Search Results (190)

Poly(lactic acid) (PLA)-based biocomposites incorporating collagen (COLL) and hydroxyapatite (HA) were produced via melt micro-compounding and subsequent injection molding. 1,4-phenylene diisocyanate (PDI) was employed as a compatibilizer, while poly(ethylene glycol) (PEG) was used as a plasticizer. The morphological, thermal, rheological, and mechanical properties, as well as surface wettability, degradation behavior, and cytotoxicity, were comprehensively evaluated. SEM and DSC analyses revealed the phase distribution and thermal transitions, while rheological measurements showed that PEG reduced melt viscosity by increasing chain mobility. Mechanical performance was evaluated using tensile, impact, and DMA tests on standard specimens, indicating that HA primarily enhanced stiffness (elastic modulus), whereas PEG improved toughness, resulting in higher impact strength. Biodegradable bone screw prototypes were produced with the same formulations and subjected to torsion, enzymatic degradation, and MTT cytotoxicity tests. Degradation results indicated that biocomposites containing PEG, collagen, and HA exhibited accelerated mass loss. Overall, the 70/20/10 PLA/COLL/HA/PEG/PDI formulation was more suitable for soft (trabecular) bone tissue, while the 70/10/20 PLA/COLL/HA/PDI formulation showed advantages for hard (cortical) bone tissue applications. Full article

This work presents a comparative study of micro- and nano-scale fillers in liquid composite molding processes, focusing on how particle size and morphology affect resin rheology, flow behavior, and filler filtration within fiber preforms. Glass microspheres and organo-modified montmorillonite were dispersed in epoxy resin and injected through glass-mat preforms at different fiber volume fractions (ranging from 0.27 to 0.47). Our study integrates rheological characterization, in situ flow-front tracking, unsaturated permeability analysis, thermogravimetric quantification of retained particles, and microstructural observations by SEM. Despite their smaller loading, nanoclay suspensions showed a markedly higher viscosity increase than microsphere systems, yet their permeability remained nearly unchanged. In contrast, microsphere-filled resins exhibited strong filtration at the flow inlet, density-driven settling near the lower tool face, and significant permeability loss. The results demonstrate that nano-fillers, although more viscous, maintain homogeneous distribution and flow continuity, whereas micro-fillers promote cake formation and local compaction. This controlled side-by-side comparison clarifies how filler size and shape govern filtration mechanisms in liquid composite molding (LCM), providing design guidelines for processing filled resin systems without compromising part quality. Full article

The transition to a circular economy requires assessment tools that capture not only the environmental and economic performance of products but also their circular design, functionality, and durability. While Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) are widely used, they alone do not capture modularity, reparability, reuse potential, or product lifespan. This study introduces a novel, integrated framework combining LCA, LCC, and product-level circularity indicators to provide a holistic evaluation of sustainability and circularity. In this study, two types of injection molds for plastic part production are compared: a conventionally manufactured mold and an additively manufactured metal mold produced by Laser Powder Bed Fusion (L-PBF) technology. The comparison integrates Life Cycle Assessment (LCA), Life Cycle Costing (LCC), and a set of micro-circularity indicators, including the Material Circularity Indicator (MCI), Recycling Desirability Index (RDI), circular design guidelines (CDG), Disassembly Effort Index (DEI), longevity indicator (LI), and Circular Economy Indicator Prototype (CEIP). Results show that the AM mold exhibits lower environmental impacts across almost all categories, while its slightly higher initial cost is largely offset by reduced indirect costs over the product lifecycle. Micro-circularity indicators reveal that the AM mold achieves higher material circularity and better circular design performance (MCI, CDG, CEIP) but shows only minor improvements in disassembly and recyclability (DEI, RDI) and lower longevity (LI) compared to the conventional mold, highlighting potential limitations for remanufacturing and end-of-life recovery. The novelty of this study lies in the integrated application of LCA, LCC, and multiple micro-circularity indicators, providing an operational framework for evaluating circular design, reparability, and durability in additive manufacturing and enabling informed, holistic decision-making for truly circular products. Full article

Microfluidics provides precise control of microscale fluid transport and has become central to biomedical, pharmaceutical, and industrial technologies. However, conventional fabrication methods such as photolithography and soft lithography require cleanroom facilities, use costly materials, and offer limited capability for constructing complex or multi-material architectures. This review highlights emerging manufacturing strategies, focusing on polymer-based micro-milling as an accessible and cost-effective alternative for microfluidic device production. Advances in micro-milling now enable the fabrication of microchannels and functional features with improved dimensional accuracy and surface quality, while additive manufacturing offers complementary rapid prototyping and design flexibility. Micro-milling is particularly promising for rapid prototyping of polymeric biosensor chips designed for point-of-care diagnostics. The technique supports diverse materials and eliminates reliance on cleanroom processing. Critical parameters, including tool geometry, spindle speed, and feeding rate, strongly influence fidelity and surface roughness, which directly affect biosensor sensitivity. Despite its advantages, challenges such as tool wear, burr formation, and limits on minimum feature size continue to hinder reproducibility. Recent progress in toolpath optimization, hybrid additive–subtractive methods, and real-time process monitoring shows the potential to overcome these barriers. Overall, micro-milling offers a scalable and economical route for fabricating accessible microfluidic and biosensing platforms, with future work needed to standardize processes and improve integration with surface functionalization methods. Full article

Dissolvable microneedles (DMNs) represent an innovative approach to patient-friendly drug delivery, eliminating the need for conventional hypodermic injections. This study reports on the fabrication, Confocal Laser Scanning Microscopy (CLSM)-based optical visualization of drug distribution, and mechanical characterization of maltose-based DMNs impregnated with lignocaine, a local anesthetic. Microneedles were fabricated using a micro-molding technique and dried for nine hours. Structural integrity was evaluated using Field Emission Scanning Electron Microscopy (FESEM); drug distribution was examined via CLSM; and mechanical strength was assessed using nanoindentation. The FESEM results showed uniform microneedle formation with sharp tips and smooth surfaces, averaging 435 µm in height and 116 µm in width, with no significant dimensional variability (p > 0.5). CLSM analysis indicated even distribution of lignocaine throughout the matrix. Mechanical testing showed that each microneedle withstood 0.6 N, surpassing the 0.1 N threshold required for skin insertion. These results support the viability of maltose-based DMNs for local anesthetic delivery, with implications for outpatient, pediatric, and self-administered care settings. Future investigations will include Franz diffusion and in vitro dissolution studies to examine release kinetics. Full article

The flexible micro-structured surface found in biological skins exhibits remarkable drag reduction properties, inspiring applications in the aerospace industry, underwater exploration, and pipeline transportation. To address the challenge of efficiently replicating such structures, this study presents a composite flexible polymer film with a bio-inspired micro-dimple array, fabricated via an integrated process of precision milling, polishing, and micro-injection molding using thermoplastic polyurethane (TPU). We systematically investigated the influence of key injection parameters on the shape accuracy and surface quality of the film. The experimental results show that polishing technology can significantly reduce mold core surface roughness, thereby enhancing film replication accuracy. Among the parameters, melt temperature and holding time exerted the most significant effects on shape precision PV and bottom roughness R_a, while injection speed showed the least influence. Under optimized conditions of a melt temperature of 180 °C, injection speed of 60 mm/s, holding pressure of 7 MPa, and holding time of 13 s, the film achieved a micro-structure shape accuracy of 13.502 μm and bottom roughness of 0.033 μm. Numerical simulation predicted a maximum drag reduction rate of 10.26%, attributable to vortex cushion effects within the dimples. This performance was experimentally validated in a flow velocity range of 0.6–2 m/s, with the discrepancy between simulated and measured drag reduction kept within 5%, demonstrating the efficacy of the proposed manufacturing route for flexible bio-inspired drag reduction film. Full article

In the microinjection molding process, continuous monitoring is important for optimization of the process and control. In microfluidic or lab-on-chip devices, defective microfeatures can compromise biological assays and diagnostic results, and therefore, the quality of these features is a critical issue. Microfeatures can be inspected using advanced inspection and microscopic techniques, but these are expensive, time-consuming, and difficult to use for full-scale production. We present here a new technique for quality control of microfeatures, which uses the filling of a controlled microcavity inside or outside the molded part as a quality control tool for filling microfeatures. Micro gaps (checkpoints) are used as an indicator of microfeature filling. Two micro gaps can be used for filling (checkpoints) as a Go/No-Go gauge. Full article

Tissue engineering offers a promising solution by developing scaffolds that mimic the extracellular matrix and guide cellular growth and differentiation. Recent evidence suggests that scaffolds must provide not only biocompatibility and appropriate mechanical properties, but also the structural complexity and heterogeneity characteristic of natural tissues. Particle-based scaffolds represent an emerging paradigm in regenerative medicine, wherein micro- and nanoparticles serve as primary building blocks rather than minor additives. This approach offers exceptional control over scaffold properties through precise selection and combination of particles with varying composition, size, rigidity, and surface characteristics. The presented review examines the fundamental principles, fabrication methods, and properties of particle-based scaffolds. It discusses how interparticle connectivity is achieved through techniques such as selective laser sintering, colloidal gel formation, and chemical cross-linking, while scaffold architecture is controlled via molding, templating, cryogelation, electrospinning, and 3D printing. The resulting materials exhibit tunable mechanical properties ranging from soft injectable gels to rigid load-bearing structures, with highly interconnected porosity that is essential for cell infiltration and vascularization. Importantly, particle-based scaffolds enable sophisticated pharmacological functionality through controlled delivery of growth factors, drugs, and bioactive molecules, while their modular nature facilitates the creation of spatial gradients mimicking native tissue complexity. Overall, the versatility of particle-based approaches positions them as prospective tools for tissue engineering applications spanning bone, cartilage, and soft tissue regeneration, offering solutions that integrate structural support with biological instruction and therapeutic delivery on a single platform. Full article

This article evaluates the influence of replicated natural structures, produced by micro-machining, on the wettability of plastic parts made from hydrophilic and hydrophobic polymer materials under various temperature and pressure conditions. Although many studies have focused on biomimetic surface design, the effect of specific processing parameters on the accurate replication of natural topologies and their resulting wettability has been only partially explored. This study addresses this gap by systematically analyzing the effect of melt temperature and packing pressure on the functional replication of micro-machined biomimetic structures. The research describes the design of hierarchical microstructures inspired by biomimetics and their fabrication by micro-milling on molded parts. Test samples were prepared from polypropylene (PP), acrylonitrile butadiene styrene (ABS), and polyamide 6.6 (PA 6.6) under different processing parameters, and wettability was assessed using contact angle (CA) measurements. The results confirmed significant variations in surface wettability depending on polymer type, melt temperature, and packing pressure. For the hydrophilic relief (Rock Moss), contact angles below 90° were obtained for all tested polymers, including PP, which decreased from 98.7° on a flat surface to 82.4° at 220 °C and 500 bar. In PA 6.6, a reduction of up to 12% in contact angle was observed compared to smooth samples at 310 °C and 500 bar. For hydrophobic reliefs (Three-part Hibiscus and Tricolor Pansy), contact angles exceeded 100–110°, with the highest value of 108.3 ± 1.6° for PP at 200 °C and 500 bar. Suitable combinations of melt temperature and packing pressure enabled accurate replication of microstructures while preserving their functional wettability, demonstrating the possibility of tuning surface properties through topological design. Full article

In response to the problems encountered during the pressure-driven oil recovery process in low-permeability oil reservoirs, such as slow pressure transmission, poor liquid supply, vulnerability of the reservoir to damage, and difficulties in injection and production, in order to achieve the goal of high-quality water injection development, based on the theories of rock mechanics and seepage mechanics, combined with large-scale physical model experiments, acoustic emission crack monitoring, and microscopic scanning technology, an oil reservoir and fracture model was established to conduct a feasibility analysis of pressure-driven assisted pressure reduction and enhanced injection, and it was successfully applied in the exploration and development practice of the Shengli Oilfield. The research shows the following: (1) During the pressure-driven process, the distribution of the fracture network system is relatively limited. In the early stages of the process, there will be minor fractures, but they do not communicate or activate effectively. The improvement of physical properties and pore-throat structure is negligible. As the injection flow rate increases, the effective fracture network system begins to be established, and the range of fluid coverage begins to expand. With the progress of the pressure-driven process, the hydraulic fractures gradually extend, the number of activated original fractures gradually increases, the communication area between hydraulic fractures and original fractures gradually increases, and the reservoir modification effect gradually improves. (2) Based on the compression cracking experiment of large object molds, it is concluded that generating effective micro-cracks and activating them to form efficient diversion channels is the key to pressure flooding injection. Combining the mechanical characteristics of the rock in the target layer to precisely control the injection speed and injection pressure can maximize the fracture network, thereby improving the reservoir to achieve the purpose of pressure reduction and injection increase. (3) Different pressure flooding injection parameters were set for the low-permeability oil reservoirs in the study area to simulate the fracture network expansion. Finally, it was concluded that the optimal injection speed for fracture expansion was 1.2 m³/min and the optimal total injection volume was 20,000 m³. Through research, the mechanism of pressure-driven injection and the extent of reservoir modification caused by this pressure-driven process have been enhanced in terms of understanding. Full article

This publication presents an improved manufacturing method for tetrahedral metal effect pigment particles that demonstrates reduced flowlines in injection-molded polymer components compared with conventional platelet-shaped pigment particles. The previously published cold forming process for tetrahedral particles, made entirely from aluminum, faced manufacturing challenges, resulting in a high reject rate due to particle adhesion to the micro-structured mold roller. In contrast, this study introduces a new manufacturing method for tetrahedral particles, now consisting of metallized UV-cured thermoset polymer. These particles, dispersed in amorphous matrix thermoplastics, have shown to maintain their shape during the injection molding process. The manufacturing technique for these novel particles is based on UV imprint lithography, omitting the reject rates compared with the previously presented cold rolling process of tetrahedral full aluminum particles. Thus, the novel manufacturing technique for tetrahedral pigment particles shows increased potential for automation through roll-to-roll manufacturing in the future. Full article

Ultra-high molecular weight polyethylene (UHMWPE) is widely used in orthopedic and prosthetic applications due to its excellent wear resistance and biocompatibility. However, its high molecular weight presents significant challenges in terms of processing and formability, particularly at the micro scale. This study investigates the flowability characteristics of a new melt-processable UHMWPE in micro-disc geometries to evaluate its suitability for advanced prosthetic applications. Micro-injection molding experiments assessed the material’s behavior under various thermal conditions. The influence of parameters such as temperature, pressure, and disc dimensions has direct effects on the flow behavior of UHMWPE and was analyzed by simulation and experiments. Results indicate that while UHMWPE exhibits limited flow under conventional conditions, optimized processing parameters can enhance discs’ formability without compromising the material’s structural integrity, avoiding defects. These findings provide critical insights for the microfabrication of UHMWPE thin components in next-generation prosthetic devices, enabling improved design precision and functional performance. Full article

In this study, a correlative approach using Raman spectroscopy and scanning electron microscopy (SEM) is introduced to meet the challenges of identifying impurities, especially carbon-related compounds in metal injection-molded (MIM) Mg-0.6Ca specimens designed for biomedical applications. This study addresses, for the first time, the issue of carbon residuals in the binder-based powder metallurgy (PM) processing of Mg-0.6Ca materials. A deeper understanding of the material microstructure is important to assess the microstructure homogeneity at submicron levels as this later affects material degradation and biocompatibility behavior. Both spectroscopic and microscopic techniques used in this study respond to the concerns of secondary phase distributions and their possible stoichiometry. Our micro-Raman measurements performed over a large area reveal Raman modes at ~1370 cm⁻¹ and ~1560 cm⁻¹, which are ascribed to the elemental carbon, and at ~1865 cm⁻¹, related to C≡C stretching modes. Our study found that these carbonaceous residuals/contaminations in the material microstructure originated from the polymeric binder components used in the MIM fabrication route, which then react with the base material components, including impurities, at elevated thermal debinding and sintering temperatures. Additionally, using evidence from the literature on thermal carbon cracking, the presence of both free carbon and calcium carbide phases is inferred in the sintered Mg-0.6Ca material in addition to the Mg₂Ca, oxide, and silicate phases. This first-of-its-kind correlative characterization approach for PM-processed Mg biomaterials is fast, non-destructive, and provides deeper knowledge on the formed residual carbonaceous phases. This is crucial in Mg alloy development strategies to ensure reproducible in vitro degradation and cell adhesion characteristics for the next generation of biocompatible magnesium materials. Full article

Acoustic tweezers, as advanced micro/nano manipulation tools, play a pivotal role in biomedical engineering, microfluidics, and precision manufacturing. However, piezoelectric-based acoustic tweezers face performance limitations due to multi-physical coupling effects during microfabrication. This study proposes a novel approach using injection molding with embedded electronics (IMEs) technology to fabricate piezoelectric micro-ultrasonic transducers with micron-scale precision, addressing the critical issue of acoustic node displacement caused by thermal–mechanical coupling in injection molding—a problem that impairs wave transmission efficiency and operational stability. To optimize the IME process parameters, a hybrid multi-objective optimization framework integrating NSGA-II and MOPSO is developed, aiming to simultaneously minimize acoustic node displacement, volumetric shrinkage, and residual stress distribution. Key process variables—packing pressure (80–120 MPa), melt temperature (230–280 °C), and packing time (15–30 s)—are analyzed via finite element modeling (FEM) and validated through in situ tie bar elongation measurements. The results show a 27.3% reduction in node displacement amplitude and a 19.6% improvement in wave transmission uniformity compared to conventional methods. This methodology enhances acoustic tweezers’ operational stability and provides a generalizable framework for multi-physics optimization in MEMS manufacturing, laying a foundation for next-generation applications in single-cell manipulation, lab-on-a-chip systems, and nanomaterial assembly. Full article

Nanoscale amorphous calcium phosphate (ACP) exhibits superior bioactivity, degradability, and osteoblast adhesion compared to hydroxyapatite (HAp), making it a promising bioactive ceramic material for bone regeneration applications. This study explores the integration of ACP as a bioactive additive in polylactic acid/polycaprolactone (PLA/PCL) composites. Nanoscale ACP powder was synthesized through low-temperature wet chemical methods without additional reagents. The composite, consisting of 10 wt.% ACP, 80 wt.% PLA, and 20 wt.% PCL, achieved optimal tensile strength (>12 MPa) and elongation (>0.1%). Utilizing the Taguchi experimental design, the microinjection molding parameters were optimized, and they are a material temperature of 190 °C, an injection speed of 50 mm/s, and a holding pressure speed of 30 mm/s. Variance analysis identified the injection speed to be the most significant factor, contributing 50.73% to the overall effect. Immersing ACP in simulated body fluid (SBF) for six hours reduced its calcium ion concentration by 28%, with this concentration stabilizing thereafter. Biocompatibility was confirmed through an MTT assay with NIH-3T3 cells, demonstrating the PLA/PCL/ACP composite’s compatibility. Bone differentiation and mineralization tests showed the enhanced performance of both ACP and the composite material. Degradation tests indicated an initial 0.29% weight increase in the first week, followed by a 2% reduction by the fifth week. These results underscore the PLA/PCL/ACP composite’s excellent mechanical properties, biocompatibility, and suitability for injection molding, positioning it as a strong candidate for biodegradable bone screw applications. Full article