Design Of Microsystems Research Articles

Photothermal microfluidic-assisted self-cleaning effect for a highly reusable SERS sensor.

The synergistic integration of optofluidic and surface enhanced Raman scattering (SERS) sensing is a new analytical technique that provides a number of unique characteristics for enhancing the sensing performance and simplifying the design of microsystems. Here, we propose a reusable optofluidic SERS sensor by integrating Au nanoisland substrate (AuNIS)-coated fiber into a microfluidic chip. Through both systematic experimental and theoretical analysis, the sensor enables efficient self-cleaning based on its optical-to-heat-hydrodynamic energy conversion property. Besides, the sensor exhibits the instrument detection limit down to 10-13mol/L and enhancement factor of 106 for Rhodamine 6G. Our optofluidic SERS sensor with such a photothermal microfluidic-assisted self-cleaning method has the advantages of portability, simple operation, and high cleaning efficiency, which will provide a new, to the best of our knowledge, concept and approach for cost-effective and reusable sensors.

Hydrodynamic Entrance Length for Laminar Flow in Microchannels with Rectangular Cross Section

This work presents a detailed numerical investigation on the required development length (L=L/B) in laminar Newtonian fluid flow in microchannels with rectangular cross section and different aspect ratios (AR). The advent of new microfluidic technologies shifted the practical Reynolds numbers (Re) to the range of unitary (and even lower) orders of magnitude, i.e., creeping flow conditions. Therefore, accurate estimations of L at Re≤O(1) are important for microsystem design. At such low Reynolds numbers, in which inertial forces are less dominant than viscous forces, flow characteristics become necessarily different from those at the macroscale where Re is typically much larger. A judicious choice of mesh refinement and adequate numerical methods allowed obtaining accurate results and a general correlation for estimating L, valid in the ranges 0≤Re≤2000 and 0.1≤AR≤1, thus covering applications in both macro and microfluidics.

Transparent, Compliant 3D Mesostructures for Precise Evaluation of Mechanical Characteristics of Organoids.

Recently developed methods for transforming 2D patterns of thin-film materials into 3D mesostructures create many interesting opportunities in microsystems design. A growing area of interest is in multifunctional thermal, electrical, chemical, and optical interfaces to biological tissues, particularly 3D multicellular, millimeter-scale constructs, such as spheroids, assembloids, and organoids. Herein, examples of 3D mechanical interfaces are presented, in which thin ribbons of parylene-C form the basis of transparent, highly compliant frameworks that can be reversibly opened and closed to capture, envelop, and mechanically restrain fragile 3D tissues in a gentle, nondestructive manner, for precise measurements of viscoelastic properties using techniques in nanoindentation. Finite element analysis serves as a design tool to guide selection of geometries and material parameters for shape-matching 3D architectures tailored to organoids of interest. These computational approaches also quantitate all aspects of deformations during the processes of opening and closing the structures and of forces imparted by them onto the surfaces of enclosed soft tissues. Studies of cerebral organoids by nanoindentation show effective Young's moduli in the range from 1.5 to 2.5 kPa depending on the age of the organoid. This collection of results suggests broad utility of compliant 3D mesostructures in noninvasive mechanical measurements of millimeter-scale, soft biological tissues.

Multilayer microhydraulic actuators with speed and force configurations

Electrostatic motors have traditionally required high voltage and provided low torque, leaving them with a vanishingly small portion of the motor application space. The lack of robust electrostatic motors is of particular concern in microsystems because inductive motors do not scale well to small dimensions. Often, microsystem designers have to choose from a host of imperfect actuation solutions, leading to high voltage requirements or low efficiency and thus straining the power budget of the entire system. In this work, we describe a scalable three-dimensional actuator technology that is based on the stacking of thin microhydraulic layers. This technology offers an actuation solution at 50 volts, with high force, high efficiency, fine stepping precision, layering, low abrasion, and resistance to pull-in instability. Actuator layers can also be stacked in different configurations trading off speed for force, and the actuator improves quadratically in power density when its internal dimensions are scaled-down.

Yeşil sentez yoluyla mikrosistemlerde çinko oksit nanopartiküllerin üretimi ve karakterizasyonu

Nanoparticles (NP), which can be produced for many different fields and purposes; are at size vary from nanometer to a micrometer. These particles can be prepared by different approaches such as chemical, physical and biological methods. However, the biological approach is the most promising approach among other methods due to its simplicity and environmentally friendly conditions. The production of the nanoparticle by means of a biological approach does not require any high temperature, acidic/basic conditions and hazardous chemicals. Therefore, this method is named “green synthesis”. Development in microtechnology has had profound effects in many areas such as drug discovery, biology, diagnosis, and tissue engineering. Microfluidics which focuses on the processing of liquids in microscale systems has attracted wide attention in the production process of nanoparticles due to precise control and fast mixing. The main purpose of this study is to produce and characterize metal nanoparticles by combining microsystems and green synthesis approaches. For this purpose, in the first step, the design of microsystems that suitable for the flow of different phases was performed. In the second step, ZnO nanoparticle synthesis was carried out using the red cabbage (Brassica oleracea var.capitata f. Rubra) extracts. The synthesis of nanoparticles achieved by optimizing different parameters such as; extract: zinc ratio, zinc solution concentration, flow rates, and flow rates ratio in the microsystem and temperature. The results showed that the herbal red cabbage components can be used for the green synthesis of ZnO nanoparticles.

Numerical Analysis and Entropy Generation of Electrokinetic Flow of Power-Law Fluid in a Microtriangular Prism

This research aims to study the characteristics of thermal transport and analyse the entropy generation of electroosmotic flow of power-law fluids in a microtriangular prism in the presence of pressure gradient. Considering a fully developed flow subject to constant wall heat flux, the nonlinear electric potential, momentum, and linear heat transfer equations are solved numerically by developing an iterative finite difference method with a nonuniform grid. The thermal efficiency of the model is explored under the light of the second law of thermodynamics. Effect/impact of governing physical parameters on velocity, temperature, Nusselt number, and entropy distributions is studied, and the results are demonstrated graphically; we found that the Nusselt number decreases with the increase of power-law index, and average entropy generation increases with power-law index. We believe that the obtained result in the present study shall be useful for design of energy efficient microsystems which utilize the dual electrokinetic and centrifugal pumping effects.

On the dynamic response of porous functionally graded microbeam under moving load

In this article, the dynamic behavior of functionally graded (FG) microbeams with different porosity distributions and acted by a moving harmonic load is studied. A bi-dimensional FG microbeam with its material properties changing gradually along both the length and thickness directions in a power-law distribution form is presented. Besides, the porosities are distributed evenly and unevenly in the body of microbeams, and the small-scale effect is captured with the help of the modified couple stress theory. The equations describing the motions of the FG microbeam are obtained in the framework of Hamilton's principle in conjunction with the parabolic shear deformation theory. These equations are solved by employing the finite element formulation, which is validated by comparing the fundamental frequency and dynamic response with previous works. The effects of several key factors such as two grading indexes, small scale parameters, porous distribution pattern and volume fraction, as well as moving speed and motivation frequency of the acted load are investigated in detail. It is concluded that the bi-dimensional FG parameters and porous parameter play significant roles in the dynamic response of microbeams subjected to a moving load, which is helpful for the multi-functional and optimal design of microsystems.

Design and Development of Spray-Dried Microsystems to Improve Technological and Functional Properties of Bioactive Compounds from Hazelnut Shells.

An extract obtained from hazelnut shells by-products (HSE) has antioxidant and chemopreventive effects on human melanoma and cervical cancer cell lines, inducing apoptosis by caspase-3 activation. A clinical translation is limited by poor water solubility and low bioavailability. Dried plant extracts often show critical characteristics such as sticky/gummy appearance, unpleasant smell, and instability involving practical difficulties in processing for industrial use. A spray drying method has been applied to transform raw HSE in a microparticulate powder. The biopolymeric matrix was based on l-proline as loading carrier, hydroxyethylcellulose in combination with pectin as coating polymers; lecithin and ethanol were used as solubility enhancers. A Hot-Cold-Hot method was selected to prepare the liquid feed. The thus prepared powder showed good technological properties (solid-state, particle dimensions, morphology, and water dissolution rate), stability, and unchanged chemopreventive effects with respect to the unprocessed HSE.

Fluid structure interaction of cantilever micro and nanotubes conveying magnetic fluid with small size effects under a transverse magnetic field

Micro and nanotubes have found major application in fluidic systems as channels for conveying fluid. In some micro and nanofluidic applications such as drug delivery, a transverse magnetic field can be used to guide the fluid flow by generating an axial force in the flow direction. An important issue in the design of micro and nanofluidic systems is the structural vibration caused by the fluid flow. In the current study, we investigate the effect of transverse magnetic field on the vibration of cantilever micro and nanotubes conveying fluid by considering the small size effects. We couple the nonlocal Euler–Bernoulli beam model with Navier–Stokes theory to determine a fluid structure interaction (FSI) model for the vibration analysis of the system. We modify the FSI governing equation by driving a velocity correction factor to consider the effect of transverse magnetic field on the fluid flow’s pattern through the tube. Then, we use the Galerkin’s method to obtain the frequency diagrams for the instability analysis of the system. We show that the transverse magnetic field can have a substantial effect on the dynamics of tube conveying fluid by increasing the system’s natural frequencies and critical flow velocity which contributes to the flutter instability. We also discover that although the transverse magnetic field plays a crucial role on dynamics of microstructures, its effect on the dynamics of nanotubes is not significant and can be ignored.

Technological Deconstruction and Reorganization Process of Industrial Design Driven Product Innovation

The work aims at discussing the essence of technology deconstruction and reorganization, and establishing the core value of technical decision-making in product micro-system design, In view of the current reality of neglecting product technology innovation. It clarifies the content of product technology and explores the ways and methods of product technology deconstruction and restructuring in the industrial design process. Industrial design is integration and inclusion, parallel design and collaborative design is the overall trend of its development, product technology design and modeling, man-machine and other design will eventually become unified. The innovation of working principle is the process of replacing the basic elements and modules or optimizing the state of material, information and energy transfer; product structure optimization is the process of mathematically finding the minimum design variables that meet the design requirements; the innovation of modeling material solutions is to solve the decision-making problem of the target multi-scheme; the processing technology improvement is to solve the process route optimization problem under multi-constraint conditions.

Modeling Living Cells Within Microfluidic Systems Using Cellular Automata Models

Several computational models, both continuum and discrete, allow for the simulation of collective cell behaviors in connection with challenges linked to disease modeling and understanding. Normally, discrete cell modelling employs quasi-infinite or boundary-less 2D lattices, hence modeling collective cell behaviors in Petri dish-like environments. The advent of lab- and organ-on-a-chip devices proves that the information obtained from 2D cell cultures, upon Petri dishes, differs importantly from the results obtained in more biomimetic micro-fluidic environments, made of interconnected chambers and channels. However, discrete cell modelling within lab- and organ-on-a-chip devices, to our knowledge, is not yet found in the literature, although it may prove useful for designing and optimizing these types of systems. Consequently, in this study we focus on the establishment of a direct connection between the computer-aided designs (CAD) of microfluidic systems, especially labs- and organs-on-chips (and their multi-chamber and multi-channel structures), and the lattices for discrete cell modeling approaches aimed at the simulation of collective cell interactions, whose boundaries are defined directly from the CAD models. We illustrate the proposal using a quite straightforward cellular automata model, apply it to simulating cells with different growth rates, within a selected set of microsystem designs, and validate it by tuning the growth rates with the support of cell culture experiments and by checking the results with a real microfluidic system.

Heat transfer characteristics and entropy generation of electroosmotic flow in a rotating rectangular microchannel

This study aims to investigate thermal transport characteristics and analyze entropy generation of thermally fully-developed electroosmotic flow (EOF) in a rotating rectangular microchannel subject to constant wall heat flux. In the two-dimensional rectangular domain, the solutions for electric potential and flow velocity are obtained in terms of eigenfunction series by means of separation of variables technique, and the temperature field, which takes into consideration the effects of heat convection, Joule heating and viscous dissipation, is numerically solved. Results are generated to show the influences due to various factors, including rotational frequency, depth/width ratio of the rectangular channel, distribution of zeta potentials, strength of Joule heating and magnitude of wall heat flux, on the thermal transport characteristics. In particular, how the Nusselt number and the entropy generation vary with these factors are explored in details. To pursue optimization in energy utilization, an optimal aspect ratio is found at which the minimum entropy generation can be achieved. We believe that the findings in the present study will be useful in the design of energy efficient micro-systems which utilize the dual electrokinetic and centrifugal pumping effects.

Numerical analysis of capture and isolation of magnetic nanoparticles in microfluidic system

Rapid capturing and isolation of magnetic nanoparticles is critical for microfluidic biodetection system. A numerical model based on multiphysics coupled-field finite-element method is developed for evaluating the capture and segregation of magnetic nanoparticles in microfluidic channel. The model consists of microfluidic channels surrounded by four electromagnets changed periodically. The trajectories and trapping efficiencies are numerically analyzed for multiple magnetic nanoparticles released in microfluidic channel. Simulation results showed that magnetic pole current, inlet velocity and diameter of magnetic nanoparticles have an impact on the capture efficiency of magnetic nanoparticle. Thus, the model with the optimal parameters can reasonably predict and evaluate completely trapping of 180 nm magnetic nanoparticles in the simulation. The numerical analysis will encouraging for the design and development of new microfluidic bioseparation and detection microsystems.

Shock response of electrostatically coupled microbeams under the squeeze-film damping effect

This paper presents a theoretical investigation of the dynamic response of electrostatically coupled microcantilever beams under the combined effect of squeeze-film damping and mechanical shock for MEMS applications. We consider two different microsystem designs, namely single and dual beams, operating at varying conditions to explore their possible use based on the application of interest. The single-beam system is actuated via a fixed electrode (uncoupled actuation), while the electric actuation of the dual-beam system, comprising two movable microbeams, is achieved by applying a DC voltage among them (coupled actuation). We develop a multi-physics model to simulate the dynamic response of single and dual microbeams while accounting for the fringing field effect, the squeeze-film damping resulting from the interactions between the vibrating microbeams and the surrounding fluid, and the mechanical shock. The squeeze-film damping is incorporated using a nonlinear analytical expression rather than solving the fully coupled fluid–structure problem. Numerous studies have shown the validity of this analytical approach under the assumption of long beams and neglecting the fluid compressibility. Some benchmark cases are considered to verify the predictive capability of the numerical model. The simulation results are in good qualitative and quantitative agreements with those reported in the literature. A parametric study is then conducted to investigate the effects of the initial gap distance, the fluid viscosity, and the beam geometry on the shock response of the microsystem. The squeeze-film damping enables the protection of the vibrating microbeams from hitting the substrate under mechanical shock and can be exploited to enhance the reliability of MEMS devices. However, this protection can be significantly reduced by increasing the gap distance or decreasing the operating pressure. The numerical study shows that the dual-beam systems withstand better to a mechanical shock. Breaking the symmetry of the dual-beam system in terms of the beams’ geometry is found to reduce significantly the resistance to shocks. On the other hand, given their high sensitivity to a mechanical shock, single-beam systems are observed to be more attractive for deployment as microswitches.

Functionalizing cell-mimetic giant vesicles with encapsulated bacterial biosensors.

The design of vesicle microsystems as artificial cells (bottom-up synthetic biology) has traditionally relied on the incorporation of molecular components to impart functionality. These cell mimics have reduced capabilities compared with their engineered biological counterparts (top-down synthetic biology), as they lack the powerful metabolic and regulatory pathways associated with living systems. There is increasing scope for using whole intact cellular components as functional modules within artificial cells, as a route to increase the capabilities of artificial cells. In this feasibility study, we design and embed genetically engineered microbes (Escherichia coli) in a vesicle-based cell mimic and use them as biosensing modules for real-time monitoring of lactate in the external environment. Using this conceptual framework, the functionality of other microbial devices can be conferred into vesicle microsystems in the future, bridging the gap between bottom-up and top-down synthetic biology.

Material selection for Micro-Electro-Mechanical-Systems (MEMS) using Ashby's approach

A key aspect in design optimization of a product or a system is the selection of materials that best meet the design needs, ensuring maximum performance and minimum cost. Ashby's approach, originally introduced for macro-systems and products, has been very successfully employed for Micro-Electro-Mechanical-Systems (MEMS)/micromachined sensors, actuators and devices. This paper presents a comprehensive review and critical analysis of MEMS material selection studies using Ashby's approach reported in the literature during the last two decades. Performance and Material Indices derived for various microsystems and MEMS devices have been summarized. Moreover, all MEMS materials reported in the literature and the most suitable materials proposed for a variety of MEMS systems and devices have also been consolidated. A material selection case study utilizing micro-scale properties of 51 MEMS compatible materials has been presented to demonstrate that the use of different materials' bulk properties is not the best choice for MEMS materials selection. This paper will serve as a reference guide and useful resource for researchers and engineers engaged in the design and fabrication of various microsystems and MEMS sensors, actuators and devices.

Nonlinear analysis and characteristics of electrically-coupled microbeams under mechanical shock

Several studies have shown that MEMS devices deploying electrically-actuated vibrating beams, such as resonant sensors and RF filters may fail to operate when undergoing mechanical shocks due to the pull-in instability. To this end, we investigate the possibility to overcome or exploit this issue by considering different microsystem designs based on the application of interest. This objective is carried out through developing a nonlinear reduced-order model to simulate the dynamic response of single and dual microbeams under varying electric actuation and shock loads. The actuation of the single-beam system is made via a fixed electrode (uncoupled actuation) while the dual-beam system, composed of two movable microbeams, is actuated by applying a voltage among them (coupled actuation). We use the Galerkin method to discretize the governing equations in space and the Runge–Kutta method to integrate the resulting nonlinear ordinary differential equations. We first perform the static analysis to determine the pull-in voltage. We formulate the coupled eigenvalue problem to compute the natural frequencies of the microsystems under investigation for different applied DC voltages. Then, we introduce the AC excitation and generate the frequency-response curves. Finally, we analyze the impact of the mechanical shock (represented by an impact pulse acceleration) on the microsystems’ dynamic behavior. The present results are in good agreement with those obtained from previously-published theoretical and experimental studies. We observe a significant reduction in the static pull-in voltage and switching time when considering the dual-beam system in comparison with the single-beam case. The frequency-response curves show expanded dynamic pull-in bandwidth when operating the dual-beam system near the primary resonance. We notice that the dual-beam systems are more robust in terms of resistance to mechanical shock. This shows the suitability of such design for the operation and reliability of MEMS devices in harsh environments characterized by high mechanical shock levels. On the other hand, single-beam systems seem to be more attractive for use as microswitches which are intended to trigger a signal once receiving a mechanical shock or abrupt change in acceleration to activate safety functionalities, such as airbag systems.

Skin-interfaced systems for sweat collection and analytics.

Recent interdisciplinary advances in materials, mechanics, and microsystem designs for biocompatible electronics, soft microfluidics, and electrochemical biosensors establish the foundations for emerging classes of thin, skin-interfaced platforms capable of capturing, storing, and performing quantitative, spatiotemporal measurements of sweat chemistry, instantaneous local sweat rate, and total sweat loss. This review summarizes scientific and technical progress in this area and highlights the implications in real time and ambulatory modes of deployment during physical activities across a broad range of contexts in clinical health, physiology research, fitness/wellness, and athletic performance.

Monolithic 3D labs- and organs-on-chips obtained by lithography-based ceramic manufacture

In this study, we present a novel approach for the design and development of three-dimensional monolithic ceramic microsystems with complex geometries and with potential applications in the biomedical field, mainly linked to labs-on-chips and organs-on-chips. The microsystem object of study stands out for its having a complex three-dimensional geometry, for being obtained as a single integrated element, hence reducing components, preventing leakage and avoiding post-processes, and for having a cantilever porous ceramic membrane aimed at separating cell culture chambers at different levels, which imitates the typical configuration of transwell assays. The design has been performed taking account of the special features of the manufacturing technology and includes ad hoc incorporated supporting elements, which do not affect overall performance, for avoiding collapse of the cantilever ceramic membrane during debinding and sintering. The manufacture of the complex three-dimensional microsystem has been accomplished by means of lithography-based ceramic manufacture, the additive manufacturing technology which currently provides the most appealing compromises between overall part size and precision when working with ceramic materials. The microsystem obtained provides one of the most remarkable examples of monolithic bio-microsystems and, to our knowledge, a step forward in the field of ceramic microsystems with complex geometries for lab-on-chip and organ-on-chip applications. Cell culture results help to highlight the potential of the proposed approach and the adequacy of using ceramic materials for biological applications and for interacting at a cellular level.

Temperature of a nanoparticle above a substrate under radiative heating and cooling

Controlling the temperature in architectures involving nanoparticles and substrates is a key issue for applications involving micro and nanoscale heat transfer. We study the thermal behavior of a single nanoparticle interacting with a flat substrate under external monochromatic illumination, and with thermal radiation as the unique heat loss channel. We develop a model to compute the temperature of the nanoparticle, based on an effective dipole-polarizability approach. Using numerical simulations, we thoroughly investigate the impacts of various parameters affecting the nanoparticle temperature, such as the nanoparticle-to-substrate gap distance, the incident light wavelength and polarization, or the material resonances. This study provides a tool for the thermal characterization and design of micro or nanoscale systems coupling substrates with nanoparticles or optical antennas.