Hajjaj, Amal; Nanaiah, Karumbaiah Chappanda; Batra, Nitin M; Hafiz, Md Abdullah Al; Da Costa, Pedro M. F. J.; Younis, Mohammad I.(Sensors and Actuators A: Physical, Elsevier BV, 2019-04-05)[Article]
Conventional pressure sensors rely on diaphragms with large surface areas, which deform in response to pressure. Down scalability of these devices is one of the major challenges of the technology along with reducing the overall actuation voltage and achieving ultra-high sensitivity. We present a sensitive miniature pressure sensor based on the change in the physisorbed gases with the pressure of the surrounding air. The sensor consists of a suspended individual multiwall carbon nanotube (MWCNT) clamped on Au electrodes by electron-beam-induced deposition (EBID) of Pt. The variation in the surrounding pressure is shown to be tracked by monitoring the change in the resistivity, hence resistance, of the MWCNT bridge structure due to the change in percentage of oxygen and humidity in the surrounding medium with pressure. The experimental data reveal the practicability and simplicity of the proposed pressure sensor.
We report a novel modular plug-and-play microfluidic device for versatile emulsion generation, which consists of three parts: a top module for the dispersed phase supply, a glass capillary for emulsion creation and a bottom module for the continuous phase supply. By combining different modules and tapered glass capillaries, single emulsions, Janus emulsions and double emulsions have been successfully produced. The hybrid strategy allows us to produce smaller droplets through the tapered glass nozzles compared to current fully 3D-printed devices. On the other hand, it provides a simple and plug-and-play assembly manner compared to conventional microfluidic devices. Screw-thread plus gasket strategy has been proved to successfully seal the device and separate different liquid phases. Finally, magnetically responsive microparticles are synthesized based on the droplet templates produced in our device, which can be potentially applied in sensor and actuator fields.
Ilyas, Saad; Nanaiah, Karumbaiah Chappanda; Hafiz, Md Abdullah Al; Ramini, Abdallah; Younis, Mohammad I.(Sensors and Actuators A: Physical, Elsevier BV, 2016-06-27)[Article]
We present an experimental and theoretical investigation of the static and dynamic behavior of electrostatically coupled laterally actuated silicon microbeams. The coupled beam resonators are composed of two almost identical flexible cantilever beams forming the two sides of a capacitor. The experimental and theoretical analysis of the coupled system is carried out and compared against the results of beams actuated with fixed electrodes individually. The pull-in characteristics of the electrostatically coupled beams are studied, including the pull-in time. The dynamics of the coupled dual beams are explored via frequency sweeps around the neighborhood of the natural frequencies of the system for different input voltages. Good agreement is reported among the simulation results and the experimental data. The results show considerable drop in the pull-in values as compared to single microbeam resonators. The dynamics of the coupled beam resonators are demonstrated as a way to increase the bandwidth of the resonator near primary resonance as well as a way to introduce increased frequency shift, which can be promising for resonant sensing applications. Moreover the dynamic pull-in characteristics are also studied and proposed as a way to sense the shift in resonance frequency.
Ilyas, Saad; Carreno, Armando Arpys Arevalo; Bayes, Ernesto; Foulds, Ian G.; Younis, Mohammad I.(Sensors and Actuators A: Physical, Elsevier BV, 2015-10-28)[Article]
In this work we demonstrate torsion based complementary MEMS logic device, which is capable, of performing INVERTER, AND, NAND, NOR, and OR gates using one physical structure within an operating range of 0-10 volts. It can also perform XOR and XNOR with one access inverter using the same structure with different electrical interconnects. The paper presents modeling, fabrication and experimental calculations of various performance features of the device including lifetime, power consumption and resonance frequency. The fabricated device is 535 μm by 150 μm with a gap of 1.92 μm and a resonant frequency of 6.51 kHz. The device is capable of performing the switching operation with a frequency of 1 kHz.
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