Search Results (209)

The influence of axial ultrasonic vibration (the dominant vibration mode) on the filling behavior of polymer melt in microcavities and its effect on microstructure formation remains inadequately understood. Based on the plasticization location and the extent to which the microcavity is covered by the ultrasonic sonotrode action surface, existing ultrasonic plasticization molding technologies were classified into three types—ultrasonic pressing (UP), ultrasonic plasticizing and pressing (UPP), and ultrasonic plasticization injection molding (UPIM). The effects of these configurations on melt fluidity and filling performance were evaluated and compared through slit flow tests. The interaction mechanisms between polymer melts and templates were elucidated based on melt pressure measurements and morphological changes in nickel micropillar arrays and silicon templates after molding. The results indicated that polymer melt exhibits improved flow behavior within microcavities when under the coverage area of the ultrasonic sonotrode action surface and subjected to the axial ultrasonic vibration. Continuous ultrasonic vibration contributed to sustaining melt fluidity during micropore filling. Among the three technologies, the most complex and intense mechanical interactions on the template microstructure were observed in UP, followed by UPP and then UPIM. Full article

This study presents a non-invasive three-dimensional cell manipulation technique based on acoustic microfluidic chips, which generates acoustic flow fields through the vibration of micropillars induced by bulk acoustic waves to achieve precise multi-dimensional rotational manipulation of cells. Moreover, the characteristics of the acoustic flow field under linear, quasi-circular, elliptical, and higher-order vibration modes were intensively studied, and the rotational manipulation performance of polystyrene microbeads and cancer cells was optimized by adjusting the frequency and voltage. The results showed that the rotational speed and direction of the particles varied significantly in different vibration modes, with the particles and cells achieving the highest rotational speed in the elliptical vibration mode (frequency: 44.9 kHz, and voltage: 60 Vpp). In addition, the technique successfully achieved in-plane and out-of-plane rotation of cancer cells, and cell viability tests showed that 94% of the cells remained active after manipulation, demonstrating the low damage and biocompatibility of the method. This study provides a new, efficient, precise and gentle approach to three-dimensional manipulation of cells, which holds significant potential in biomedical research and clinical applications. Full article

Micro-pillar compression is a popular experimental technique used for characterizing the mechanical behavior of nano- and micro-laminates. The compressive stress–strain response of the column-shaped thin-film composite can be measured, and the deformation and damage features can be revealed by post-test cross-section microscopy. The development of plastic instability in the form of localized strain concentration (shear bands), leading to eventual failure, is frequently observed. In the present study, a computational approach is used to illustrate the commonality of shear band formation from a continuum standpoint. Systematic finite element analyses are conducted, showing that the strain field tends to become localized once plastic yielding commences. Distinct shear offsets of the layered structure can be revealed from the numerical model, which is similar to those observed in experiments. The actual appearance of shear bands depends on the materials’ constitutive behavior and precise geometries. Post-yield strain hardening reduces the propensity of shear band formation, while strain softening enhances it. Imperfections such as the undulated layer geometry, as well as the frictional characteristics between the specimen and test apparatus, can also influence the shear band morphology and overall stress–strain response. Full article

A low-carbon ferrite/martensite-laminated 0.1C5Mn3Al dual-phase steel was hot-rolled to an engineering strain of 98%, and a tensile strength of 1277 ± 44 MPa and a total elongation of 11.8 ± 0.4% was obtained in the steel. Hot-rolling induces a laminated/layered structure characterized by alternating ferrite phases and martensite phases distributed perpendicular to the rolling direction. A deformation mechanism was evaluated using nano-indentation and in situ compression of micropillars in a scanning electron microscope. The excellent mechanical properties of the steel are attributed to the refinement of ferrite/martensite layers and ultra-fine martensite laths. The synergistic deformation of the ferrite and martensite laminates provides the steel with a good combination of high strength and tensile elongation. Full article

The integration of organoids with biosensors serves as a miniaturized model of human physiology and diseases, significantly transforming the research frameworks surrounding drug development, toxicity testing, and personalized medicine. This review aims to provide a comprehensive framework for researchers to identify suitable technical approaches and to promote the advancement of organoid sensing towards enhanced biomimicry and intelligence. To this end, several primary methods for technology integration are systematically outlined and compared, which include microfluidic integrated systems, microelectrode array (MEA)-based electrophysiological recording systems, optical sensing systems, mechanical force sensing technologies, field-effect transistor (FET)-based sensing techniques, biohybrid systems based on synthetic biology tools, and label-free technologies, including impedance, surface plasmon resonance (SPR), and mass spectrometry imaging. Through multimodal collaboration such as the combination of MEA for recording electrical signals from cardiac organoids with micropillar arrays for monitoring contractile force, these technologies can overcome the limitations inherent in singular sensing modalities and enable a comprehensive analysis of the dynamic responses of organoids. Furthermore, this review discusses strategies for integrating strategies of multimodal sensing approaches (e.g., the combination of microfluidics with MEA and optical methods) and highlights future challenges related to sensor implantation in vascularized organoids, signal stability during long-term culture, and the standardization of clinical translation. Full article

The evaporation dynamics of droplets on smooth and inclined micro-pillar surfaces were experimentally investigated. The surface temperature was increased from 50 °C to 120 °C, with the inclination angles being 0°, 30°, 45°, and 60° respectively. The dynamic parameters, including contact area, nucleation density, bubble stable diameter, and droplet asymmetry, were recorded using two high-speed video cameras, and the corresponding evaporation performance was analyzed. Experimental results showed that the inclination angle had a significant influence on the evaporation of micro-pillar surfaces than smooth surfaces as well as a positive correlation between the enhancement performance of the micro-pillars and increasing inclination angles. This angular dependence arises from surface inclination-induced tail elongation and the corresponding asymmetry of droplets. With definition of the one-dimensional asymmetry factor (ε) and volume asymmetry factor (γ), it was proven that although the asymmetric thickness of the droplets reduces the nucleation density and bubble stable diameter, the droplet asymmetry significantly increased the heat exchange area, resulting in a 37% improvement in the evaporation rate of micro-pillar surfaces and about a 15% increase in its enhancement performance to smooth surfaces when the inclination angle increased from 0°to 60°. These results indicate that asymmetry causes changes in heat transfer conditions, specifically, a significant increase in the wetted area and deformation of the liquid film, which are the direct enhancement mechanisms of inclined micro-pillar surfaces. Full article

The rapid development of high-power-density semiconductor devices has rendered conventional thermal management techniques inadequate for handling their extreme heat fluxes. This manuscript presents and implements an embedded microchannel cooling solution for such devices. By directly integrating micropillar arrays within the near-junction region of the substrate, efficient forced convection and flow boiling mechanisms are achieved. Finite element analysis was first employed to conduct thermo–fluid–structure simulations of micropillar arrays with different geometries. Subsequently, based on our simulation results, a complete multilayer microstructure fabrication process was developed and integrated, including critical steps such as deep reactive ion etching (DRIE), surface hydrophilic/hydrophobic functionalization, and gold–stannum (Au-Sn) eutectic bonding. Finally, an experimental test platform was established to systematically evaluate the thermal performance of the fabricated devices under heat fluxes of up to 1200 W/cm². Our experimental results demonstrate that this solution effectively maintains the device operating temperature at 46.7 °C, achieving a mere 27.9 K temperature rise and exhibiting exceptional thermal management capabilities. This manuscript provides a feasible, efficient technical pathway for addressing extreme heat dissipation challenges in next-generation electronic devices, while offering notable references in structural design, micro/nanofabrication, and experimental validation for related fields. Full article

High-entropy alloy (HEA) particle-reinforced metal matrix composites (MMCs) are a new generation of MMCs with potential applications as orthopedic material in automotive, aerospace, and biomedical fields. In this study, AlCoCrFeNi HEA-reinforced Ti-6Al-4V metal matrix composites (MMCs) were prepared by microwave sintering. The microstructural aspects of the MMC were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), with an emphasis on the interdiffusion (ID) layer. The mechanical properties of the composites were studied by micro-pillar compression at the micro-length scale. The results show that the ID layer exists between the HEA particles and the matrix, is equiaxed in nature, and leads towards metallurgical bonding within the composite. The strength of this ID layer (1573 MPa of yield strength and 1867 MPa of compressive strength) and its Young’s modulus (570 MPa) were about 1.5 times lower than that of the matrix. The HEA particles exhibit the highest strength (2157 MPa of yield strength and 3356 MPa of compressive strength) and Young’s modulus (643 MPa), whereas the matrix falls in between 2372 MPa of yield strength and 2661 MPa of compressive strength, and a Young’s modulus of 721 MPa. Full article

This work presents a novel microfabrication process that addresses the interference of thiol groups on off-stoichiometry thiolene (OSTE) surfaces with the curing of polydimethylsiloxane (PDMS) by integrating the high-performance polymer Parylene-C. The process utilizes a Parylene-C coating to encapsulate the active thiol groups on the OSTE surface, enabling precise replication of PDMS microstructures. Based on this method, PDMS micropillar arrays and microwell arrays were successfully fabricated and applied in passive plasma separation and polymorphic crystal formation, respectively. The experimental results demonstrate that the plasma-separation chip efficiently isolates plasma from whole-blood samples with varying hematocrit (HCT) levels, achieving a separation efficiency of up to 57.5%. Additionally, the microwell array chip exhibits excellent stability and controllability in the growth of salt and protein crystals. This study not only provides a new approach for microfabricating microfluidic chips, but also highlights its potential applications in biomedical diagnostics and materials science. Full article

Femtosecond laser micromachining was utilized to build up a micro-through-hole array into a sacrificial film, which was coated onto a copper specimen. This micro-through hole was shaped in the paraboloidal profile, with its micro-dimple on the interface between the copper substrate and the film. This profile was simply in correspondence with the laser energy profile. The array was used as a nucleation and growth site for nickel cluster deposition during wet plating. The micro-pillared unit cells nucleated at the micro-dimple and grew on the inside of the micro-through hole. After removing the sacrificial film, cleansing, and polishing, the nickel micro-pillar array was obtained, standing on the copper substrate. These unit cells and their alignments were measured through scanning electron microscopy and laser microscopy. Thermographic microscopy with FT-IR was utilized to measure the IR emittance as a function of wavelength. The focused areas were varied by controlling the aperture to analyze the effects of arrayed microtextures on the IR emittance. Full article

Mg–Zn–Mn-based biocomposites hold prospects as potential orthopedic material. The composition of these composites can be modulated, based on applications, by selective elemental alloying. Towards that, the addition of silicon (Si), hydroxyapatite (HA), or both is considered, followed by the consolidation method, such as spark plasma sintering (SPS). In this study, the micro-mechanical properties of Mg–Zn–Mn–(Si–HA) composites were investigated through the micro-pillar compression method. The effect of Si and HA incorporation on the mechanical characteristics and deformation mechanism was also elucidated. The microstructure of the composite presents porosity, together with different bioactive phases, such as Mg–Zn, CaMg, Mn–P, MgSi₂, Mn–Si, Mn–CaO, CaMgSi, and Ca–Mn–O. Such porous structures were determined to facilitate cell growth when used as an implant, particularly for musculoskeletal-related disabilities. The yield stress (YS) and compressive stress of the Mg–Zn–Mn–Si–HA were about 1543 ± 99 MPa and 1825 ± 102 MPa, respectively. These values were about 5.8 and 4.8 times higher, respectively, than those of Mg–Zn–Mn–HA composites (266 ± 42 MPa and 380 ± 10 MPa, respectively), and the same was observed for the elastic modulus. Besides that, alloying with HA and Si alters the deformation mechanism from brittle (for Mg–Zn–Mn–Si composites) or ductile (for Mg–Zn–Mn–HA composites) to predominant ductile failure without compromising the attained mechanical properties. Full article

Boiling heat transfer, utilizing latent heat during phase change, has widely been used due to its high thermal efficiency and plays an important role in existing and next-generation cooling technologies. The most critical parameter in boiling heat transfer is critical heat flux (CHF), which represents the maximum heat flux a heated surface can sustain during boiling. CHF is primarily influenced by the wicking performance, which governs liquid supply to the surface. This study experimentally and numerically analyzed the wicking performance of micropillar structures at various temperatures (20–95 °C) using distilled water as the working fluid to provide fundamental data for CHF prediction. Infrared (IR) visualization was used to extract the wicking coefficient, and the experimental data were compared with computational fluid dynamics (CFD) simulations for validation. At room temperature (20 °C), the wicking coefficient increased with larger pillar diameters (D) and smaller gaps (G). Specifically, the highest roughness factor sample (D04G10, r = 2.51) exhibited a 117% higher wicking coefficient than the lowest roughness factor sample (D04G20, r = 1.51), attributed to enhanced capillary pressure and improved liquid supply. Additionally, for the same surface roughness factor, the wicking coefficient increased with temperature, showing a 49% rise at 95 °C compared to 20 °C due to reduced viscous resistance. CFD simulations showed strong agreement with experiments, with error within ±10%. These results confirm that the proposed numerical methodology is a reliable tool for predicting wicking performance near boiling temperatures. Full article

The glass–glass interfaces (GGIs) play an important role during the plastic deformation of metallic nano-glasses (NGs) such as Sc-Fe NGs. In this work, Co-P nano-glasses are synthesized by pulse electrodeposition. Their mechanical properties are characterized by micro-pillar compression and compared to those obtained by molecular dynamics (MD) simulation. The MD simulation reveals that the GGIs with a particular incline angle (about 50.0°) in the direction of applied uniaxial strain is preferable for the accommodation of localized plastic deformation in NGs. The results are consistent with those obtained by spherical aberration-corrected transmission electron microscopy, which reveals that most of shear bands form an angle of about 58.7° to the direction of compressive strain applied on the Co-P micro-pillar. The phenomena are explained with the differences in chemical composition and atom diffusion in the glassy grain interiors and in the GGI regions. This work sheds some light on the deformation mechanisms of NGs and provides guidelines for designing NGs with improved mechanical properties. Full article

Electrode surface microstructuring involves the engineering of the topographical features of an electrode to enhance its performance in electrochemical sensing applications. By creating controlled micro- or nano-scale patterns, the active surface area can significantly increase, which leads to improved electron transfer and enhanced sensitivity to target analytes in devices such as biosensors. Geometrical parameters such as diameter, height, pitch, and position of the patterns can be optimized to enhance sensor detection. This paper introduces an electrochemical biosensor designed to detect Moraxella catarrhalis, a respiratory pathogen affecting young children. This paper investigates the effects of the radius of micropillars on adsorption in the electrochemical biosensor using COMSOL Multiphysics (Version: 6.0). The model demonstrates that the rate of surface adsorption depends on the position of the micropillars on the electrode. The paper also presents the effects of analyte concentration on the detection current of the biosensor using Cottrell’s equation. Full article

Superhydrophobic surfaces with arrayed pillar structures have huge application prospects in various industrial fields, such as self-cleaning, waterproofing, anti-corrosion, and anti-icing. The knowledge gap regarding the liquid–solid interaction between impacting droplets and microstructured surfaces must be addressed to guide the practical engineering applications more effectively. In this study, the effects of the stationary and horizontally moving superhydrophobic micro-pillar surfaces on the droplet impact dynamic behavioral characteristics are investigated numerically, focusing on the droplet morphology, spreading diameter, contact time, and energy conversion. Based on the numerical simulation results, new prediction correlations of the dimensionless maximum spreading diameter for droplets impacting stationary and horizontally moving micro-pillar surfaces are proposed. Moreover, significant rolling phenomena occur when droplets impact horizontally moving micro-pillar surfaces, which leads to an increase in viscous dissipation and forms a competitive mechanism with the asymmetric spreading–retraction process of the droplets. Two different stages are recognized according to the analysis of the contact time and velocity restitution coefficient. This study may provide new insights into understanding the dynamic behavior of droplets on microstructured surfaces. Full article