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

Recent work has shown the successful demonstration of design techniques for straight, rectangular apertures at an incident angle of 30 degrees  In the present work, some of the cases in which the straight rectangular shape may have limited usefulness are addressed For example, grating lobes become a consideration when the bandwidth required to include the new frequency of 7165 GHz conflicts with the desired incident angle of 30 degrees  For this case, the cross shape's increased packing density and bandwidth could make it desirable When a sharp frequency response is required to separate two closely spaced Ka-band frequencies, the stepped rectangular aperture might be advantageous >

Design of thick frequency selective surfaces with complex apertures: Dichroics with cross-shaped and stepped rectangular apertures

Transmitters of the JPL/NASA Deep Space Network (DSN) typically operate at power levels in excess of 100 kW. This causes heat dissipation and loss problems even in the conventional DSN transmit frequencies of the S and X bands. These problems are compounded by operation in continuous mode, rather than in pulsed operation where the average power is low. In an effort to avoid the heat dissipation, waveguide loss, and arcing problems aggravated by high average power, the DSN has helped pioneer the development of beam waveguide antennas. These beam waveguide antennas use quasi-optical techniques to confine the fields, eliminating waveguide usage and their associated losses. The development of quasi-optical, non-reciprocal devices is natural to the beam waveguide environment. The present paper discusses the use of a ferrite circulator in this context.

Scattering from the quasi-optical ferrite circulator using a coupled integral equation/FEM solution

The proposed Aerosol/Cloud/Ecosystems (ACEs) mission development would advance cloud profiling radar from that used in CloudSat by adding a 35-GHz (Ka-band) channel to the 94-GHz (W-band) channel used in CloudSat. In order to illuminate a single antenna, and use CloudSat-like quasi-optical transmission lines, a spatial diplexer is needed to add the Ka-band channel. A dichroic filter separates Ka-band from W-band by employing advances in electrical discharge machining (EDM) and mode-matching analysis techniques developed and validated for designing dichroics for the Deep Space Network (DSN), to develop a preliminary design that both met the requirements of frequency separation and mechanical strength. First, a mechanical prototype was built using an approximately 102-micron-diameter EDM process, and tolerances of the hole dimensions, wall thickness, radius, and dichroic filter thickness measured. The prototype validated the manufacturing needed to design a dichroic filter for a higher-frequency usage than previously used in the DSN. The initial design was based on a Ka-band design, but thicker walls are required for mechanical rigidity than one obtains by simply scaling the Ka-band dichroic filter. The resulting trade of hole dimensions for mechanical rigidity (wall thickness) required electrical redesign of the hole dimensions. Updates to existing codes in the linear solver decreased the analysis time using mode-matching, enabling the electrical design to be realized quickly. This work is applicable to missions and instruments that seek to extend W-band cloud profiling measurements to other frequencies. By demonstrating a dichroic filter that passes W-band, but reflects a lower frequency, this opens up the development of instruments that both compare to and enhance CloudSat.

/pdf/dichroic-filter-for-separating-w-band-and-ka-band-55xfma5vz3.pdf

Dichroic Filter for Separating W-Band and Ka-Band

Recent work has shown the successful demonstration of design techniques for straight, rectangular apertures at an incident angle of 30 degrees . In the present work, some of the cases in which the straight rectangular shape may have limited usefulness are addressed. For example, grating lobes become a consideration when the bandwidth required to include the new frequency of 7.165 GHz conflicts with the desired incident angle of 30 degrees . For this case, the cross shape's increased packing density and bandwidth could make it desirable. When a sharp frequency response is required to separate two closely spaced Ka-band frequencies, the stepped rectangular aperture might be advantageous. >

Design of thick frequency selective surfaces with complex apertures: dichroics with cross-shaped and stepped rectangular apertures

This document represents a presentation offered by the Jet Propulsion Laboratory, with assistance from researchers from Brown University and Northrop Grumman. The presentation took place in Seoul, Korea in July 2003 and attempted to demonstrate the fabrication approach regarding the development of high quality factor (high-Q) mechanical oscillators (in the forms of a tunable nanotube resonator and a nanotube array radio frequency [RF] filter) aimed at signal processing and based on carbon nanotubes. The presentation also addressed parallel efforts to develop both in-plane single nanotube resonators as well as vertical array power devices.

Larry Epp

Papers

Design of thick frequency selective surfaces with complex apertures: Dichroics with cross-shaped and stepped rectangular apertures

Scattering from the quasi-optical ferrite circulator using a coupled integral equation/FEM solution

Dichroic Filter for Separating W-Band and Ka-Band

Design of thick frequency selective surfaces with complex apertures: dichroics with cross-shaped and stepped rectangular apertures

Engineered Carbon Nanotube Materials for High-Q Nanomechanical Resonators