Microscale Technologies Research Articles

Multi-Criteria Decision Analysis of Selecting Biomass Feedstocks for Sustainable Energy Production

Abstract Five well-known biomass resources are used as feedstocks for biomass thermal power plants in the Philippines: rice husks (RH), sugarcane bagasse (SB), Napier grass (NG), coconut shells (CS), and Paraserianthes falcataria (PF). Given the complexity of socio-economic and biophysical systems and the multi-dimensionality of the sustainability goal, the best biomass feedstock was determined using TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution), a multi-criteria decision analysis (MCDA) that has gained popularity in the decision-making for sustainable energy. Sugarcane bagasse (SB), with a TOPSIS score of 0.5416, was found to be the best biomass feedstock for maximizing the benefits to people and the environment. It has a relatively high calorific value of 19.30 MJ/kg, an annual volume of 7.32 million tons, and can solely be used for energy production. The second-best option is Paraserianthes falcataria (PF), but it is not widely grown because it is only used in the construction and furniture industries, and its demand is very limited. However, because it grows so quickly, it has the greatest potential for energy generation. Coconut shells are the third best option. It is the biomass feedstock with the highest energy content at 20.88 MJ/kg, with a TOPSIS score of 0.4090. Coconut shells are waste materials from coconut fruits used to make activated carbon and are primarily used for cooking, heating, and industrial use. Because coconut shells are widely available, particularly in remote communities, it may be able to meet its electricity needs using a micro-scale biomass power technology that requires only a small amount of coconut shells.

Down-streaming Small-Scale Green Ammonia to Nitrogen-Phosphorus Fertilizer Tablets for Rural Communities

This study aims to evaluate the growth and production of sweet corn plants in response to the application of commercial NPK fertilizer and various doses of nitrogen-phosphorus fertilizer tablets. From early October 2022 to late January 2023, research was conducted at Research and Development Luas Birus Utama to produce nitrogen-phosphorus fertilizer tablets and at Research and Development Syngenta Indonesia Cikampek Station, Karawang, to perform a semi-field analysis. A factorial randomized block design with two treatment factors was employed in this study. The first factor was five types of nitrogen-phosphorus fertilizer tablets, namely, A (0% nitrogen and 6.3% phosphorus), B (0.81% nitrogen and 6.3% phosphorus), C (1.57% nitrogen and 6.1% phosphorus), D (2.33% nitrogen and 6.2% phosphorus), and E (3.06% nitrogen and 6.2% phosphorus). The second factor was F (standard nitrogen, phosphorus, and potassium). The results revealed that applying different dosages of nitrogen-phosphorus fertilizer tablets in combination with potassium chloride fertilizer yielded no different effect on the growth, biomass, and yield components of sweet corn plants when compared to applying NPK fertilizer. A comparison between the soil test results before and after application revealed that the formulation of fertilizers in tablet form helps plants to effectively absorb the required nutrients. It is currently possible to develop small-scale or microscale green ammonia production technology to fulfill the fertilizer requirements of rural communities because of its low cost, low carbon emissions, and low renewable energy consumption. The scarcity of fertilizer supplies endangers Indonesia’s food sustainability. Nitrogen-phosphorus fertilizer tablet production technology can be used in areas with a scarcity of inorganic fertilizers but with the potential for low-grade phosphate mines using commercial ammonia solutions. Thus, understanding how to produce nitrogen-phosphorus fertilizer tablets from ammonia solution will aid in the acceptance of microscale green ammonia production technology. Doi: 10.28991/ESJ-2024-08-02-016 Full Text: PDF

Thermophoretic Assay for Biosensing

AbstractThermophoresis refers to the directional movement of particles driven by temperature gradients, which is ubiquitous in nature. This phenomenon can be conveniently used to manipulate molecules and objects such as biomolecules, colloids, metal nanoparticles, and cells. Because of these advantages, thermophoresis is widely used in biosensing. In vitro diagnosis, as an important field of biosensing, is highly compatible with thermophoresis. Compared with traditional in vitro diagnostic techniques, thermophoretic diagnosis is a homogeneous system that boasts high efficiency and rapid detection as well as a wide detection range; thus, thermophoresis has a myriad of applications. The emergence of microscale and multifield coupling thermophoresis technologies yield widespread applications of thermophoresis in the field of in vitro diagnostics. This study presents the history of thermophoresis and reviews various cases of biosensors utilizing thermophoresis. Those biosensors are widely used in in vitro diagnostics, biomarker discovery, and other fields. Furthermore, it assesses the advantages of thermophoresis, and finally discusses its current challenges and future development.

X-ray scattering tensor tomography based finite element modelling of heterogeneous materials

Among micro-scale imaging technologies of materials, X-ray micro-computed tomography has evolved as most popular choice, even though it is restricted to limited field-of-views and long acquisition times. With recent progress in small-angle X-ray scattering these downsides of conventional absorption-based computed tomography have been overcome, allowing complete analysis of the micro-architecture for samples in the dimension of centimetres in a matter of minutes. These advances have been triggered through improved X-ray optical elements and acquisition methods. However, it has not yet been shown how to effectively transfer this small-angle X-ray scattering data into a numerical model capable of accurately predicting the actual material properties. Here, a method is presented to numerically predict mechanical properties of a carbon fibre-reinforced polymer based on imaging data with a voxel-size of 100 μm corresponding to approximately fifteen times the fibre diameter. This extremely low resolution requires a completely new way of constructing the material’s constitutive law based on the fibre orientation, the X-ray scattering anisotropy, and the X-ray scattering intensity. The proposed method combining the advances in X-ray imaging and the presented material model opens for an accurate tensile modulus prediction for volumes of interest between three to six orders of magnitude larger than those conventional carbon fibre orientation image-based models can cover.

BLISS: Interplanetary exploration with swarms of low-cost spacecraft

Leveraging advancements in micro-scale technology, we propose a fleet of autonomous, low-cost, small solar sails for interplanetary exploration. The Berkeley Low-cost Interplanetary Solar Sail (BLISS) project aims to utilize small-scale technologies to create a fleet of tiny interplanetary spacecraft for rapid, low-cost exploration of the inner solar system. This paper describes the hardware required to build a ∼10 g spacecraft using a 1 m2 solar sail steered by micro-electromechanical systems (MEMS) inchworm actuators. The trajectory control to a NEO, here 101955 Bennu, is detailed along with the low-level actuation control of the solar sail and the specifications of proposed onboard communication and computation. Two other applications are also shortly considered: sample return from dozens of Jupiter-family comets and cometary nuclei imaging. The paper concludes by discussing the fundamental scaling limits and future directions for steerable autonomous miniature solar sails with onboard custom computers and sensors.

Characterization of Photocurable IP-PDMS for Soft Micro Systems Fabricated by Two-Photon Polymerization 3D Printing.

Recent developments in micro-scale additive manufacturing (AM) have opened new possibilities in state-of-the-art areas, including microelectromechanical systems (MEMS) with intrinsically soft and compliant components. While fabrication with soft materials further complicates micro-scale AM, a soft photocurable polydimethylsiloxane (PDMS) resin, IP-PDMS, has recently entered the market of two-photon polymerization (2PP) AM. To facilitate the development of microdevices with soft components through the application of 2PP technique and IP-PDMS material, this research paper presents a comprehensive material characterization of IP-PDMS. The significance of this study lies in the scarcity of existing research on this material and the thorough investigation of its properties, many of which are reported here for the first time. Particularly, for uncured IP-PDMS resin, this work evaluates a surface tension of 26.7 ± 4.2 mN/m, a contact angle with glass of 11.5 ± 0.6°, spin-coating behavior, a transmittance of more than 90% above 440 nm wavelength, and FTIR with all the properties reported for the first time. For cured IP-PDMS, novel characterizations include a small mechanical creep, a velocity-dependent friction coefficient with glass, a typical dielectric permittivity value of 2.63 ± 0.02, a high dielectric/breakdown strength for 3D-printed elastomers of up to 73.3 ± 13.3 V/µm and typical values for a spin coated elastomer of 85.7 ± 12.4 V/µm, while the measured contact angle with water of 103.7 ± 0.5°, Young's modulus of 5.96 ± 0.2 MPa, and viscoelastic DMA mechanical characterization are compared with the previously reported values. Friction, permittivity, contact angle with water, and some of the breakdown strength measurements were performed with spin-coated cured IP-PDMS samples. Based on the performed characterization, IP-PDMS shows itself to be a promising material for micro-scale soft MEMS, including microfluidics, storage devices, and micro-scale smart material technologies.

Advances in Bioelectrode Design for Developing Electrochemical Biosensors.

The critical performance factors such as selectivity, sensitivity, operational and storage stability, and response time of electrochemical biosensors are governed mainly by the function of their key component, the bioelectrode. Suitable design and fabrication strategies of the bioelectrode interface are essential for realizing the requisite performance of the biosensors for their practical utility. A multifaceted attempt to achieve this goal is visible from the vast literature exploring effective strategies for preparing, immobilizing, and stabilizing biorecognition elements on the electrode surface and efficient transduction of biochemical signals into electrical ones (i.e., current, voltage, and impedance) through the bioelectrode interface with the aid of advanced materials and techniques. The commercial success of biosensors in modern society is also increasingly influenced by their size (and hence portability), multiplexing capability, and coupling in the interface of the wireless communication technology, which facilitates quick data transfer and linked decision-making processes in real-time in different areas such as healthcare, agriculture, food, and environmental applications. Therefore, fabrication of the bioelectrode involves careful selection and control of several parameters, including biorecognition elements, electrode materials, shape and size of the electrode, detection principles, and various fabrication strategies, including microscale and printing technologies. This review discusses recent trends in bioelectrode designs and fabrications for developing electrochemical biosensors. The discussions have been delineated into the types of biorecognition elements and their immobilization strategies, signal transduction approaches, commonly used advanced materials for electrode fabrication and techniques for fabricating the bioelectrodes, and device integration with modern electronic communication technology for developing electrochemical biosensors of commercial interest.

State-of-the-art review of micro to small-scale wind energy harvesting technologies for building integration

The utilisation of wind power in buildings has gained significant interest, but deploying wind turbines in built environments presents unique challenges due to highly turbulent wind patterns. Existing small wind turbines may not be as efficient in such complex conditions, and their transient loads and vibrations can compromise their durability. This study aims to assess the recent status, challenges, and limitations of building-integrated wind turbines and micro or small-scale wind-induced vibration technologies to enhance their performance, efficiency, reliability, and cost-effectiveness. The research evaluates advancements, applications, and technical features that optimise these technologies to function effectively in non-uniform wind flows and a wide range of wind speeds. Modeling conventional systems, including horizontal axis and vertical axis wind turbines, is well-established using computational fluid dynamics and blade element momentum methods. Micro or small-scale wind-induced vibration technologies have demonstrated power outputs ranging from milliwatts to kilowatts, making them suitable for powering actuators and low-powered sensors used in buildings. The study emphasises the importance of harnessing wind velocity acceleration induced by the building's roof shape when incorporating wind energy harvesting technologies. Nevertheless, research on wind-induced vibration harvesting primarily takes place in controlled environments, neglecting the influence of real buildings. This represents a significant research gap, considering the potential for wind-induced vibration technologies to provide power to off-grid communities and facilitate building integration. The lack of comprehensive analysis concerning the energy, economic, and environmental aspects of micro-energy harvesting technologies hinder their widespread adoption and a comprehensive understanding of their potential. Addressing these research gaps is essential to promote the implementation and efficacy of micro-scale wind energy harvesting technologies in various real-world scenarios.

Experimental Realization of a Colloidal Ratchet Effect in a non-Newtonian Fluid

The transport of matter via a ratchet effect represents a convenient way to extract useful work from a thermodynamic system, and can have direct applications in several microscale fluid-based technologies. Most realizations so far have been centered on using Newtonian fluids. This study shows how to achieve directed transport of magnetic microparticles in a non-Newtonian shear-thinning fluid under a square-wave magnetic force. This technique could be used in active microrheology, to infer the nonlinear properties of viscoelastic media.

Using microfluidic models to evaluate whether monocyte preconditioning plays a role in tumor-associated macrophage mediated resistance to hormone therapy in men with prostate cancer.

228 Background: While men with metastatic castrate-resistant prostate cancer benefit greatly from 2nd generation androgen targeted therapies (ATTs), the utility of these therapies is inevitably limited by the development of resistance. Tumor associated macrophages (TAMs) are a myeloid immune cell population within the prostate tumor microenvironment (TME) that have been shown to play an integral role in development of ATT-resistance. However, the pathways that underlie TAM-mediated ATT resistance remain under investigation. In particular, many TAMs within the TME are derived from circulating monocytes and it is not yet clear whether the pathways driving TAM-mediated resistance are activated exclusively within the TME or if the activation of critical resistance pathways begins while the cells are circulating as monocytes. In this study, we utilized novel microscale technologies to investigate the transcriptome of monocytes and macrophages derived from patients progressing and responding to ATTs as well as the degree to which the macrophages promote ATT resistance in prostate tumor models. Methods: Primary monocytes were isolated from 22 men with prostate cancer who were either progressing or responding to 2ndgeneration ATTs. A portion of the monocytes from each patient were isolated for transcriptome analysis and the rest were differentiated into monocyte-derived macrophages (MDMs). MDMs were then cultured in monoculture or in co-culture with androgen-independent prostate tumor cells (22Rv1 and C42B). Each culture was then left untreated or treated with enzalutamide therapy. Following culture/treatment, each macrophage condition was isolated for transcriptome analysis and tumor cell populations from each condition were evaluated for treatment cytotoxicity. Results: Viability data from MDM-C42B co-culture demonstrated a 20% increase in tumor cell viability following enzalutamide treatment when C42B cells were cultured with primary MDMs from castrate-sensitive patients as compared to MDMs from castrate-resistant patients. Subsequent transcriptome analysis demonstrated key signatures in monocyte/macrophage populations that were associated ATT response. Conclusions: Leveraging a novel microfluidic culture platform known as Stacks, we were able to utilize primary, patient-derived cells to demonstrate that the role of TAMs in ATT resistance within the prostate TME is dependent, at least in part, on factors that are present prior to extravasation into the TME. Transcriptome analysis identified candidate pathways, which may be driving TAM-mediated differences in ATT response. These findings have the potential to lead to future use of circulating monocytes as a predictive biomarker as well as lead to the identification and targeting of ATT resistance pathways in patients.

A Comprehensive Assessment of Two-Phase Flow Boiling Heat Transfer in Micro-Fin Tubes Using Pure and Blended Eco-Friendly Refrigerants

This review study examines flow boiling heat transfer in micro-fin tubes using mixed and pure refrigerants with zero ozone-depleting potential (ODP) and minimal global warming potential (GWP). This investigation focuses on the extraordinary relationship between heat transfer coefficients (HTCs) and vapor quality. Since the introduction of micro-fin heat exchanger tubes over 30 years ago, refrigerant-based cooling has improved significantly. Air conditioning and refrigeration companies are replacing widely used refrigerants, with substantial global warming impacts. When space, weight, or efficiency are limited, micro-fin heat exchangers with improved dependability are preferred. This review article discusses flow boiling concepts. The researchers used several refrigerants under different testing conditions and with varying micro-fin tube parameters. Micro-fin tubes are promising for improved heat transfer techniques. This tube increases the heat transfer area, fluid disturbance, flow speed, and direction owing to centrifugal force and HTC. As the focus shifts to improving heat transfer, pressure drop, mean vapor quality, and practical devices, this subject will grow more intriguing. A radical shift will reduce equipment size for certain traditional heat transfer systems and bring new products using micro-scale technologies. This suggested review effort helps comprehend saturation flow boiling through micro-fin tubes and find the right correlation for a given application. This domain’s challenges and future relevance are also discussed.

Extensional-Flow Impedance Cytometer for Contactless and Optics-Free Erythrocyte Deformability Analysis.

Deformability is an essential feature of red blood cells (RBCs), enabling them to undergo significant shape change in response to external forces. Impaired erythrocyte deformability is associated with several pathologic conditions, and quantitative measurement of RBC deformability is critical to understanding and diagnosing RBC related diseases. Whereas traditional approaches to cell mechanical characterization generally have limited throughput, emerging microscale technologies are opening new opportunities for high-throughput deformability cytometry at the single-cell level. In this work, we propose an innovative microfluidic system based on (i) a hyperbolic microchannel to induce erythrocyte deformation by extensional flow, and (ii) an electrical sensing zone with coplanar electrodes to evaluate the deformed cell shape. RBC deformation under extensional flow is achieved, and the deformed cell shape is quantified by means of an electrical anisotropy index, at a throughput of 300 cell/s. Measurements of healthy and chemically stiffened RBCs demonstrate that the anisotropy index can be used to characterize RBC deformability, as an alternative to deformation indices based on high-speed image processing. A contactless and optics-free approach for RBC deformability analysis has been presented. Due to its simplicity and potential for integration, the proposed approach holds promises for fast and low-cost erythrocyte deformability assays, especially in point-of-care and resource-limited settings.

Optical microscopy image restoration and its application in strain measurement by digital image correlation method

As a direct and effective non-contact, full-field optical measurement method, digital image correlation (DIC) method has been widely used in 2D/3D displacement and strain measurement of materials and structures in various fields. Combined with advanced micro-scale speckle preparation technology, in-situ loading experiments can be carried out under the microscope, which allows micro-scale displacement and strain measurement by DIC. However, out-of-plane displacement is inevitable during the loading process. Due to the limited depth of field of the optical microscope, even a slight out-of-plane displacement can result in significant blurring of the speckle pattern. This will bring negative effects to the deformation measurement. In order to reduce the error caused by the image blurring, the blind deconvolution method was used in this paper to restore the blurred speckle image. Furthermore, Gaussian filtering was applied to solve the noise problem. The effect of the image restoration on the measurement accuracy of the DIC was analyzed quantitatively. A tensile experiment was carried out on the indium tin oxide (ITO) films. The experimental results showed that the error of the measured elastic modulus was reduced by 13.91%. The results indicate the measurement accuracy was improved effectively after image restoration.

The weaving of the carbon fiber using induced-charge electro-osmosis with DC–AC alternating switching

Controlling the self-organizing structure is important for the use of self-organizing materials in a variety of applications. Here, we report the weaving method of the carbon fiber using induced-charge electro-osmosis (ICEO) with DC–AC alternating switching treatment. Specifically, we report that the spread low-density carbon fibers having a dendritic structure grow by applying a DC voltage, while the spread fibers shrink irreversibly with contacting and entangling by applying an AC voltage. Consequently, a weaving structure of carbon fibers can be achieved. Although the micro-scale weaving technology for polymers has been developed mainly in the field of tissue engineering, the weaving technology for conductive carbon fibers that can be used as a cilium-like ICEO actuator in a microfluidic circuit has not been explored so far; thus, we have first demonstrated that the woven structures of the conductive carbon microfibers can be made by the electrokinetic phenomena using a DC–AC alternating electric field. Moreover, through the visualization of the flow fields during the DC–AC weaving process, we clarified the mechanism of the DC–AC weaving phenomenon related to the dielectrophoresis and ICEO phenomena. Our technology should open a different design strategy to improve the structure of self-organizing materials that can be used in microfluidic circuits.

Multi-Objective Optimization via GA Based on Micro Laser Line Scanning Data for Micro-Scale Surface Modeling

Industry 4.0 represents high-level methodologies to make intelligent, autonomous, and self-adaptable manufacturing systems. Additionally, the surface modeling technology has become a great tool in industry 4.0 for representing the surface point cloud. Thus, the micro-scale machining technology requires efficient models to represent micro-scale flat and free-form surfaces. Therefore, it is fundamental to perform surface modeling through artificial intelligence for representing small surfaces. This study addressed multi-objective optimization via genetic algorithms and micro laser line projection to accomplish surface models for representing micro-scale flat and free-form surfaces, where an optical microscope system retrieves micro-scale topography via micro laser line coordinates and the multi-objective optimization constructs the flat and free-form surface models through genetic algorithms and micro-scale topography. The multi-objective optimization determines the surface model parameters through exploration and exploitation, and the solution space is deduced via surface data. The surface model generated through the multi-objective optimization fit accurately to the micro-scale target surface. Thus, the proposed technique enhanced the fitting of micro-scale flat and free-form surface models, which were deduced via gray-level images of an optical microscope. This enhancement was validated by a discussion between the multi-objective optimization via genetic algorithms and the micro-scale surface modeling via optical microscope imaging systems.

Microfluidic Techniques for Next‐Generation Organoid Systems

AbstractOrganoids are 3D multicellular structures derived from pluripotent stem cells (PSCs) or adult stem cells (ASCs), which have attracted increasing interest in the fields of drug screening, cell therapy, and regenerative medicine. Despite considerable success in culturing organoids with native microanatomy, challenges to achieving a physiologically relevant microenvironment remain. Complex dynamic feedback between cells and the extracellular matrix and uncontrollable mechano‐physiological cues hamper the further study of organoid systems. Innovative engineering approaches are needed to produce, control, and analyze organoids and their microenvironment. Organoids‐on‐a‐chip, inspired by organs‐on‐a‐chip, presents a major technological breakthrough in providing physiologically relevant environmental parameters. Organoids cultured on a chip recapitulate the anatomical and physiological features of organs during development and disease. In this review, the authors examine how microfluidic approaches integrate biomaterials, microscale technology, and stem cell biology to construct a biomimetic microenvironment that is suitable for building high‐fidelity human organ structures in vitro. Applying engineering techniques in organoids‐on‐a‐chip, such as genome editing and omics analysis, can greatly contribute to a better understanding of molecular pathogenesis. Moreover, the next‐generation organoid culture system may integrate multiple organoids in a single chip device to explore multi‐organoid platforms to fulfill the goal of building 3D organotypic models.

Advances and challenges in developing smart, multifunctional microneedles for biomedical applications.

Microneedles (MNs) have been developed as minimally invasive tools for diagnostic and therapeutic applications. However, in recent years, there has been an increasing interest in developing smart multifunctional MN devices to provide automated and closed-loop systems for body fluid extraction, biosensing, and drug delivery in a stimuli-responsive manner. Although this technology is still in its infancy and far from being translated into the clinic, preclinical trials have shown some promise for the broad applications of multifunctional MN devices. The main challenge facing the fabrication of smart MN patches is the integration of multiple modules, such as drug carriers, highly sensitive biosensors, and data analyzers in one miniaturized MN device. Researchers have shown the feasibility of creating smart MNs by integrating stimuli-responsive biomaterials and advanced microscale technologies, such as microsensors and microfluidic systems, to precisely control the transportation of biofluids and drugs throughout the system. These multifunctional MN devices can be envisioned in two distinct strategies. The first type includes individual drug delivery and biosensing MN units with a microfluidic system and a digital analyzer responsible for fluid transportation and communication between these two modules. The second type relies on smart biomaterials that can function as drug deliverers and biosensors by releasing drugs in a stimuli-responsive manner. These smart biomaterials can undergo structural changes when exposed to external stimuli, such as pH and ionic changes, mimicking the biological systems. Studies have demonstrated a high potential of hydrogel-based MN devices for a wide variety of biomedical applications, such as drug and cell delivery, as well as interstitial fluid extraction. Biodegradable hydrogels have also been advantageous for fabricating multifunctional MNs due to their high loading capacity and biocompatibility with the drug of choice. Here, we first review a set of MN devices that can be employed either for biosensing or delivery of multiple target molecules and compare them to the conventional and more simple systems, which are mainly designed for single-molecule sensing or delivery. Subsequently, we expand our insight into advanced MN systems with multiple competencies, such as body fluid extraction, biosensing, and drug delivery at the point of care. The improvement of biomaterials knowledge and biofabrication techniques will allow us to efficiently tune the next generation of smart MNs and provide a realistic platform for more effective personalized therapeutics.

Numerical study on heat transfer enhancement by viscoelastic fluid pulsating laminar flow in rectangular microchannel heat sinks

Efficient heat transfer technique at microscale is a long-term demand for development of microelectronic device. Simple-structured microchannel heat sinks (MHSs) have the advantages of easier fabrication processes and profound applicability, which are however limited by the laminar flow with lower heat transfer efficiency. Against this backdrop, a new type of heat transfer enhancement (HTE) techniques by viscoelastic fluid pulsating laminar flow (VPL flow) is proposed and evaluated from different aspects in this research. First of all, the effects of VPL flow on the thermal performance in a rectangular microchannel heat sink (RMHS) are numerically studied with the focus on the parametric effects on HTE. It indicates that the overall heat transfer performance can be significantly augmented by VPL flow and possesses an optimal enhancement under cases of exerted pulsation frequencies closed to the characteristic frequency of viscoelastic fluid flow. The characteristic frequency is determined from the Poiseuille start-up flow of the viscoelastic fluid flow and can be summarized by a power-law function with the relationship of Reynold number (Re) and Elasticity number (El). Moreover, the optimal HTE of RMHS increases with external pulsation amplitude and El but decreases with Re, which can also be summed up with them in a power-law function. Then, by analyzing of flow performance, the reversal flow and the resonance effects by VPL flow are regarded as the reasons for the HTE, which results from a balance between relaxation time of viscoelastic microstructures deformation and external pulsation period. Finally, the law of HTE by VPL flow is extended and verified in a carefully designed leaf-type microchannel heat sink (LMHS), suggesting a promising micro-scale heat transfer enhancement technology by VPL flow which however still needs further investigations on the optimal operating conditions in the future.

A novel optimized design of a piezoelectric-driven 4-stage amplified compliant microgripper using a 2-step multi-objective algorithm

Advancements in microscale technologies have prompted a demand for high precision micro-manipulation. Microgrippers are the primary means of conducting micro-scale operations, and they significantly affect the procedure's performance. This paper presents a novel optimized design for compliant microgrippers, intending to enhance functionality and durability. The mainframe of the proposed microgripper is based on a compact flexure-based compliant structure with four stages of movement amplification. Experiments were designed based on the L25 Taguchi orthogonal arrays. The experiments were conducted using the finite element method in Abaqus 6.14 workbench. Range of motion and maximum created mechanical stress are selected as the two fundamental goals of the optimization. A variety of designs are achieved using the proposed algorithm. The use of Analytical Hierarchy Process has led to the presentation of an efficient and well-defined algorithm to perform decisions. The decision process can be performed with regard to specific requirements of various applications. The presented design process of microgrippers has the potential for customized manufacturing for specific applications.Article HighlightsFinding correlations between design parameters and outputs (Amplification factor & Stress), using Taguchi's method in design of experiments (DOE).Optimization of dimensional inputs using a multi-objective genetic algorithm process to achieve an optimal Pareto-front instead of a single design point.Selecting the desirable point on the optimal Pareto-front for specific applications using Analytic Hierarchy Process (AHP) to prevent possible decision-making errors.

Design and Investigation of Optimal Dissolving Polymeric Microneedles for Ocular Application by Using Three-Level Factorial Design

Dissolving microneedles (dis-MNs) are very attractive micro-scale technology and a minimally invasive method to be used as a tool for transdermal delivery, leading to increased bioavailability of drugs bypassing ocular tissue barrier and painless treatment method. This study aims to design and investigate the optimal dis-MNs as a potential device for ocular application using a three-level factorial design. The dis-MNs were fabricated by micromolding technique using chitosan and polyvinyl alcohol (PVA) polymer. The physical appearance of dis-MNs was observed under a digital microscope. The mechanical strength (resistance force and insertion force) was tested with a texture analyzer. The penetration depth and dissolution time at a predetermined time were tested on porcine ocular tissue. The data illustrated that the optimal dis-MNs formulation was 3%chitosan and 20%PVA in 20%PVA in a weight ratio of 1:4. The physical appearance showed pyramidal microneedles with an average 609.01±1.01 µm in height and 200.21+3.57 μm in base width. The optimal dis-MNs showed a resistance force of 40.14±2.10 N. The insertion force into the cornea tissue (1.78 N/225 arrays) was higher than sclera tissue (0.95 N/225 arrays), indicating that the optimal dis-MNs could create micro-channels on both cornea and sclera tissues. The dissolution study showed that the optimal dis-MNs formulation was completely dissolved on cornea tissue (1 min) faster than sclera tissue (3 min). In conclusion, the optimal dis-MNs presented suitable dis-MNs properties with minimally invasive device for ocular tissue, acting as an appropriate dis-MNs model for the ophthalmic drug delivery system.