Development Of Microsystems Research Articles

An intelligent wearable artificial pancreas patch based on a microtube glucose sensor and an ultrasonic insulin pump

In order to improve the living standards of diabetes patients and reduce the negative health effects of this disease, the medical community has been actively searching for more effective treatments. In recent years, an artificial pancreas has emerged as an important approach to managing diabetes. Despite these recent advances, meeting the requirements for miniaturized size, accurate sensing and large-volume pumping capability remains a great challenge. Here, we present a novel miniaturized artificial pancreas based on a long microtube sensor integrated with an ultrasonic pump. Our device meets the requirements of achieving both accurate sensing and high pumping capacity. The artificial pancreas is constructed based on a long microtube that is low cost, painless and simple to operate, where the exterior of the microtube is fabricated as a glucose sensor for detecting diabetes and the interior of the microtube is used as a channel for delivering insulin through an ultrasonic pump. This work successfully achieved closed-loop control of blood glucose and treatment of diabetes in rats. It is expected that this work can open up new methodologies for the development of microsystems, and advance the management approach for diabetes patients.

Thickness-dependent thermoelectric properties of ultrathin polymer film on self-assembled monolayers

Conductive polymers have attracted attention for wearable and implantable thermoelectric devices due to their lightweight, flexibility, and solubility. With the development of microsystems, thermoelectric power generation devices are trending toward miniaturization, flexibility, high integration, and lightweight thin films. Therefore, the study of the thickness of thermoelectric materials has become increasingly important. In this study, we prepared ultrathin polymer thermoelectric (TE) films with different thicknesses (14–52 nm) by modifying the substrate with self-assembled monolayers (SAMs). The thickness-dependent thermoelectric performances on SAMs are investigated. It is found that SAMs regulate the carrier concentration in polymer ultrathin TE films, and a smoother surface contributes to the improvement of carrier mobility, thus optimizing the thermoelectric performance. The maximum modulation of thermoelectric performance is observed at a film thickness of approximately 35 nm, which contains nine molecular layers.

Evolution of the Microrobots: Stimuli-Responsive Materials and Additive Manufacturing Technologies Turn Small Structures into Microscale Robots.

The development of functional microsystems and microrobots that have characterized the last decade is the result of a synergistic and effective interaction between the progress of fabrication techniques and the increased availability of smart and responsive materials to be employed in the latter. Functional structures on the microscale have been relevant for a vast plethora of technologies that find application in different sectors including automotive, sensing devices, and consumer electronics, but are now also entering medical clinics. Working on or inside the human body requires increasing complexity and functionality on an ever-smaller scale, which is becoming possible as a result of emerging technology and smart materials over the past decades. In recent years, additive manufacturing has risen to the forefront of this evolution as the most prominent method to fabricate complex 3D structures. In this review, we discuss the rapid 3D manufacturing techniques that have emerged and how they have enabled a great leap in microrobotic applications. The arrival of smart materials with inherent functionalities has propelled microrobots to great complexity and complex applications. We focus on which materials are important for actuation and what the possibilities are for supplying the required energy. Furthermore, we provide an updated view of a new generation of microrobots in terms of both materials and fabrication technology. While two-photon lithography may be the state-of-the-art technology at the moment, in terms of resolution and design freedom, new methods such as two-step are on the horizon. In the more distant future, innovations like molecular motors could make microscale robots redundant and bring about nanofabrication.

The simulation study of high-performance micro-inductors Based on MEMS 3D coils

With the development of flexible electronics and microsystems, the demand for the miniaturization of electronic components is becoming increasingly urgent. Due to the advantages of miniaturization, low power consumption, and easy integration, the micro-inductors fabricated by microfabrication technology get more and more attention. However, the traditional two-dimensional inductors are no longer able to meet the growing needs of today’s society in terms of occupied areas, inductance values, and packaging costs. So, this paper proposes a three-dimensional structure thin film solenoid micro-inductor based on MEMS and analyzes it by using finite element method (FEM). The simulation focuses on recording the inductance values and quality factors of the micro-inductors with varying parameters in the frequency range of 0-2, 000 MHz. Additionally, the maximum current values corresponding to the micro-inductors with different parameters are recorded at the operating temperature of polyimide, specifically addressing the current-carrying capacity. The simulation result has certain theoretical guidance for high-performance micro-inductors design.

Torsional Vibration and Sensitivity Analysis of Microcantilever in Liquid

Development of microsystems and ever-increasing advances of nanotechnology have resulted in growing applications of microcantilevers (MCs), including Atomic Force Microscopy (AFM). In AFM, transverse vibration of microfiber from a liquid medium results in resonance of unwanted hydrodynamic and electrostatic forces, which can be minimized by torsional mode. In the present study, the differential equation of the vibrational motion is extracted by acquiring the hydrodynamic force applied to MCs aiming to investigate the torsional vibration behavior of MCs in a liquid medium; and the extracted equation is solved to study the behavior of MCs in a liquid medium. Considering the significant effect of MC geometry on its torsional vibrations in a liquid medium, Sobol's variance-based sensitivity analysis method was utilized to investigate the effectiveness of MC geometry on torsional vibration. The sensitivity analysis results show that length and width have the most significant effects on the quality factor and the resonance frequency of MCs.

Investigation of the Processing Behavior and Stability of Different Glass Frit Materials

Glass frit wafer bonding is a widely used process in the development and production of microsystems, especially for integrating sensors and their signal conditioning circuits. As a result, glass frit bonded wafers must withstand subsequent process modules, such as silicon (wafer) through vias (TSVs) processing. The properties of glass materials for wafer bonding play a crucial role in ensuring the performance and reliability of such wafers. With the advent of new environmental regulations, Lead-free glass frit materials are being developed to replace the current Lead-containing glasses. In this context, four different glass frit materials were investigated and compared in detail, and the bonding behaviors of these materials were analyzed. It was found that the low-melting main components of these glasses determined their properties and performance. The glasses' electrical and chemical properties were also investigated, and their impact on the bonding process was analyzed. The results of this study provide guidance for the process integration of glass frit wafer bonding and open up new possibilities. In addition, the study highlights the need for practical evaluations for specific applications and related details.

Laser-powder bed fusion molds without post-processing for micro-injection molding of mini/micro-products

The use of additive manufacturing (AM) processes at the micro-scale helps to increase the development of micro-systems, thus enabling shorter tooling development to be exploited for other micro-technologies, such as micro-injection molding (µ-IM). In recent years, these process combinations have shown their capability of providing greater flexibility to micro-technologies and facilitating a high production rate, in particular allowing µ-IM to be economically feasible for low-volume production. Therefore, in order to assess the feasibility of micro-metal AM for µ-IM mold production, a set of mini- and micro-polymeric parts injected by using molds realized via the laser-powder bed fusion (L-PBF) process is discussed in this paper. The molds were manufactured in low-carbon steel and have been characterized and tested experimentally, without any post-process treatment. Two selected geometries, corresponding to a mini dogbone for tensile tests and a flexural hinge with features at the micro-scale, were designed and realized by the µ-IM process. These were replicated in order to assess the accuracy of the whole process. The obtained results of replication accuracy and mechanical tests confirm that the µ-IM process, performed with an L-PBF-made mold insert, is feasible and affordable for micro-production, although great accuracy, especially in mold design, fabrication, and assembly, is required.

Signal Transduction in Artificial Cells.

In recent years, significant progress has been made in the emerging field of constructing biomimetic soft compartments with life-like behaviors. Given that biological activities occur under a flux of energy and matter exchange, the implementation of rudimentary signaling pathways in artificial cells (protocells) is a prerequisite for the development of adaptive sense-response phenotypes in cytomimetic models. Herein, recent approaches to the integration of signal transduction modules in model protocells prepared by bottom-up construction are discussed. The approaches are classified into two categories involving invasive biochemical signals or non-invasive physical stimuli. In the former mechanism, transducers with intrinsic recognition capability respond with high specificity, while in the latter, artificial cells respond through intra-protocellular energy transduction. Although major challenges remain in the pursuit of a sophisticated artificial signaling network for the orchestration of higher-order cytomimetic models, significant advances have been made in establishing rudimentary protocell communication networks, providing novel organizational models for the development of life-like microsystems and new avenues in protoliving technologies.

NDE-Based Failure Analysis of an LTCC-Eddy Current Sensor Exposed to High Temperature Using 3-D X-Ray μ-CT

Sensors based on Low Temperature Co-fired Ceramic (LTCC) technology have shown great potential for in-situ Structural Health Monitoring (SHM) of engineering components exposed to high temperatures (HT) [1]. LTCC is a unique of its kind materials technology offering significant advantages for the development of micro-systems with integrated sensors. Nevertheless, there are still metrological issues like thermal and mechanical stresses associated with the fabrication process and subsequently the sensor fails while in use. This communication deals with the Non Destructive Evaluation (NDE) based failure analysis of an LTCC-based Eddy Current (EC) sensor exposed to HT. It aims at monitoring the in-situ performance and efficacy of the sensor exposed to HT for prolonged duration. The sensor was instrumented and placed inside the furnace (~ 650 °C) and in-situ EC response was monitored using an automated EC measurement set-up. We found that the sensor failed to operate by losing its electrical attributes after ~ 350 hours of continuous operation. Subsequently, a detailed investigation on NDE-based failure analysis of the sensor was carried out using an ultra-high resolution 3D X-ray μ-Computer Tomography (μ-CT) imaging system. The most common flaws include alignment errors, conductor swelling, conductor creeps, layer shrinkage, interconnect via voids, coil expansion and micro-cracks on conductor tracks and pads. A comparison study is drawn to create a database that will lead to optimizing the fabrication process flow and setting operational limits of the LTCC sensor.

Thermodynamic Multi-Field Coupling Optimization of Microsystem Based on Artificial Intelligence

An efficient multi-objective optimization method of temperature and stress for a microsystem based on particle swarm optimization (PSO) was established, which is used to map the relationship between through-silicon via (TSV) structural design parameters and performance objectives in the microsystem, and complete optimization temperature, stress and thermal expansion deformation efficiently. The relationship between the design and performance parameters is obtained by a finite element method (FEM) simulation model. The neural network is built and trained in order to understand the mapping relationship. Then, the design parameters are iteratively optimized using the PSO algorithm, and the FEM results are used to verify the efficiency and reliability of the optimization methods. When the optimization target of peak temperature, bump temperature, TSV temperature, maximum stress and maximum thermal deformation are set as 100 °C, 55 °C, 35 °C, 180 Mpa and 12 μm, the optimization results are as follows: the peak temperature is 97.90 °C, the bump temperature is 56.01 °C, the TSV temperature is 31.52 °C, the maximum stress is 247.4 Mpa and the maximum expansion deformation is 11.14 μm. The corresponding TSV structure design parameters are as follows: the radius of TSV is 10.28 μm, the pitch is 65 μm and the thickness of SiO2 is 0.83 μm. The error between the optimization result and the target temperature is 2.1%, 1.8%, 9.9%, 37.4% and 7.2% respectively. The PSO method has been verified by regression analysis, and the difference between the temperature and deformation optimization results of the FEM method is not more than 3%. The stress error has been analyzed, and the reliability of the developed method has been verified. While ensuring the accuracy of the results, the proposed optimization method reduces the time consumption of a single simulation from 2 h to 70 s, saves a lot of time and human resources, greatly improves the efficiency of the optimization design of microsystems, and has great significance for the development of microsystems.

Computer simulation of obtaining thin films of silicon carbide.

Silicon carbide films are potential candidates for the development of microsystems with harsh environmental conditions. In this work, the production of high-purity silicon carbide films by the electrolytic method is reproduced in a computer model. Single-layer SiC films were deposited on nickel, copper, and graphite substrates. The kinetic and structural characteristics related to the Si and C atoms in this compound are presented. The coefficient of self-diffusion of C atoms on all substrates is higher than that of Si atoms. In addition, the diffusion of atoms on a graphite substrate occurs much more intensively than on metallic (Ni and Cu) substrates. The first maximum of the radial distribution function g(r)SiC is at a shorter distance when the film is deposited on the graphite substrate. A detailed analysis of the structure, based on the construction of Voronoi polyhedra, indicates that the degree of crystallinity of the film increases when changing the substrate in the order from nickel to graphite. The resulting SiC films are subject to local stresses, the strongest of which appear on the copper substrate, however the average stresses in the film do not appear to be high.

Bioprinting on Organ-on-Chip: Development and Applications.

Organs-on-chips (OoCs) are microfluidic devices that contain bioengineered tissues or parts of natural tissues or organs and can mimic the crucial structures and functions of living organisms. They are designed to control and maintain the cell- and tissue-specific microenvironment while also providing detailed feedback about the activities that are taking place. Bioprinting is an emerging technology for constructing artificial tissues or organ constructs by combining state-of-the-art 3D printing methods with biomaterials. The utilization of 3D bioprinting and cells patterning in OoC technologies reinforces the creation of more complex structures that can imitate the functions of a living organism in a more precise way. Here, we summarize the current 3D bioprinting techniques and we focus on the advantages of 3D bioprinting compared to traditional cell seeding in addition to the methods, materials, and applications of 3D bioprinting in the development of OoC microsystems.

A microexplosive shockwave-based drug delivery microsystem for treating hard-to-reach areas in the human body

Implantable drug-delivery microsystems have the capacity to locally meet therapeutic requirements by maximizing local drug efficacy and minimizing potential side effects. The internal organs of the human body including the esophagus, gastrointestinal tract, and respiratory tract, with anfractuos contours, all manifest with endoluminal lesions often located in a curved or zigzag area. The ability of localized drug delivery for these organs using existing therapeutic modalities is limited. Spraying a drug onto these areas and using the adhesion and water absorption properties of the drug powder to attach to lesion areas can provide effective treatment. This study aimed to report the development and application of microsystems based on microshockwave delivery of drugs. The devices comprised a warhead-like shell with a powder placed at the head of the device and a flexible rod that could be inserted at the tail. These devices had the capacity to deposit drugs on mucous membranes in curved or zigzag areas of organs in the body. The explosive impact characteristics of the device during drug delivery were analyzed by numerical simulation. In the experiment of drug delivery in pig intestines, we described the biosafety and drug delivery capacity of the system. We anticipate that such microsystems could be applied to a range of endoluminal diseases in curved or zigzag regions of the human body while maximizing the on-target effects of drugs.

Mechanical Force Acting on Ferrogel in a Non-Uniform Magnetic Field: Measurements and Modeling.

The development of magnetoactive microsystems for targeted drug delivery, magnetic biodetection, and replacement therapy is an important task of present day biomedical research. In this work, we experimentally studied the mechanical force acting in cylindrical ferrogel samples due to the application of a non-uniform magnetic field. A commercial microsystem is not available for this type of experimental study. Therefore, the original experimental setup for measuring the mechanical force on ferrogel in a non-uniform magnetic field was designed, calibrated, and tested. An external magnetic field was provided by an electromagnet. The maximum intensity at the surface of the electromagnet was 39.8 kA/m and it linearly decreased within 10 mm distance from the magnet. The Ferrogel samples were based on a double networking polymeric structure which included a chemical network of polyacrylamide and a physical network of natural polysaccharide guar. Magnetite particles, 0.25 micron in diameter, were embedded in the hydrogel structure, up to 24% by weight. The forces of attraction between an electromagnet and cylindrical ferrogel samples, 9 mm in height and 13 mm in diameter, increased with field intensity and the concentration of magnetic particles, and varied within 0.1–30 mN. The model provided a fair evaluation of the mechanical forces that emerged in ferrogel samples placed in a non-uniform magnetic field and proved to be useful for predicting the deformation of ferrogels in practical bioengineering applications.

Printed electronics for extreme high temperature environments

There is a rapidly growing interest in the development of electronic microsystems that can maintain functionality in high temperature environments, particularly in power generation and aircraft engines where the operating temperatures can exceed 500 °C. The current work presents a major advancement toward development of additively printed electronics made for high temperature applications. Here, the electronic system is represented by gold-based electrical structures that have been printed on 3D printed ceramic substrates. The substrate is alumina-based with a purity level of 99.8% and was fabricated through photopolymerization digital light processing (DLP). An aerosol jet printing technique that can deposit an ink stream down to 10 µm was utilized to fabricate gold-based electronic structures. The gold ink printability and its adhesion to the ceramic substrate were assessed. Furthermore, the microwave dielectric constant and loss tangent of the alumina substrate were extracted through measurements of the scattering parameters of transmission lines up to 750 °C. A 3D printed conformal broadband antenna was successfully fabricated and tested at temperatures up to 850 °C. The printed gold structures showed excellent stability and adhesion after aging at temperatures up to 750 °C. The substrate dielectric constant slightly increased for temperatures up to 450 °C and significantly increased for temperatures between 450 °C and 750 °C. It was found that the dielectric loss increased as the temperature increased. This work presents an entirely additive manufacturing-based approach to fabricate electronic components including substrates, interconnects, and RF elements for high temperature applications.

Low-threshold miniaturized core-shell GaAs/InGaAs nanowire/quantum-dot hybrid structure nanolasers

A core-shell GaAs/InGaAs nanowire/quantum dot hybrid structure nanolaser is proposed and studied by the finite-difference time-domain method. The results show that the coupled nanowire cavity-emitter system enables enhancement of the spontaneous radiation rate of quantum dots, resulting in a high Purcell factor of 15.5 at a diameter of 330 nm. Due to the quantum confinement and reduced propagation loss, the hybrid structure laser exhibits a threshold lower by 1–2 magnitudes than that of the pure nanowire laser. In addition, by incorporating multiple quantum dots, the lasing intensity is significantly enhanced at the expense of threshold. This work may pave the way for the development of ultra-small low-consumption near infrared lasers and related microsystems.

Triggerable Protocell Capture in Nanoparticle-Caged Coacervate Microdroplets.

Controlling the dynamics of mixed communities of cell-like entities (protocells) provides a step toward the development of higher-order cytomimetic behaviors in artificial cell consortia. In this paper, we develop a caged protocell model with a molecularly crowded coacervate interior surrounded by a non-cross-linked gold (Au)/poly(ethylene glycol) (PEG) nanoparticle-jammed stimuli-responsive membrane. The jammed membrane is unlocked by either exogenous light-mediated Au/PEG dissociation at the Au surface or endogenous enzyme-mediated cleavage of a ketal linkage on the PEG backbone. The membrane assembly/disassembly process is used for the controlled and selective uptake of guest protocells into the caged coacervate microdroplets as a path toward an all-water model of triggerable transmembrane uptake in synthetic protocell communities. Active capture of the guest protocells stems from the high sequestration potential of the coacervate interior such that tailoring the surface properties of the guest protocells provides a rudimentary system of protocell sorting. Our results highlight the potential for programming surface-contact interactions between artificial membrane-bounded compartments and could have implications for the development of protocell networks, storage and delivery microsystems, and microreactor technologies.

The Depth Measurement of Digital Stereomicroscope System

With the continuous development of micro-systems, micro-control and relevant technologies, the demands for micro-measurements in industrial automations of production and inspection are increasing rapidly. Meanwhile, more critical requirements accuracy, efficiency, and cost are expected. To address this situation, a digital microscopic depth measurement system is constructed with a common stereo microscope and two cameras. In the work, a specific fixture is designed to connect the cameras and the microscope to enable easy optical alignment and calibration. Then a formula is summarized to build an accurate relation between disparity and depth corresponding to the specific microscopic system. Next, a CUDA enhanced fast stereo matching algorithm is proposed and practiced to give live disparity map. Finally, the disparity map is transformed into the depth map so that can achieve the depth measurement of microscopic target and perform accuracy analysis. The adjustable magnification of microscope gives feasibility for different view cope and precision requirement. The system takes several types of microcapacitors as the object of analysis, and quantitatively studies the relevance between measurement resolution-parallax-precision at the same time. Compared with some existing research, experimental results show a micron level precision and great efficiency that promises various real applications.

PVDF–HFP/PZT nanocomposite thin films: preparation, structure and piezoelectric properties

Piezoelectric nanocomposites have attracted considerable attention from researchers during these last years for their wide use in the development of electromechanical microsystems (MEMS). In this paper, piezoelectric lead titanate zirconate (PZT) are used with poly(vinylidene fluoride-hexafuoropropylene) (PVdF-HFP) polymer matrix to prepare the piezo thin nanocomposite film. An improvement in the β phase in PVdF-HFP was created by the reaction between the PZT nanoparticles and PVdF-HFP. The process used for the preparation of the film results in the enhancement of the ferroelectric and piezoelectric properties of PVdF-HFP. These polymer nanocomposite films were made by the solvent casting method under ultra-sonication using THF as a solvent, with different percentages of PZT. The results confirm that incorporating PZT nanoparticles in the PVDF-HFP matrix increases the β-phase fraction, enhancing the efficiency of energy harvesting.

RF acoustic microsystems based on suspended lithium niobate thin films: advances and outlook

This paper presents a review of the radio frequency thin-film lithium niobate (LiNbO3) based acoustic microsystems. Thanks to their high electromechanical coupling (k 2), low loss, and great frequency scalability, thin-film LiNbO3 has outperformed state-of-the-art acoustic technologies in the past decade. This paper first reviews the acoustic wave transduction and propagation in thin-film LiNbO3 and then showcases the emerging acoustic applications. Outlook for further platform development and more functions is offered for future thin-film LiNbO3 based acoustic microsystems development.