J.C.M. Hwang

Lehigh University, Bethlehem, Pennsylvania, United States

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Publications (166)167.31 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: To resolve the dilemma of cell clogging or solution parasitics encountered by Coulter counters and to evolve a general-purpose electrical detection technique, we used broadband microwave measurements to overcome electrode polarization, ac dielectrophoresis to precisely place cells between narrowly spaced electrodes, and relatively wide microfluidic channels to prevent cell clogging. This unique combination of approaches resulted in reproducible sensing of single Jurkat and HEK cells, both live and dead, of different cultures at different times.
    IEEE Transactions on Microwave Theory and Techniques 09/2014; 62(9):1905-1911. DOI:10.1109/TMTT.2014.2342660 · 2.24 Impact Factor
  • C. Palego · Y. Ning · V. Gholizadeh · X. Luo · J. C. M. Hwang · C. L. Goldsmith ·
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    ABSTRACT: Novel phase shifters were designed by using only two MEMS switches to control a metamaterial-based slow-wave structure in each unit cell. A unit cell with an area smaller than 1 mm2 exhibited a phase shift of 54±15°, an insertion loss of less than 0.9 dB, and a return loss of higher than 15 dB between 12 GHz and 18 GHz. Modeling not only agrees with the measured data, but also points out possibilities for future improvement. With compact size and small number of MEMS switches, these phase shifters can have high yield, high reliability and low cost.
    2014 IEEE/MTT-S International Microwave Symposium - MTT 2014; 06/2014
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    ABSTRACT: This paper experimentally quantified the long-term effects of RF burn-in, in terms of burn-in and recovery times, and found the effects to be semipermanent. Specifically, most of the benefit could be realized after approximately 20 min of RF burn-in, which would then last for several months. Additionally, since similar effects were observed on both real and faux switches, the effects appeared to be of electrical rather than mechanical nature. These encouraging results should facilitate the application of the switches in RF systems, where high RF power could be periodically applied to rejuvenate the switches.
    IEEE Transactions on Device and Materials Reliability 03/2013; 13(1):310-315. DOI:10.1109/TDMR.2013.2246567 · 1.89 Impact Factor
  • J.C.M. Hwang · C.L. Goldsmith ·
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    ABSTRACT: This paper reviews the progress over the past decade in improving the reliability of MEMS capacitive switches. The emphasis is on mitigating the dielectric-charging problem as it currently limits the lifetime of these switches. The most critical is to distinguish charging of the dielectric surface from that of the dielectric bulk, and then mitigate them separately. Once surface charging is eliminated and bulk charging is greatly reduced, the switch lifetime can be prolonged almost indefinitely by using an intelligent closed-loop CMOS control circuit. This will facilitate the use of MEMS capacitive switches in military and commercial systems.
    Wireless Symposium (IWS), 2013 IEEE International; 01/2013
  • Xi Luo · Yaqing Ning · D. Molinero · C. Palego · J.C.M. Hwang · C.L. Goldsmith ·
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    ABSTRACT: For the first time, intermodulation distortion of micro-electromechanical capacitive switches in the actuated state was analyzed both theoretically and experimentally. The distortion, although higher than that of switches in the suspended state, was found to decrease with increasing bias voltage but to depend weakly on modulation frequencies between 55 kHz and 1.1 MHz. This dependence could be explained by the orders-of-magnitude increase of the spring constant when the switches were actuated. Additionally, the analysis suggested that increasing the spring constant and decreasing the contact roughness could improve the linearity of actuated switches. These results are critical to micro-electromechanical capacitive switches used in tuners, filters, phase shifters, etc. where the linearity of both suspended and actuated states are critical.
    Microwave Measurement Conference (ARFTG), 2013 81st ARFTG; 01/2013
  • C. Palego · C. Merla · Y. Ning · C.R. Multari · X. Cheng · D.G. Molinero · G. Ding · X. Luo · J.C.M. Hwang ·
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    ABSTRACT: A novel broadband microchamber for electrical detection of live and dead biological cells was designed, fabricated and tested. The microchamber was formed between a gold coplanar waveguide fabricated on a quartz slide and the microfluidic channels fabricated in a polydimethylsiloxane cover. The coplanar waveguide allowed broadband impedance matching and efficient cell trapping. The microfluidic channels delivered single cells precisely. Tests on Jurkat cells in both time and frequency domains showed that live cells had lower resistance but higher capacitance than that of dead cells.
    Microwave Symposium Digest (IMS), 2013 IEEE MTT-S International; 01/2013
  • A. Denzi · C. Merla · C. Palego · F. Apollonio · J.C.M. Hwang · M. Liberti ·
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    ABSTRACT: Recently, the promising effects induced by pulsed electric fields with high intensity and short duration have been highlighted. At the nanosecond time scale, electric pulse targets become both the plasmatic membrane and the sub-cellular structures (possibility of intracellular manipulation). In this paper, a circuit cell model with nucleus is presented, validated and used in order to assess the different cellular and sub-cellular (i.e. nucleus) effects, comparing ideal nanosecond pulsed electric fields (nsPEFs) waveforms with the ones measured from a planar, broadband matched microchamber.
    Microwave Symposium Digest (IMS), 2013 IEEE MTT-S International; 01/2013
  • D. Molinero · C. Palego · X. Luo · Y. Ning · G. Ding · J.C.M Hwang · C.L. Goldmisth ·
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    ABSTRACT: Intermodulation distortion in MEMS capacitive switches was analyzed both theoretically and experimentally as a function of tone spacing and RF power. The theory and experiment consistently showed that, under high RF power, additional distortion was caused by self-heating of the switch membrane by the RF power, which decreased the membrane spring constant significantly. The results implied that, well before the input RF power triggers self-actuation, the distortion might increase rapidly to an unacceptable level, so that the power-handling capacity of MEMS capacitive switches would be limited by intermodulation distortion instead of self-actuation.
    Microwave Symposium Digest (IMS), 2013 IEEE MTT-S International; 01/2013
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    ABSTRACT: This paper analyzes the dielectric charging effects in microelectromechanical capacitive switches with dielectric-dielectric contacts. Measurements were performed on switches with different contact topologies to characterize the charging of the surface and the bulk of the dielectric under different hold-down voltages and periods. The results showed a strong correlation between surface charging and surface treatment as well as contact area. With proper surface treatment and contact bumps, surface charging was suppressed and the remaining bulk charging was sufficiently small to allow the switches to withstand long-term hold-down tests.
    Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS & EUROSENSORS XXVII), 2013 Transducers & Eurosensors XXVII: The 17th International Conference on; 01/2013
  • G. Ding · W. Wang · S. Halder · C. Palego · D. Molinero · J.C.M. Hwang · C.L. Goldsmith ·
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    ABSTRACT: A CMOS control circuit capable of closed-loop capacitance sensing and control of RF MEMS switches was designed, fabricated, and tested. The control was based on fine-tuning the magnitude of the bias voltage of the switches according to the difference between sensed and targeted capacitances. Intelligence could be programmed by periodically alternating the sign of the bias voltage when its magnitude to maintain the targeted capacitance drifted significantly due to dielectric charging. Such an intelligent control could also be used to compensate for process variation, ambient temperature change, and RF power loading, which would make RF MEMS capacitive switches not only more reliable, but also more robust.
    Microwave Symposium Digest (MTT), 2012 IEEE MTT-S International; 06/2012
  • C. Palego · J. C. M. Hwang · C. Merla · F. Apollonio · M. Liberti ·
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    ABSTRACT: A nanopore test circuit is proposed for single-strand DNA sequencing, which allows real-time sensing of the electric conductance of individual sections of a DNA strand as it is pulled through the nanopore by an electric current at a controlled speed. The test circuit is based on a planar microchamber with a nanochannel drilled through its multilayer graphene electrode by an electron beam. The nanochannel is self-aligned with a nanopore created in the lipid bilayer membrane of liposomes by nanosecond electric pulses. Simulation shows that by carefully controlling the magnitude, period, and repetition rate of the pulses, the diameter of the nanopore can be optimized for the best speed the DNA is pulled through the nanopore.
  • C. Palego · D. Molinero · Yaqing Ning · Xi Luo · J.C.M. Hwang · C.L. Goldsmith ·
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    ABSTRACT: For the first time, both pull-in and release transients were characterized under high RF power levels on electrostatically actuated capacitive switches that exhibited little ambient temperature dependence under small-signal conditions. In spite of the complication of buckling, thermal resistances and time constants were extracted for both pulled-in and released states. In the pulled-in state, the extracted thermal resistance and time constant were approximately 5000°C/W and 40μs, respectively. In the released state, the corresponding values were approximately 3000°C/W and 100μs, respectively. These extracted parameters could serve as the foundation for physical understanding, as well as compact modeling of large-signal transients. They could also help improve the design of switches that are more robust against temperature change and RF loading.
    Microwave Integrated Circuits Conference (EuMIC), 2012 7th European; 01/2012
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    ABSTRACT: This paper reports on the first RF MEMS capacitive switch with a capacitance ratio of 130 that is stable almost up to 3 W of RF power. From an RF point of view the device behaves as a shunt capacitive switch, but employs an ohmic contact between the movable membrane and a floating metal deposited on the dielectric-coated stationary electrode, which is used to provide a high and repeatable ON state capacitance. In addition strain-relief anchor springs guarantee almost stable performances at high temperature and high power.
    Microwave Integrated Circuits Conference (EuMIC), 2012 7th European; 01/2012
  • D. Molinero · C. Palego · X. Luo · J.C.M. Hwang · C.L. Goldsmith ·
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    ABSTRACT: We report, for the first time, the benefit of RF burn-in at power levels significantly higher than the nominal handling capacity of micro-electromechanical capacitive switches. The benefit appears to be permanent, so that, after burn-in, the switches remain less vulnerable to dielectric charging and, presumably, more reliable. It was speculated that high RF power permanently changed the bond configuration of the silicon-dioxide dielectric, which prevented charge injection under DC bias. Obviously, more detailed study is needed to elucidate the detailed burn-in mechanism. However, this initial result is very encouraging and can facilitate the application of these switches in many RF systems.
    Microwave Symposium Digest (MTT), 2012 IEEE MTT-S International; 01/2012
  • C.L. Goldsmith · J.C.M. Hwang · C. Gudeman · O. Auciello · J.L. Ebel · H.S. Newman ·
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    ABSTRACT: RF MEMS switches have evolved significantly since the early days of testing unpackaged devices in an uncontrolled environment with failure modes that could only be guessed at. Today, MEMS switch technology has effective, RF-friendly wafer-level packaging, demonstrated temperature robustness, and failure modes that can be characterized and modeled from accelerated testing. This presentation overviews the advances in packaging, reliability, and environmental robustness for RF MEMS switches made on DARPA's HERMIT program. It also includes more recent developments in novel nanostructured switch dielectrics, CMOS co-integration, intelligent CMOS control, and operation of RF MEMS in adverse thermal and radiation environments.
    Microwave Symposium Digest (MTT), 2012 IEEE MTT-S International; 01/2012
  • P. D.ye · B.yang · K. K.ng · J.bude · G. D.wilk · S.halder · J. C. M.hwang ·
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    ABSTRACT: We report on a GaN metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT) using atomic layer deposition (ALD) Al2O3 film as a gate dielectric and for surface passivation simultaneously. Compared to the conventional AlGaN/GaN HEMT of the same design, six order of magnitude smaller gate leakage current and tripled drain current at forward gate bias demonstrate the effectiveness of ALD Al2O3 as a gate dielectric. The high transconductance and high effective two-dimensional electron mobility verify the high-quality of Al2O3/AlGaN interface with low interface trap density. The Al2O3 passivation effect is also studied by sheet resistance measurement and short pulse drain characterization.
    International Journal of High Speed Electronics and Systems 11/2011; 14(03). DOI:10.1142/S0129156404002843
  • G Ding · J Deng · L Zhou · Q Gan · J C M Hwang · V Dierolf · F J Bartoli · C Mazuir · W V Schoenfeld ·
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    ABSTRACT: Optical properties of Al nanogrids of different pitches and gaps were investigated both theoretically and experimentally. Three-dimensional finite-difference time-domain simulation predicted that surface plasmons at the air/Al interface would enhance ultraviolet transmission through the subwavelength gaps of the nanogrid, making it an effective electrode on GaN-based photodetectors to compensate for the lack of transparent electrode and high p-type doping. The predicted transmission enhancement was verified by confocal scanning optical microscopy performed at 365 nm. The quality of the nanogrids fabricated by electron-beam lithography was verified by near-field scanning optical microscopy and scanning electron microscopy. Based on the results, the pitch and gap of the nanogrids can be optimized for the best trade-off between electrical conductivity and optical transmission at different wavelengths. Based on different cutoff wavelengths, the nanogrids can also double as a filter to render photodetectors solar-blind.
    Optics Letters 09/2011; 36(18):3663-5. DOI:10.1364/OL.36.003663 · 3.29 Impact Factor
  • Source
    Weike Wang · James C M Hwang · Yi Xuan · Peide D. Ye ·
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    ABSTRACT: The electron mobility in Al<sub>2</sub>O<sub>3</sub>/In x Ga<sub>1-</sub> x As ( x = 0.53, 0.65, or 0.75) metal-oxide-semiconductor field-effect transistors was analyzed for scattering by oxide charge, as well as interface charge and roughness, and compared with measured transfer characteristics from depletion to inversion. The analysis showed that, under strong inversion, the electron mobility was mainly limited by interface roughness. The extracted interface roughness from the measured data was two to seven times that of the interface between a high- k dielectric and Si, assuming the correlation lengths were comparable. Therefore, to fully benefit from the high bulk mobility of InGaAs, its interface roughness with the gate oxide needs to be further improved.
    IEEE Transactions on Electron Devices 08/2011; 58(7-58):1972 - 1978. DOI:10.1109/TED.2011.2146255 · 2.47 Impact Factor
  • C. Palego · S. Halder · J.C.M. Hwang · C. Merla · M. Liberti · F. Apollonio · A. Paffi ·
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    ABSTRACT: Compact measurement setup and test structure for nanosecond electroporation of biological cells were demonstrated. The test structure was based on a coplanar waveguide with a defected ground structure that afforded broadband impedance match with little dispersion or parasitic. The defected ground structure with a 10-μm gap formed a microchamber to readily accept biological solutions and to allow the measurement to be quickly performed before the solution evaporated or the cell activity changed. The measured results in conjunction with detailed electromagnetic analysis of a three-layer spherical cell model showed that the present measurement setup was capable of delivering a nanosecond 0.1-V potential across a plasmatic membrane. This transmembrane potential, although an order of magnitude lower than the typical threshold for membrane poration, could be increased by using nanosecond pulses with order-of-magnitude higher amplitude or 10-ns pulses with three times higher amplitude.
    Microwave Symposium Digest (MTT), 2011 IEEE MTT-S International; 07/2011
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    ABSTRACT: form only given, as follows. RF power, when approaching the handling capacity of microelectromechanical capacitive switches, was found to accelerate both the charging and discharging of the dielectric in the switches. The amount of acceleration appeared to be greater than what could be explained by self biasing and self heating. Since the long-term reliability of the switches is limited by dielectric charging, the RF power-handling capacity of the switches may have to be derated to ensure long-term reliability.
    IEEE MTT-S International Microwave Symposium digest. IEEE MTT-S International Microwave Symposium 06/2011; DOI:10.1109/MWSYM.2011.5973339

Publication Stats

3k Citations
167.31 Total Impact Points


  • 1992-2014
    • Lehigh University
      • Department of Electrical and Computer Engineering
      Bethlehem, Pennsylvania, United States
  • 2001
    • Nanyang Technological University
      • School of Electrical and Electronic Engineering
      Tumasik, Singapore
  • 1993
    • Westinghouse Electric Company
      Monroeville, Pennsylvania, United States
  • 1986
    • General Electric
      Fairfield, California, United States