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Technologies
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Microswitching Technologies
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Microswitching Technologies

A special issue of Technologies (ISSN 2227-7080).

Deadline for manuscript submissions: closed (30 August 2019) | Viewed by 43143

Special Issue Editor

Prof. Dr. Ronald A. Coutu, Jr.

E-Mail Website
Guest Editor
Department of Electrical and Computer Engineering, Marquette University, Milwaukee, WI 53233, USA
Interests: microelectromechanical systems (MEMS); smart sensors; device fabrication; micro-electrical contacts; phase change materials; energy harvesting; renewable energy; micro-grids; energy storage
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Microswitching technology includes areas like radio frequency (RF) microelectromechanical systems (MEMS) switches for high frequency applications, MEMS switches for direct current (DC) or dry switching applications, and new and emerging technologies relative to the micro electrical contact areas including: advanced modeling, promising new contact materials, and novel micro contact geometries. In addition, novel solid state switching topologies and materials including phase change materials and metal-insulator transition materials are being investigated as for applications requiring highly reliable microswitching devices. This Special Issue is intended to report on the recent advances in the multidisciplinary field of microswitching technologies and also address critical technology gaps that are currently limiting microswitch presence in the market place.

Prof. Dr. Ronald A. Coutu, Jr.
Guest Editor

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Keywords

  • RF MEMS
  • MEMS
  • microswitch
  • micro-contacts
  • contact materials
  • contact geometry
  • phase change materials

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Published Papers (6 papers)

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Research

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13 pages, 4021 KiB  
Article
An Improved Calculation Model for the Prediction of the Wear of Coated Electrical Contacts
by Haomiao Yuan and Jian Song
Technologies 2019, 7(4), 77; https://doi.org/10.3390/technologies7040077 - 31 Oct 2019
Cited by 3 | Viewed by 4977
Abstract
To connect terminals in a cyber–physical system, large quantities of electrical contacts are used. In order to guarantee a high reliability of the system, the lifetime of the electrical contacts should be very long. Thus, it is of great importance to understand the [...] Read more.
To connect terminals in a cyber–physical system, large quantities of electrical contacts are used. In order to guarantee a high reliability of the system, the lifetime of the electrical contacts should be very long. Thus, it is of great importance to understand the failure mechanism and then to predict the lifetime of the electrical contacts. For the applications under high thermal and/or mechanical loads, noble plating is a good choice, considering its inertness to oxidation. For noble plating, one of the most critical failure mechanisms is the fretting wear. Wear debris generated in the contact area, acting as the third bodies, will greatly influence the further wear behavior and electrical performance. In this study, the state of the art regarding third bodies is firstly reviewed, and then the influence of the third bodies on the wear and electrical performance is investigated, from the aspects of lifetime and the element distributions in contact area. Finally, an example of prediction of the wear of noble plating is shown with the consideration of the third bodies. Based on this study, by involving the third bodies, the wear of noble plating can be predicted with a higher accuracy. Full article
(This article belongs to the Special Issue Microswitching Technologies)
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12 pages, 4490 KiB  
Article
Transient Contact Opening Forces in a MEMS Switch Using Au/MWCNT Composite
by Thomas G. Bull and John W. McBride
Technologies 2019, 7(4), 69; https://doi.org/10.3390/technologies7040069 - 23 Sep 2019
Cited by 1 | Viewed by 4997
Abstract
Most failures in micro electromechanical system (MEMS) switches can be attributed to the degradation of contact surfaces and sticking contacts. A wear-tolerant composite contact material, composed of a Au film supported by multi walled carbon nanotubes (Au/MWCNT), has been engineered to provide wear [...] Read more.
Most failures in micro electromechanical system (MEMS) switches can be attributed to the degradation of contact surfaces and sticking contacts. A wear-tolerant composite contact material, composed of a Au film supported by multi walled carbon nanotubes (Au/MWCNT), has been engineered to provide wear resistance and enhanced switching lifetime with conductive properties close to pure Au. Switching lifetimes of billions of cycles have been demonstrated, representing greatly increased performance over thin film Au. Below the arcing threshold (~12 V) the wear mechanism has been shown to be a combination of the fine transfer of contact material by the molten metal bridge (MMB) phenomenon and a delamination of the Au. In this study, the composite contact is hot switched at low current DC conditions (4 V DC and 20 mA) while the contact force is measured at the micro Newton scale in nanosecond resolution. The characteristic voltage waveform associated with the MMB is observed with forces detected as the contact softens, melts, and separates. The presence of a delamination event (DE) is also observed, where the contact opens abruptly with no MMB phenomenon apparent. The DE contact openings are associated with a transient peak force of 21.6 ± 2.3 µN while the MMBs are linked to a lower peak force of 18.1 ± 2.5 µN. Full article
(This article belongs to the Special Issue Microswitching Technologies)
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15 pages, 11927 KiB  
Article
In-Situ Contact Surface Characterization in a MEMS Ohmic Switch under Low Current Switching
by Thomas G. Bull and John W. McBride
Technologies 2018, 6(2), 47; https://doi.org/10.3390/technologies6020047 - 4 May 2018
Cited by 14 | Viewed by 5249
Abstract
To develop robust microelectromechanical systems (MEMS) switching technology for low voltage direct current (DC) applications (1–12 V) there is a requirement for the investigation of wear caused by hot switching (contact operated while carrying a current load). Previous investigation of contact wear in [...] Read more.
To develop robust microelectromechanical systems (MEMS) switching technology for low voltage direct current (DC) applications (1–12 V) there is a requirement for the investigation of wear caused by hot switching (contact operated while carrying a current load). Previous investigation of contact wear in the ohmic MEMS switch has been limited to either the completion of the contact switching cycles, where the device is destructively opened, or by low switching rates, making lifetime testing impractical. A novel MEMS testing platform is described that is capable of both resolving microscale changes on the contact surface between switching events and sustained high frequency switch cycling, enabling practical lifetime testing. The platform is used to investigate early surface changes in a thin-film Au contact pair on a cycle-by-cycle basis. The contact is closed at forces representative of a practical MEMS contact (<1 mN). The apparatus reveals the microscopic surface change between individual switching events. Hot switched contact wear is dominated by the molten metal bridge (MMB) phenomenon, linked to a characteristic voltage transient at contact opening and the gradual process of contact material transfer; however, during hot switching delamination phenomena are also observed, and associated with a step change in contact voltage and a greater level of surface damage. Full article
(This article belongs to the Special Issue Microswitching Technologies)
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11 pages, 3174 KiB  
Article
Experimental Validation of External Load Effects for Micro-Contacts under Low Frequency, Low Amplitude Alternating Current (AC) Test Conditions
by Protap Mahanta, Ronald A. Coutu, Jr. and Dushyant Tomer
Technologies 2018, 6(2), 46; https://doi.org/10.3390/technologies6020046 - 2 May 2018
Cited by 3 | Viewed by 5400
Abstract
The use of micro-contacts has been demonstrated in various radio frequency (RF) applications. However, the premature failure of such devices under alternating current (AC) operations is still a hurdle to further development. In this work, modified gray scale lithography is performed to fabricate [...] Read more.
The use of micro-contacts has been demonstrated in various radio frequency (RF) applications. However, the premature failure of such devices under alternating current (AC) operations is still a hurdle to further development. In this work, modified gray scale lithography is performed to fabricate two types of gold–gold (Au–Au) micro-contacts: hemispherical-planar and hemispherical-2D pyramid. The performance of these devices was investigated under low frequency, low amplitude AC conditions with external circuit loads. A custom-made experimental setup which uses various load configurations, controls the frequency of the applied voltage and modifies the cycle rate of switch operation to obtain the contact resistance as a function of number of cycles (up to 107 cycles). Nearly 87% of the tested devices (13 out of 15 hemispherical-planar micro-contacts) were found to be in good operational condition and passed the 10 million cycle mark successfully. A steady gain and large swing in the value of contact resistance was also observed near the end of all, but one, tests. Such changes in contact resistance were found to be permanent as none of the devices recovered completely. On the other hand, the hemispherical-2D pyramid micro-contact performed better than the planar one as it also passed 107 cycle mark with low and remarkably stable contact resistance throughout the testing span. This study suggests that micro-contacts with ‘engineered’ surface structures with external loads applied are a viable solution to premature failure and high contact resistance in micro-contacts under low frequency AC operations. Full article
(This article belongs to the Special Issue Microswitching Technologies)
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Review

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28 pages, 7498 KiB  
Review
Nematic Liquid Crystal Composite Materials for DC and RF Switching
by Mohiuddin Munna, Farhana Anwar and Ronald A. Coutu, Jr.
Technologies 2019, 7(2), 32; https://doi.org/10.3390/technologies7020032 - 2 Apr 2019
Cited by 18 | Viewed by 12154
Abstract
Liquid Crystals (LCs) are widely used in display devices, electro-optic modulators, and optical switches. A field-induced electrical conductivity modulation in pure liquid crystals is very low which makes it less preferable for direct current (DC) and radio-frequency (RF) switching applications. According to the [...] Read more.
Liquid Crystals (LCs) are widely used in display devices, electro-optic modulators, and optical switches. A field-induced electrical conductivity modulation in pure liquid crystals is very low which makes it less preferable for direct current (DC) and radio-frequency (RF) switching applications. According to the literature, a conductivity enhancement is possible by nanoparticle doping. Considering this aspect, we reviewed published works focused on an electric field-induced conductivity modulation in carbon nanotube-doped liquid crystal composites (LC-CNT composites). A two to four order of magnitude switching in electrical conductivity is observed by several groups. Both in-plane and out-of-plane device configurations are used. In plane configurations are preferable for micro-device fabrication. In this review article, we discussed published works reporting the elastic and molecular interaction of a carbon nanotube (CNT) with LC molecules, temperature and CNT concentration effects on electrical conductivity, local heating, and phase transition behavior during switching. Reversibility and switching speed are the two most important performance parameters of a switching device. It was found that dual frequency nematic liquid crystals (DFNLC) show a faster switching with a good reversibility, but the switching ratio is only two order of magnitudes. A better way to ensure reversibility with a large switching magnitude is to use two pairs of in-plane electrodes in a cross configuration. For completeness and comparison purposes, we briefly reviewed other nanoparticle- (i.e., Au and Ag) doped LC composite’s conductivity behavior as well. Finally, based on the reported works reviewed in this article on field induced conductivity modulation, we proposed a novel idea of RF switching by LC composite materials. To support the idea, we simulated an LC composite-based RF device considering a simple analytical model. Our RF analysis suggests that a device made with an LC-CNT composite could show an acceptable performance. Several technological challenges needed to be addressed for a physical realization and are also discussed briefly. Full article
(This article belongs to the Special Issue Microswitching Technologies)
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26 pages, 8571 KiB  
Review
Performance Comparison of Phase Change Materials and Metal-Insulator Transition Materials for Direct Current and Radio Frequency Switching Applications
by Protap Mahanta, Mohiuddin Munna and Ronald A. Coutu, Jr.
Technologies 2018, 6(2), 48; https://doi.org/10.3390/technologies6020048 - 4 May 2018
Cited by 16 | Viewed by 9706
Abstract
Advanced understanding of the physics makes phase change materials (PCM) and metal-insulator transition (MIT) materials great candidates for direct current (DC) and radio frequency (RF) switching applications. In the literature, germanium telluride (GeTe), a PCM, and vanadium dioxide (VO2), an MIT [...] Read more.
Advanced understanding of the physics makes phase change materials (PCM) and metal-insulator transition (MIT) materials great candidates for direct current (DC) and radio frequency (RF) switching applications. In the literature, germanium telluride (GeTe), a PCM, and vanadium dioxide (VO2), an MIT material have been widely investigated for DC and RF switching applications due to their remarkable contrast in their OFF/ON state resistivity values. In this review, innovations in design, fabrication, and characterization associated with these PCM and MIT material-based RF switches, have been highlighted and critically reviewed from the early stage to the most recent works. We initially report on the growth of PCM and MIT materials and then discuss their DC characteristics. Afterwards, novel design approaches and notable fabrication processes; utilized to improve switching performance; are discussed and reviewed. Finally, a brief vis-á-vis comparison of resistivity, insertion loss, isolation loss, power consumption, RF power handling capability, switching speed, and reliability is provided to compare their performance to radio frequency microelectromechanical systems (RF MEMS) switches; which helps to demonstrate the current state-of-the-art, as well as insight into their potential in future applications. Full article
(This article belongs to the Special Issue Microswitching Technologies)
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