Versatile Micro Research Articles

Black Phosphorus and E7-Functionalized Sulfonated Polyetheretherketone with Effective Osteogenicity and Antibacterial Activity

Given its excellent biological properties and the matching of its elastic modulus with that of human bone tissue, medical polyetheretherketone (PEEK) is considered a desirable candidate for bone-implant materials. However, its poor osseointegrative and antibacterial properties greatly limit its clinical application. To address these concerns, a functional PEEK implant is needed. Herein, a novel photo-responsive multifunctional PEEK-based implant material (sPEEK/BP/E7) with both effective osteogenesis and good disinfection properties was constructed via the self-assembly of black phosphorus (BP) nanosheets, mussel-inspired polydopamine (PDA), and bioactive short peptide E7 on sulfonated PEEK (sPEEK). The versatile micro-/nano-structured PEEK surface provides superior hydrophilicity, a favorable osteogenic microenvironment, and excellent photothermal effects under near-infrared (NIR) irradiation. The in vitro results showed that sPEEK/BP/E7 displays enhanced cytocompatibility and osteogenicity in terms of cell adhesion, proliferation, alkaline phosphatase (ALP) activity, matrix mineralization, and osteogenesis-related gene expression, superior to those of the sPEEK and sPEEK/BP samples. In addition to osteogenesis, the multifunctional coating exhibited strong antibacterial activity against both Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Furthermore, it was confirmed in a rat femoral infection model that sPEEK/BP/E7 effectively resisted infection caused by S. aureus under NIR light irradiation and promoted osseointegration in vivo. Thus, this work presents a facile strategy to realize improvement of the “functional integration” of new polymer bone-implant materials and provide new ideas for their clinical application.

A versatile surface micro structure design strategy for porous-based pressure sensors to enhance electromechanical performance

Pressure sensors based on porous structures offer comfortable user experiences and can adapt to the flexible movement of human limbs, which makes them attractive options for human–computer interaction and health monitoring. However, ascribed to the limitation of porous surfaces, foam-based pressure sensors are difficult to achieve accurate electric responses and stable signal output, limiting their great potential in wide application fields. Herein, a surface structure design strategy is proposed for improving the performance of porous foam-based pressure sensors. The coupling of microstructures and the collaboration of dual sensing mechanisms endow the sensor with high performance, achieving a ∼ 12 times signal fluctuation stability when compared to the sensor without any surface design. Even when working under complex vibration conditions, the developed sensor can also maintain a ∼ 7 times more stable output. An intelligent insole based on the algorithm model of a sensor array and multi-layer perceptron was developed for the diagnosis of human foot arch health. The sensors with surface structure could capture and differentiate signals more accurately, which results in a diagnostic accuracy of 99.75 % for the smart insole. The strategy for enhancement of sensor performance proposed in this work can be applied to foam sensors with multiple material systems, which is expected to broaden the potential application of porous flexible devices in fields like the Internet of Things, medical monitoring and brain-computer interface.

THE EFFECT OF FOREIGN DIRECT INVESTMENTS ON CORPORATE TAX REVENUES: AN EMPIRICAL ANALYSIS FOR OECD COUNTRIES

Foreign direct investment (FDI) increased globally in the 1980s, parallel to the increasing liberalization of financial markets, the reduction of exchange rate controls, increased capital mobilization, and accelerated technological developments. FDIs offer versatile macro and micro scale positive effects to the host economies. In this context, FDIs have been the focus of academicians and policymakers for reasons such as filling the domestic savings gap, providing financial stability, achieving economic growth targets, and increasing social welfare, which is needed for developing and developed countries. Therefore, governments tend to build attractive investment zones for FDIs by providing tax cuts/advantages and bureaucratic conveniences in financial legislation. In this study, using system-GMM estimator, the effect of FDIs on corporate tax revenues for 35 OECD member countries in the 2005-2020 period was examined and it was understood that the said effect was limited but negative.

Metamaterials for light extraction and shaping of micro-scale light-emitting diodes: from the perspective of one-dimensional and two-dimensional photonic crystals.

Metamaterials have attracted broad attention owing to their unique versatile micro- and nano-structures. As a kind of typical metamaterial, photonic crystals (PhCs) are capable of controlling light propagation and constraining spatial light distribution from the chip level. However, introducing metamaterial into micro-scale light-emitting diodes (µLED) still exists many unknowns to explore. This paper, from the perspective of one-dimensional and two-dimensional PhCs, studies the influence of metamaterials on the light extraction and shaping of µLEDs. The µLEDs with six different kinds of PhCs and the sidewall treatment are analyzed based on finite difference time domain (FDTD) method, in which the optimal match between the PhCs type and the sidewall profile is recommended respectively. The simulation results show that the light extraction efficiency (LEE) of the µLEDs with 1D PhCs increases to 85.3% after optimizing the PhCs, and is further improved to reach 99.8% by the sidewall treatment, which is the highest design record so far. It is also found that the 2D air ring PhCs, as a kind of left-handed metamaterials, can highly concentrate the light distribution into 30° with the LEE of 65.4%, without help of any light shaping device. The surprising light extraction and shaping capability of metamaterials provides a new direction and strategy for the future design and application of µLED devices.

A Novel Plastic‐Crystal Electrolyte with Fast Ion‐Transport Channels for Solid Zinc‐Ion Batteries

AbstractMiniaturized solid zinc‐ion batteries that are safe, environmentally friendly, and low‐cost are ideal candidates for powering emerging microelectronics. However, sluggish Zn2+ mobility in solid phases hampers the viability of solid Zn2+ electrolytes and hence their practicability. Here, nanoscale Zn2+ channels are successfully engineered in a plastic‐crystal electrolyte, thus activating fast Zn2+ solid‐state transport. The ion‐dipole interaction exerted by water molecules orients amphiphilic anions in bilayers, further forming a layered architecture backed by long‐range van der Waals attractive forces. In the interlayer, the heteroleptic coordination contributed by the water molecule and anion frees the Zn2+ from anionic traps, leading to a high Zn2+ conductivity of 2.2 × 10−3 S cm−1. This elaborately tailored texture confers a combination of robust mechanical characteristics and outstanding electrochemical performance upon the resultant electrolyte. The applicability is demonstrated by the high Zn2+ platting/stripping efficiency (99.6%), durable longevity of symmetric Zn‐Zn and Zn‐MnO2 cells, as well as the engineering of versatile micro batteries (MBs). This work provides new perspectives for developing super multivalent ion conductors through the innovative design of ion‐conducting nanochannels.

Ultrasound nanotheranostics: Toward precision medicine.

Ultrasound (US) is a mechanical wave that can penetrate biological tissues and trigger complex bioeffects. The mechanisms of US in different diagnosis and treatment are different, and the functional application of commercial US is also expanding. In particular, recent developments in nanotechnology have led to a wider use of US in precision medicine. In this review, we focus on US in combination with versatile micro and nanoparticles (NPs)/nanovesicles for tumor theranostics. We first introduce US-assisted drug delivery as a stimulus-responsive approach that spatiotemporally regulates the deposit of nanomedicines in target tissues. Multiple functionalized NPs and their US-regulated drug-release curves are analyzed in detail. Moreover, as a typical representative of US therapy, sonodynamic antitumor strategy is attracting researchers' attention. The collaborative efficiency and mechanisms of US and various nano-sensitizers such as nano-porphyrins and organic/inorganic nanosized sensitizers are outlined in this paper. A series of physicochemical processes during ultrasonic cavitation and NPs activation are also discussed. Finally, the new applications of US and diagnostic NPs in tumor-monitoring and image-guided combined therapy are summarized. Diagnostic NPs contain substances with imaging properties that enhance US contrast and photoacoustic imaging. The development of such high-resolution, low-background US-based imaging methods has contributed to modern precision medicine. It is expected that the integration of non-invasive US and nanotechnology will lead to significant breakthroughs in future clinical applications.

Versatile Micro and Nano Patterning Technique for TiO2 and TiN‐Based Sol–Gel Thin Films

AbstractThis paper describes a tailored and versatile technology route to achieve micro and nanopatterning of both TiO2 and TiN thin films using a direct photo patternable sol–gel approach combined with a rapid thermal annealing and nitridation process. The approach consists in multi‐scale structuring TiO2 using laser direct writing or mask/colloidal lithography on a wide range of substrates including materials and of diverse geometry. These patterned TiO2 layers can subsequently be converted into a micro‐structured metallic TiN layer using a direct rapid thermal nitridation process that results in metallic thin films (TiN). This work demonstrates the versatility of this complete chain of soft chemistry based new process for patterning TiO2 and TiN thin films thereby avoiding expensive processes such as etching and lift‐off, while preserving their diffractive properties and high thermal stability, that is, up to 1000 °C under vacuum. The process is compatible with different kinds of substrates of different shapes and sizes. These results pave the way for developing a cost‐effective and time‐saving approach to different cutting‐edge applications such as metasurfaces, sensors, and applications in the luxury and decoration sector.

Smart acoustic 3D cell construct assembly with high-resolution

Precise and flexible three-dimensional (3D) cell construct assembly using external forces or fields can produce micro-scale cellular architectures with intercellular connections, which is an important prerequisite to reproducing the structures and functions of biological systems. Currently, it is also a substantial challenge in the bioengineering field. Here, we propose a smart acoustic 3D cell assembly strategy that utilizes a 3D printed module and hydrogel sheets. Digitally controlled six wave beams offer a high degree of freedom (including wave vector combination, frequency, phase, and amplitude) that enables versatile biomimetic micro cellular patterns in hydrogel sheets. Further, replaceable frames can be used to fix the acoustic-built micro-scale cellular structures in these sheets, enabling user-defined hierarchical or heterogeneous constructs through layer-by-layer assembly. This strategy can be employed to construct vasculature with different diameters and lengths, composed of human umbilical vein endothelial cells and smooth muscle cells. These constructs can also induce controllable vascular network formation. Overall, the findings of this work extend the capabilities of acoustic cell assembly into 3D space, offering advantages including innovative, flexible, and precise patterning, and displaying great potential for the manufacture of various artificial tissue structures that duplicate in vivo functions.

Calcium carbonate nano- and microparticles: synthesis methods and biological applications.

Calcium carbonate micro- and nanoparticles are considered as chemically inert materials. Therefore, they are widely considered in the field of biosensing, drug delivery, andasfillermaterial in plastic, paper, paint, sealant, and adhesive industries. The unusual properties of calcium carbonate-based nanomaterials, such as biocompatibility, high surface-to-volume ratio, robust nature, easy synthesis, and surface functionalization, and ability to exist in a variety of morphologies and polymorphs, make them an ideal candidate for both industrial and biomedical applications. Significant research efforts have been devoted for developing novel synthesis methods of calcium carbonate particles in micrometer and nanometer dimensions. This review highlights different approaches of the synthesis of calcium carbonate micro- and nanoparticles, such as precipitation, slow carbonation, emulsion, polymer-mediated method, including in-situ polymerization, mechano-chemical, microwave-assisted method, and biological methods. The applications of these versatile calcium carbonate micro- and nanoparticles in the biomedical field (such as in drug delivery, therapeutics, tissue engineering, antimicrobial activity, biosensing applications), in industries, and environmental sector has also been comprehensively covered.

3D Electrospun Synthetic Extracellular Matrix for Tissue Regeneration

Electrospinning is considered the most versatile micro‐/nanofiber fabrication technology. The electrospun fibers hold high surface area, desired mechanical properties, controlled topography, as well as the ease of biochemical functionalization. The 3D electrospun fibrous structures closely mimic the hierarchical architecture and fibrous features of the extracellular matrices (ECM), which greatly contribute to biomaterials design to stimulate tissue regeneration. Herein, the recent advances in electrospinning technology for 3D production of ECM‐mimicking biomaterial scaffolds are systematically summarized and the applications in neural, cardiac, bone, skin, and vascularized tissue regeneration are thoroughly discussed. Challenges and future scopes related to each field of tissue regeneration are discussed after each subsection. A few examples of liver, kidney, esophageal tissue engineering are also discussed. Finally, the key challenge in the cost‐effective upscale of the electrospinning technique to mature and prevalent industrial applications is outlined. Herein, a systematic, thorough summary of the recent evolutions in electrospinning and its emerging applications for a broad range of tissue regenerations is provided.

FeCoP nanosheets@Ni-Co carbonate hydroxide nanoneedles as free-standing electrode material for hybrid supercapacitors

Developing advanced battery-type electrode materials with versatile morphologies and micro-/nanostructures is crucial to realize high-performance hybrid supercapacitors with high energy density and excellent cycle life. Herein, a facile approach is proposed to design free-standing FeCoP nanosheets decorated by Ni substituted Co carbonate hydroxide (Ni-CoCH) nanoneedles on carbon cloth as a novel cathode for hybrid supercapacitor. This smart hetero-network assembled by conductive FeCoP nanosheets as a core and redox active Ni-CoCH nanoneedles as a shell exhibits increased surface area, improved availability of redox active sites, and facilitated ion/electron transport for faradaic reactions when compared to a single component. Benefiting from its unique core/shell nanostructure, multifunctionality and synergistic effect of two components, the as-prepared FeCoP@Ni-CoCH electrode acquires a high specific capacity of 795.5 C g−1 at a current density of 1 A g−1 and outstanding rate capability and good long-term cyclic stability (89.7% of the initial capacitance after 5000 cycles). Furthermore, a hybrid supercapacitor device consisting of FeCoP@Ni-CoCH as cathode and hierarchical porous carbon as anode in 2 M KOH electrolyte delivers a high energy density of 72.7 Wh kg−1 at a power density of 404.9 W kg−1 and superior cyclic stability.

Sequential injection solvent dispersive micro solid phase extraction (SI-SD-μSPE) platform coupled with atomic absorption spectrometry for lead determination in water samples

A novel automatic versatile sequential injection solvent dispersive micro solid phase extraction platform coupled with flame atomic absorption spectrometry is developed for the first time. The analytical procedure is based on chemical dispersion of benzophenone and ternary component systems. The full dispersion of sorbent into the aqueous phase, in the shape of micro particles, is achieved by on-line mixing of the two flows; a small flow of methanol containing the sorbent in a low concentration and a higher one of the aqueous sample solution. The resulted cloudy mixture is consisted of sorbent's fine particles, which are dispersed into the whole aqueous phase. Via this continuous process, metal chelating complexes are retained onto the sorbent particles. An integrated, easy and fast reusable syringe filter was studied for the on-line collection and dissolution of the sorbent. The potentials of this novel schema were demonstrated for trace Pb(II) determination in water samples. All the critical parameters affecting the performance of the proposed method were optimized. For a sample consumption of 11.0 mL, the working range was 5.28–400.0 μg L−1, while the enhancement factor, the detection limit and the relative standard deviation were 120, 1.59 μg L-1 and 2.4% (at 50.0 μg L−1) respectively. The developed method was evaluated by analyzing certified reference materials and applied to the analysis of environmental water samples.

Design of an Ultra-High Bypass Ratio Fan Stage for a Research Turbojet Engine

At the Department of Aeronautics, Naval Architecture and Railway Vehicles of Budapest University of Technology and Economics there is a versatile micro turbojet test bench based on TS-21 turbostarter engine. Besides research and developement purposes it offers a more practical study and experience for the aerospace engineering students. In this study the authors have accomplished a theoretical design of an additional fan stage to the original TS-21 engine. Based on the results of this study a decision can be made, whether the modification of the present device is worth or not. For supplementing this decision, a complex feasability study was carried out from a simple one-dimensional flow analysis through computational fluid dynamics and stress analysis of the mechanical parts. If the designed equipment will be manufactured, the resulting turbofan engine can be used to model large scale types for various research and educational purposes.

Steric-Hindrance-Controlled Laser Switch Based on Pure Metal–Organic Framework Microcrystals

Herein, we demonstrated a steric-hindrance-controlled laser switch in pure metal-organic framework (MOF) microcrystals. The well-faceted MOF microwires with aggregation-induced emission (AIE) lumnogens as linkers function as typical Fabry-Pérot microlasers. The steric hindrance around the AIE linkers can be reduced by the loss of guest molecules, which lead to the enhanced rotation of linkers with red-shifted gain behavior. On this basis, the gain region was readily switched through changing the steric hindrance via the desorption/adsorption of guests. As a result, the reversible switching of the dual-wavelength lasing from MOF microwires was achieved. The results provide a promising route to the development of versatile micro-/nanolasers with desired applications.

Cell-Like Micromotors.

In the past decade, versatile micro- and nanosized machines have emerged as active agents for large-scale detoxification, sensing, microfabrication, and many other promising applications. Micromachines have also been envisioned as the next advancement in dynamic therapy with numerous proof-of-concept studies in drug delivery, microsurgery, and detoxification. However, the practical use of synthetic micromotors in the body requires the development of fully biocompatible designs facilitating micromotor movement in biological fluids of diverse composition and displaying desired functions in specific locations. The combination of the efficient movement of synthetic micromotors with the biological functions of natural cells has resulted in cell-like micromotors with expanded therapeutic and toxin-removing capabilities toward different biological applications. Thus, these biocompatible and biomimetic cell-like micromotors can provide efficient movement in complex biofluids and mimic the functionalities of natural cells. This Account highlights a variety of recent proof-of-concept examples of cell-like micromotors, based on different designs and actuation mechanisms, which perform diverse in vivo tasks. The cell-like micromotors are divided into two groups: (i) cell membrane-coated micromotors, which use natural cell membranes derived from red blood cells, platelets, or a combination of different cells to cloak and functionalize synthetic motors, and (ii) cell-based micromotors, which directly use entire cells such as blood cells, spermatozoa, and bacteria as the micromotor engine. Cell-like micromotors, composed of different cellular components and actuated by different mechanisms, have shown unique advantages for operation in complex biofluids such as blood. Due to the inherent biocompatibility of cell-derived materials, these cell-like micromotors do not provoke an immune response while utilizing useful secondary functions of the blood cells such as strong ability to soak up foreign agents or bind toxins. Additionally, the utilization of autonomously motile cells (e.g., bacteria) allows for built-in chemotactic motion, which eliminates the need for harmful fuels or complex actuation equipment. Furthermore, a broad range of cells, both passive and motile, can be incorporated into micromachine designs constituting a large library of functional components depending on the limits of the desired application. The coupling of cellular and artificial components has led to active biohybrid swimming microsystems with greatly enhanced capabilities and functionalities compared to the individual biological or synthetic components. These characteristics have positioned these cell-like micromotors as promising biomimetic dynamic tools for potential actuation in vivo. Finally, the key challenges and limitations of cell-like micromotors are discussed in the context of expanded future clinical uses and translation to human trials.

Suspended Silicon Microphotodiodes for Electrochemical and Biological Applications.

Local electric stimulation of tissues and cells has gained importance as therapeutic alternative in the treatment of many diseases. These alternatives aim to deliver a less invasively stimuli in liquid media, making imperative the development of versatile micro- and nanoscale solutions for wireless actuation. Here, a simple microfabrication process to produce suspended silicon microphotodiodes that can be activated by visible light to generate local photocurrents in their surrounding medium is presented. Electrical characterization using electrical probes confirms their diode behavior. To demonstrate their electrochemical performance, an indirect test is implemented in solution through photoelectrochemical reactions controlled by a white-LED lamp. Furthermore, their effects on biological systems are observed in vitro using mouse primary neurons in which the suspended microphotodiodes are activated periodically with white-LED lamp, bringing out observable morphological changes in neuronal processes. The results demonstrate a simplified and cost-effective wireless tool for photovoltaic current generation in liquid media at the microscale.

An improved cutting force model for micro milling considering machining dynamics

Micro milling, as a versatile micro machining process, is kinematically similar to conventional milling; however, it is significantly different from conventional milling with respect to chip formation mechanisms and uncut chip thickness modelling, due to the comparable size of the edge radius to the chip thickness, and the small per-tooth feeding. Considering tool runout and dynamic displacement between the tool and the workpiece, the contour of the workpiece left by previous tool paths is typically in a wavy form, and the wavy surface provides a feedback mechanism to cutting force generation because the instantaneous uncut chip thickness changes with both the vibration during the current tool path and the surface left by the previous tool paths. In this study, a more accurate uncut chip thickness model was established including the precise trochoidal trajectory of the cutting edge, tool runout and dynamic modulation caused by the machine tool system vibration. The dynamic regenerative effect is taken into account by considering the influence of all the previous cutting trajectories using numerical iteration; thus, the multiple time delays (MTD) are considered in this model. It is found that transient separation of the tool-workpiece occurring at a low feed per tooth, caused by MTD and the existing cutting force models, is no longer applicable when transient tool-workpiece separation occurs. Based on the proposed uncut chip thickness model, an improved cutting force model of micro milling is developed by full consideration of the ploughing effect and elastic recovery of the workpiece material. The proposed cutting force model is verified by micro end milling experiments, and the results show that the proposed model is capable of producing more accurate cutting force prediction than other existing models, particularly at small feed per tooth.

Assembly of a Versatile Micro Dispenser Using Off-The-Shelf Components for Applications in Microfluidics

AbstractWe designed and constructed a drop-on-demand (DOD) droplet dispenser using the piezo inkjet technique that is simple to construct and operate and makes use of readily available components. The droplet dispenser can be easily fitted with cost effective glass nozzles and can be readily tuned to produce consistent drop sizes. The dynamics of the droplet motion are obtained using a calibrated analog video imaging system. We observed very high accelerations for the ejected droplets that corroborate with the applied drive pulse amplitudes. The acceleration measured, near the ejection nozzle, was many times the acceleration of gravity with the largest value of 34g’s. We successfully dispensed glycol water solutions and aqueous suspensions of titanium oxide nanoparticles, with values greater than 10 in the measured pH. For the inkjet droplets deposited on smooth gold/chromium substrates (±3nm surface roughness variation), we observed the well-known coffee ring effect using optical microscopy and nanoparticle morphology using an atomic force microscope.

A simple and versatile micro contact printing method for generating carbon nanotubes patterns on various substrates

We present an optimized process for generating at low cost, patterns of carbon nanotubes (CNTs) on a large variety of substrates through a simple micro contact printing method. This method meets the requirements for the integration of CNTs into microdevices, for applications in microelectronics (interconnects), flexible electronics (printed conductive electrodes) and biodevices (biosensors and biosystems for regenerative medicine). We have optimized a new method for inking PolyDiMethylSiloxane (PDMS) stamps with CNTs that turned out to improve significantly the quality of the printed features over large surfaces. This inking step is performed by adapting a spray-coating process leading to a dense and homogeneous coating of the stamp with a thin layer of CNTs. The printing step is performed using a solvent mediation, allowing us to pattern this thin layer of CNTs onto various substrates by contact through a thin film of liquid. We demonstrate that this soft and rapid methodology can lead to the realization of CNTs patterns with versatile geometries onto various substrates at the micron scale. Examples of applications for CNTs interconnects and flexible electronics are rapidly shown.

Biomimicry via Electrospinning

Electrospinning, an efficient technique to produce long fibers with micro- or nanoscale diameters, has attracted tremendous interests during past decades. By orchestrating parameters in electrospinning, diverse forms of fibrous assemblies and individual fibers with hierarchical structures can be successfully achieved. Some of these versatile micro- and nanostructures display a remarkable resemblance to the materials and objects existing in nature, such as honeycomb, spider webs, extracellular matrix, plant tendril and leaf, etc. The emerging field of biomimicry enables one to mimic biology or nature to develop novel nanomaterials as well as to improve processes for materials via electrospinning. In this review, we present a full panorama of recent studies on biomimicry via electrospinning, and highlight some of biomimicked one-dimensional nanomaterials as well as their functions and applications to date.