Search Results (85)

This study systematically investigates the effects of manufacturing errors on the drag reduction performance of micro-grooves fabricated using roll-to-roll hot embossing technology. Numerical simulations were conducted to analyze the drag reduction characteristics of spanwise micro-grooves under a 0.4 Ma incoming flow, with a focus on the influence mechanisms of groove array straightness error (δ) and bottom corner rounding error (σ) on aerodynamic performance. The results indicate that straightness errors induce periodic pressure pulsations, which disrupt large-scale turbulent structures and lead to a linear degradation in drag reduction performance. In contrast, bottom corner rounding errors modulate small-scale turbulence by altering the local curvature at the groove bottom. Positive deviations in particular cause an upward shift of the vortex core and enhanced energy dissipation, significantly impairing drag reduction. Based on these findings, an optimized processing window is proposed, recommending that the straightness error δ and bottom corner rounding error σ be controlled within −4% to 2% and −20% to 4%, respectively. Under these conditions, the fluctuation in the drag reduction rate can be confined within 20%. This study provides important theoretical insights and practical guidance for the precision manufacturing of drag-reducing micro-groove surfaces on aircraft. Full article

The roll-to-plate (R2P) hot-embossing process is a newly developed molding technique for the high-throughput, high-efficiency fabrication of large-area microstructured optical elements. However, this technology is limited to flat surfaces, because the thickness of the freeform optical plate varies constantly due to its specific optical design, while the roll stays cylindrical during rolling. Therefore, we developed a new profile-tunable roll with several groups of semiconductor heater/coolers (SHCs) attached around the inside wall of the roll. These SHCs can achieve tunable roll profiles at desirable positions by regulating the current for the semiconductor and then the roll temperature, thereby producing optics with a selected freeform. In this paper, the circumferential bulging profiles and corresponding roll temperature fields were thoroughly investigated under various heater/cooler layouts and roll sizes. A circumferential finite element model of the profile-tunable roll was established using the finite element software MSC.MARC 2020 and then verified on the experimental platform. In addition, the fundamental relationship between the bulging values and temperature distributions of the roll and parameters, such as the outer diameter and inner diameter of the roll, the temperature of the semiconductor heater/cooler, and the single piece influence angle, was eventually established. This paper offers a unique fabrication method for high-volume optical freeform plates at extremely low cost and builds a foundation for further research on the axial deformation and temperature distribution of the developed roll for freeform optics and R2P hot-embossing experiments for freeform optical components. Full article

Icing on aircraft surfaces during operation poses a threat to flight safety. As a passive anti-icing technology, hydrophobic microstructure can achieve long-term anti-icing. In this work, a composite process combining hot-embossing of PVD-coated punches with a low surface energy fluoride-modification scheme is proposed to generate nanoscale cluster structures on hundreds of microns array channels to construct a superhydrophobic micro-nano composite structure. The droplet freezing and frosting behavior of the hydrophobic microstructures was analyzed, and it was found that the anti-icing and anti-frost properties of the microstructure surface improved with an increase in the microstructure period size (T). Compared with the original surface, the freezing time of the microstructure at T = 500 μm was delayed by 214.3% (7 s → 22 s), and the frost layer coverage time was delayed by 75.7% (70 s → 123 s). The maximum water contact angle of the superhydrophobic micro-nano composite structure was 153.3°, and the droplet freezing time was delayed to 95 s, which is a 1166.67% difference, indicating that the multi-stage micro-nano composite structure can significantly improve surface anti-icing performance. The main reason for this result is that the bottom of the microstructure can store air pockets, preventing droplet wetting and heat exchange. Full article

Aluminum alloy surface microstructures possess functional characteristics such as hydrophilicity/hydrophobicity and anti-icing and have important applications in fields such as aerospace and power systems. In order to improve the filling quality of the microstructure and verify the anti-icing property of the microstructure, this work develops a scheme for achieving large-area hot embossing of anti-icing functional microstructures based on a multi-arc ion-plating mold. Compared with conventional steel, the hardness of the PVD-coated steel increases by 44.7%, the friction coefficient decreases by 66.2%, and the wear resistance is significantly enhanced. The PVD-coated punch-assisted embossing could significantly improve filling properties. While the embossing temperature is 300 °C, the PVD-coated punch-assisted embossing can ensure the complete filling of the micro-array channels. In contrast, under-filling defects occur in conventional hot embossing. Then, a large-area micro-channel specimen of 100 cm² was precisely formed without warping, and the average surface roughness Ra was better than 0.8 µm. The maximum freezing fraction of the micro-array channel was reduced by about 53.2% compared with the planar, and the complete freezing time was delayed by 193.3%. The main reason is that the air layer trapped by the hydrophobic structures hinders heat loss at the solid–liquid interface. Full article

Polymeric optical waveguides represent an essential component in photonic technology thanks to their ability to guide light through controlled structures, enabling applications in telecommunications, sensors, and integrated devices. With the development of new materials and increasingly versatile manufacturing methods, these structures are being integrated into various systems at a rapid pace, while their dimensions are constantly being reduced. This article explores the main fabrication methods for polymeric optical waveguides, such as traditional and maskless photolithography, laser ablation, hot embossing, nanoimprint lithography, the Mosquito method, inkjet printing, aerosol jet printing, and electrohydrodynamic (EHD) printing. The operating principle of each method, the equipment and materials used, and their advantages, limitations, and practical applications are evaluated, in addition to the propagation losses and characterization of the waveguides obtained with each method. Full article

This paper presents an experimental study of a novel automated manufacturing process that integrates cold embossing to add complex features, such as micro-Fresnel lens designs, onto a 3D-printed ABS polymer component. The research demonstrates that precise control over process parameters, including embossing time (E_t) and velocity (E_v), is critical for successful feature replication. Gloss analysis confirmed that surface softening as a crucial prerequisite for embossing was successfully achieved using a vapour smoothing (VS) chamber that was developed and optimised for the process. High-speed automation using a 6-axis KUKA robot allowed 48 embosses to be completed in just over one minute, highlighting its efficiency over conventional hot embossing (HE) methods. Results showed that an E_t (0.01 s) prevented feature replication as there was insufficient time to allow for polymer flow, while an optimal E_t (0.1 s) produced high-quality embosses across all test segments. Additionally, this study identified that while insufficient cycle times hinder polymer flow, extended durations can lead to surface hardening, prohibiting replication. These findings pave the way for integrating Diffractive Optical Elements into 3D-printed parts, potentially enhancing precision, functionality, and productivity beyond the capabilities of standard 3D-printing processes. Full article

Poly(butylene adipate-co-terephthalate) (PBAT) is a promising degradable polymer for replacing non-degradable traditional plastics to mitigate pollution. However, its low softening temperature and poor hardness impede its application. Herein, PBAT and stereocomplex polylactide (sc-PLA) blends were fabricated through a melt-blending process to balance the heat resistance and mechanical strength of PBAT in this research. The effects of the PLA content and hot embossing temperature on the blend properties were comprehensively investigated. The results demonstrate that the sc-crystal content in the PBAT/sc-PLA blend increased by 493% as the PLA content rose from 10% to 30%. The blend with 15% PLLA and 15% PDLA, hot embossed at 190 °C, exhibited the highest sc-PLA crystallinity of 23.3% and the largest fraction of sc-crystallites at 66%, leading to the optimal comprehensive performance. Its Vicat softening temperature (VST) reached 92.2 °C, and a nonlinear increase trend in accordance with the power-law model between VST and the mass ratio of sc-crystal was obtained. Compared with the mechanical properties of neat PBAT, a maximum tensile yield stress of 9.7 MPa and a Young’s modulus of 82.5 MPa were achieved and improved approximately by 107% and 361%, respectively. This research offers an effective strategy for synergistically enhancing the heat resistance and mechanical strength of PBAT. Full article

The organ-on-a-chip (OoC) technology holds significant promise for biosensors and personalized medicine by enabling the creation of miniature, patient-specific models of human organs. This review studies the recent advancements in the application of polydimethylsiloxane (PDMS) microfluidics for OoC purposes. It underscores the main fabrication technologies of PDMS microfluidic systems, such as photolithography, injection molding, hot embossing, and 3D printing. The review also highlights the crucial role of integrated biosensors within OoC platforms. These electrochemical, electrical, and optical sensors, integrated within the microfluidic environment, provide valuable insights into cellular behavior and drug response. Furthermore, the review explores the exciting potential of PDMS-based OoC technology for personalized medicine. OoC devices can forecast drug effectiveness and tailor therapeutic strategies for patients by incorporating patient-derived cells and replicating individual physiological variations, helping the healing process and accelerating recovery. This personalized approach can revolutionize healthcare by offering more precise and efficient treatment options. Understanding OoC fabrication and its applications in biosensors and personalized medicine can play a pivotal role in future implementations of multifunctional OoC biosensors. Full article

The development of hydrophobicity on polymer surfaces in mass production is one of the most critical challenges in the plastic industry. This paper deals with a novel combined hot embossing process in which femtosecond laser ablation is utilized to texture the embossing stamps. By controlling the process temperature and axial forces, the laser textures were transferred to polymer surfaces, successfully resulting in hydrophobicity. Four different polymers, including ABS, PP, PA, and PC, along with two different laser textures, namely ball and pyramid, were tested. The laser and hot embossing parameters under which the textures were transferred to the polymers are introduced. The critical micro- and nano-features of the transferred textures that resulted in high hydrophobic contact angles are also discussed. The results indicate that PP and ABS have higher contact angles, respectively, while under the given parameters, PA and PC did not exhibit hydrophobic surfaces. Full article

The roller-to-plate (R2P) hot-embossing process is an effective, low-cost method for producing high-quality micro-/nano-optical components. In the field of night vision applications, the fabrication of chalcogenide glass microstructures is emerging as a promising alternative to traditional infrared glass. This trend is driven by the potential of chalcogenide glass to surpass conventional materials in terms of performance. However, the development of R2P hot embossing faces challenges, such as the high cost of curved mold manufacturing, the reliance on roll-to-roll processes for nano hot embossing, the limitations of plastic materials, and the unclear viscoelastic properties of infrared glass. In this study, a novel R2P hot-embossing process was developed to fabricate flat chalcogenide glass structures. The key parameters, such as roller temperature, speed, and embossing pressure, were investigated to understand their impact on the glass-filling performance. The deformation mechanism of the glass microstructures was also analyzed. The experimental results show that the R2P hot-embossing method offers excellent reproducibility, achieving a maximum filling rate of 96% and an average roughness deviation of 8.36 nm. The increase in the roller temperature and embossing force increased the filling height of the glass microstructure arrays, while an increase in the roller speed decreased the filling height. Different embossing methods, including variations in speed, temperature, and force, are summarized to analyze the structural changes during embossing. This study provides a foundation and a basis for future research on the roller-to-plate hot embossing process. Full article

Hot embossing is a manufacturing technique used to create microchannels on polymer substrates. In recent years, microchannel fabrication technology based on hot embossing has attracted considerable attention due to its convenience and low cost. A new evaluation method of microchannels, as well as an approach to obtaining optimal hot embossing conditions based on the Taguchi method, is proposed in this paper to fabricate precise microchannels for a flexible proton-exchange membrane fuel cell (PEMFC). Our self-made hot embossing system can be used to fabricate assorted types of micro-channel structures on polymer substrates according to various applications, whose bottom width, top width, height and cross-sectional area vary in the aims of different situations. In order to obtain a high effective filling ratio, a new evaluation method is presented based on the four parameters of channel structures, and the Taguchi method is utilized to arrange three main factors (temperature, force and time) affecting the hot embossing in orthogonal arrays, quickly finding the optimal condition for the embossing process. The evaluation method for microchannels proposed in this paper, compared to traditional evaluation methods, incorporates the area factor, providing a more comprehensive assessment of the fabrication completeness of the microchannels. Additionally, it allows for the quick and simple identification of optimal conditions. The experimental results indicate that after determining the optimal embossing temperature, pressure and time using the Taguchi method, the effective filling rate remains above 95%, thereby enhancing the power density. Through variance analysis, it was found that temperature is the most significant factor affecting the hot embossing of microchannels. The high filling rate makes the process suitable for PEMFCs. The results demonstrate that under optimized process conditions, a self-made hot embossing system can effectively fabricate columnar structure microchannels for PEMFCs. Full article

This study aims to establish and optimize a process for the fabrication of 3D microstructures of the biocompatible polymer Parylene C using hot embossing techniques. The different process parameters such as embossing temperature, embossing force, demolding temperature and speed, and the usage of a release agent were optimized, utilizing adhesive micropillars as a use case. To enhance compatibility with conventional semiconductor fabrication techniques, hot embossing of Parylene C was adapted from conventional stainless steel substrates to silicon chip platforms. Furthermore, this adaptation included an investigation of the effects of the hot embossing process on metal layers embedded in the Parylene C, ensuring compatibility with the ultra-thin Parylene printed circuit board (PCB) demonstrated previously. To evaluate the produced microstructures, a combination of characterization methods was employed, including light microscopy (LM) and scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR). These methods provided comprehensive insights into the morphological, chemical, and structural properties of the embossed Parylene C. Considering the improved results compared to existing patterning techniques for Parylene C like plasma etching or laser ablation, the developed hot embossing approach yields a superior structural integrity, characterized by increased feature resolution and enhanced sidewall smoothness. These advancements render the method particularly suitable for diverse applications, including but not limited to, sensor optical components, adhesive interfaces for medical wearables, and microfluidic systems. Full article

Water-lubricated material is the fundamental ingredient of a water-lubricated bearing (WLB), of which the friction and wear properties directly affect the working performance and service life of a WLB. We designed a micron-scale stripe texture and fabricated a negative microtexture mold by femtosecond laser etching. The microtextures were fabricated onto the surface of Thordon and polyurethane water-lubricated materials by a precision thermoforming machine. Tribological tests showed that the microstripe texture on water-lubricated materials had lower friction and wear properties than that on pristine surface materials. The results demonstrated that the presence of the microstripe texture effectively improved the friction and anti-wear properties of the water-lubricated materials. This study provides a new idea for the design and preparation of water-lubricated materials with good water-lubricating and anti-wear properties. Full article

A novel non-isothermal glass hot embossing system utilizes a silicon mold core coated with a three-dimensional carbide-bonded graphene (CBG) coating, which acts as a thin-film resistance heater. The temperature of the system significantly influences the electrical conductivity properties of silicon with a CBG coating. Through simulations and experiments, it has been established that the electrical conductivity of silicon with a CBG coating gradually increases at lower temperatures and rapidly rises as the temperature further increases. The CBG coating predominantly affects electrical conductivity until 400 °C, after which silicon becomes the dominant factor. Furthermore, the dimensions of CBG-coated silicon and the reduction of CBG coating also affect the rate and outcome of conductivity changes. These findings provide valuable insights for detecting CBG-coated silicon during the embossing process, improving efficiency, and predicting the mold core’s service life, thus enhancing the accuracy of optical lens production. Full article

The filling efficiency during the hot embossing process at micro scale is essential for micro-component replication. The presence of the unfilled area is often due to the inadequate behavior law applied to the embossed materials. This research consists of the identification of viscoplastic law (two-layer viscoplastic model) of polymers and the optimization of processing parameters. Mechanical tests have been performed for two polymers at 20 °C and 30 °C above their glass transition temperature. The viscoplastic parameters are characterized based on stress–strain curves from the compression tests. The influences of imposed displacement, temperature, and friction on mold filling are investigated. The processing parameters are optimized to achieving the complete filling of micro cavities. The replication of a micro-structured cavity has been effectuated using this process and the experimental observations validate the results in the simulation, which confirms the efficiency of the proposed numerical approach. Full article