Electromechanical Investigation of Low Dimensional Nanomaterials for NEMS Applications

Successful operation of Nano-ElectroMechanical Systems (NEMS) critically depends on their working environment and component materials' electromechanical properties. It is equally important that ambient or liquid environment to be seriously considered for NEMS to work as high sensitivity sensors with commercial viabilities. Firstly, to understand interaction between NEMS oscillator and fluid, transfer function of suspended gold nanowire NEMS devices in fluid was calculated. It was found that NEMS's resonance frequency decreased and energy dissipation increased, which constrained its sensitivity. Sensitivity limit of NEMS oscillators was also considered in a statistical framework. Subsequently, suspended gold nanowire NEMS devices were magnetomotively actuated in vacuum and liquid. Secondly, electromechanical properties of gold nanowires were carefully studied and the observed size effect was found to agree with theory, which predicted small changes of electromechanical property compared with bulk gold materials. Finally, it is well recognized that continuous development of new NEMS devices demands novel materials. Mechanical properties of new two-dimensional hexagonal Boron Nitride films with a few atomic layers were studied. Outlook of utilizing ultrathm BN films in next generation NEMS devices was discussed

Graphene resonators for mass sensing applications

PhD ThesisGraphene’s exceptional physical and mechanical properties make it an excellent nanomaterial for MEMS/NEMS devices with wide reaching applications. This thesis explores graphene as a nanomaterial, its use in mass sensing applications and the suitability of existing theoretical models to describe its behaviour as a rectangular resonator. Several local and nonlocal continuum models have been proposed in literature for the vibration analysis of graphene resonators. But with very little experimental data to validate these theoretical models, most of the solutions employed to solve these models compare their results with results from other theoretical models, leading to doubts about their validity and accuracy. In addition to providing a guide for determining the suitable theoretical model for different sized rectangular graphene resonators, this work establishes that a small-scale parameter 0 of any value between 0 and 2 needs to be incorporated in any local continuum modelled applied to micro-sized graphene sheets to avoid overestimation of the frequency of the sheets. A fabrication route for NEMS and MEMS devices with rectangular graphene resonators up to 32 by 7 is also developed with the provision for magnetomotive actuation via Lorentz force with possible capacitive readout capabilities. This is important as the use of graphene in MEMS/NEMS is being hurriedly transitioned from the Research space to the marketplace

Nanomechanical Resonators: Toward Atomic Scale

The quest for realizing and manipulating ever smaller man-made movable structures and dynamical machines has spurred tremendous endeavors, led to important discoveries, and inspired researchers to venture to new grounds. Scientific feats and technological milestones of miniaturization of mechanical structures have been widely accomplished by advances in machining and sculpturing ever shrinking features out of bulk materials such as silicon. With the flourishing multidisciplinary field of low-dimensional nanomaterials, including one-dimensional (1D) nanowires/nanotubes, and two-dimensional (2D) atomic layers such as graphene/phosphorene, growing interests and sustained efforts have been devoted to creating mechanical devices toward the ultimate limit of miniaturization— genuinely down to the molecular or even atomic scale. These ultrasmall movable structures, particularly nanomechanical resonators that exploit the vibratory motion in these 1D and 2D nano-to-atomic-scale structures, offer exceptional device-level attributes, such as ultralow mass, ultrawide frequency tuning range, broad dynamic range, and ultralow power consumption, thus holding strong promises for both fundamental studies and engineering applications. In this Review, we offer a comprehensive overview and summary of this vibrant field, present the state-of-the-art devices and evaluate their specifications and performance, outline important achievements, and postulate future directions for studying these miniscule yet intriguing molecular-scale machines

Laser-driven micro-transfer printing for MEMS/NEMS integration

Heterogeneous materials integration, motivated by material transfer processes, has evolved to address the technology gap between the conventional micro-fabrication processes and multi-layer functional device integration. In its basic embodiment, micro-transfer printing is used to deterministically transfer and micro-assemble prefabricated microstructures/devices, referred to as “ink,” from donor substrates to receiving substrates using a viscoelastic elastomer stamp, usually made out of polydimethylsiloxane (PDMS). Thin-film release is, in general, difficult to achieve at the micro-scale (surface effects dominate). However, it becomes dependent on the receiving substrate’s properties and preparation. Laser Micro-Transfer Printing (LMTP) is a laser-driven version of the micro-transfer printing process that enables non-contact release of the microstructure by inducing a mismatch thermal strain at the ink-stamp interface; making the transfer printing process independent from the properties or preparation of the receiving substrate. In this work, extensive studies are conducted to characterize, model, predict, and improve the capabilities of the LMTP process in developing a robust non-contact pattern transfer process. Using micro-fabricated square silicon inks and varying the lateral dimensions and thickness of the ink, the laser pulse duration required to drive the delamination, referred to as “delamination time,” is experimentally observed using high-speed camera recordings of the delamination process for different laser beam powers. The power absorbed by the ink is measured to estimate the total energy stored in the ink-stamp system and available to initiate and propagate the delamination crack at the interface. These experiments are used as inputs for an opto-thermo-mechanical model to understand how the laser energy is converted to thermally-induced stresses at the ink-stamp interface to release the inks. The modeling approach is based on first developing an analytical optical absorption model, based on Beer-Lambert law, under the assumption that optical absorption during the LMTP process is decoupled from thermo-mechanical physics. The optical absorption model is used to estimate the heating rate of the ink-stamp system during the LMTP process that, in turn, is used as an input to the coupled thermo-mechanical Finite Element Analysis (FEA) model. Fracture mechanics quantities such as the Energy Release Rate (ERR) and the Stress Intensity Factors (SIFs) are estimated using the model. Then, the thermal stresses at the crack tip, evaluated by the SIFs, are decomposed into two components based on originating causes: CTE mismatch between the ink and the stamp, and thermal gradient within the PDMS stamp. Both the delamination time from the high-speed camera experiments and thermo-mechanical FEA model predictions are used to understand and improve the process’s performance under different printing conditions. Several studies are conducted to understand the effect of other process parameters such as the dimensions and materials of the stamp, the ink-stamp alignment, and the transferred silicon ink shape on the process performance and mechanism. With an objective of reducing the delamination time, the delamination energy, and the temperature of the ink-stamp interface during printing, different patterned stamp designs (cavity, preloading, and thin-walls) have been proposed. Cavity, preloading, and thin-wall stamps are designed to generate thermally-induced air pressure at the ink-stamp interface, to store strain energy at the interface, and to generate thermally-induced air pressure at the preloaded interface, respectively. Cohesive Zone Modeling (CZM) based models are developed to estimate the equilibrium solution of the collapsed patterned stamp after the ink pick-up process, and to evaluate the patterned stamps’ performance during the LMTP process. The patterned stamps show significant improvements in delamination times and delamination energies (up to 35%) and acceptable improvement of the interface temperature at the delamination point (up to 16%) for given printing conditions

Nanomechanical Resonators: Toward Atomic Scale

The quest for realizing and manipulating ever smaller man-made movable structures and dynamical machines has spurred tremendous endeavors, led to important discoveries, and inspired researchers to venture to previously unexplored grounds. Scientific feats and technological milestones of miniaturization of mechanical structures have been widely accomplished by advances in machining and sculpturing ever shrinking features out of bulk materials such as silicon. With the flourishing multidisciplinary field of low-dimensional nanomaterials, including one-dimensional (1D) nanowires/nanotubes and two-dimensional (2D) atomic layers such as graphene/ phosphorene, growing interests and sustained effort have been devoted to creating mechanical devices toward the ultimate limit of miniaturization--genuinely down to the molecular or even atomic scale. These ultrasmall movable structures, particularly nanomechanical resonators that exploit the vibratory motion in these 1D and 2D nano-to-atomic-scale structures, offer exceptional device-level attributes, such as ultralow mass, ultrawide frequency tuning range, broad dynamic range, and ultralow power consumption, thus holding strong promises for both fundamental studies and engineering applications. In this Review, we offer a comprehensive overview and summary of this vibrant field, present the state-of-the-art devices and evaluate their specifications and performance, outline important achievements, and postulate future directions for studying these miniscule yet intriguing molecular-scale machines

NEMS by sidewall transfer lithography

A batch fabrication process for nano-electro-mechanical systems (NEMS) based on sidewall transfer lithography (STL) is developed and demonstrated. The STL is used to form nanoscale flexible silicon suspensions entirely by conventional lithography. A two-step process is designed for single-layer STL to fabricate simple electrothermal actuators, while a three-step process is designed to allow nanoscale features intersecting with each other for more complicated device lay-outs. Fabricated nanoscale features has a minimum in-plane width of approx. 100nm and a high aspect ratio of 50 : 1. Combined structures with microscale and nanoscale parts are transferred together into silicon by deep reactive etching (DRIE). Suspensions are achieved either by plasma undercut or HF vapour etch based on BSOI. The STL processes are used to form nanoscale suspensions while conventional lithography is used to form localised microscale features such as anchors. A wide variety of demonstrator devices have been fabricated with high feature quality. Analytic models have been developed to compare with experimental characterization and finite element analysis (FEA) predictions. Lattice structures fabricated by multi-layer STL have also be investigated as a novel type of mechanical metamaterial. Thus, the process could allow low-cost and mass parallel fabrication of future NEMS with a wider range of potential applications.Open Acces

Microelectromechanical Systems and Devices

The advances of microelectromechanical systems (MEMS) and devices have been instrumental in the demonstration of new devices and applications, and even in the creation of new fields of research and development: bioMEMS, actuators, microfluidic devices, RF and optical MEMS. Experience indicates a need for MEMS book covering these materials as well as the most important process steps in bulk micro-machining and modeling. We are very pleased to present this book that contains 18 chapters, written by the experts in the field of MEMS. These chapters are groups into four broad sections of BioMEMS Devices, MEMS characterization and micromachining, RF and Optical MEMS, and MEMS based Actuators. The book starts with the emerging field of bioMEMS, including MEMS coil for retinal prostheses, DNA extraction by micro/bio-fluidics devices and acoustic biosensors. MEMS characterization, micromachining, macromodels, RF and Optical MEMS switches are discussed in next sections. The book concludes with the emphasis on MEMS based actuators

Volume 3 – Conference

We are pleased to present the conference proceedings for the 12th edition of the International Fluid Power Conference (IFK). The IFK is one of the world’s most significant scientific conferences on fluid power control technology and systems. It offers a common platform for the presentation and discussion of trends and innovations to manufacturers, users and scientists. The Chair of Fluid-Mechatronic Systems at the TU Dresden is organizing and hosting the IFK for the sixth time. Supporting hosts are the Fluid Power Association of the German Engineering Federation (VDMA), Dresdner Verein zur Förderung der Fluidtechnik e. V. (DVF) and GWT-TUD GmbH. The organization and the conference location alternates every two years between the Chair of Fluid-Mechatronic Systems in Dresden and the Institute for Fluid Power Drives and Systems in Aachen. The symposium on the first day is dedicated to presentations focused on methodology and fundamental research. The two following conference days offer a wide variety of application and technology orientated papers about the latest state of the art in fluid power. It is this combination that makes the IFK a unique and excellent forum for the exchange of academic research and industrial application experience. A simultaneously ongoing exhibition offers the possibility to get product information and to have individual talks with manufacturers. The theme of the 12th IFK is “Fluid Power – Future Technology”, covering topics that enable the development of 5G-ready, cost-efficient and demand-driven structures, as well as individual decentralized drives. Another topic is the real-time data exchange that allows the application of numerous predictive maintenance strategies, which will significantly increase the availability of fluid power systems and their elements and ensure their improved lifetime performance. We create an atmosphere for casual exchange by offering a vast frame and cultural program. This includes a get-together, a conference banquet, laboratory festivities and some physical activities such as jogging in Dresden’s old town.:Group 8: Pneumatics Group 9 | 11: Mobile applications Group 10: Special domains Group 12: Novel system architectures Group 13 | 15: Actuators & sensors Group 14: Safety & reliabilit