Field Of Micro Research Articles

Analytical study of electromechanical buckling of a micro spherical elastic film on a compliant substrate part I: Formulation and linear buckling of periodic patterns

This work presents an analytical study of the electromechanical buckling of a micro spherical thin film bonded to a compliant elastic substrate. The spherical film is subjected to electrostatic attraction forces that are induced by applying a voltage difference between an outer spherical elastic film electrode and inner rigid, fixed and grounded spherical electrode. When the applied voltage is small, the film contracts while maintaining its complete spherical shape. However, when the applied voltage reaches a critical value, the film buckles into high-ordered periodic patterns (i.e. elastic surface wrinklings). Motivated by experimental results of other studies, this work examines the critical buckling state of one-dimensional, square checkerboard and hexagonal patterns. As will be shown, the above considered patterns are associated with the same critical state, and therefore, all patterns have equal buckling voltage and critical wavelength. Furthermore, with increasing radius of the film/substrate system the electromechanical buckling response converges to the electromechanical pull-in instability of the well-known two parallel plate electrodes, as will be revealed by the asymptotic analytical solution. Finally, the elastic ripples of the electromechanically buckled film can be generated or removed by a simple On/Off switching of the applied voltage. The ability to generate and remove elastic ripples tremendously increases the potential of such microsystem to be utilized in different applications in the field of Micro and Nano electromechanical systems.

Dynamics Study of the Deformation of Red Blood Cell by Optical Tweezers

In recent years, extensive research has been carried out on red blood cells in order to investigate their mechanical properties. The interest in these studies has been possible thanks to the technological innovations made in the field of micro or nano manipulation of biological and non-biological particles without physical contact. In the present project, we have developed a new approach to study the deformation of red blood cells moving against a trapped microbead by applying a sinusoidal voltage (DC offset 3.5 Vpp) to the stage at 0.4 Hz frequencies. The oscillating movement imposed on the stage highlights the indentation test and the tensile test known for the study of mechanical behavior of materials. The mechanical properties found are: the modulus of elasticity (Young Modulus), the shear modulus, the coefficient of hardening and erythrocyte resistance coefficient. The axial shear modulus 25.00 ± 1.5 μN/m and the transversal shear modulus 15.7 ± 4.63 μN/m were compared to those in the literature. These values were respectively determined by Hooke’s law and the Hertz model.

Научные открытия в области микро-, нано-, пико-, фемто- и аттотрибологии. Планк и квант последействия

Научные открытия в области микро-, нано-, пико-, фемто- и аттотрибологии. Планк и квант последействия

Curvature effects in two-dimensional optical devices inspired by transformation optics

Light transport in curved quasi two-dimensional waveguides is considered theoretically. Within transformation optics and tensor theory, a concise description of curvature effects on transverse electric and magnetic waves is derived. We show that the curvature can induce light focusing and photonic crystal properties, which are confirmed by finite element simulations. Our results indicate that the curvature is an effective parameter for designing quasi two-dimensional optical devices in the fields of micro and nano photonics.

There’s Plenty of Fractional at the Bottom, I: Brownian Motors and Swimming Microrobots

Abstract The only purpose of this paper is to show how fractional calculus can contribute to the development of the very interesting and promising field of micro and nano machines, from the deeper understanding of the world in which they work, to their design and control. The essentials of Brownian motors and untethered swimming microrobots are briefly presented, and two naive examples on how fractional calculus can contribute to open new perspectives are given.

Molecular Dynamics Study of Gas–Surface Interactions in a Force-Driven Flow of Argon through a Rectangular Nanochannel

ABSTRACTIn recent times, flows through micro- and nanochannels have gained prominence due to their applicability to the fast growing fields of micro- and nanotechnology among others. Understanding gas–surface interactions in such flows is crucial, because the size of the micro/nanoscale devices is typically comparable to boundary layer thickness near a wall and the surface starts playing a significant role. An attempt is made to understand these interactions by modeling simple force-driven argon gas flow between two parallel platinum plates by the molecular dynamics method. One of the most important parameters that describes gas–surface interactions—that is, the tangential momentum accommodation coefficient, along with flow properties such as velocity and density—is calculated for a range of Knudsen numbers in the early transitional flow regime. A deeper insight into the flow physics is obtained by considering various case studies for the variation of aforesaid properties with respect to external driving forces and gas–wall interaction strengths.

MicroRNA: emerging biomarkers in human disease and profiling challenges

Over the last decade, a rapid growth in the field of micro(mi)RNA research has been evident. Profiles of miRNAs have been shown to reflect pathological conditions and have been implicated as potential biomarkers in the diagnosis and evaluation of human diseases. In this article, an overview of miRNA discovery and biogenesis is provided. Recent advances in using circulating miRNA as biomarkers in human diseases are discussed, along with the challenges researchers are facing in miRNA profiling and future diagnostic prospects.

Fabrication of Hydrophobic Nanostructured Surfaces for Microfluidic Control.

In the field of micro- and nanofluidics, various kinds of novel devices have been developed. For such devices, not only fluidic control but also surface control of micro/nano channels is essential. Recently, fluidic control by hydrophobic nanostructured surfaces have attracted much attention. However, conventional fabrication methods of nanostructures require complicated steps, and integration of the nanostructures into micro/nano channels makes fabrication procedures even more difficult and complicated. In the present study, a simple and easy fabrication method of nanostructures integrated into microchannels was developed. Various sizes of nanostructures were successfully fabricated by changing the plasma etching time and etching with a basic solution. Furthermore, it proved possible to construct highly hydrophobic nanostructured surfaces that could effectively control the fluid in microchannels at designed pressures. We believe that the fabrication method developed here and the results obtained are valuable contributions towards further applications in the field of micro- and nanofluidics.

Mechanism Design Theory: The Development in Economics and Management

In the last two decades, mechanism design theory is the fastest growing branch in the field of micro- economic with a very broad application space in the practical economy. Also, mechanism design theory brings new study framework for management. Instead of management function theory, mechanism design theory can reveal management activities better. This article will review the development of mechanism design theory in economics and management science, so that it can lay the foundation for future research.

Dynamic contact angle and three-phase contact line of water drop on copper surface

Nowadays there is a lack of experimental data describing the physical process of drop spreading on a solid metal surface for developing wetting and spreading theory. The experimental data obtained by using the high speed video-recording will allow to identify unknown previously spreading modes as well as the change of the dynamic contact angle and the three-phase contact line. The purpose of the work is to determine the effect of the drop growth rate and the copper substrate surface roughness on the dynamic contact angle and the three-phase contact line speed at distilled water drop spreading. Shadow and Schlieren methods are used to obtain experimental data. Three drop spreading modes on the rough surfaces were identified. Time dependences of the dynamic contact angle and contact line speed were obtained. Experimental results can be used for assessing the validity of the developed mathematical models of wetting and spreading processes in the field of micro- and nanoelectronics, ink jet printing, thin-film coatings, spray cooling, and optoelectronics.

Commentary on the special topic: nanoenergy and nanosystem

In the internationally renowned journal—Science China Technological Sciences—a good selection of articles dedicated to the field of micro-/nanotechnologies have reported several advanced technologies in nanoenergy and nanosystems. Five papers written with great care by international experts are targeting to address technical challenges in self-powered chaotic signal generators and new batteries based on nanomaterials. I read these papers and found them interesting and beneficial to researchers working in the above-mentioned areas. The paper written by Zhang et al. [1] has analyzed the power consumption of a chaotic circuit. Chaotic circuits are key elements in communication and neural systems, where they serve functions of adding extra protections to the communicated signals and simulations of brain working mechanism. The power consumption of such circuits is extremely important particularly in applications such as portable and implanted devices, where it is almost impossible to perform in vivo battery replacement, drastically reducing the lifetime of the devices. In the paper, rigorous theoretical analysis of power consumption of the chaotic circuits was conducted. It has been shown in the paper that the total power of the linear elements equals the power

Anomalous Viscosity Reduction and Hydrodynamic Interactions of Polymeric Nanocolloids in Polymers

One of the central dogmas of fluid physics is the no-slip boundary condition, whose validity has come under scrutiny, especially in the fields of micro and nanofluidics. Although various studies show the violation of the no-slip condition its effect on flow of colloidal particles in viscous media has been rarely explored. Here we report unusually large reduction of effective viscosity experienced by polymeric nano colloids moving through a highly viscous and confined polymer, well above its glass transition temperature. The extent of reduction in effective interface viscosity increases with decreasing temperature and polymer film thickness. Concomitant with the reduction in effective viscosity we also observe apparent divergence of the wave vector dependent hydrodynamic interaction function of these colloids with an anomalous power law exponent of similar to 2 at the lowest temperatures and film thickness studied. Such strong hydrodynamic interactions are not expected for polymeric colloidal motion in polymer melts. We suggest hydrodynamics, especially slip present at the colloid-polymer interface which determines the observed reduction in interface viscosity and presence of strong hydrodynamic interactions.

Atmospheric dual laser deposited dielectric coating on electrodes for electrochemical micromachining

Electrochemical machining (ECM) is a non-conventional manufacturing technology widely used in various industries. Recent developments in the fields of micro- and nanotechnology have precipitated the evolution of ECM to electrochemical micromachining (μECM). In μECM, the stray current between the electrode and the workpiece would severely degrade the accuracy. A dielectric coating on the electrode is the simplest effective way to reduce the stray current. Pulsed laser deposition provides an efficient coating method for a wide range of materials. In this paper, we proposed a dual laser-assisted deposition method in the atmospheric environment for dielectric TiO2/TiN film deposition on WC electrodes. The deposition process is in an ambient condition, and no vacuum is needed. With an assisting 2nd laser, the dielectric film had better adhesion to the electrode. With the 5-μm thick film, the electrode is well protected and is not consumed in the ECM process. The machining results showed that the overcut can be reduced by 60% with the dielectric coating, and the depth can be increased by 15%.

Experimental performance of a piston expander in a small- scale organic Rankine cycle

Volumetric expanders are suitable for more and more applications in the field of micro- and small-scale power system as waster heat recovery or solar energy. This paper present an experimental study carried out on a swatch-plate piston expander. The expander was integrated into an ORC test-bench using R245fa. The performances are evaluated in term of isentropic efficiency and filling factor. The maximum efficiency and power reached are respectively 53% and 2 kW. Inside cylinder pressure measurements allow to compute mechanical efficiency and drown P-V diagram. A semi-empirical simulation model is then proposed, calibrated and used to analyse the different sources of losses.

Fracture Testing at Small-Length Scales: From Plasticity in Si to Brittleness in Pt

The field of micro-/nano-mechanics of materials has been driven, on the one hand by the development of ever smaller structures in devices, and, on the other, by the need to map property variations in large systems that are microstructurally graded. Observations of ‘smaller is stronger’ have also brought in questions of accompanying fracture property changes in the materials. In the wake of scattered articles on micro-scale fracture testing of various material classes, this review attempts to provide a holistic picture of the current state of the art. In the process, various reliable micro-scale geometries are shown, challenges with respect to instrumentation to probe ever smaller length scales are discussed and examples from recent literature are put together to exhibit the expanse of unusual fracture response of materials, from ductility in Si to brittleness in Pt. Outstanding issues related to fracture mechanics of small structures are critically examined for plausible solutions.

Table-top deterministic and collective colloidal assembly using videoprojector lithography

In the field of micro- and nanotechnology, most lithography and fabrication tools coming from the microelectronic industry are expensive, time-consuming and may need some masks that have to be subcontracted. Such approach is not suitable for other fields that require rapid prototyping such as chemistry, life science or energy and may hinder research creativity. In this work, we present two table-top equipments dedicated to the fabrication of deterministic colloidal particles assemblies onto micro-structured substrates. We show that, with a limited modification of the optics of a standard videoprojector, it is possible to quickly obtain substrates with thousands of micrometric features. Then, we combine these substrates with thermodynamic colloidal assembly and generate arrays of particles without defects. This work opens the way to a simple and table-top fabrication of devices based on colloidal particles.

A multifinger microtriode with carbon nanotubes field emission cathode operating at GHz frequency

Vacuum microelectronic devices play an important role in the field of micro- and nano-electronics and they have been strongly developed in recent decades. Vacuum microelectronics are mainly based on the field emission effect and the employment of electrons in vacuum in a device with dimensions from tenths to hundredths of a micrometer. In this work, we present the development of a carbon-nanotube-based multifinger microtriode operating from 0.5 to 2 GHz. In this frequency range, a minimum RF signal gain of 5 dB is achieved. Such a device represents an optimized alternative to the standard Spindt-type microtriode. The advantage of such multifinger architecture consists in the possibility to reduce the cathode-grid capacitance by reducing the overlap between the two electrodes using a parallel patterning. This approach allows increasing the cut-off frequency of the devices with respect to the Spindt-type triode. We realized a prototype of the multifinger triode and the field emission properties have been characterized. The frequency behavior has been measured, demonstrating the possibility to amplify RF signal.

Designing Piezoelectric Actuators for Micro Deep Drawing of Rectangular Work Pieces

Micro forming process is a promising micro manufacturing technology for producing micro parts due to its high efficiency, low production cost and good product quality. Deep drawing provides a great application potential for the manufacturing of parts with complex shapes, even in very small dimensions. Using piezoelectric actuator which is implied in this paper can be considered as a novel approach in the field of micro deep drawing. Micromachines based on piezoelectric actuators are kind of actuators assures even up to several kilo-Newton forces and movement accuracy theoretically in atomic scale. In this paper, scaled investigations are carried out with different scales of rectangular punches and the blank with different thicknesses then appropriate piezoelectric actuators are designed for each scale.

In memory of professor Alexey Volkov

The article briefly outlines the life and scientific activities of Professor Alexey Volkov, the chief researcher of the Image Processing Systems Institute of the RAS, Doctor of Engineering, a well-known specialist in the field of micro - and nanotechnologies.

Analysis and Design for Rapid Prototyping Mechanism Using Hybrid Flexural Pivots

High performance motion systems play an important role in modern technology especially in the area of metrology and process equipment related to the field of micro- and nanotechnology. The purpose of this study is to show how to properly design and fabricate prototyped mechanisms that integrate metal-polymer flexural pivots for precision motion applications. Finite element simulations are used to understand the mechanical behavior of these components leading to dimensions that minimize the work done by the polymer structures. Simulations indicate that, the penetration distance of the metallic inserts into the polymer structures should be around one half of the total insert length and that the profile of the pressure interference can be modified to enhance the performance of the composite structure. A cantilever beam with a flexural pivot is used to test the performance of the design and a piezoelectric-actuated four bar mechanism is prototyped and studied as a general application of these types of structures to the precision motion field. The methodology implemented in this work poses a simple and affordable way to fabricate, assemble and customize low-cost devices for precision motion application and it applies to both, systems fabricated by polymer and metal rapid prototyping technologies.