The Experts below are selected from a list of 7800 Experts worldwide ranked by ideXlab platform
Zhongping Chen - One of the best experts on this subject based on the ideXlab platform.
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miniaturized probe based on a Microelectromechanical System mirror for multiphoton microscopy
Optics Letters, 2008Co-Authors: Woonggyu Jung, Suo Tang, Daniel T Mccormic, Tiquiang Xie, Yehchan Ahn, I V Tomov, Tatiana B Krasieva, Bruce J Tromberg, Zhongping ChenAbstract:A factor that limits the use of multiphoton microscopy (MPM) in clinical and preclinical studies is the lack of a compact and flexible probe. We report on a miniaturized MPM probe employing a Microelectromechanical System (MEMS) scanning mirror and a double-clad photonic crystal fiber (DCPCF). The use of a MEMS mirror and a DCPCF provides many advantages, such as size reduction, rapid and precise scanning, efficient delivery of short pulses, and high collection efficiency of fluorescent signals. The completed probe was 1 cm in outer diameter and 14 cm in length. The developed probe was integrated into an MPM System and used to image fluorescent beads, paper, and biological specimens.
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in vivo three dimensional spectral domain endoscopic optical coherence tomography using a Microelectromechanical System mirror
Optics Letters, 2007Co-Authors: Woonggyu Jung, Matthew Brenner, Yehchan Ahn, Daniel T Mccormick, Ali Sepehr, Brian J F Wong, N C Tien, Zhongping ChenAbstract:A biopsy is a well-known medical test used to evaluate tissue abnormality. Biopsy specimens are invasively taken from part of a lesion and visualized by microscope after chemical treatment. However, diagnosis by means of biopsy is not only variable due to depth and location of specimen but may also damage the specimen. In addition, only a limited number of specimens can be obtained, thus, the entire tissue morphology cannot be observed. We introduce a three-dimensional (3-D) endoscopic optical biopsy via optical coherence tomography employing a dual-axis Microelectromechanical System scanning mirror. Since this technique provides high-resolution, noninvasive, direct, and multiple visualization of tissue, it could function as a clinical biopsy with advanced performance. The device was integrated with a conventional endoscope and utilized to generate in vivo 3-D clinical images in humans and animals.
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in vivo endoscopic optical coherence tomography by use of a rotational Microelectromechanical System probe
Optics Letters, 2004Co-Authors: Peter H Tran, David Mukai, Matthew Brenner, Zhongping ChenAbstract:A novel endoscopic optical coherence tomography probe was designed and constructed with a 1.9-mm Microelectromechanical System (MEMS) motor. The new MEMS endoscopic probe design eliminates the need to couple the rotational energy from the proximal to the distal end of the probe. Furthermore, the endoscopic probe's sheath and fiber have the advantages of having a much smaller diameter and being more flexible than traditional endoscopes since no reinforcement is needed to couple the rotational torque. At the distal end, a prism mounted on a micromotor deflects the light rays to create a transverse circular-scanning pathway. Because our MEMS scanner does not require the coupling of a rotational single-mode fiber, a high scanning speed is possible while eliminating unstable optical signals caused by nonuniform coupling.
G Papaioannou - One of the best experts on this subject based on the ideXlab platform.
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determination of long time discharge current in Microelectromechanical System capacitive switches
Applied Physics Letters, 2011Co-Authors: M Koutsoureli, G PapaioannouAbstract:An improved method to study the long term discharge current through the dielectric film in Microelectromechanical System capacitive switches is presented. The method allows the detection of currents in the sub-fempto-Ampere range by monitoring the decay of the bias for minimum capacitance in the pull-up state. The method has been applied for time interval in excess of 10 000 s. Finally, it is shown that in carefully designed devices the method allows the calculation of the current that arises from the charge fluctuation decay.
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floating electrode Microelectromechanical System capacitive switches a different actuation mechanism
Applied Physics Letters, 2011Co-Authors: G Papaioannou, F Giacomozzi, E Papandreou, B MargesinAbstract:The paper investigates the actuation mechanism in floating electrode Microelectromechanical System capacitive switches. It is demonstrated that in the pull-in state, the device operation turns from voltage to current controlled actuation. The current arises from Poole-Frenkel mechanism in the dielectric film and Fowler-Nordheim in the bridge-floating electrode air gap. The pull-out voltage seems to arise from the abrupt decrease of Fowler-Nordheim electric field intensity. This mechanism seems to be responsible for the very small difference with respect to the pull-in voltage.
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effect of space charge polarization in radio frequency Microelectromechanical System capacitive switch dielectric charging
Applied Physics Letters, 2006Co-Authors: G Papaioannou, M Exarchos, V Theonas, J Psychias, G Konstantinidis, D Vasilache, Alexandru Muller, D NeculoiuAbstract:The letter presents the investigation of the temperature dependence of the charging mechanism of dielectric layer in radio frequency Microelectromechanical System switch. The accumulated charge kinetics are monitored through the transient response of device capacitance when a bias greater than pull-in is applied. The capacitance transient response is shown to follow a stretched exponential law. The “time scale” of the stretched exponential process is found to be thermally activated, with an activation energy that is determined from Arrhenius plot.
Francis Bony - One of the best experts on this subject based on the ideXlab platform.
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mems accelerometer embedded in a self mixing displacement sensor for parasitic vibration compensation
Optics Letters, 2011Co-Authors: Usman Zabit, Thierry Bosch, Olivier Daniel Bernal, Francis BonyAbstract:A self-mixing (SM) laser displacement sensor coupled with a Microelectromechanical System (MEMS) accelerometer is presented that enables reliable displacement measurements even in the case of a nonstationary laser head. The proposed technique allows the use of SM-based sensors for embedded applications. The System resolution is currently limited to approximately 300 nm due to the noise characteristics of the currently used accelerometer. It is shown that this resolution can be greatly improved by the use of a low noise accelerometer.
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mems accelerometer embedded in a self mixing displacement sensor for parasitic vibration compensation
Optics Letters, 2011Co-Authors: Usman Zabit, Thierry Bosch, Olivier Daniel Bernal, Francis BonyAbstract:A self-mixing (SM) laser displacement sensor coupled with a Microelectromechanical System (MEMS) accelerometer is presented that enables reliable displacement measurements even in the case of a nonstationary laser head. The proposed technique allows the use of SM-based sensors for embedded applications. The System resolution is currently limited to approximately 300 nm due to the noise characteristics of the currently used accelerometer. It is shown that this resolution can be greatly improved by the use of a low noise accelerometer.
Alan S. Edelstein - One of the best experts on this subject based on the ideXlab platform.
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Validation of the Microelectromechanical System flux concentrator concept for minimizing the effect of 1/f noise
Journal of Applied Physics, 2009Co-Authors: Alan S. Edelstein, J. E. Burnette, William E. Egelhoff, E R Nowak, K. Olver, Shu Fan ChengAbstract:With the Microelectromechanical System (MEMS) flux concentrator, we have been able to increase the operating frequency of small magnetic sensors above the region where 1/f noise dominates. The device accomplished this by modulating the field via the oscillatory motion of flux concentrators on MEMS flaps. Electrostatic comb drives were used to drive the MEMS flaps. We have demonstrated an increase in the signal to noise ratio at 1 Hz, that the power signal correctly depends on V4 where V is the amplitude of the voltage energizing the comb drives, and that the signal increases dramatically with vacuum packaging.
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Minimizing 1/f noise in magnetic sensors using a Microelectromechanical System flux concentrator
Journal of Applied Physics, 2002Co-Authors: Alan S. EdelsteinAbstract:A device, a Microelectromechanical System flux concentrator, is described that can minimize 1/f noise in magnetic sensors by modulating the magnetic field at the position of the sensor. This has the effect of shifting the operating frequency to higher frequencies where the 1/f noise can be 1 or 2 orders of magnitude smaller. Magnetic and mechanical modeling results on a design that will operate at 29 kHz are presented.
Shu Fan Cheng - One of the best experts on this subject based on the ideXlab platform.
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Validation of the Microelectromechanical System flux concentrator concept for minimizing the effect of 1/f noise
Journal of Applied Physics, 2009Co-Authors: Alan S. Edelstein, J. E. Burnette, William E. Egelhoff, E R Nowak, K. Olver, Shu Fan ChengAbstract:With the Microelectromechanical System (MEMS) flux concentrator, we have been able to increase the operating frequency of small magnetic sensors above the region where 1/f noise dominates. The device accomplished this by modulating the field via the oscillatory motion of flux concentrators on MEMS flaps. Electrostatic comb drives were used to drive the MEMS flaps. We have demonstrated an increase in the signal to noise ratio at 1 Hz, that the power signal correctly depends on V4 where V is the amplitude of the voltage energizing the comb drives, and that the signal increases dramatically with vacuum packaging.
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progress toward a thousandfold reduction in 1 f noise in magnetic sensors using an ac Microelectromechanical System flux concentrator invited
Journal of Applied Physics, 2006Co-Authors: A S Edelstein, M Pedersen, E R Nowak, Shu Fan ChengAbstract:The potential advantage of some magnetic sensors having a large response is greatly decreased because of the 1∕f noise. We are developing a device, the Microelectromechanical System (MEMS) flux concentrator, that will mitigate the effect of this 1∕f noise. It does this by placing flux concentrators on MEMS structures that oscillate at kilohertz frequencies. By shifting the operating frequency, the 1∕f noise will be reduced by one to three orders of magnitude depending upon the sensor and the desired operating frequency. We have succeeded in fabricating the necessary MEMS structures and observing the desired kilohertz normal-mode resonant frequencies. Only microwatts are required to drive the motion. We have used spin valves for our magnetic sensors. The measured field enhancement provided by the flux concentrators agrees to within 4% with the value estimated from finite element calculations. No difference was detected in noise measurements on spin valves with and without the flux concentrators. This resul...
