to nanometer-scale articles, including nanoscale wires which can be selectively doped at various locations and at various levels. In some cases, the articles may be single crystals. The nanoscale wires can be doped, for example, differentially along their length, or radially, and either in terms of identity of dopant, concentration of dopant, or both. This may be used to provide both n-type and p-type conductivity in a single item, or in different items in close proximity to each other, such as in a crossbar array. The fabrication and growth of such articles is described, and the arrangement of such articles to fabricate electronic, optoelectronic, or spintronic devices and components. For example, semiconductor materials can be doped to form n-type and p-type semiconductor regions for making a variety of devices such as field effect transistors, bipolar transistors, complementary inverters, tunnel diodes, light emitting diodes, sensors, and the like.

Nanoscale wires and related devices

An aperture coupled patch splits energy from two different polarization components to different locations to spread heat. In addition, there is no physical electrical connection between the slot (154, 156), patch (106), and circuitry (150). The circuitry (150) is located under a ground plane (152) which shields against harmonic radiation back to the RF source.

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A dual polarized, heat spreading rectenna

An energy transfer system is disclosed The system includes patch elements, shielding layers, and energy rectifying circuits The patch elements receive and couple radio frequency energy The shielding layer includes at least one opening that allows radio frequency energy to pass through The openings are formed and positioned to receive the radio frequency energy and to minimize any re-radiating back toward the source of energy The energy rectifying circuit includes a circuit for rectifying the radio frequency energy into dc energy A plurality of energy rectifying circuits is arranged in an array to provide a sum of dc energy generated by the energy rectifying circuit

/pdf/rectenna-for-high-voltage-applications-4mqtaz7o9s.pdf

Rectenna for high-voltage applications

A new method for finding radiation patterns and the reflection coefficients associated with an axisymmetric waveguide fed horn is presented. The approach is based on a hybrid finite element method (FEM) wherein the electromagnetic fields in the FEM region are coupled to the fields outside by two surface integral equations. Because of the local nature of the FEM, this formalism allows for the presence of inhomogeneities to be included in the problem domain. The matrix equation which results from the application of this method is shown to be complex-symmetric. Comparisons of calculated and measured data for two different horns show good agreement.

A hybrid finite-element method for axisymmetric waveguide-fed horns

In order to add the capability of an X-band up-link onto the NASA/JPL Deep Space Network (DSN) 70-m antenna, a new dichroic plate is needed to replace the Pyle-guide shaped dichroic plate currently in use. The replacement dichroic plate must exhibit an additional pass band at the new up-link frequency of 7.165 GHz, while maintaining a pass band at the existing down-link frequency of 8.425 GHz. Because of the wide frequency separation of these two pass bands, conventionally designed air-filled dichroic plates exhibit grating lobe problems. A new method of solving this problem using a dichroic plate with cross-shaped holes is presented and verified experimentally. Two checks of the integral equation solution are described here. One is the comparison to a modal analysis for the limiting cross shape of a square hole. As a final check a prototype dichroic plate with cross-shaped holes was built and measured. >

Experimental verification of an integral equation solution for a thin-walled dichroic plate with cross-shaped holes

The 2007 Decadal Survey for the National Aeronautics and Space Administration recommended an Aerosol/Cloud/Ecosystems (ACE) mission with a new advanced cloud profiling radar. In this letter, we describe ACERAD, a radar design that could meet the goals for the ACE mission. ACERAD has 35 GHz (Ka-band) and 94 GHz (W-band) channels. It would scan at Ka-band and be nadir looking at W-band. The scanning antenna geometry is a classical Dragonian illuminated by a feed array; a reduced-size prototype of the antenna has been successfully fabricated and tested. ACERAD also uses a quasi-optical transmission line at W-band for low-loss routing of the signal from the transmitter to the antenna and from the antenna to the receiver. This letter briefly describes the ACERAD instrument design and test results for some of the major technologies needed for ACERAD implementation.

Larry Epp

Papers

A dual polarized, heat spreading rectenna

Rectenna for high-voltage applications

A hybrid finite-element method for axisymmetric waveguide-fed horns

Experimental verification of an integral equation solution for a thin-walled dichroic plate with cross-shaped holes

System Design and Subsystem Technology for a Future Spaceborne Cloud Radar