Electromagntic Applications in Nanotechnology

Team:
Gerald DeJean, Daniela Staiculescu, Trang Thai, Justin Ratner, Li Yang

Carbon nanotubes (CNTs)

  • Hexagonal networks of carbon atoms
    • 1nm in diameter
    • 1 to 100 microns of length
  • Layer of graphite rolled up into a cylinder
  • Manufactured:
    • Carbon arc-discharge technique
    • Laser-ablation technique
    • Chemical vapor decomposition technique (CVD)
  • Dielectric proces controlled through:
    • Tube diameter
    • Chirality
    • Doping

  • Single Wall Nanotube – 1 Wall
  • Double Wall Nanotube – 2 Walls
  • Multi-Wall Nanotube ~ 50 Walls

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CNT Mixtures/Composites Properties

  • Different mixtures of CNTs (Ceramic/SWNT, Epoxy/SWNT, Epoxy/MWNT, etc.)
        => conductivity ranging from 10-3 to 102
  • Control weight % of CNTs in the composites
        => dielectric constant in the range of 1-16 around 1-20GHz range
  • Adsorption of different gases cause different changes in:
    • Dielectric constant
    • Loss tangent
  • Funtionalized CNTs in composites to improve gas sensitivity
  • Vertically allignment of CNTs in composites to improve gas sensitivity
  • Quick response time (smaller than contemporary sensors)
  • Ultra-high sensitivty (order of part-per-billion and part-per-million)
  • System is reversible, however long recovery time

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CNT based Transmission Line for Gas Sensing

  • The substrate is a CNT based materials that are sensitive to gases such as NOx, Nitrogen, Carbon dioxide, etc.
  • When in contact with intruding gases, the dielectric constant and conductivity of the CNT material are altered.
  • A co-planar transmission line with CNT based substrate was known to produce magnitude and phase changes in the transmitted signal when in contact with the intruding gases.
  • The CNT transmission line is utilized with our designed antenna and system in Figure 1 to produce observable parameters for easy detection in wireless gas sensing.

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Surface Plasmon Applications

  • Using Surface Plasmon Resonance (SPR) to detect changes in electrical properties of CNT based material thin films
  • Grating structure to couple waves in microwave range frequencies
        => integrating with standard wireless network
  • The shift in frequency (hundred of MHz in the operating range of 60 GHz) and changes in magnitude of the reflected waves allows accurate remote gas sensing.
  • Our designed sensor is completely passive and capable of selective sensing.

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CNT based Gas Sensing Using Surface Plasmons

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A Novel Front-End Radio Frequency Pressure Transducer Based on a Dual-band Resonator for Wireless Sensing

Team:
Trang Thai, Gerald DeJean

Pressure Sensor Applications

  • Automation: measuring full/empty tank os liquid, leakage monitoring, etc.
  • Process control
  • Electronics: microphones
  • Automotive: engine condition, airbag, acceleration monitoring, tire pressure, etc.
  • Medical: blood, artery, intracranial pressure monitoring, hearing aid equipments, etc.
  • Public safety: weather, food processing, use together with gas sensors

RF Wireless Pressure Transducer Concept

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RF Wireless Pressure Transducer

  • Fewer components
  • Smaller system size
  • Less power consumption

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RF Pressure Transducer

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Simulation Results at 30 – 55 GHz

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Prototype for Implementation at 5-8 GHz Range

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Measured Results at 5-8 GHz Range

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Conclusions

  • A new highly sensitive radio frequency pressure transducer at millimeter wave frequency range
  • Seamlessly integrated with other RF circuits in the LTCC multilayer packaging technology
  • Dualband between 30-55 GHz:
    • A wireless communications link
    • A remote sensing differential pressure indicator
  • Simplify the design process, reduce the device’s size, and reduce power consumption of the sensor at device level
  • Providing a sensitivity of 116 MHz/um
  • Proof-of-concept prototype at 5-8 GHz: sensitivity 250 MHz/787um
  • Future work:
    • The millimeter wave prototype based on LTCC using Si membrane
    • Modifications for multilayer organics, such as LCP that allow realization of wireless implantable sensors for biomedical applications

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Characterization and Testing of Novel Polarized Nanomaterial Textiles for Ultrasensitive Wireless Gas Sensor

Team:
Trang Thai, Justin Ratner, Gerald DeJean


Collaborator:
Wenhua Chen (State Key Lab on Microwave & Digital Communication, Tsinghua University, Beijing, China)

Polarized Nano-material (PNM)

  • Carbon nanotubes (CNTs) are grown on a Silicon substrate into super-aligned nanotube arrays
  • PNM samples are formed by continuous yarns of pure CNT bundles aligned parallel to one another due to van der Waals interations
  • Highly polarized and excellent shielding effect
  • Investigated at Ka-band (26.5 – 40 GHz) for millimeter wave applications such as ultrasensitive gas sensing

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Characterization set up

  • 20 layers of PNM textile are weaved one by one on to the waveguide aperture, embedded between 2 waveguide sections
  • The waveguides are WR-28 operating in Ka-band of 26.5 – 40 GHz
  • Scattering parameters of 3 different polarization schemes are measured

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S-parameter Measurements

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Impedance Analysis

  • The impedance profiles of polarizations 1 and 3 show the distinct resonance characteristics of radiators
  • The first time the collective resonance behavior of the carbon nanotubes is shown in the microwave range due to highly aligned CNTs in the PNM layers

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Study of Graphene Nanoribbons in Microwave frequency range

Team:
Trang Thai, Gerald DeJean


Collaborator:
Dr. DeHeer’s Expitaxial Graphene Lab (School of Physics, Georgia Institute of Technology)

Properties and Applications

  • Extraordinary electrical and mechanical properties similar to carbon nanotubes
  • Capable of being patterned into desired geometry
  • High carrier mobility => ideal material for detecting THz radiation
  • Passive components such as antennas and interconnects (transmission lines) => enable complete integrated graphene based electronics
  • We investigate the planar epitaxial graphene structures grown on SiC substrates:
    • Conductance and scattering parameter study of GNRs in 2-port network at millimeter and sub-millimeter wave signals
    • Gas sensing capability of GNRs for highly sensitive wireless sensors

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