| 1. |
- Fan, Xuge, et al.
(författare)
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Manufacture and characterization of graphene membranes with suspended silicon proof masses for MEMS and NEMS applications
- 2020
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Ingår i: MICROSYSTEMS & NANOENGINEERING. - : NATURE PUBLISHING GROUP. - 2055-7434. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- Graphene's unparalleled strength, chemical stability, ultimate surface-to-volume ratio and excellent electronic properties make it an ideal candidate as a material for membranes in micro- and nanoelectromechanical systems (MEMS and NEMS). However, the integration of graphene into MEMS or NEMS devices and suspended structures such as proof masses on graphene membranes raises several technological challenges, including collapse and rupture of the graphene. We have developed a robust route for realizing membranes made of double-layer CVD graphene and suspending large silicon proof masses on membranes with high yields. We have demonstrated the manufacture of square graphene membranes with side lengths from 7 mu m to 110 mu m, and suspended proof masses consisting of solid silicon cubes that are from 5 mu mx5 mu mx16.4 mu m to 100 mu mx100 mu mx16.4 mu m in size. Our approach is compatible with wafer-scale MEMS and semiconductor manufacturing technologies, and the manufacturing yields of the graphene membranes with suspended proof masses were >90%, with >70% of the graphene membranes having >90% graphene area without visible defects. The measured resonance frequencies of the realized structures ranged from tens to hundreds of kHz, with quality factors ranging from 63 to 148. The graphene membranes with suspended proof masses were extremely robust, and were able to withstand indentation forces from an atomic force microscope (AFM) tip of up to 7000nN. The proposed approach for the reliable and large-scale manufacture of graphene membranes with suspended proof masses will enable the development and study of innovative NEMS devices with new functionalities and improved performances.
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| 2. |
- Fan, Xuge, et al.
(författare)
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Resonant Transducers Consisting of Graphene Ribbons with Attached Proof Masses for NEMS Sensors
- 2023
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Ingår i: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 7:1, s. 102-109
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Tidskriftsartikel (refereegranskat)abstract
- The unique mechanical and electrical properties of graphene make it an exciting material for nanoelectromechanical systems (NEMS). NEMS resonators with graphene springs facilitate studies of graphene's fundamental material characteristics and thus enable innovative device concepts for applications such as sensors. Here, we demonstrate resonant transducers with ribbon-springs made of double-layer graphene and proof masses made of silicon and study their nonlinear mechanics at resonance both in air and in vacuum by laser Doppler vibrometry. Surprisingly, we observe spring-stiffening and spring-softening at resonance, depending on the graphene spring designs. The measured quality factors of the resonators in a vacuum are between 150 and 350. These results pave the way for a class of ultraminiaturized nanomechanical sensors such as accelerometers by contributing to the understanding of the dynamics of transducers based on graphene ribbons with an attached proof mass.
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| 3. |
- Gevari, Moein Talebian, et al.
(författare)
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Engineered Lateral Roughness Element Implementation and Working Fluid Alteration to Intensify Hydrodynamic Cavitating Flows on a Chip for Energy Harvesting
- 2020
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Ingår i: Micromachines. - : MDPI. - 2072-666X. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Hydrodynamic cavitation is considered an effective tool to be used in different applications, such as surface cleaning, ones in the food industry, energy harvesting, water treatment, biomedical applications, and heat transfer enhancement. Thus, both characterization and intensification of cavitation phenomenon are of great importance. This study involves design and optimization of cavitation on chip devices by utilizing wall roughness elements and working fluid alteration. Seven different microfluidic devices were fabricated and tested. In order to harvest more energy from cavitating flows, different roughness elements were used to decrease the inlet pressure (input to the system), at which cavitation inception occurs. The implemented wall roughness elements were engineered structures in the shape of equilateral triangles embedded in the design of the microfluidic devices. The cavitation phenomena were also studied using ethanol as the working fluid, so that the fluid behavior differences in the tested cavitation on chip devices were explained and compared. The employment of the wall roughness elements was an effective approach to optimize the performances of the devices. The experimental results exhibited entirely different flow patterns for ethanol compared to water, which suggests the dominant effect of the surface tension on hydrodynamic cavitation in microfluidic channels.
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| 4. |
- Ghorbani, Morteza, et al.
(författare)
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Intensifying cavitating flows in microfluidic devices with poly(vinyl alcohol) (PVA) microbubbles
- 2018
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Ingår i: Physics of fluids. - : American Institute of Physics (AIP). - 1070-6631 .- 1089-7666. ; 30:10
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Tidskriftsartikel (refereegranskat)abstract
- Cavitation and the energy associated with the collapse of resulting cavitation bubbles constitute an important research subject. The collapse of the hydrodynamic cavitation bubbles at the outlet of the flow elements leads to a high energy release and generates localized shock waves and a large temperature rise on exposed surfaces. The concept of “hydrodynamic cavitation on chip” is an emerging topic which emphasizes phase change phenomena in microscale and their utilizations in energy and biomedical applications. This study is aimed to investigate the potential of poly(vinyl alcohol) (PVA) Microbubbles (MBs) to generate cavitation bubbles and to evaluate their effects on flow regimes and energy dissipation. For this, three different microchannel configurations with different roughness elements were considered. The structural side wall and surface roughened channels were fabricated along with the smooth channel according to the techniques adopted from semiconductor based microfabrication. The upstream pressure varied from 1 to 7 MPa, and the flow patterns were recorded and analyzed using a high-speed camera. The pressure was locally measured at three locations along the microfluidic devices to determine the conditions for fully developed cavitating flows. The results were compared to the pure water case, and different trends for the cavitating flow pattern transitions were obtained for the water-PVA MB solution case. Accordingly, the twin cavity clouds extended to the end of the side wall roughened channel at a lower upstream pressure for the case of PVA MBs, while the smooth and surface roughened channels do not demonstrate this flow pattern. In addition, the cavitation number has the lowest values under the same working conditions for the case of PVA MBs. Moreover, the impact pressure generated by the bubble collapse inside the side wall roughened channel for the case of PVA MBs was notably higher than that for pure water.
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| 5. |
- Moreno, Daniel, et al.
(författare)
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Proof of concept of a graphene-based resonant accelerometer
- 2021
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Ingår i: 2021 34th IEEE international conference on micro electro mechanical systems (MEMS 2021). - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 838-840
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Konferensbidrag (refereegranskat)abstract
- Acceleration measurements are fundamental in applications such as consumer electronics, navigation, automotive safety and Internet of things (IoT). In comparison with capacitive or piezoresistive MEMS accelerometers, resonant graphene accelerometers have the potential to be smaller. If demonstrated, they could be a step forward in miniaturization and could enable emerging applications. In this paper. accelerations are measured with a NEMS resonant accelerometer based on graphene. The devices are made of a suspended proof mass attached by graphene ribbons [1-3]. For device evaluation, they are attached to a shaker to produce accelerations. Using a Laser Doppler Vibrometer, the changes in the resonant frequency of the devices caused by the acceleration arc quantified. The results show a linear dependence between the shifts in resonance of the devices and input accelerations at 160 Hz.
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| 6. |
- Pagliano, Simone, et al.
(författare)
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A 3D-Printed Functional Mems Accelerometer
- 2023
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Ingår i: 2023 IEEE 36TH INTERNATIONAL CONFERENCE ON MICRO ELECTRO MECHANICAL SYSTEMS, MEMS. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 594-597
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Konferensbidrag (refereegranskat)abstract
- 3D printing of MEMS devices could enable the cost-efficient production of custom-designed and complex 3D MEMS for prototyping and for low-volume applications. In this work, we present the first micro 3D-printed functional MEMS accelerometers using two-photon polymerization combined with the evaporation of metal strain gauge transducers. We measured the resonance frequency, the responsivity, and the signal stability over a period of 10 h of the 3D-printed accelerometer.
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| 7. |
- Pagliano, Simone, et al.
(författare)
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Micro 3D printing of a functional MEMS accelerometer
- 2022
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Ingår i: MICROSYSTEMS & NANOENGINEERING. - : Springer Nature. - 2055-7434. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Microelectromechanical system (MEMS) devices, such as accelerometers, are widely used across industries, including the automotive, consumer electronics, and medical industries. MEMS are efficiently produced at very high volumes using large-scale semiconductor manufacturing techniques. However, these techniques are not viable for the costefficient manufacturing of specialized MEMS devices at low- and medium-scale volumes. Thus, applications that require custom-designed MEMS devices for markets with low- and medium-scale volumes of below 5000-10,000 components per year are extremely difficult to address efficiently. The 3D printing of MEMS devices could enable the efficient realization and production of MEMS devices at these low- and medium-scale volumes. However, current micro-3D printing technologies have limited capabilities for printing functional MEMS. Herein, we demonstrate a functional 3D-printed MEMS accelerometer using 3D printing by two-photon polymerization in combination with the deposition of a strain gauge transducer by metal evaporation. We characterized the responsivity, resonance frequency, and stability over time of the MEMS accelerometer. Our results demonstrate that the 3D printing of functional MEMS is a viable approach that could enable the efficient realization of a variety of custom-designed MEMS devices, addressing new application areas that are difficult or impossible to address using conventional MEMS manufacturing.
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| 8. |
- Rokhsar Talabazar, Farzad, et al.
(författare)
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Design and fabrication of a vigorous "cavitation-on-a-chip" device with a multiple microchannel configuration
- 2021
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Ingår i: Microsystems & Nanoengineering. - : Springer Nature. - 2055-7434. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- Hydrodynamic cavitation is one of the major phase change phenomena and occurs with a sudden decrease in the local static pressure within a fluid. With the emergence of microelectromechanical systems (MEMS), high-speed microfluidic devices have attracted considerable attention and been implemented in many fields, including cavitation applications. In this study, a new generation of 'cavitation-on-a-chip' devices with eight parallel structured microchannels is proposed. This new device is designed with the motivation of decreasing the upstream pressure (input energy) required for facile hydrodynamic cavitation inception. Water and a poly(vinyl alcohol) (PVA) microbubble (MB) suspension are used as the working fluids. The results show that the cavitation inception upstream pressure can be reduced with the proposed device in comparison with previous studies with a single flow restrictive element. Furthermore, using PVA MBs further results in a reduction in the upstream pressure required for cavitation inception. In this new device, different cavitating flow patterns with various intensities can be observed at a constant cavitation number and fixed upstream pressure within the same device. Moreover, cavitating flows intensify faster in the proposed device for both water and the water-PVA MB suspension in comparison to previous studies. Due to these features, this next-generation 'cavitation-on-a-chip' device has a high potential for implementation in applications involving microfluidic/organ-on-a-chip devices, such as integrated drug release and tissue engineering.
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| 9. |
- Shafaghi, Ali Hosseinpour, et al.
(författare)
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On cavitation inception and cavitating flow patterns in a multi-orifice microfluidic device with a functional surface
- 2021
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Ingår i: Physics of fluids. - : AMER INST PHYSICS. - 1070-6631 .- 1089-7666. ; 33:3
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Tidskriftsartikel (refereegranskat)abstract
- During the last decade, hydrodynamic cavitation has been implemented in various applications such as energy harvesting and biomedical applications. Facile hydrodynamic cavitation methods are required for fulfilling the requirements in these applications. In this study, a new generation microfluidic device containing eight parallel micro-orifices with a new design was fabricated and tested with the purpose of intensifying the cavitating flows and early cavitation inception. The roughness elements in the micro-orifices facilitated cavitation inception. This study presents a general perspective of occurrence of different cavitating flow patterns in microscale and addresses the ambiguities about the conditions for the formation of a specific flow pattern. Cavitation inception occurred with the appearance of small bubbles emerging from roughness elements at a rather low upstream pressure in the open loop experimental setup. A reduction in the cavitation number resulted in the formation of different flow patterns such as cavitation clouds, twin cavities, sheet cavities, and bubbly flows. Having several flow patterns with different intensities all together within a single microfluidic device is the main advantage of the proposed device over the state of the art microfluidic devices. Generation of flow patterns with various released energy levels makes this proposed device a unique multi-functional platform, which can be implemented to a lab on a chip platform for applications such as nanoparticle synthesis and wound healing.
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