5 research outputs found

    Plasmonic-resonant bowtie antenna for carbon nanotube photodetectors

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    The design of bowtie antennas for carbon nanotube (CNT) photodetectors has been investigated. CNT photodetectors have shown outstanding performance by using CNT as sensing element. However, detection wavelength is much larger than the diameter of the CNT, resulting in small fill factor. Bowtie antenna can confine light into a subwavelength volume based on plasmonic resonance, thus integrating a bowtie antenna to CNT photodetectors can highly improve photoresponse of the detectors. The electric field enhancement of bowtie antennas was calculated using the device geometry by considering fabrication difficulties and photodetector structure. It is shown that the electric field intensity enhancement increased exponentially with distance reduction between the CNT photodetector to the antenna. A redshift of the peak resonance wavelength is predicted due to the increase of tip angles of the bowtie antennas. Experimental results showed that photocurrent enhancement agreed well with theoretical calculations. Bowtie antennas may find wide applications in nanoscale photonic sensors. Copyright © 2012 Hongzhi Chen et al.Link_to_subscribed_fulltex

    Automated nanomanufacturing system to assemble carbon nanotube based devices

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    In this paper we report the design and implementation of a novel automated manufacturing system for carbon nanotube (CNT)-based nanodevices, which integrates a new dielectrophoretic (DEP) microchamber into a robotic-based deposition workstation. The microchamber has been fabricated to separate and select CNTs with the desired electronic property by using DEP force. Moreover, a series of tools for mass-producing consistent nanodevices has been developed with the CNT deposition workstation, such as computer-controllable micromanipulators and a micro-active nozzle. Detailed experimental studies of the CNT separation and deposition processes have been performed on both single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). Preliminary results show that CNTs could be manipulated to multiple pairs of microelectrodes repeatedly. Consistent I-V characteristics and CNT formations of the fabricated devices were obtained. The yield of semi-conducting CNTs was also increased by using our system. Therefore, by using the proposed CNT separation and deposition system, CNT-based nanodevices with specific and consistent electronic properties can be manufactured automatically and effectively.Link_to_subscribed_fulltex

    Design and fabrication of precision carbon nanotube-based flexural transducers

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    Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 179-197).As mechanical devices move towards the nanoscale, smaller and more sensitive force and displacement sensors need to be developed. Currently, many biological, materials science, and nanomanufacturing applications could benefit from multi-axis micro- and nanoscale sensors with fine force and displacement resolutions. Unfortunately, such systems do not yet exist due to the limitations of traditional sensing techniques and fabrication procedures. Carbon nanotube-based (CNT) piezoresistive transducers offer the potential to overcome many of these limitations. Previous research has shown the potential for the use of CNTs in high resolution micro- and nanoscale sensing devices due to the high gauge factor and inherent size of CNTs. However, a better understanding of CNT-based piezoresistive sensors is needed in order to be able to design and engineer CNT-based sensor systems to take advantage of this potential. The purpose of this thesis is to take CNT-based strain sensors from the single element test structures that have been fabricated and turn them into precision sensor systems that can be used in micro- and nanoscale force and displacement transducers. In order to achieve this purpose and engineer high resolution CNT-based sensor systems, the design and manufacturing methods used to create CNT-based piezoresistive sensors were investigated. At the system level, a noise model was developed in order to be able to optimize the design of the sensor system. At the element level, a link was established between the structure of the CNT and its gauge factor using a theoretical model developed from quantum mechanics. This model was confirmed experimentally using CNT-based piezoresistive sensors integrated into a microfabricated test structure. At the device level, noise mitigation techniques including annealing and the use of a protective ceramic coating were investigated in order to reduce the noise in the sensor. From these investigations, best practices for the design and manufacturing of CNT-based piezoresistive sensors were established. Using these best practices, it is possible to increase the performance of CNT-based piezoresistive sensor systems by more than three orders of magnitude. These best practices were implemented in the design and fabrication of a multi-axis force sensor used to measure the adhesion force of an array of cells to the different material's surfaces for the development of biomedical implants. This force sensor is capable of measuring forces in the z-axis as well as torques in the [theta]x and [theta]y axis. The range and resolution of the force sensor were determined to be 84 [mu]N and 5.6 nN, respectively. This corresponds to a dynamic range of 83 dB, which closely matches the dynamic range predicted by the system noise model used to design the sensor. The accuracy of the force sensor is better than 1% over the device's full range.by Michael A. Cullinan.Ph.D
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