David Dubuc

Experimental determination of microwave attenuation and electrical permittivity of double-walled carbon nanotubes

The attenuation and the electrical permittivity of the double-walled carbon nanotubes (DWCNTs) were determined in the frequency range of 1–65GHz. A micromachined coplanar waveguide transmission line supported on a Si membrane with a thickness of 1.4μm was filled with a mixture of DWCNTs. The propagation constants were then determined from the S parameter measurements. The DWCNTs mixture behaves like a dielectric in the range of 1–65GHz with moderate losses and an abrupt change of the effective permittivity that is very useful for gas sensor detection.

Microwave biosensor dedicated to the dielectric spectroscopy of a single alive biological cell in its culture medium

This paper presents a biosensor dedicated to the dielectric spectroscopy of a single and living biological cell in its liquid culture medium in the micro and millimeter wave ranges. This detector works in the near field and involves a capacitive gap to perform the electromagnetic sensing, while a microfluidic system has been developed and adapted to the RF circuit to precisely localize the single biological cell under study. Both capacitive and conductive contrasts of a living biological cell measured in its culture medium are accessible. A living B lymphoma cell has then been measured from 40 MHz up to 40 GHz, with a measured capacitive contrast of the order of several hundreds of attofarads.

Investigation of charging mechanisms in Metal-Insulator-Metal structures

In this paper we have investigated the temperature dependence of the charging effects in Metal-Insulator-Metal structures, aiming to obtain a better insight on the charging mechanism of RF-MEMS switch insulating layer. The accumulated charge kinetics have been monitored through the transient response of the depolarization current. The transient response is shown to follow rather a stretched exponential law. The time scale of the process is found to be thermally activated with activation energy determined by Arrhenius plot. The results have been compared to thermally stimulated depolarization current assessment.

Microwave signatures of alive B-lymphoma cells suspensions

This publication deals with the determination of the microwave dielectric signatures of tumorous B-lymphoma cells (NHL) up to 40 GHz. It is demonstrated that in-liquid microwave detection permits to warrant cells living without deterioration of the analysis capabilities. The key role of the microwave absorption parameter for cells detection is moreover pointed out. The richness of the microwave signature combined with the non invasivity of such a technique provide to biologists new way to investigate cells, to identify tumorous vs non tumorous ones.

Millimeter wave carbon nanotube gas sensor

This Letter reports experimental observations regarding the significant changes in the transmission modulus and phase of the propagating microwave signals up to 110 GHz in a micromachined coplanar waveguide supported on a dielectric membrane with a thickness of 1.4u2009μm filled with a mixture of carbon nanotubes when exposed to nitrogen gas. These large shifts of amplitude and phase of microwave signals due to gas absorption represent the experimental basis on which a miniature wireless gas sensor could be implemented.

Nanoelectromechanical switches based on carbon nanotubes for microwave and millimeter waves

In this letter the authors analyze two configurations of nanoelectromechanical switches, which are working in the microwave and millimeter wave frequency ranges. Metallic nanotubes vertically or horizontally positioned on a propagating high frequency planar waveguide disable or enable the electromagnetic field propagation, whether they are actuated or not by a dc electric field of a few volts. Although the dimensions of metallic nanotubes are very small in comparison with the planar waveguide dimensions and the operating wavelengths, these switches are very efficient and agile.

High performance thin film bulk acoustic resonator covered with carbon nanotubes

This letter presents experimental results concerning a thin film bulk acoustic wave resonator realized on a thin GaN membrane and covered with a thin film of double walled carbon nanotube mixture. The quality factor was measured before and after the coating of the resonator with the nanotube thin film. The quality factor has increased more than ten times when the resonator was coated with nanotubes, due to their high elasticity modulus and low density, which confers a much higher acoustic impedance of the resonator electrodes and thus confines much better the longitudinal acoustic standing waves inside the resonator.

Original MEMS-Based Single Pole Double Throw topology for millimeter wave space communications

This paper presents the design, fabrication and characterization of a MEMS-Based Single Pole Double Throw (SPDT) circuit for millimeterwave applications. High performances are achieved thanks to an original circuit design based on MEMS synthesized quarter wave line combined with surface and bulk micromachinings of silicon. 0.6 dB insertion loss of the SPDT circuit was measured with an isolation of 21dB at 30GHz.

Investigation of Stiction Effect in Electrostatic Actuated RF MEMS Devices

The main failure mode of electrostatic actuated RF MEMS, the stiction of the bridge due to dielectric charging, is investigated using an appropriate methodology based on the MEMS microwave performances measurement for the failure detection and on the threshold voltages evolution monitoring for the failure analysis. The authors present an advanced investigation of this failure mode, the dynamic S21(V) measurement, in order to extract some failure driving parameters and the authors finally propose a solution to avoid this failure and improve RF MEMS reliability

Microwave dielectric spectroscopy of a single biological cell with improved sensitivity up to 40 GHz

This paper presents the sensitivity optimization of a microwave biosensor dedicated to the analysis of a single living biological cell from 40 MHz to 40 GHz, directly in its culture medium. To enhance the sensor sensitivity, different capacitive gap located in the center of the biosensor, below the cell position, have been evaluated with different beads sizes. The best capacitive and conductive contrasts have been reached for a gap width of 5 μm with beads exhibiting diameters of 10 and 20 μm, due to electromagnetic field penetration in the beads. Contrasts improvement of 40 and 60 % have been achieved with standard deviations in the order of only 4% and 6% for the capacitive and conductive contrasts respectively. This sensor therefore permits to measure single living biological cells directly in their culture medium with capacitive and conductive contrasts of 0.4 fF at 5 GHz and 85 μS at 40 GHz, and associated standard deviations estimated at 7% and 14% respectively.