Journal articles on the topic 'PDMS Replica molding'
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Huang, Chiung Fang, Jeol Long Lee, Yung Kang Shen, Chi Wei Wu, Yi Lin, Sung Chih Hsu, Ming Wei Wu, and Chung Yu Kao. "Analysis for Replication and Surface Roughness of Micro-Feature of Silicon Mold Insert by UV-LIGA Method." Advanced Materials Research 47-50 (June 2008): 443–46. http://dx.doi.org/10.4028/www.scientific.net/amr.47-50.443.
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This study demonstrates the replication property and surface roughness for metal micro-mold that combines the replica molding (REM) and electroforming techniques. The micro-mold firstly uses the silicon wafer to fabricate the master mold by UV-LIGA method, and then uses the sputtering method to sputter the Ni element as the seed layer on the surface of master mold. The electroforming method manufactures the Ni mold insert from the master mold with seed layer. Finally, this study uses the PDMS material to replicate the micro-feature from the Ni mold insert by replica molding. This study indicates the replication property and surface roughness of different micro-feature shapes and sizes (concave and convex) for Ni mold insert and molded PDMS.
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Li, Kan, Yaokang Zhang, Hongyu Zhen, Helin Wang, Shenghua Liu, Feng Yan, and Zijian Zheng. "Versatile biomimetic haze films for efficiency enhancement of photovoltaic devices." Journal of Materials Chemistry A 5, no. 3 (2017): 969–74. http://dx.doi.org/10.1039/c6ta07586j.
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Willems, Stan B. J., Jaccoline Zegers, Anton Bunschoten, R. Martijn Wagterveld, Fijs W. B. van Leeuwen, Aldrik H. Velders, and Vittorio Saggiomo. "COvalent monolayer patterns in Microfluidics by PLasma etching Open Technology – COMPLOT." Analyst 145, no. 5 (2020): 1629–35. http://dx.doi.org/10.1039/c9an02407g.
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Plasma microcontact patterning (PμCP) and replica molding were combined to make PDMS/glass microfluidic devices with β-cyclodextrin (β-CD) patterns attached covalently on the glass surface inside microchannels.
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Fang, Tao, Chen, Wang, Wu, Zhang, Zeng, Zhu, and Liu. "Microlens Fabrication by Replica Molding of Electro-Hydrodynamic Printing Liquid Mold." Micromachines 11, no. 2 (February 3, 2020): 161. http://dx.doi.org/10.3390/mi11020161.
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In this paper, we synergistically combine electrohydrodynamic (EHD) printing and replica molding for the fabrication of microlenses. Glycerol solution microdroplets was sprayed onto the ITO glass to form liquid mold by an EHD printing process. The liquid mold is used as a master to fabricate a polydimethylsiloxane (PDMS) mold. Finally, the desired micro-optical device can be fabricated on any substrate using a PDMS soft lithography mold. We demonstrate our strategy by generating microlenses of photocurable polymers and by characterizing their optical properties. It is a new method to rapidly and cost-effectively fabricate molds with small diameters by exploiting the advantages of EHD printing, while maintaining the parallel nature of soft-lithography.
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Shih, Teng-Kai, Chia-Fu Chen, Jeng-Rong Ho, and Fang-Tzu Chuang. "Fabrication of PDMS (polydimethylsiloxane) microlens and diffuser using replica molding." Microelectronic Engineering 83, no. 11-12 (November 2006): 2499–503. http://dx.doi.org/10.1016/j.mee.2006.05.006.
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Amadeo, Filippo, Prithviraj Mukherjee, Hua Gao, Jian Zhou, and Ian Papautsky. "Polycarbonate Masters for Soft Lithography." Micromachines 12, no. 11 (November 13, 2021): 1392. http://dx.doi.org/10.3390/mi12111392.
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Fabrication of microfluidic devices by soft lithography is by far the most popular approach due to its simplicity and low cost. The approach relies on casting of elastomers, such as polydimethylsiloxane (PDMS), on masters fabricated from photoresists on silicon substrates. These masters, however, can be expensive, complicated to fabricate, and fragile. Here we describe an optimized replica molding approach to preserve the original masters by heat molding of polycarbonate (PC) sheets on PDMS molds. The process is faster and simpler than previously reported methods and does not result in a loss of resolution or aspect ratio for the features. The generated PC masters were used to successfully replicate a wide range of microfluidic devices, including rectangular channels with aspect ratios from 0.025 to 7.3, large area spiral channels, and micropost arrays with 5 µm spacing. Moreover, fabrication of rounded features, such as semi-spherical microwells, was possible and easy. Quantitative analysis of the replicated features showed variability of <2%. The approach is low cost, does not require cleanroom setting or hazardous chemicals, and is rapid and simple. The fabricated masters are rigid and survive numerous replication cycles. Moreover, damaged or missing masters can be easily replaced by reproduction from previously cast PDMS replicas. All of these advantages make the PC masters highly desirable for long-term preservation of soft lithography masters for microfluidic devices.
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Hlúbiková, D., A. T. Luís, V. Vaché, L. Ector, L. Hoffmann, and P. Choquet. "Optimization of the replica molding process of PDMS using pennate diatoms." Journal of Micromechanics and Microengineering 22, no. 11 (September 28, 2012): 115019. http://dx.doi.org/10.1088/0960-1317/22/11/115019.
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Folch, A., A. Ayon, O. Hurtado, M. A. Schmidt, and M. Toner. "Molding of Deep Polydimethylsiloxane Microstructures for Microfluidics and Biological Applications." Journal of Biomechanical Engineering 121, no. 1 (February 1, 1999): 28–34. http://dx.doi.org/10.1115/1.2798038.
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Here we demonstrate the microfabrication of deep (>25 μm) polymeric microstructures created by replica-molding polydimethylsiloxane (PDMS) from microfabricated Si substrates. The use of PDMS structures in microfluidics and biological applications is discussed. We investigated the feasibility of two methods for the microfabrication of the Si molds: deep plasma etch of silicon-on-insulator (SOI) wafers and photolithographic patterning of a spin-coated photoplastic layer. Although the SOI wafers can be patterned at higher resolution, we found that the inexpensive photoplastic yields similar replication fidelity. The latter is mostly limited by the mechanical stability of the replicated PDMS structures. As an example, we demonstrate the selective delivery of different cell suspensions to specific locations of a tissue culture substrate resulting in micropatterns of attached cells.
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Zhang, Zhongle, Yuan Luo, Xiaofeng Nie, Duli Yu, and Xiaoxing Xing. "A one-step molded microfluidic chip featuring a two-layer silver-PDMS microelectrode for dielectrophoretic cell separation." Analyst 145, no. 16 (2020): 5603–14. http://dx.doi.org/10.1039/d0an01085e.
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Ko, Yong Jun, Dae Jin Kim, Woong Cho, Yoo Min Ahn, and Seung Yong Hwang. "Glass-Polydimethysiloxane Hybrid Microthermostat for Restriction Enzyme Digestion." Materials Science Forum 544-545 (May 2007): 335–38. http://dx.doi.org/10.4028/www.scientific.net/msf.544-545.335.
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This paper reports a low-cost microthermostat that is able to maintain a constant temperature necessary for restriction enzyme digestion. Polydimethylsiloxane (PDMS) and Pyrex glass were used to make the microthermostat, because PDMS is a cheap and mass-producible material and both PDMS and glass have very good biocompatibility compared to the more commonly used silicon. A heater made of Au wiring patterned on Pyrex glass was used to control the temperature. A PDMS replica molding technique was used to fabricate a reaction chamber with 3.6 μl capacity. Restriction enzyme digestion was performed by using the fabricated microthermostat and by a conventional method. Then, using gel electrophoresis, we compared results between the microthermostat and conventional methods. It was found that restriction enzyme digestion using the microthermostat required 5 min of heating.
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Dhall, Atul, Tim Masiello, Suhasini Gattu, Matt Strohmayer, Logan Butt, Lewdeni Pathirannehelage Madhubhani Hemachandra, Sandra Schujman, et al. "Characterization and Neutral Atom Beam Surface Modification of a Clear Castable Polyurethane for Biomicrofluidic Applications." Surfaces 2, no. 1 (February 1, 2019): 100–116. http://dx.doi.org/10.3390/surfaces2010009.
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Polyurethanes (PU) are a broad class of polymers that offer good solvent compatibility and a wide range of properties that can be used to generate microfluidic layers. Here, we report the first characterization of a commercially available Shore 80D polyurethane (Ultraclear™ 480N) for biomicrofluidic applications. Studies included comparing optical clarity with Polydimethylsiloxane (PDMS) and using high-fidelity replica molding to produce solid PU structures from the millimeter to nanometer scales. Additionally, we report the first use of NanoAccel™ treatment in Accelerated Neutral Atom Beam (ANAB) mode to permanently roughen the surface of PU and improve the adhesion of breast cancer cells (MDA-MB-231) on PU. Surface energy measurements using Owens-Wendt equations indicate an increase in polar and total surface energy due to ANAB treatment. Fourier-transform infrared (FTIR) spectroscopy in attenuated total reflectance (ATR) mode was used to demonstrate that the treatment does not introduce any new types of functional groups on the surface of Ultraclear™ PU. Finally, applicability in rapid prototyping for biomicrofluidics was demonstrated by utilizing a 3D-printing-based replica molding strategy to create PU microfluidic layers. These layers were sealed to polystyrene (PS) bases to produce PU-PS microfluidic chips. Ultraclear™ PU can serve as a clear and castable alternative to PDMS in biomicrofluidic studies.
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Sczech, Ronny, Steffen Howitz, and Michael Mertig. "Diffusion and Electrophoretic Transport of DNA Polymers in Microfluidic Channels Made of PDMS." Defect and Diffusion Forum 312-315 (April 2011): 1091–96. http://dx.doi.org/10.4028/www.scientific.net/ddf.312-315.1091.
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DNA molecules can be transported through microchannels with help of electrophoresis and flow. Confinement of DNA molecules leads to elongation of their unconstrained equilibrium configuration when passing the microchannel. Application of electrical fields reduces the mobility and entails DNA trapping because of high gradients of the field due to a decrease in the channels’ magnitude. Microfluidic channels in polydimethylsiloxane (PDMS) were formed by soft replica molding technology combining micro- and nanofluidic features. The applicability of the hybrid micro- and nanofluidic PDMS structures for single molecule observation and manipulation was demonstrated by introducing single molecules of λ-DNA into the channels using optimized conditions for the applied potential and flow.
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Ng, Pui Fai, Ka I. Lee, Mo Yang, and Bin Fei. "Fabrication of 3D PDMS Microchannels of Adjustable Cross-Sections via Versatile Gel Templates." Polymers 11, no. 1 (January 4, 2019): 64. http://dx.doi.org/10.3390/polym11010064.
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Flexible gel fibers with high stretchability were synthesized from physically cross-linked agar and covalently cross-linked polyacrylamide networks. Such gel material can withstand the temperature required for thermal curing of polydimethylsiloxane (PDMS), when the water in the gel was partially replaced with ethylene glycol. This gel template supported thermal replica molding of PDMS to produce high quality microchannels. Microchannels with different cross sections and representative 3D structures, including bifurcating junction, helical and weave networks, were smoothly fabricated, based on the versatile manipulation of gel templates. This gel material was confirmed as a flexible and reliable template in fabricating 3D microfluidic channels for potential devices.
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Bae, Eun-Jeong, Hyeong-Kyu Maeng, Ji-Soo Shin, Dong-Wook Park, Young-Wook Park, and Dong-Hyun Baek. "Micro-Sphere PDMS for Enhancing Light Extraction in Organic Light-Emitting Devices." Nanomaterials 12, no. 12 (June 10, 2022): 2007. http://dx.doi.org/10.3390/nano12122007.
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We present a micro-sphere PDMS film to improve the external quantum efficiency (EQE) in OLEDs. The micro-sphere PDMS film was fabricated with the breath figure (BF) and replica molding process. The polymer template was prepared through stabilization of the water droplets at the polymer/water interface. The micro-sphere PDMS film was fabricated by pouring PDMS on the polymer template. At a 45 mg/mL concentration, the size of the spheres was approximately 12.3 µm and they had the most circular shape, so this condition yielded the best performance, with an improvement of 33% in the EQE and the widest viewing angle ranging from 0° to 50°. As a result, the sphere film’s size and distribution seem to play important roles in enhancing the EQE in OLEDs. Furthermore, the flexible sphere film based on polymeric materials could offer an effective, large-scale, mass-produced product and a simple process and approach to achieve high efficiency in flexible OLEDs.
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Zhong, Kejun, Yiqing Gao, Feng Li, Zhimin Zhang, and Ningning Luo. "Fabrication of PDMS microlens array by digital maskless grayscale lithography and replica molding technique." Optik 125, no. 10 (May 2014): 2413–16. http://dx.doi.org/10.1016/j.ijleo.2013.10.082.
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Ongaro, C., A. Betti, B. Zardin, V. Siciliani, L. Orazi, J. Bertacchini, and M. Borghi. "An Alternative Solution for Microfluidic Chip Fabrication." Journal of Physics: Conference Series 2385, no. 1 (December 1, 2022): 012029. http://dx.doi.org/10.1088/1742-6596/2385/1/012029.
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Abstract This paper focuses on microfluidic devices, widely used in bioengineering. Their fabrication for research is almost entirely made of PDMS (a silicone), using photolithography and replica molding technologies, which involve many processing steps, sealed with a glass layer by plasma bonding. Our solution fabricates devices in just two steps, laser ablation of a glass layer, technology already extensively tested, and sealing with a commercial silicone layer by plasma bonding, drastically reducing skilled human operations and lead time. The paper describes the technologies with PDMS and with our solution, the design of a microfluidic test chip, the laser ablation and assessment by a confocal microscope of the microfluidic circuit in the glass layer of the chip, the plasma bonding of glass layers with PDMS and two other commercial silicones utilizing a grid of different plasma parameters, the qualitative assessment of the plasma bonding and choosing of a silicone as PDMS substitute, the extensive test on the bonding quality by two different pressure circuits on a batch of microfluidic chips realized with our proposed technology.
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Abidin, Ummikalsom, Burhanuddin Yeop Majlis, and Jumril Yunas. "Design, Simulation and Fabrication of Polydimethylsiloxane (PDMS) Microchannel for Lab-on-Chip (LoC) Applications." Applied Mechanics and Materials 819 (January 2016): 420–24. http://dx.doi.org/10.4028/www.scientific.net/amm.819.420.
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Microchannel of micron-to milimeter in dimension has been immensely used for fluid handling in transporting, mixing and separating biological cells in Lab-on-Chip (LoC) applications. In this paper, design, simulation and fabrication of Polydimethylsiloxane (PDMS) microfluidic channel are presented. The microchannel is designed with one inlet and outlet. A reservoir or chamber is proposed as an extra component in the microchannel design for ease of separating the intended biological cells as used in LoC magnetic separator and micro-incubator. Finite Element Analysis (FEA) shows laminar flow characteristic is maintained in the proposed microchannel design operating at volumetric flow rate between 0.5 to 1000 μL/min. In addition, pressure drop data across the microchannel are also been obtained from the FEA in determining the safe operation limit of the microchannel. The PDMS microchannels of two different chamber geometries have been successfully fabricated using replica molding technique from SU-8 negative photoresist mold. The fabricated SU-8 mold and the PDMS microchannel structure dimension are characterized using Scanning Electron Microscopy (SEM). Reversible bonding of PDMS microchannel layer and PDMS tubing layer has successfully accomplished by activating the PDMS surfaces using corona discharge. The preliminary testing of the microchannel confirmed its function for LoC continuous flow applications.
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Dong, Shen, Xiao Li Zhao, Jing He Wang, Zheng Qiang Li, Tao Sun, and Ying Chun Liang. "Fabrication of Patterned Metal Films on Organic Substrates by Transfer Printing." Materials Science Forum 532-533 (December 2006): 524–27. http://dx.doi.org/10.4028/www.scientific.net/msf.532-533.524.
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Here a simple and direct method based on transfer printing has beep developed, in which rigid stamps transfer metal films deposited on the relief surface of the stamps onto patterned organic substrates. Ultra-precision machining technology is combined with conventional photolithography to fabricate patterned Si stamps and organic substrates by replica molding. Experiment results indicate that patterned metal films on Silicon stamps were successfully transferred onto PDMS substrates. Fabrication of patterned metal films on organic substrates by transfer printing may suit for fabricating sub-micrometer and nanometer scale features in a single process.
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Thakur, Raviraj, and Gene Y. Fridman. "Low Cost, Ease-of-Access Fabrication of Microfluidic Devices Using Wet Paper Molds." Micromachines 13, no. 9 (August 27, 2022): 1408. http://dx.doi.org/10.3390/mi13091408.
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Rapid prototyping methods enable the widespread adoption of microfluidic technologies by empowering end-users from non-engineering disciplines to make devices using processes that are rapid, simple and inexpensive. In this work, we developed a liquid molding technique to create silicone/PDMS microfluidic devices by replica molding. To construct a liquid mold, we use inexpensive adhesive-backed paper, an acetate backing sheet, and an off-the-shelf digital cutter to create paper molds, which we then wet with predetermined amounts of water. Due to the immiscibility of water and PDMS, mold patterns can be effectively transferred onto PDMS similarly to solid molds. We demonstrate the feasibility of these wet paper molds for the fabrication of PDMS microfluidic devices and assess the influence of various process parameters on device yield and quality. This method possesses some distinct benefits compared to conventional techniques such as photolithography and 3D printing. First, we demonstrate that the shape of a channel’s cross-section may be altered from rectangular to semicircular by merely modifying the wetting parameters. Second, we illustrate how electrical impedance can be utilized as a marker for inspecting mold quality and identifying defects in a non-invasive manner without using visual tools such as microscopes or cameras. As a proof-of-concept device, we created a microfluidic T-junction droplet generator to produce water droplets in mineral oil ranging in size from 1.2 µL to 75 µL. We feel that this technology is an excellent addition to the microfluidic rapid prototyping toolbox and will find several applications in biological research.
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Graf, Neil J., and Michael T. Bowser. "Effect of cross sectional geometry on PDMS micro peristaltic pump performance: comparison of SU-8 replica molding vs. micro injection molding." Analyst 138, no. 19 (2013): 5791. http://dx.doi.org/10.1039/c3an00671a.
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Cho, Woong, Yong Jun Ko, Yoo Min Ahn, Joon Yong Yoon, and Nahm Gyoo Cho. "Surface Modification Effect of Wettability on the Performance of PDMS-Based Valveless Micropump." Key Engineering Materials 326-328 (December 2006): 297–300. http://dx.doi.org/10.4028/www.scientific.net/kem.326-328.297.
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Experimental investigation and numerical simulation on the effect of surface wettability on the performance of a polydimethylsiloxane (PDMS) based diffuser micropump are presented. A valveless micro membrane pump with piezoelectric actuation has been examined. Using a replica molding technique, the valveless micropump was made of PDMS on a Pyrex glass substrate. A thin piezoelectric (PZT) disc was used as an actuator. Poly vinyl alcohol (PVA) and octadecyltrichlorosilane (OTS) coatings, which make the coated surface hydrophilic and hydrophobic, respectively, were used to modify the surface wettability inside the pump. In our experiments, the contact angle of the PDMS surface changed from 96.6 o to 29.1 o and 99.6 o by PVA and OTS coatings, respectively, and the contact angle of glass changed from 33.2 o to 17.5 o and 141.8 o. A self-priming process was numerically simulated in a diffuser element using a computational fluid dynamics program (CFD-ACE+). The results show that fewer gas bubbles were created in the hydrophilic coated pump than in the hydrophobic coated one as time progressed. This agrees well with experimental observations. Steady-state flow rates of the micropump were measured. Compared to the non-coated pump, the flow rate increased slightly with the hydrophobic coating but decreased with the hydrophilic coating. We determine that surface wettability significantly affects the performance of a PDMS-based micropump.
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Schneider, Stefan, Eduardo J. S. Brás, Oliver Schneider, Katharina Schlünder, and Peter Loskill. "Facile Patterning of Thermoplastic Elastomers and Robust Bonding to Glass and Thermoplastics for Microfluidic Cell Culture and Organ-on-Chip." Micromachines 12, no. 5 (May 18, 2021): 575. http://dx.doi.org/10.3390/mi12050575.
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The emergence and spread of microfluidics over the last decades relied almost exclusively on the elastomer polydimethylsiloxane (PDMS). The main reason for the success of PDMS in the field of microfluidic research is its suitability for rapid prototyping and simple bonding methods. PDMS allows for precise microstructuring by replica molding and bonding to different substrates through various established strategies. However, large-scale production and commercialization efforts are hindered by the low scalability of PDMS-based chip fabrication and high material costs. Furthermore, fundamental limitations of PDMS, such as small molecule absorption and high water evaporation, have resulted in a shift toward PDMS-free systems. Thermoplastic elastomers (TPE) are a promising alternative, combining properties from both thermoplastic materials and elastomers. Here, we present a rapid and scalable fabrication method for microfluidic systems based on a polycarbonate (PC) and TPE hybrid material. Microstructured PC/TPE-hybrid modules are generated by hot embossing precise features into the TPE while simultaneously fusing the flexible TPE to a rigid thermoplastic layer through thermal fusion bonding. Compared to TPE alone, the resulting, more rigid composite material improves device handling while maintaining the key advantages of TPE. In a fast and simple process, the PC/TPE-hybrid can be bonded to several types of thermoplastics as well as glass substrates. The resulting bond strength withstands at least 7.5 bar of applied pressure, even after seven days of exposure to a high-temperature and humid environment, which makes the PC/TPE-hybrid suitable for most microfluidic applications. Furthermore, we demonstrate that the PC/TPE-hybrid features low absorption of small molecules while being biocompatible, making it a suitable material for microfluidic biotechnological applications.
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Jeon, Won Jin, Chee Burm Shin, and Jong Heop Yi. "Fabrication of a Microfluidic Device for the Detection of a Specific Biomolecule." Advances in Science and Technology 57 (September 2008): 105–10. http://dx.doi.org/10.4028/www.scientific.net/ast.57.105.
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Mutation and aggregation of superoxide dismutase (SOD) are reported as one of the causes of amyotrophic lateral sclerosis (ALS). To detect SOD1 protein from the motor neuron, surface plasmon resonance (SPR) analysis was adopted due to its advantages in the in-situ biomolecular recognition by surface analysis without labeling. For the patterning of protein antigens at Au surface for use in SPR imaging experiments, microfluidic devices were fabricated with polydimethylsiloxane (PDMS) by replica molding method. They were designed for the solution to flow by capillary force only without using any additional pumping equipments or flow controllers. Performance of microfluidic devices was verified by the simple microfluidic experiments, and multiple protein-patterned sensor surfaces were constructed by using these microfluidic devices.
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Baczyński, Szymon, Piotr Sobotka, Kasper Marchlewicz, Artur Dybko, and Katarzyna Rutkowska. "Low-cost, widespread and reproducible mold fabrication technique for PDMS-based microfluidic photonic systems." Photonics Letters of Poland 12, no. 1 (March 31, 2020): 22. http://dx.doi.org/10.4302/plp.v12i1.981.
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In this letter the possibility of low-cost fabrication of molds for PDMS-based photonic microstructures is considered. For this purpose, three different commercially available techniques, namely UV-curing of the capillary film, 3D SLA printing and micromilling, have been analyzed. Obtained results have been compared in terms of prototyping time, quality, repeatability, and re-use of the mold for PDMS-based microstructures fabrication. Prospective use for photonic systems, especially optofluidic ones infiltrated with liquid crystalline materials, have been commented. Full Text: PDF References:K. Sangamesh, C.T. Laurencin, M. Deng, Natural and Synthetic Biomedical Polymers (Elsevier, Amsterdam 2004). [DirectLink]A. Mata et. al, "Characterization of Polydimethylsiloxane (PDMS) Properties for Biomedical Micro/Nanosystems", Biomed. Microdev. 7(4), 281 (2005). [CrossRef]I. Rodríguez-Ruiz et al., "Photonic Lab-on-a-Chip: Integration of Optical Spectroscopy in Microfluidic Systems", Anal. Chem. 88(13), 6630 (2016). [CrossRef]SYLGARD™ 184 Silicone Elastomer, Technical Data Sheet [DirectLink]N.E. Stankova et al., "Optical properties of polydimethylsiloxane (PDMS) during nanosecond laser processing", Appl. Surface Science 374, 96 (2016) [CrossRef]J.C. McDonald et al., "Fabrication of microfluidic systems in poly(dimethylsiloxane)", Electrophoresis 21(1), 27 (2000). [CrossRef]T. Fujii, "PDMS-based microfluidic devices for biomedical applications", Microelectronic Eng. 61, 907 (2002). [CrossRef]F. Schneider et al., "Process and material properties of polydimethylsiloxane (PDMS) for Optical MEMS", Sensors Actuat. A: Physical 151(2), 95 (2009). [CrossRef]T.K. Shih et al., "Fabrication of PDMS (polydimethylsiloxane) microlens and diffuser using replica molding", Microelectronic Eng. 83(11-12), 2499 (2006). [CrossRef]K. Rutkowska et al. "Electrical tuning of the LC:PDMS channels", PLP, 9, 48-50 (2017). [CrossRef]D. Kalinowska et al., "Studies on effectiveness of PTT on 3D tumor model under microfluidic conditions using aptamer-modified nanoshells", Biosensors Bioelectr. 126, 214 (2019).[CrossRef]N. Bhattacharjee et al., "The upcoming 3D-printing revolution in microfluidics", Lab on a Chip 16(10), 1720 (2016). [CrossRef]I.R.G. Ogilvie et al., "Reduction of surface roughness for optical quality microfluidic devices in PMMA and COC", J. Micromech. Microeng. 20(6), 065016 (2010). [CrossRef]D. Gomez et al., "Femtosecond laser ablation for microfluidics", Opt. Eng. 44(5), 051105 (2005). [CrossRef]Y. Hwang, R.N. Candler, "Non-planar PDMS microfluidic channels and actuators: a review", Lab on a Chip 17(23), 3948 (2017). [CrossRef]
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Kim, Minseok S., Hyundoo Hwang, Youn-Suk Choi, and Je-Kyun Park. "Microfluidic Micropillar Arrays for 3D Cell Culture." Open Biotechnology Journal 2, no. 1 (August 6, 2008): 224–28. http://dx.doi.org/10.2174/1874070700802010224.
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Cell-based assays are one of the most important steps to select huge amount of drug candidates in drug discovery. To get more credible assay results, cell culture in the form of microscale environment and three-dimension has been exploited by microfluidic hydrodynamic focusing. However, the method still needs an enhanced reliability of scaffold formation and fast cell immobilization in a microchannel. In this report, we fabricated a microfluidic micropillar arrays (MMA) platform for cell culture using a poly(dimethylsiloxane) (PDMS) replica molding process. Peptide hydrogel and Matrigel were nicely patterned along the micropillars by surface tension. In addition, a linear concentration gradient profile was presented in a stripe-shaped Matrigel matrix and the simulation result with computational fluid dynamics (CFD) solver was corresponded to the experimental profile. The MMA platform was successfully applied to the hepatocellular carcinoma cell (HepG2) culture for 2 days.
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Milana, Edoardo, Tommaso Santaniello, Paolo Azzini, Lorenzo Migliorini, and Paolo Milani. "Fabrication of High-Aspect-Ratio Cylindrical Micro-Structures Based on Electroactive Ionogel/Gold Nanocomposite." Applied Nano 1, no. 1 (October 26, 2020): 59–69. http://dx.doi.org/10.3390/applnano1010005.
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We present a fabrication process to realize 3D high-aspect-ratio cylindrical micro-structures of soft ionogel/gold nanocomposites by combining replica molding and Supersonic Cluster Beam Deposition (SCBD). Cylinders’ metallic masters (0.5 mm in diameter) are used to fabricate polydimethylsiloxane (PDMS) molds, where the ionogel is casted and UV cured. The replicated ionogel cylinders (aspect ratio > 20) are subsequently metallized through SCBD to integrate nanostructured gold electrodes (150 nm thick) into the polymer. Nanocomposite thin films are characterized in terms of electrochemical properties, exhibiting large double layer capacitance (24 μF/cm2) and suitable ionic conductivity (0.05 mS/cm) for charge transport across the network. Preliminary actuation tests show that the nanocomposite is able to respond to low intensity electric fields (applied voltage from 2.5 V to 5 V), with potential applications for the development of artificial smart micro-structures with motility behavior inspired by that of natural ciliate systems.
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Lee, Woo Ram, Changkyun Im, Hae-Yong Park, Jong-Mo Seo, and Jun-Min Kim. "Fabrication of Convex PDMS–Parylene Microstructures for Conformal Contact of Planar Micro-Electrode Array." Polymers 11, no. 9 (September 2, 2019): 1436. http://dx.doi.org/10.3390/polym11091436.
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Polymer-based micro-electrode arrays (MEAs) are gaining attention as an essential technology to understand brain connectivity and function in the field of neuroscience. However, polymer based MEAs may have several challenges such as difficulty in performing the etching process, difficulty of micro-pattern generation through the photolithography process, weak metal adhesion due to low surface energy, and air pocket entrapment over the electrode site. In order to compensate for the challenges, this paper proposes a novel MEA fabrication process that is performed sequentially with (1) silicon mold preparation; (2) PDMS replica molding, and (3) metal patterning and parylene insulation. The MEA fabricated through this process possesses four arms with electrode sites on the convex microstructures protruding about 20 μm from the outermost layer surface. The validity of the convex microstructure implementation is demonstrated through theoretical background. The electrochemical impedance magnitude is 204.4 ± 68.1 kΩ at 1 kHz. The feasibility of the MEA with convex microstructures was confirmed by identifying the oscillation in the beta frequency band (13–30 Hz) in the electrocorticography signal of a rat olfactory bulb during respiration. These results suggest that the MEA with convex microstructures is promising for applying to various neural recording and stimulation studies.
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Jiménez-Díaz, Edgar, Mariel Cano-Jorge, Diego Zamarrón-Hernández, Lucia Cabriales, Francisco Páez-Larios, Aarón Cruz-Ramírez, Genaro Vázquez-Victorio, Tatiana Fiordelisio, and Mathieu Hautefeuille. "Micro–Macro: Selective Integration of Microfeatures Inside Low-Cost Macromolds for PDMS Microfluidics Fabrication." Micromachines 10, no. 9 (August 30, 2019): 576. http://dx.doi.org/10.3390/mi10090576.
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Microfluidics has become a very promising technology in recent years, due to its great potential to revolutionize life-science solutions. Generic microfabrication processes have been progressively made available to academic laboratories thanks to cost-effective soft-lithography techniques and enabled important progress in applications like lab-on-chip platforms using rapid- prototyping. However, micron-sized features are required in most designs, especially in biomimetic cell culture platforms, imposing elevated costs of production associated with lithography and limiting the use of such devices. In most cases, however, only a small portion of the structures require high-resolution and cost may be decreased. In this work, we present a replica-molding method separating the fabrication steps of low (macro) and high (micro) resolutions and then merging the two scales in a single chip. The method consists of fabricating the largest possible area in inexpensive macromolds using simple techniques such as plastics micromilling, laser microfabrication, or even by shrinking printed polystyrene sheets. The microfeatures were made on a separated mold or onto existing macromolds using photolithography or 2-photon lithography. By limiting the expensive area to the essential, the time and cost of fabrication can be reduced. Polydimethylsiloxane (PDMS) microfluidic chips were successfully fabricated from the constructed molds and tested to validate our micro–macro method.
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Kafash Hoshiar, Ali, Sungwoong Jeon, Kangho Kim, Seungmin Lee, Jin-young Kim, and Hongsoo Choi. "Steering Algorithm for a Flexible Microrobot to Enhance Guidewire Control in a Coronary Angioplasty Application." Micromachines 9, no. 12 (November 23, 2018): 617. http://dx.doi.org/10.3390/mi9120617.
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Magnetically driven microrobots have been widely studied for various biomedical applications in the past decade. An important application of these biomedical microrobots is heart disease treatment. In intravascular treatments, a particular challenge is the submillimeter-sized guidewire steering; this requires a new microrobotic approach. In this study, a flexible microrobot was fabricated by the replica molding method, which consists of three parts: (1) a flexible polydimethylsiloxane (PDMS) body, (2) two permanent magnets, and (3) a micro-spring connector. A mathematical model was developed to describe the relationship between the magnetic field and the deformation. A system identification approach and an algorithm were proposed for steering. The microrobot was fabricated, and the models for steering were experimentally validated under a magnetic field intensity of 15 mT. Limitations to control were identified, and the microrobot was steered in an arbitrary path using the proposed model. Furthermore, the flexible microrobot was steered using the guidewire within a three-dimensional (3D) transparent phantom of the right coronary artery filled with water, to show the potential application in a realistic environment. The flexible microrobot presented here showed promising results for enhancing guidewire steering in percutaneous coronary intervention (PCI).
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Koppaka, Saisneha, Kevin S. Zhang, Myra Kurosu Jalil, Lucas R. Blauch, and Sindy K. Y. Tang. "Fabrication of 3D Micro-Blades for the Cutting of Biological Structures in a Microfluidic Guillotine." Micromachines 12, no. 9 (August 24, 2021): 1005. http://dx.doi.org/10.3390/mi12091005.
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Micro-blade design is an important factor in the cutting of single cells and other biological structures. This paper describes the fabrication process of three-dimensional (3D) micro-blades for the cutting of single cells in a microfluidic “guillotine” intended for fundamental wound repair and regeneration studies. Our microfluidic guillotine consists of a fixed 3D micro-blade centered in a microchannel to bisect cells flowing through. We show that the Nanoscribe two-photon polymerization direct laser writing system is capable of fabricating complex 3D micro-blade geometries. However, structures made of the Nanoscribe IP-S resin have low adhesion to silicon, and they tend to peel off from the substrate after at most two times of replica molding in poly(dimethylsiloxane) (PDMS). Our work demonstrates that the use of a secondary mold replicates Nanoscribe-printed features faithfully for at least 10 iterations. Finally, we show that complex micro-blade features can generate different degrees of cell wounding and cell survival rates compared with simple blades possessing a vertical cutting edge fabricated with conventional 2.5D photolithography. Our work lays the foundation for future applications in single cell analyses, wound repair and regeneration studies, as well as investigations of the physics of cutting and the interaction between the micro-blade and biological structures.
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Mittal, Ekansh, and Young Bock Kang. "Abstract 6031: Microfluidics: Simulating the gut microbiome for early cancer detection." Cancer Research 82, no. 12_Supplement (June 15, 2022): 6031. http://dx.doi.org/10.1158/1538-7445.am2022-6031.
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Abstract Background: Cancer is the second leading cause of death globally and ~39.5% of people will be diagnosed with cancer at some point during their lifetimes. Thus, there is an unmet need to identify novel strategies for early cancer detection and prevention. The emerging evidence suggests that the gut microbiome has a role in promoting cancer. This microbiome including bacteria plays a vital role in maintaining homeostasis in the body. An imbalance in bacterial composition may cause diseases including cancer. Here we developed a microfluidic chip that can accurately simulate the gut microbiome to test the effects of bacteria and therapies on cancer cells. Methods and Results: To test the causal effect of bacteria on cancer, we developed a new high-throughput microfluidic device for simulating the environment of the gut. Initially, we used the photolithography technique where we designed the chip in AutoCAD and fabricated using photoresist resins and Polydimethylsiloxane (PDMS). Next, we tested the effect of bacteria on the growth of colorectal cancer cells. For this, we cultured colorectal cancer cells (HCT-116) with lipopolysaccharide (LPS), which is found in the outer membrane of bacteria, as well as the Bacillus bacteria in our microfluidics. Our data show that both LPS and Bacillus significantly accelerate the growth of cancer cells 2.02 times (p value = 0.012) and 1.58 times (p value = 0.011), respectively, over a 4 day culture period. These results show that the increased presence of certain bacteria can promote cancer cell growth and that our chip can be used to test the specific correlation between bacteria and cancer cell growth. The previously described method was inefficient and time-consuming. To overcome this limitation, we designed a new chip that allows running 16 samples at once with improved efficiency and accuracy. The template of the device that had 16 microfluidic channels was printed by a 3D printer and used for PDMS replica molding. The PDMS device was attached to the modified multiwell plate to feed media to and collect waste from each channel in a high-throughput manner. In the initial design, the bacteria grew faster than cancer cells taking over the chips. Our new design has dual layered chambers to keep bacteria and cancer cells separated by a membrane, allowing only bacterial secretions to pass through the membrane to cancer cells, mimicking the human gut. The new design also allowed the chip to maintain continuous microfluidic flow and a hypoxic environment. Conclusion: Our research demonstrates that the new microfluidic device has broader implications including simulating other body organs such as the lung and liver, and testing the impact of viruses such as influenza and COVID-19 on human cells. This device can be used to test both the effect of bacteria and new treatment on clinical samples for the identification of personalized therapy, thus reducing the need for mouse model testing, which is a lengthy and expensive process. Citation Format: Ekansh Mittal, Young Bock Kang. Microfluidics: Simulating the gut microbiome for early cancer detection [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6031.
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Snyder, Jessica, Ae Rin Son, Qudus Hamid, and Wei Sun. "Fabrication of Microfluidic Manifold by Precision Extrusion Deposition and Replica Molding for Cell-Laden Device." Journal of Manufacturing Science and Engineering 138, no. 4 (October 27, 2015). http://dx.doi.org/10.1115/1.4031551.
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A PED (precision extrusion deposition)/replica molding process enables scaffold guided tissue engineering of a heterocellular microfluidic device. We investigate two types of cell-laden devices: the first with a 3D microfluidic manifold fully embedded in a PDMS (polydimethylsiloxane) substrate and the second a channel network on the surface of the PDMS substrate for cell printing directly into device channels. Fully embedded networks are leak-resistant with simplified construction methods. Channels exposed to the surface are used as mold to hold bioprinted cell-laden matrix for controlled cell placement throughout the network from inlet to outlet. The result is a 3D cell-laden microfluidic device with improved leak-resistance (up to 2.0 mL/min), pervasive diffusion and control of internal architecture.
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Abidin, Ummikalsom, Jumril Yunas, and Burhanuddin Yeop Majlis. "FABRICATION AND TESTING OF POLYDIMETHYLSILOXANE (PDMS) MICROCHANNEL FOR LAB-ON-CHIP (LOC) MAGNETICALLY-LABELLED BIOLOGICAL CELLS SEPARATION." Jurnal Teknologi 78, no. 8-4 (August 16, 2016). http://dx.doi.org/10.11113/jt.v78.9587.
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Microfluidics channel of micron- to millimeter in dimension has been widely used for fluid handling in transporting, mixing and separating biological cells in Lab-on-Chip (LoC) applications. In this research, fabrication and testing of Polydimethylsiloxane (PDMS) microfluidic channel for Lab-on-chip magnetically-labelled biological cells separation is presented. The microchannel is designed with one inlet and outlet. A reservoir or chamber is proposed as an extra component of the microchannel design for ease of trapping the intended biological cells in LoC magnetic separator system. The PDMS microchannel of circular-shaped chamber geometry has been successfully fabricated using replica molding technique from SU-8 negative photoresist mold. An agglomerate-free microbeads flowing has been observed using the fabricated PDMS microchannel. Trapping of microbeads in the trapping chamber with 2.0 A current supply in the continuous microfluidics flow > 100 mL/min has also been demonstrated. In conclusion, a separation of biological cells labelled with magnetic microbeads is expected to be realized using the fabricated PDMS microchannel.
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Koh, Won-Gun, and Dae Nyun Kim. "Use of hydrogel microstructures as templates for protein immobilization." MRS Proceedings 1095 (2008). http://dx.doi.org/10.1557/proc-1095-ee08-08.
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AbstractIn this study, protein micropatterns were created on the surface of three-dimensional hydrogel microstructures. Poly(ethylene glycol)(PEG)-based hydrogel microstructures were fabricated on a glass substrate using a poly(dimethylsiloxane) (PDMS) replica as a molding insert and photolithography. The lateral dimension and height of the hydrogel microstructures were easily controlled by the feature size of the photomask and depth of the PDMS replica, respectively. Bovine serum albumin (BSA), a model protein, was covalently immobilized to the surface of the hydrogel microstructure via a 5-azidonitrobenzoyloxy N-hydroxysuccinimide bifunctional linker, which has a phenyl azide group and a protein-binding N-hydroxysuccinimide group on either end. The immobilization of BSA on the PEG hydrogel surface was demonstrated with XPS by confirming the formation of a new nitrogen peak, and the selective immobilization of fluorescent-labeled BSA on the outer region of the three-dimensional hydrogel micropattern was demonstrated by fluorescence. A hydrogel microstructure could immobilize two different enzymes separately, and sequential bienzymatic reaction was demonstrated by reacting glucose and Amplex Red with a hydrogel microstructure where glucose oxidase was immobilized on the surface and peroxidase was encapsulated.
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Borenstein, Jeffrey T., Kevin R. King, Hidetomi Terai, and Joseph P. Vacanti. "Capillary Formation In Microfabricated Polymer Scaffolds." MRS Proceedings 711 (2001). http://dx.doi.org/10.1557/proc-711-gg1.3.1.
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ABSTRACTOne of the primary challenges for engineering thick, complex tissues such as vital organs is the requirement for a vascular supply for nutrient and metabolite transfer. Earlier work has shown that Solid Freeform Fabrication techniques such as Three-Dimensional Printing (3DP) are capable of producing biodegradable scaffolds for the subsequent formation of a wide range of tissues and organs. While this approach shows great promise as a method for constructing complex tissues and organs in vitro, the resolution of the process is currently limited to length scales larger than the narrowest capillaries in the microcirculation. In this work, microfabrication technology is demonstrated as an approach for organizing endothelial cells in vitro at the size scale of the microcirculation. Standard process techniques utilized to build MEMS (MicroElectroMechanical Systems) devices include photolithography, silicon and glass micromachining, and polymer replica molding. Photolithography is used to print a model network of blood vessels on silicon wafers; the network is designed to replicate the fluid dynamics of the vasculature of a particular tissue or organ. A reverse image of the channel network is formed either by Deep Reactive Ion Etching (DRIE) of silicon or through the use of a thick negative-polarity photoresist (SU-8). Polymeric scaffolds are formed by replica molding, using the silicon wafer as a master mold. Microfluidic chambers have been constructed from PDMS and other biocompatible polymers. Initial cell seeding experiments demonstrate that rat lung endothelial cells attach in a single layer to the walls of these structures without occluding them, providing early evidence that MEMS process technology can serve as a method for organizing capillary networks.
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Graf, N. J., and M. T. Bower. "A Soft-Polymer Piezoelectric Bimorph Cantilever-Actuated Peristaltic Micropump." Journal of Medical Devices 3, no. 2 (June 1, 2009). http://dx.doi.org/10.1115/1.3147498.
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For this work, a peristaltic micropump was fabricated. Actuation of the micropump was accomplished with piezoelectric cantilevers. To date, a minimal number of soft polymer-based micropump designs, have explored the use of piezoelectric materials as actuators. The fluidic channel for the micropump was fabricated using PDMS and soft lithography. A novel and very simple template fabrication process was employed, where the use of a mask and clean room facilities was not required. Replica molding to the template produces both, a channel measuring ∼95μm in height, and a rounded cross-sectional geometry, the latter of which is known to be favorable for complete valve shutoff. Clamps were adhered to the tips of the cantilevers, and used to secure in place aluminum valves. The valves had finely machined tips [3mm×200μm(L×W)] on one surface. These tips served as contact points for the valve making contact with the PDMS membrane surface, and were used for the purpose of opening and closing the channels. The cantilevers were secured in place with in-house manufactured micropositioners, which were used to position the valves directly over the PDMS channel. The micropump was thoroughly tested where the variables characterized were maximum attainable backpressure, flow rate, valve open/close characteristics, and valve leakage. The effect of the phase difference (60°, 90°, and 120°) between the square wave signals delivered to each of the three cantilevers was investigated for flow rate and maximum attainable backpressure. Of the three signal phases, the 120° signal demonstrated the largest flow rate range of 52–575 nL/min (0.1–25 Hz), as well as the highest attainable backpressure value of 36,800 Pa (5.34 psi). The valve shutoff characteristics for this micropump was also examined. Fluorescein was trapped inside the microchannel, where the fluorescent signal was monitored throughout the valves open/close cycle with the aid of an epifluorescent microscope. It was found that the fluorescent signal went to zero with the valve fully closed, supporting the conclusion that the valve completely closes off the channel. Further evidence of this claim was demonstrated by observing the valve leakage characteristics. An electronic pressure sensor was used to collect data for this experiment, where it was found the valve was able to hold off 36,800 Pa (5.34 psi), only loosing 2% of this pressure over 10 minutes. In conclusion, it has been shown this micropump outperforms many existing micropump designs, and is suitable for integration into a variety of both macro, and microdevice platforms. Experiments are currently underway to examine how the flow and valving characteristics change for valves with different tip dimensions. A discussion will also be given for improved fabrication techniques, where injection molding is currently being used as the fabrication method to examine the performance changes associated with different cross-sectional PDMS channel geometries. The end goal for use of this micropump is twofold; 1) integration into a micro-free flow separation device, and 2) integration into a capillary electrophoresis instrument for use in direct-sampling neuroscience experiments.
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Choi, Kyung M., and John A. Rogers. "New Advances in Molding and Printing Processes for Organic/Plastic Electronics Using Chemically Modified Stiff, Photocured Poly (dimethylsiloxane) (PDMS) Elastomers Designed for Nano-Resolution Soft Lithography." MRS Proceedings 788 (2003). http://dx.doi.org/10.1557/proc-788-l9.6.
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ABSTRACTThe development of new materials for organic/plastic electronics allows us to fabricate novel devices through unconventional approaches. The ‘soft lithography technique’ has been widely used in replicating and fabricating small features. This technique is a low cost alternative to photolithography by generating structures from masters to substrates, which employ ‘elastomeric materials’, such as highly stretchable silicon elastomer, polydimethylsiloxane (PDMS) to replicate or transfer the original features to a variety of substrates by molding and printing processes. Since the resolution of pattern transfer significantly relies on the performance of polydimethylsiloxane (PDMS) stamp materials, commercial PDMS materials have shown limitations in high fidelity pattern transfer due to their low physical toughness and high thermal expansion coefficients. For those reasons, pattern fabrications using conventional PDMS materials are unable to satisfy our set of diverse demands, especially in the area of nano-scale replication. To achieve high performance in molding and printing, here we introduce a new strategy, design and synthesis of a modified PDMS silicon elastomer that is a stiffer and photocurable element to achieve our specific task of nano-scale resolution soft lithography. We then demonstrated its unique capabilities for the case of nano-features (300 nm wide) with narrow and tall heights (600 nm height) of photoresist, which is one of the most challenging ‘nano-patterning’ tasks in advanced soft lithography, which is often limited in its use at the nano-scale with other commercially available elastomers.
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Grabowski, M., and A. Buchenauer. "Valve Concepts for Microfluidic Cell Handling." Acta Polytechnica 50, no. 4 (January 4, 2010). http://dx.doi.org/10.14311/1229.
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In this paper we present various pneumatically actuated microfluidic valves to enable user-defined fluid management within a microfluidic chip. To identify a feasible valve design, certain valve concepts are simulated in ANSYS to investigate the pressure dependent opening and closing characteristics of each design. The results are verified in a series of tests. Both the microfluidic layer and the pneumatic layer are realized by means of soft-lithographic techniques. In this way, a network of channels is fabricated in photoresist as a molding master. By casting these masters with PDMS (polydimethylsiloxane) we get polymeric replicas containing the channel network. After a plasma-enhanced bonding process, the two layers are irreversibly bonded to each other. The bonding is tight for pressures up to 2 bar. The valves are integrated into a microfluidic cell handling system that is designed to manipulate cells in the presence of a liquid reagent (e.g. PEG – polyethylene glycol, for cell fusion). For this purpose a user-defined fluid management system is developed. The first test series with human cell lines show that the microfluidic chip is suitable for accumulating cells within a reaction chamber, where they can be flushed by a liquid medium.