Search Results (72)

Microfluidic device prototyping demands rapid, cost-effective, and high-precision mould fabrication, yet ultrashort pulsed laser structuring of polymer inserts remains underexplored. This study presents a novel method for fabricating microfluidic mould inserts using femtosecond (fs) laser ablation of polyimide (PI) films, achieving high precision from design to prototype. PI films (250 µm) were structured using a 355 nm fs laser (300 fs, 500 kHz, 0.95 J/cm²) in a photochemically dominated ablation regime and bonded to reusable steel plates. Injection moulding trials with cyclic olefin copolymer (COC) and polymethyl methacrylate (PMMA) were conducted with diverse designs, including concentration gradient generators (CGG), organ-on-chip (OOC) with 20 µm bridges, and double emulsion droplet generators (DEDG) with 100–500 µm channels, ensuring robustness across complex geometries. The method achieved near 1:1 replication (errors < 2%, microchannel height tolerances < 1%, Sa = 0.02 µm in channels, 0.26 µm in laser-structured areas), machining times under 2 h, and mould durability over 100 cycles without significant deterioration. The PI’s heat-retarding effect mimicked variothermal moulding, ensuring complete micro-penetration without specialised equipment. By reducing material costs using PI films and reusable steel plates, enabling rapid iterations within hours, and supporting industry-compatible prototyping, this approach lowers barriers for small-scale labs. It enables rapid prototyping of diagnostic lab-on-chip devices and supports decentralised manufacturing for biomedical, chemical, and environmental applications, offering a versatile, cost-effective tool for early-stage development. Full article

Guided mode resonance (GMR) sensors are known for their ultrasensitive and label-free detection, achieved by assessing refractive index (RI) variations on grating surfaces. However, conventional systems often require manual adjustments, which limits their practical applicability. Therefore, this study enhances the practicality of GMR sensors by introducing an optimized detection system based on the Jones matrix method. In addition, finite element method simulations were performed to optimize the GMR sensor structure parameter. The GMR sensor chip consists of three main components: a cyclic olefin copolymer (COC) substrate with a one-dimensional grating structure of a period of ~295 nm, a height of ~100 nm, and a ~130 nm thick TiO₂ waveguide layer that enhances the light confinement; an integrated COC microfluidic module featuring a microchannel; and flexible tubes for efficient sample handling. A GMR sensor in conjunction with a specially designed system was used to perform RI measurements across varying concentrations of sucrose. The results demonstrate its exceptional performance, with a normalized sensitivity (S_n) and RI resolution (R_s) of 0.4 RIU⁻¹ and 8.15 × 10⁻⁵ RIU, respectively. The proposed detection system not only offers improved user-friendliness and cost efficiency but also delivers an enhanced performance, making it ideal for scientific and industrial applications, including biosensing and optical metrology, where precise polarization control is crucial. Full article

Cyclic Olefin Copolymer (COC) is an amorphous thermoplastic polymer synthesized through the catalytic copolymerization of α-olefin and cyclic olefin. When used in pre-filled syringes and pharmaceutical packaging, COCs require radiation sterilization. The radiation sterilization alters the microstructure of COC, which ultimately affects its performance and biosafety. In this study, to investigate the effects of γ-radiation on COC microstructures, ethylene-norbornene copolymers with various compositions, representative of COC, are studied by nuclear magnetic resonance (NMR) and small angle X-ray scattering (SAXS) techniques. During irradiation, the COC containing 35 mol% norbornene produced free radicals that triggered migration and reaction processes, leading to the formation of entanglements within flexible chain segments. This, in turn, affected nearby ring structures with high steric hindrance, resulting in a 9.2% decrease in internal particle size and an increase in particle spacing. Conversely, when the norbornene content in COC was increased to 57 mol%, the internal particle size increased by 17.9%, while the particle spacing decreased. Full article

Precision micromilling is currently widely used for the fabrication of injection mold inserts for the mass production of microfluidic devices. However, for complex devices with micrometer-scale and high density of structures, micromilling results in high production times and costs for production runs of hundreds or thousands of units. Femtosecond laser (fs-laser) technology has emerged as a promising solution for high-precision micromachining. This study analyzes the potential of fs-laser micromachining for the fabrication of injection mold inserts for the large-scale production of thermoplastic microfluidic devices. For the evaluation of technology, a reference design was defined. The parameters of the fs-laser process were optimized to achieve high resolution of the structures and optimal surface quality, aiming to minimize production times and costs while ensuring the quality of the final part. The microstructures were replicated in two different grades of COC (Cyclic Olefin Copolymer) by injection molding. The dimensional tolerance of the structures and the surface finish achieved both in the insert and the polymer parts were characterized by scanning electron microscopy (SEM) and confocal microscopy. The surface quality of the final parts and its suitability for microfluidic fabrication were also assessed performing chemical bonding tests. The fs-laser machining process has shown great potential for the mass production of microfluidic devices. The developed process has enabled for a reduction of up to 90% in the fabrication times of the insert compared to micromilling. The parts exhibited very smooth surfaces, with roughness values (Sa) of 64.6 nm for the metallic insert and 71.8 nm and 72.9 nm for the COC E-140 and 8007S-04 replicas, respectively. The dimensional tolerance and the surface quality need to be improved to be competitive with the finishes achieved with precision micromilling. Nonetheless, there is still room for improvement considering the significant reduction in the production times through new laser processing strategies. Full article

This work presents a multilamination method for fabricating microfluidic devices or analytical microsystems using commercial 3D printers and photocurable resins as primary components. The developed method was validated by fabricating devices for the colorimetric measurement of copper ions in aqueous solutions, achieving results comparable to traditional cyclic olefin copolymer (COC) systems. The microfluidic platforms demonstrated stability and functionality over a twelve-week testing period. Channels with minimum dimensions of 0.4 mm × 0.4 mm were fabricated, and the feasibility of using resin modules for optical applications was demonstrated. This study highlights the potential of combining 3D printing with multilamination procedures as a versatile alternative, offering flexibility through the selection of a variety of available resins and commercial printers, as well as the ease of design development. This method offers significant reductions in cost, time, and manufacturing complexity by eliminating the need for equipment such as CNC machines, presses, and ovens, which are typically required in other multilamination technologies like LTCC and COC. Full article

This study presents the formulation and comprehensive characterization of compatibilized polyamide 6 (PA6)/cyclic olefin copolymer (COC) blends with the aim of developing a self-healing matrix for thermoplastic structural composites. Rheological analysis highlighted the compatibilizing effect of ethylene glycidyl methacrylate (E-GMA), as evidenced by an increase in viscosity, melt strength (MS), and breaking stretching ratio (BSR), thus improving the processability during film extrusion. E-GMA also decreased COC domain size and improved the interfacial interaction with PA6, which was at the basis of a higher tensile strength and strain at break compared to neat PA6/COC blends. E-GMA also significantly boosted the healing efficiency (HE), measured via fracture toughness tests in quasi-static and impact conditions. The optimal healing temperature was identified as 160 °C, associated with an HE of 38% in quasi-static mode and 82% in impact mode for the PA6/COC blends with an E-GMA content of 5 wt% (PA6COC_5E-GMA). The higher healing efficiency under impact conditions was attributed to the planar fracture surface, which facilitated the flow of the healing agent in the crack zone, as proven by fractography analysis. This work demonstrates the potential of E-GMA in fine-tuning the thermomechanical properties of PA6/COC blends. PA6COC_5E-GMA emerged as the formulation with the best balance between processability and self-healing efficiency, paving the way for advanced multifunctional self-healing thermoplastic composites for structural applications. Full article

While submissions of microfluidic-based medical devices to the Food and Drug Administration (FDA) have increased in recent years, leakage remains a common but difficult failure mode to detect in microfluidic systems. Here, we have developed a sensitive tool to measure and verify leakages ranging from 0.1% to 10% in leakage detection systems, which can then be used to detect leak in microfluidic devices. Our methodology includes an analytical model that applies hydrodynamic resistance using different fluid-contacting elements (e.g., tubing, junctions, and connectors) to tune the leakage rate based on the application-specific acceptance criteria. We then used three polymer-based microfluidic systems to target leakage rates of approximately 0.1, 1.0, and 10%. The experimental uncertainties in Polyether Ether Ketone (PEEK) tubing were 23.08%, 13.64%, and 1.16%, respectively, while the PEEK-Coated Fused Silica (PEEKsil) tubing system had errors of 0.00%, 0.72%, and 1.59%, respectively, relative to the theoretical values for the same target leak rates. The commonly used commercial grade Cyclic Olefin Copolymer (COC) microfluidic chips produced errors of 7.69% and 5.05%, respectively, for target leakage rates of 0.24% and 1.88%. We anticipate that the proposed bench test method can be useful for device developers as a verification tool for leakage detection systems before assessing flow-mediated leakage failure modes in microfluidic medical devices. Full article

The microfluidic industry faces a significant challenge due to the lack of sensitive and standardized methods. One critical need is the measurement of internal channel dimensions in fully assembled chips. This study presents and compares several protocols for measuring these dimensions, including optical profilometry, optical microscopy, and tiled digital imagery. Standardized chips made from two materials commonly used in microfluidics (borosilicate glass and Cyclic Olefin Copolymer) were evaluated using each protocol. A consistency analysis using normalized error statistics identified optical profilometry as the most reliable method, offering the lowest uncertainty and the highest consistency with nominal geometry values. However, all protocols encountered difficulties with vertical depth measurements of internal structures. Future research should focus on addressing these limitations, including investigating the influence of multiple refractive surfaces on optical profilometry and exploring confocal microscopy. In conclusion, this work provides a comprehensive comparison of measurement protocols for internal microfluidic structures and offers a practical solution for applications in the microfluidic industry, while also identifying important directions for future research. Full article

Terahertz radiation patterns can be registered using various detectors; however, in most cases, the scanning resolution is limited. Thus, we propose an alternative method for the detailed scanning of terahertz light field distributions after passing simple and complex structures. Our method relies on using a dielectric waveguide to achieve better sampling resolution. The optical properties of many materials were analyzed using time-domain spectroscopy. A cyclic olefin copolymer (COC) was chosen as one of the most transparent. This study contains a characterization of the losses introduced by the waveguide and a discussion of the setup’s geometry. As a structure introducing the radiation pattern, a 2D quasi-periodic amplitude grating was chosen to observe the Talbot effect (self-imaging). Moreover, some interesting physical phenomena were observed and discussed due to the possibility of detailed scanning, with subwavelength resolution, registering the terahertz wavefront changes behind the structure. Full article

Extracellular vesicles (EVs) are promising biomarkers for diagnosing complex diseases such as cancer and neurodegenerative disorders. Yet, their clinical application is hindered by challenges in isolating cancer-derived EVs efficiently due to their broad size distribution in biological samples. This study introduces a microfluidic device fabricated using off-stoichiometry thiol-ene and cyclic olefin copolymer, addressing the absorption limitations of polydimethylsiloxane (PDMS). The device streamlines a standard laboratory assay into a semi-automated microfluidic chip, integrating sample mixing and magnetic particle separation. Using the microfluidic device, the binding kinetics between EVs and anti-CD9 nanobodies were measured for the first time. Based on the binding kinetics, already after 10 min the EV capture was saturated and comparable to standard laboratory assays, offering a faster alternative to antibody-based immunomagnetic protocols. Furthermore, this study reveals the binding kinetics of EVs to anti-CD9 nanobodies for the first time. Our findings demonstrate the potential of the microfluidic device to enhance clinical diagnostics by offering speed and reducing manual labor without compromising accuracy. Full article

Initial studies indicate that structured polymer surfaces can support the attachment and biofilm formation of bacteria and thereby provide enhanced positive effects of beneficial bacteria, for instance in biocontrol in aquacultures. In this study, we demonstrate a test platform to further explore the surface topography for bacterial attachment and biofilm growth. It is based on a cyclic olefin copolymer (COC) materials platform, and nanoimprint technology was used for the replication of microstructures. The use of nanoimprint technology ensures precise micropattern transfer, enabling easy prototyping. Further, the process parameters of the mold preparation and nanoimprinting are discussed, with the purpose of optimizing the polymer pattern profile. This study has the potential to identify promising surfaces for biofilm growth of beneficial bacteria. Full article

Understanding the performance of polymer dielectrics at different temperatures is becoming increasingly important due to the rapid development of electric cars, electromagnetic devices, and new energy production solutions. Cyclic olefin copolymers (COCs) are an attractive material due to their low water absorption, good electrical insulation, long-term stability of surface treatments, and resistance to a wide range of acids and solvents. This work focused on the dielectric and electrical properties of cyclic olefin copolymer (COC)/Al₂O₃ composites over a wide range of temperature and frequency domains, from room temperature to cryogenic temperatures (around 125 K). Permittivity, electrical conductivity, and electrical modulus are given consideration. A composite of up to 50% Al₂O₃ mixed with COC was prepared via a conventional melt-blending method. The final samples were formed in sheets and processed using injection and extrusion moldings. It was found that formulations with Al₂O₃ concentrations ranging from 10 to 50% resulted in higher electrical conductivity while maintaining the viscosity of the composite at a level acceptable for polymer-processing machinery. Our data show that COC/alumina composites present substantial potential as materials for high-frequency applications, even at the regime of cryogenic temperatures. Full article

In terahertz (THz) optical systems, polymer-based manufacturing processes are employed to ensure product quality and the material performance necessary for proper system maintenance. Therefore, the precise manufacturing of system components, such as optical elements, is crucial for the optimal functioning of the systems. In this study, the authors investigated the impact of various 3D printing parameters using fused deposition modeling (FDM) on the optical properties of manufactured structures within the THz radiation range. The measurements were conducted on 3D printed samples using highly transparent and biocompatible cyclic olefin copolymer (COC), which may find applications in THz passive optics for “in vivo” measurements. The results of this study indicate that certain printing parameters significantly affect the optical behavior of the fabricated structures. The improperly configured printing parameters result in the worsening of THz optical properties. This is proved through a significant change in the refractive index value and undesirable increase in the absorption coefficient value. Furthermore, such misconfigurations may lead to the occurrence of defects within the printed structures. Finally, the recommended printing parameters, which improve the optical performance of the manufactured structures are presented. Full article

With increasing demands for data transfer, the production of components with low dielectric loss is crucial for the development of advanced antennas, which are needed to meet the requirements of next-generation communication technologies. This study investigates the impact of a variation in energy density on the part properties of a low-loss cyclic olefin copolymer (COC) in the SLS process as a way to manufacture complex low-dielectric-loss structures. Through a systematic variation in the laser energy, its impact on the part density, geometric accuracy, surface quality, and dielectric properties of the fabricated parts is assessed. This study demonstrates notable improvements in material handling and the quality of the manufactured parts while also identifying areas for further enhancement, particularly in mitigating thermo-oxidative aging. This research not only underscores the potential of COC in the realm of additive manufacturing but also sets the stage for future studies aimed at optimizing process parameters and enhancing material formulations to overcome current limitations. Full article

This study investigated the self-healing properties of PA6/COC blends, in particular, the impact of three compatibilizers on the rheological, microstructural, and thermomechanical properties. Dynamic rheological analysis revealed that ethylene glycidyl methacrylate (E-GMA) played a crucial role in reducing interfacial tension and promoting PA6 chain entanglement with COC domains. Mechanical tests showed that poly(ethylene)-graft-maleic anhydride (PE-g-MAH) and polyolefin elastomer-graft-maleic anhydride (POE-g-MAH) compatibilizers enhanced elongation at break, while E-GMA had a milder effect. A thermal healing process at 140 °C for 1 h was carried out on specimens broken in fracture toughness tests, performed under quasi-static and impact conditions, and healing efficiency (HE) was evaluated as the ratio of critical stress intensity factors of healed and virgin samples. All the compatibilizers increased HE, especially E-GMA, achieving 28.5% and 68% in quasi-static and impact conditions, respectively. SEM images of specimens tested in quasi-static conditions showed that all the compatibilizers induced PA6 plasticization and crack corrugation, thus hindering COC flow in the crack zone. Conversely, under impact conditions, E-GMA led to the formation of brittle fractures with planar surfaces, promoting COC flow and thus higher HE values. This study demonstrated that compatibilizers, loading mode, and fracture surface morphologies strongly influenced self-healing performance. Full article