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1
Akiyama, Yoshikatsu, Masayuki Yamato, and Teruo Okano. "Preparation of Poly(N-isopropylacrylamide) Grafted Polydimethylsiloxane by Using Electron Beam Irradiation." Journal of Robotics and Mechatronics 25, no. 4 (August 20, 2013): 631–36. http://dx.doi.org/10.20965/jrm.2013.p0631.
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A poly(N-isopropylacrylamide) (PIPAAm) grafted poly(dimethylsiloxane) (PDMS) surface was prepared as a temperature-responsive cell culture surface by using electron beam (EB) irradiation. Different chemical treatments to modify the bare PDMS surface were investigated for subsequent grafting of PIPAAm, and treatment conditions were optimized to prepare the temperature-responsive cell culture surface. The PDMS surface was initially activated to form silanol groups with conventional O2 plasma or hydrochloric acid (HCl) treatment. Activated PDMS surfaces were individually immobilized with three different conventional silane compounds, i.e., 3-mercaptopropyltrimethoxysilane (MerTMS), 3-methacryloxypropyltrimethoxysilane (MetTMS), and 3-aminopropyltrimethoxysilane (AmiTMS). O2 plasma treatment made PDMS more hydrophilic. In contrast, PDMS surfaces activated with HCl treatment were relatively hydrophobic. Observation of the activated PDMS surface modified with MerTMS, MetTMS, and AmiTMS indicated that these silane compounds had been favorably immobilized on plasma-treated PDMS surfaces. FT-IR/ATR analysis demonstrated that immobilized silane compounds enabled PIPAAm grafting on the PDMS surface. Cell attachment and detachment analysis also suggested that the PDMS surface sequentially treated with O2 plasma and AmiTMS compound was a substrate appropriate for preparing a temperature-responsive cell culture surface by EB irradiation-induced PIPAAm grafting method. The intelligent surface may further be applied to mechanically stretchable temperature-responsive cell culture surfaces.
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Kemkemer, Ralf, Zhang Zenghao, Yang Linxiao, Kiriaki Athanasopulu, Kerstin Frey, Zhishan Cui, Haijia Su, and Liu Luo. "Surface modification of Polydimethylsiloxane by hydrogels for microfluidic applications." Current Directions in Biomedical Engineering 5, no. 1 (September 1, 2019): 93–96. http://dx.doi.org/10.1515/cdbme-2019-0024.
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AbstractIn vitro, hydrogel-based ECMs for functionalizing surfaces of various material have played an essential role in mimicking native tissue matrix. Polydimethylsiloxane (PDMS) is widely used to build microfluidic or organ-on-chip devices compatible with cells due to its easy handling in cast replication. Despite such advantages, the limitation of PDMS is its hydrophobic surface property. To improve wettability of PDMS-based devices, alginate, a naturally derived polysaccharide, was covalently bound to the PDMS surface. This alginate then crosslinked further hydrogel onto the PDMS surface in desired layer thickness. Hydrogel-modified PDMS was used for coating a topography chip system and in vitro investigation of cell growth on the surfaces. Moreover, such hydrophilic hydrogel-coated PDMS is utilized in a microfluidic device to prevent unspecific absorption of organic solutions. Hence, in both exemplary studies, PDMS surface properties were modified leading to improved devices.
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Wang, Bin, J. Hugh Horton, and Richard D. Oleschuk. "Sulfonated-polydimethylsiloxane (PDMS) microdevices with enhanced electroosmotic pumping and stability." Canadian Journal of Chemistry 84, no. 4 (April 1, 2006): 720–29. http://dx.doi.org/10.1139/v06-044.
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Polydimethylsiloxane (PDMS) microfluidic devices offer several advantages in terms of cost and ease of fabrication compared with those fabricated from both glass and silicon materials. PDMS, however, has some potential disadvantages compared with other materials including high hydrophobicity, which makes filling the micron-sized channels difficult, and minimal surface charge resulting in reduced electroosmotic flow (EOF). Here, we describe the oxidation of the PDMS surface to form silanol groups using both air plasma and a discharge from a Tesla coil, and subsequent modification to form sulfonated-PDMS surfaces. The flow performance of freshly prepared and aged sulfonated-PDMS chips was determined at pH 5 and compared with those of unmodified and oxidized PDMS chips. The electroosmotic mobility (µeo) for a sulfonated-PDMS microdevice was determined at various pH values (pH 3~8) and compared with that for an oxidized PDMS chip. The lower pKa of a sulfonic acid modified surface compared with a silanol modified surface generated a stronger EOF over the entire pH range studied. Chemical force titrations were used to characterize the changes in functional groups present on the surface of freshly prepared and aged sulfonated-PDMS surfaces. These experiments show that the sulfonated-PDMS is a superior material for use in microfluidic applications because (i) it supports EOF over a much wider range of pH than similar polymer materials and (ii) is less susceptible to degradation of its EOF rate owing to air aging effects and surface reorganization.Key words: polydimethylsiloxane (PDMS), sulfonated surface modification, electroosmotic flow (EOF), aging effect, chemical force titrations.
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Lopera, S., and R. D. Mansano. "Plasma-Based Surface Modification of Polydimethylsiloxane for PDMS-PDMS Molding." ISRN Polymer Science 2012 (April 3, 2012): 1–5. http://dx.doi.org/10.5402/2012/767151.
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We present and compare two processes for plasma-based surface modification of Polydimethylsiloxane (PDMS) to achieve the antisticking behavior needed for PDMS-PDMS molding. The studied processes were oxygen plasma activation for vapor phase silanization and plasma polymerization with tetrafluoromethane/hydrogen mixtures under different processing conditions. We analyzed topography changes of the treated surfaces by atomic force microscopy and contact angle measurements. Plasma treatment were conducted in a parallel plate reactive ion etching reactor at a pressure of 300 mTorr, 30 Watts of RF power and a total flow rate of 30 sccm of a gas mixture. We found for both processes that short, low power, treatments are better to create long-term modifications of the chemistry of the polymer surface while longer processes or thicker films tend to degrade faster with the use leaving rough surfaces with higher adherence to the molded material.
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Azizipour, Neda, Rahi Avazpour, Mohamad Sawan, Abdellah Ajji, and Derek H. Rosenzweig. "Surface Optimization and Design Adaptation toward Spheroid Formation On-Chip." Sensors 22, no. 9 (April 21, 2022): 3191. http://dx.doi.org/10.3390/s22093191.
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Spheroids have become an essential tool in preclinical cancer research. The uniformity of spheroids is a critical parameter in drug test results. Spheroids form by self-assembly of cells. Hence, the control of homogeneity of spheroids in terms of size, shape, and density is challenging. We developed surface-optimized polydimethylsiloxane (PDMS) biochip platforms for uniform spheroid formation on-chip. These biochips were surface modified with 10% bovine serum albumin (BSA) to effectively suppress cell adhesion on the PDMS surface. These surface-optimized platforms facilitate cell self-aggregations to produce homogenous non-scaffold-based spheroids. We produced uniform spheroids on these biochips using six different established human cell lines and a co-culture model. Here, we observe that the concentration of the BSA is important in blocking cell adhesion to the PDMS surfaces. Biochips treated with 3% BSA demonstrated cell repellent properties similar to the bare PDMS surfaces. This work highlights the importance of surface modification on spheroid production on PDMS-based microfluidic devices.
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Swart, Morne, and Peter E. Mallon. "Hydrophobicity recovery of corona-modified superhydrophobic surfaces produced by the electrospinning of poly(methyl methacrylate)-graft-poly(dimethylsiloxane) hybrid copolymers." Pure and Applied Chemistry 81, no. 3 (January 1, 2009): 495–511. http://dx.doi.org/10.1351/pac-con-08-08-15.
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Superhydrophobicity is dependent on both the surface energy and the texture of the surface. These factors are discussed in terms of a series of electrospun poly(methyl methacrylate)-graft-poly(dimethylsiloxane) (PMMA-g-PDMS) copolymers with different poly(dimethylsiloxane) (PDMS) content. These copolymers are synthesized via conventional free radical copolymerization of methyl methacrylate (MMA) and monomethacryloxypropyl-terminated PDMS macromonomers. It is shown how these copolymers can be electrospun to produce copolymer fibers with diameters in the 100-1000 nm range. The effect of the copolymer composition (and hence the surface energy) and the electrospinning tip-to-collector distance (TCD) on the fiber morphology is discussed. The surfaces produced by the electrospinning process show superhydrophobic properties where the preferential surface segregation of the PDMS component is combined with the roughness of the fiber surface. The surface energy of the fibers is varied by variation of the PDMS content in the copolymers as well as by post-spinning modification with corona discharge. The hydrophobicity of the surfaces shows a greater dependence on the PDMS content than on the average fiber diameter. After exposure of these fiber surfaces to corona discharge, the initial superhydrophobic surfaces become easily wettable despite the fact that much of the surface roughness is maintained after exposure. The samples show the phenomena of hydrophobocity recovery after corona exposure. The rate and extent of this recovery depends on the PDMS content and the corona exposure time. Despite the recovery, scanning electron microscopy (SEM), swelling measurements, and confocal Raman spectroscopy show that permanent surface changes have taken place. The surfaces do not recover to their original superhydrophobic state.
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Ramlan, Nadiah, Saiful Irwan Zubairi, and Mohamad Yusof Maskat. "Response Surface Optimisation of Polydimethylsiloxane (PDMS) on Borosilicate Glass and Stainless Steel (SS316) to Increase Hydrophobicity." Molecules 27, no. 11 (May 25, 2022): 3388. http://dx.doi.org/10.3390/molecules27113388.
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Particle deposition on the surface of a drying chamber is the main drawback in the spray drying process, reducing product recovery and affecting the quality of the product. In view of this, the potential application of chemical surface modification to produce a hydrophobic surface that reduces the powder adhesion (biofouling) on the wall of the drying chamber is investigated in this study. A hydrophobic polydimethylsiloxane (PDMS) solution was used in the vertical dipping method at room temperature to determine the optimum coating parameters on borosilicate glass and stainless steel substrates, which were used to mimic the wall surface of the drying chamber, to achieve highly hydrophobic surfaces. A single-factor experiment was used to define the range of the PDMS concentration and treatment duration using the Response Surface Methodology (RSM). The Central Composite Rotatable Design (CCRD) was used to study the effects of the concentration of the PDMS solution (X1, %) and the treatment duration (X2, h) on the contact angle of the substrates (°), which reflected the hydrophobicity of the surface. A three-dimensional response surface was constructed to examine the influence of the PDMS concentration and treatment duration on contact angle readings, which serve as an indicator of the surface’s hydrophobic characteristics. Based on the optimisation study, the PDMS coating for the borosilicate glass achieved an optimum contact angle of 99.33° through the combination of a PDMS concentration of X1 = 1% (w/v) and treatment time of X2 = 4.94 h, while the PDMS coating for the stainless steel substrate achieved an optimum contact angle of 98.31° with a PDMS concentration of X1 = 1% (w/v) and treatment time of X2 = 1 h. Additionally, the infrared spectra identified several new peaks that appeared on the PDMS-treated surfaces, which represented the presence of Si-O-Si, Si-CH3, CH2, and CH3 functional groups for the substrates coated with PDMS. Furthermore, the surface morphology analysis using the Field Emission Scanning Electron Microscopy (FESEM) showed the presence of significant roughness and a uniform nanostructure on the surface of the PDMS-treated substrates, which indicates the reduction in wettability and the potential effect of unwanted biofouling on the spray drying chamber. The application of PDMS and PTFE on the optimally coated substrates successfully reduced the amount of full cream milk particles that adhered to the surface. The low surface energy of the treated surface (19–27 mJ/m2) and the slightly higher surface tension of the full cream milk (54–59 mJ/m2) resulted in a high contact angle (102–103°) and reduced the adhesion work on the treated substrates (41–46 mJ/m2) as compared to the native substrates.
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Shi, Dongyan, Dan Ma, Feiqing Dong, Chen Zong, Liyue Liu, Dan Shen, Wenji Yuan, Xiangmin Tong, Hengwu Chen, and Jinfu Wang. "Proliferation and multi-differentiation potentials of human mesenchymal stem cells on thermoresponsive PDMS surfaces grafted with PNIPAAm." Bioscience Reports 30, no. 3 (December 15, 2009): 149–58. http://dx.doi.org/10.1042/bsr20090026.
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The thermo-responsivity of PNIPAAm [poly(N-isopropylcarylamide)]-grafted PDMS [poly(dimethylsiloxane)] surface is a property that could be feasibly used for detaching cells adhered on the surface. We used benzophenone-initiated photopolymerization to graft PNIPAAm on PDMS substrates to construct the PNIPAAm-grafted PDMS surface and this PDMS surface was highly thermo-responsive. hMSCs (human mesenchymal stem cells) were used to analyse the proliferation and multi-differentiation of stem cells on the PNIPAAm-grafted PDMS surface. The results showed that hMSCs could adhere on the PNIPAAm-grafted PDMS surface at 37°C and form cell colonies, and then become fibroblastic. The proliferation potential of hMSCs on the PNIPAAm-grafted PDMS surface was not significantly different from that on a plate surface coated with gelatin. However, as it proved easier to detach cells from the surface, by changing temperature, a higher viability of detached cells could be obtained with the PNIPAAm-grafted PDMS surface, using a temperature shift, compared with a gelatin-coated surface, where cells are detached by treatment with trypsin. hMSCs on the PNIPAAm-grafted PDMS surface were induced into osteoblasts, adipocytes and neurocytes under osteogenic medium, adipogenic medium and neurogenic medium respectively. The PNIPAAm-grafted PDMS surface was favourable for osteogenesis of hMSCs, although the potentials of adipogenesis and neurogenesis of hMSCs on the PNIPAAm-grafted PDMS surface were similar to those on the plate surface coated with gelatin. The above results demonstrate that the PNIPAAm-grafted PDMS surface not only kept the potentials of proliferation and multi-differentiation of hMSCs, but also increased the viability of hMSCs.
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Protsak, Iryna S., Yevhenii M. Morozov, Dong Zhang, and Volodymyr M. Gun’ko. "Surface Chemistry of Nanohybrids with Fumed Silica Functionalized by Polydimethylsiloxane/Dimethyl Carbonate Studied Using 1H, 13C, and 29Si Solid-State NMR Spectroscopy." Molecules 26, no. 19 (October 1, 2021): 5974. http://dx.doi.org/10.3390/molecules26195974.
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The investigation of molecular interactions between a silica surface and organic/inorganic polymers is crucial for deeper understanding of the dominant mechanisms of surface functionalization. In this work, attachment of various depolymerized polydimethylsiloxanes (PDMS) of different chain lengths, affected by dimethyl carbonate (DMC), to silica nanoparticles pretreated at different temperatures has been studied using 29Si, 1H, and 13C solid-state NMR spectroscopy. The results show that grafting of different modifier blends onto a preheated silica surface depends strongly on the specific surface area (SSA) linked to the silica nanoparticle size distributions affecting all textural characteristics. The pretreatment at 400 °C results in a greater degree of the modification of (i) A-150 (SSA = 150 m2/g) by PDMS-10/DMC and PDMS-1000/DMC blends; (ii) A-200 by PDMS-10/DMC and PDMS-100/DMC blends; and (iii) A-300 by PDMS-100/DMC and PDMS-1000/DMC blends. The spectral features observed using solid-state NMR spectroscopy suggest that the main surface products of the reactions of various depolymerized PDMS with pretreated nanosilica particles are the (CH3)3SiO-[(CH3)2SiO-]x fragments. The reactions occur with the siloxane bond breakage by DMC and replacing surface hydroxyls. Changes in the chemical shifts and line widths, as shown by solid-state NMR, provide novel information on the whole structure of functionalized nanosilica particles. This study highlights the major role of solid-state NMR spectroscopy for comprehensive characterization of functionalized solid surfaces.
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Lin, Wei-Chih, and Nur Mohd Razali. "Temporary Wettability Tuning of PCL/PDMS Micro Pattern Using the Plasma Treatments." Materials 12, no. 4 (February 20, 2019): 644. http://dx.doi.org/10.3390/ma12040644.
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Surface wettability plays an important role in determining the function of a wound dressing. Dressings with hydrophobic surfaces are suitable for bacterial adsorption, however, a hydrophilic surface is needed to improve cell attachment for most anchorage-dependent cell types. Furthermore, the hydrophobicity/hydrophilicity of the surface can be used to direct cellular processes such as cell initial attachment, adhesion, and migration during wound healing. Thus, a surface with an ability to switch their surface wettability improves the practicality of the dressing. In this study, we propose a temporary surface wettability tuning for surface patterning utilizing plasma treatment. Polycaprolactone (PCL) and polydimethylsiloxane (PDMS) surfaces were treated with tetrafluoromethane (CF4), sulphur hexafluoride (SF6), and oxygen (O2) plasma, and the effects on the surface wettability, roughness, and chemical composition were investigated. Based on the contact angle measurement, CF4 plasma altered surface wettability of PCL and PDMS films to hydrophobic and hydrophilic, respectively. After CF4 treatment, better attachment of primary mouse embryonic fibroblast cell (3T3) was observed on the treated PDMS surface. Embedding PCL into PDMS generated a hydrophobic-hydrophilic pattern mixture surface, which offers great potential in the tissue engineering field such as cell patterning and guidance.
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Xia, Xiaojing, Jue Liu, Yang Liu, Zijie Lei, Yutong Han, Zeping Zheng, and Jian Yin. "Preparation and Characterization of Biomimetic SiO2-TiO2-PDMS Composite Hydrophobic Coating with Self-Cleaning Properties for Wall Protection Applications." Coatings 13, no. 2 (January 18, 2023): 224. http://dx.doi.org/10.3390/coatings13020224.
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Superhydrophobic surfaces have great potential for self-cleaning, anti-icing, and drag-reducing characteristics because of their water repellent property. This study demonstrates the potential application of coatings to protect architectures from detrimental atmospheric effects via a self-cleaning approach. In this research, a SiO2-TiO2-PDMS composite coating was prepared on the surface of building walls by the sol-gel method. Tetraethyl orthosilicate (TEOS) and titanium isopropoxide (TTIP) were used as inorganic precursors, and polydimethylsiloxane (PDMS) was used as low surface energy substances. The effects of TEOS and PDMS content on microstructure, wettability, and self-cleaning performance of coating wall surfaces were investigated by conducting various tests, including scanning electron microscopy (SEM), X-ray energy spectroscopy (EDS), angle measurement, and Fourier transform infrared spectroscopy (FTIR). The results indicated that hydrolysis and condensation reactions of TEOS, TTIP, and PDMS were performed on the surface of the substrates, leading to a micro- and nano-structure similar to the surface of lotus leaves. When the molar ratio of PDMS to TEOS was 1:5, the static contact angle of the coating reached a maximum of 152.6°. At this point, the coated surface was able to resist the adhesion of particle pollutants and liquid pollutants, which could keep the walls clean and possess a good ability of self-cleaning. In conclusion, SiO2-TiO2-PDMS composite coating is potentially useful in wall protection applications with its hydrophobic and environmentally friendly superhydrophobic properties.
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Mayoussi, Fadoua, Ali Usama, Niloofar Nekoonam, Ivonne Knauer, David Böcherer, Bastian E. Rapp, and Dorothea Helmer. "Influence of Parylene F Coatings on the Wetting Properties of Soft Polydimethylsiloxane (PDMS)." Materials 16, no. 5 (February 26, 2023): 1938. http://dx.doi.org/10.3390/ma16051938.
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Understanding the wettability of soft surfaces is of key importance for the development of protective and repellent coatings and controlling droplet dynamics when required. There are many factors that affect the wetting and dynamic dewetting behavior of soft surfaces, such as the formation of wetting ridges, the adaptive behavior of the surface caused by the interaction of the fluid with the surface, or the presence of free oligomers that are washed out of the soft surface. In this work, we report the fabrication and characterization of three soft polydimethylsiloxane (PDMS) surfaces with elastic moduli ranging from 7 kPa to 56 kPa. The dynamic dewetting behavior of liquids with different surface tensions was studied on these surfaces, and the data show soft and adaptive wetting behavior of the soft PDMS, as well as the presence of free oligomers. Thin layers of Parylene F (PF) were introduced to the surfaces and their influence on the wetting properties was studied. We show that the thin layers of PF prevent adaptive wetting by preventing the diffusion of liquids into the soft PDMS surfaces and by causing the loss of the soft wetting state. The dewetting properties of the soft PDMS are enhanced, leading to low sliding angles of ≤10° for water, ethylene glycol, and diiodomethane. Therefore, the introduction of a thin PF layer can be used to control wetting states and to increase the dewetting behavior of soft PDMS surfaces.
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Tsuzuki, Tomoo, Karine Baassiri, Zahra Mahmoudi, Ayyappasamy Sudalaiyadum Perumal, Kavya Rajendran, Gala Montiel Rubies, and Dan V. Nicolau. "Hydrophobic Recovery of PDMS Surfaces in Contact with Hydrophilic Entities: Relevance to Biomedical Devices." Materials 15, no. 6 (March 21, 2022): 2313. http://dx.doi.org/10.3390/ma15062313.
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Polydimethylsiloxane (PDMS), a silicone elastomer, is increasingly being used in health and biomedical fields due to its excellent optical and mechanical properties. Its biocompatibility and resistance to biodegradation led to various applications (e.g., lung on a chip replicating blood flow, medical interventions, and diagnostics). The many advantages of PDMS are, however, partially offset by its inherent hydrophobicity, which makes it unsuitable for applications needing wetting, thus requiring the hydrophilization of its surface by exposure to UV or O2 plasma. Yet, the elastomeric state of PDMS translates in a slow, hours to days, process of reducing its surface hydrophilicity—a process denominated as hydrophobic recovery. Using Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM), the present study details the dynamics of hydrophobic recovery of PDMS, on flat bare surfaces and on surfaces embedded with hydrophilic beads. It was found that a thin, stiff, hydrophilic, silica film formed on top of the PDMS material, following its hydrophilization by UV radiation. The hydrophobic recovery of bare PDMS material is the result of an overlap of various nano-mechanical, and diffusional processes, each with its own dynamics rate, which were analyzed in parallel. The hydrophobic recovery presents a hysteresis, with surface hydrophobicity recovering only partially due to a thin, but resilient top silica layer. The monitoring of hydrophobic recovery of PDMS embedded with hydrophilic beads revealed that this is delayed, and then totally stalled in the few-micrometer vicinity of the embedded hydrophilic beads. This region where the hydrophobic recovery stalls can be used as a good approximation of the depth of the resilient, moderately hydrophilic top layer on the PDMS material. The complex processes of hydrophilization and subsequent hydrophobic recovery impact the design, fabrication, and operation of PDMS materials and devices used for diagnostics and medical procedures. Consequently, especially considering the emergence of new surgical procedures using elastomers, the impact of hydrophobic recovery on the surface of PDMS warrants more comprehensive studies.
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Akther, Fahima, Shazwani Binte Yakob, Nam-Trung Nguyen, and Hang T. Ta. "Surface Modification Techniques for Endothelial Cell Seeding in PDMS Microfluidic Devices." Biosensors 10, no. 11 (November 19, 2020): 182. http://dx.doi.org/10.3390/bios10110182.
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Microfluidic lab-on-a-chip cell culture techniques have been gaining popularity by offering the possibility of reducing the amount of samples and reagents and greater control over cellular microenvironment. Polydimethylsiloxane (PDMS) is the commonly used polymer for microfluidic cell culture devices because of the cheap and easy fabrication techniques, non-toxicity, biocompatibility, high gas permeability, and optical transparency. However, the intrinsic hydrophobic nature of PDMS makes cell seeding challenging when applied on PDMS surface. The hydrophobicity of the PDMS surface also allows the non-specific absorption/adsorption of small molecules and biomolecules that might affect the cellular behaviour and functions. Hydrophilic modification of PDMS surface is indispensable for successful cell seeding. This review collates different techniques with their advantages and disadvantages that have been used to improve PDMS hydrophilicity to facilitate endothelial cells seeding in PDMS devices.
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Akerboom, Sabine, Jeroen Appel, David Labonte, Walter Federle, Joris Sprakel, and Marleen Kamperman. "Enhanced adhesion of bioinspired nanopatterned elastomers via colloidal surface assembly." Journal of The Royal Society Interface 12, no. 102 (January 2015): 20141061. http://dx.doi.org/10.1098/rsif.2014.1061.
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We describe a scalable method to fabricate nanopatterned bioinspired dry adhesives using colloidal lithography. Close-packed monolayers of polystyrene particles were formed at the air/water interface, on which polydimethylsiloxane (PDMS) was applied. The order of the colloidal monolayer and the immersion depth of the particles were tuned by altering the pH and ionic strength of the water. Initially, PDMS completely wetted the air/water interface outside the monolayer, thereby compressing the monolayer as in a Langmuir trough; further application of PDMS subsequently covered the colloidal monolayers. PDMS curing and particle extraction resulted in elastomers patterned with nanodimples. Adhesion and friction of these nanopatterned surfaces with varying dimple depth were studied using a spherical probe as a counter-surface. Compared with smooth surfaces, adhesion of nanopatterned surfaces was enhanced, which is attributed to an energy-dissipating mechanism during pull-off. All nanopatterned surfaces showed a significant decrease in friction compared with smooth surfaces.
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Mannan, Md Abdul, Yuji Baba, Tetsuhiro Sekiguchi, Iwao Shimoyama, Norie Hirao, Masamitsu Nagano, and Hideyuki Noguchi. "Orientation of One-Dimensional Silicon Polymer Films Studied by X-Ray Absorption Spectroscopy." Journal of Nanomaterials 2012 (2012): 1–9. http://dx.doi.org/10.1155/2012/528256.
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Molecular orientations for thin films of one-dimensional silicon polymers grown by vacuum evaporation have been assigned by near-edge X-ray absorption fine structure (NEXAFS) using linearly polarized synchrotron radiation. The polymer investigated was polydimethylsilane (PDMS) which is the simplest stable silicon polymer, and one of the candidate materials for one-dimensional molecular wire. For PDMS films deposited on highly oriented pyrolytic graphite (HOPG), four resonance peaks have been identified in the SiK-edge NEXAFS spectra. Among these peaks, the intensities of the two peaks lower-energy at 1842.0 eV and 1843.2 eV were found to be strongly polarization dependent. The peaks are assigned to the resonance excitations from the Si 1s toσ∗ pyzandσ∗pxorbitals localized at the Si–C and Si–Si bonds, respectively. Quantitative evaluation of the polarization dependence of the NEXAFS spectra revealed that the molecules are self-assembled on HOPG surface, and the backbones of the PDMS are oriented nearly parallel to the surface. The observed orientation is opposite to the previously observed results for PDMS on the other surfaces such as oxide (indium tin oxide) and metal (polycrystalline copper). The flat-lying feature of PDMS observed only on HOPG surface is attributed to the interaction between CH bonds in PDMS andπorbitals in HOPG surface.
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Pergal, Marija, Jelena Nestorov, Gordana Tovilovic-Kovacevic, Petar Jovancic, Lato Pezo, Dana Vasiljevic-Radovic, and Jasna Djonlagic. "Surface characterization, hemo- and cytocompatibility of segmented poly(dimethylsiloxane)-based polyurethanes." Chemical Industry 68, no. 6 (2014): 731–41. http://dx.doi.org/10.2298/hemind141103082p.
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Segmented polyurethanes based on poly(dimethylsiloxane), currently used for biomedical applications, have sub-optimal biocompatibility which reduces their efficacy. Improving the endothelial cell attachment and blood-contacting properties of PDMS-based copolymers would substantially improve their clinical applications. We have studied the surface properties and in vitro biocompatibility of two series of segmented poly(urethane-dimethylsiloxane)s (SPU-PDMS) based on hydroxypropyl- and hydroxyethoxypropyl- terminated PDMS with potential applications in blood-contacting medical devices. SPU-PDMS copolymers were characterized by contact angle measurements, surface free energy determination (calculated using the van Oss-Chaudhury-Good and Owens-Wendt methods), and atomic force microscopy. The biocompatibility of copolymers was evaluated using an endothelial EA.hy926 cell line by direct contact assay, before and after pre-treatment of copolymers with multicomponent protein mixture, as well as by a competitive blood-protein adsorption assay. The obtained results suggested good blood compatibility of synthesized copolymers. All copolymers exhibited good resistance to fibrinogen adsorption and all favored albumin adsorption. Copolymers based on hydroxyethoxypropyl-PDMS had lower hydrophobicity, higher surface free energy, and better microphase separation in comparison with hydroxypropyl-PDMS-based copolymers, which promoted better endothelial cell attachment and growth on the surface of these polymers as compared to hydroxypropyl-PDMS-based copolymers. The results showed that SPU-PDMS copolymers display good surface properties, depending on the type of soft PDMS segments, which can be tailored for biomedical application requirements such as biomedical devices for short- and long-term uses.
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Poleni, Paul Emile, Nazare Pereira-Rodrigues, Denis Guimard, Yasuhiko Arakawa, Yasuyuki Sakai, and Teruo Fujii. "Surface Modification of Polydimethylsiloxane Using Low Pressure Chemical Vapour Deposition of Poly-Chloro-p-Xylene." Journal of Nano Research 20 (December 2012): 129–42. http://dx.doi.org/10.4028/www.scientific.net/jnanor.20.129.
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The capability to understand and modulate accurately the self-assembly of the extracellular matrix (ECM) components still one of the major fundamental objectives in the field of liver tissue engineering. In the present study, we put in evidence the suitability of poly-chloro-p-xylene (Parylene-C, ParC) for modulating the self-assembly of ECM (type-I collagen) microenvironment and cellular topography of human hepatocarcinoma (HepG2) and Human umbilical vascular endothelial (HUVEC) cells while coated on a polydimethylsiloxane (PDMS) substratum. Our findings demonstrated that the wettability of PDMS and ParC/PDMS were identical, while ParC/PDMS was significantly rougher than PDMS before and after collagen coating. However, the roughness and the wettability of ParC/PDMS were comparable to those of polystyrene (PS), a substratum commonly used for in vitro biological-related investigations. Type-I collagen adsorbed on ParC/PDMS and PS exhibited a dense network of microstructures around ~1 nm high and ~30-50 nm wide, whereas collagen adsorbed on PDMS had a low surface density of elongated fibrils that were ~2 nm thick and ~200 nm wide. This disparity in ECM microarchitecture leaded to distinct culture topographies of HepG2 cells (3D and 2D for PDMS and ParC/PDMS, respectively) and viability of HUVEC (2D viable HUVEC cells and non attached dead cells on ParC/PDMS and PDMS, respectively). To conclude, the observed changes in cell morphology and viability between ParC/PDMS and PDMS alone were directly related to the nature of the material which may impact the supramolecular organization of adsorbed ECM. We strongly believe that Low Pressure Chemical Vapour deposition (LPCVD) of ParC will offer promising insights into how microscale ECM modifications directly impact cell morphology and activity, leading to the development of advanced micro/nanosized tissue-engineered ParC/PDMS patterns with applications for liver tissue engineering.
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Vanitparinyakul, S., P. Pattamang, A. Chanhom, B. Tunhoo, T. Thiwawong, S. Porntheeraphat, and J. Nukeaw. "Study of PDMS Compounds Using the Adhesion Force Determined by AFM Force Distance Curve Measurements." Advanced Materials Research 93-94 (January 2010): 141–44. http://dx.doi.org/10.4028/www.scientific.net/amr.93-94.141.
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The atomic force microscope(AFM) was used to perform surface force measurements in contact mode to investigate surface properties of model systems at the nanoscale. Three different Polydimethylsiloxane (PDMS) compounds were observed. The first consisted of pure PDMS, the second of PDMS blend with the nanoparticles Zinc Oxide(PDMS/ZnO) and the third of PDMS blend with the nanoparticles Zinc Oxide and toluene solvent(PDMS/ZnO/toluene), respectively. Surface morphology and the adhesion force were investigated by using atomic force microscopy. Force–distance curve measurement was performed in a contact mode, which used tip as silicon nitride. Moreover, we found a significantly different of the adhesion force when modified by nanoparticles ZnO and toluene solvent.
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Yang, Rui, Yunyi Liang, Shu Hong, Shida Zuo, Yingji Wu, Jiangtao Shi, Liping Cai, et al. "Novel Low-Temperature Chemical Vapor Deposition of Hydrothermal Delignified Wood for Hydrophobic Property." Polymers 12, no. 8 (August 6, 2020): 1757. http://dx.doi.org/10.3390/polym12081757.
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As a hydrophilic material, wood is difficult to utilize for external applications due to the variable weather conditions. In this study, an efficient, facile, and low-cost method was developed to enhance the hydrophobicity of wood. By applying the low-temperature chemical vapor deposition (CVD) technology, the polydimethylsiloxane-coated wood (PDMS@wood) with hydrophobic surface was fabricated employing dichlorodimethylsilane as the CVD chemical resource. The result of water contact angle (i.e., 157.3°) revealed the hydrophobic behavior of the PDMS@wood. The microstructures of the wood samples were observed by scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS) analysis verified PDMS successfully coated on wood surfaces. The chemical functional groups of the PDMS@wood were investigated by Fourier transform infrared (FT-IR) and Raman spectra. The thermogravimetric results indicated the enhanced thermal stability of the wood after PDMS coating. In addition, the stability test of PDMS@wood indicated that the hydrophobicity properties of the PDMS@wood samples were preserved after long-time storage (e.g., 30 days). The scratch test was carried out to examine the abrasion resistance of the hydrophobic coatings on PDMS@wood surface. It was suggested that low-temperature CVD process could be a successful approach for fabricating hydrophobic wood.
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Zhao, Xiao Li, Wei Wei An, Jiu Chun Yan, Hai Cao Yu, and Li Qin Wang. "Wettability of Polymeric Bionic Surface Replicated from Ginkgo Leaves." Key Engineering Materials 625 (August 2014): 736–41. http://dx.doi.org/10.4028/www.scientific.net/kem.625.736.
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Ginkgo is one of the oldest extant seed plants through hundreds of millions of years of evolution. Ginkgo biloba has many unique properties and applications such as drug development and drinking tea. In recent years hydrophobic surfaces with bionic structures have attracted increasing interest for fundamental research and practical applications. As we all know, the Ginkgo leaf has remarkable texturing surface. In this manuscript, wettability of the bionic surface replicated from Ginkgo leaves was explored. The Ginkgo leaves were used as the original mold, from which microstructures were replicated into the surface of polydimethylsiloxane (PDMS). Compared with the topography of Ginkgo leaves, the topographical surface of PDMS was investigated by optical microscopy and scanning electron microscopy. By measuring the contact angle of polymeric bionic surfaces, there is the increase of ~20 degree than flat PDMS surfaces. Mechanical compression was applied on the polymeric bionic surfaces in one dimension, with the real-time measurement of the contact angle. The experimental results reveal that the wetting behavior of the surface can be reversibly tuned by applied mechanical stress, which induces the change in micro-scale topography. This research provides a guide for fabricating and tuning hydrophobic surfaces for various surface engineering applications.
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Sorrells, Matthew G., and Keith B. Neeves. "Adsorption and Absorption of Collagen Peptides to Polydimethlysiloxane and Its Influence on Platelet Adhesion Flow Assays." Micromachines 11, no. 1 (January 5, 2020): 62. http://dx.doi.org/10.3390/mi11010062.
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Collagen peptides are an alternative to animal derived collagens for platelet function studies under flow. The purpose of this study was to examine the use of collagen peptides in polydimethylsiloxane (PDMS) devices. Three collagen peptides with amino acid sequences and structures that capture von Willebrand factor and bind it with the platelet receptors integrin α2β1 and glycoprotein VI were patterned on glass, silicon, and PDMS. Each of these surfaces was also functionalized with tridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane (FOTS). Surfaces were characterized by their ability to support platelet adhesion, topology by atomic force microscopy, contact angle, and peptides absorption. PDMS readily absorbs collagen peptides, depleting them from solution, thus reducing their adsorption to glass and silicon substrates when used for micropatterning. Treatment of PDMS with FOTS, but not bovine serum albumin or poloxamer 407, inhibits collagen peptide absorption and supports adsorption and platelet adhesion at venous and arterial shear rates. Similarly, FOTS treatment of glass or silicon supports collagen peptide adsorption even in the presence of untreated PDMS. In conclusion, PDMS acts as an absorptive sink for collagen peptides, rendering a non-adhesive surface for platelet adhesion and competing for peptides when used for micropatterning. The absorption of collagen peptides can be overcome by functionalization of PDMS with a fluorinated alkyl silane, thus allowing its use as a material for micropatterning or as a surface for platelet adhesion flow assays.
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Joo, Haejin, Jonghyun Park, Chanutchamon Sutthiwanjampa, Hankoo Kim, Taehui Bae, Wooseob Kim, Jinhwa Choi, Mikyung Kim, Shinhyuk Kang, and Hansoo Park. "Surface Coating with Hyaluronic Acid-Gelatin-Crosslinked Hydrogel on Gelatin-Conjugated Poly(dimethylsiloxane) for Implantable Medical Device-Induced Fibrosis." Pharmaceutics 13, no. 2 (February 17, 2021): 269. http://dx.doi.org/10.3390/pharmaceutics13020269.
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Polydimethylsiloxane (PDMS) is a biocompatible polymer that has been applied in many fields. However, the surface hydrophobicity of PDMS can limit successful implementation, and this must be reduced by surface modification to improve biocompatibility. In this study, we modified the PDMS surface with a hydrogel and investigated the effect of this on hydrophilicity, bacterial adhesion, cell viability, immune response, and biocompatibility of PDMS. Hydrogels were created from hyaluronic acid and gelatin using a Schiff-base reaction. The PDMS surface and hydrogel were characterized using nuclear magnetic resonance, X-ray photoelectron spectroscopy, attenuated total reflection Fourier-transform infrared spectroscopy, and scanning electron microscopy. The hydrophilicity of the surface was confirmed via a decrease in the water contact angle. Bacterial anti-adhesion was demonstrated for Pseudomonas aeruginosa, Ralstonia pickettii, and Staphylococcus epidermidis, and viability and improved distribution of human-derived adipose stem cells were also confirmed. Decreased capsular tissue responses were observed in vivo with looser collagen distribution and reduced cytokine expression on the hydrogel-coated surface. Hydrogel coating on treated PDMS is a promising method to improve the surface hydrophilicity and biocompatibility for surface modification of biomedical applications.
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Hsu, Ming-Huai, Yao-Yang Tsai, and Sen-Yeu Yang. "Induction heating ferromagnetic particles embedded PDMS mold for microstructure embossing." Journal of Physics Communications 6, no. 2 (February 1, 2022): 025002. http://dx.doi.org/10.1088/2399-6528/ac4dd6.
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Abstract Polydimethylsiloxane (PDMS) is an excellent soft mold material with the advantages of precise replication, easy demolding, and low production cost. However, the strength and hardness of PDMS are relatively low, and PDMS cannot be directly inductively heated. In this study, PDMS is embedded with ferromagnetic powders to increase its hardness and make it heatable. Direct induction heating of the PDMS mold can raise its inherent temperature, increase the heating efficiency by 100% compared with pure PDMS, and improve the shortcomings of uneven surface temperature distribution from high thermal resistance. Furthermore, adding the ferromagnetic metal powder to PDMS can improve its conductivity and make the mold a high-low surface temperature gap as low as 1.6 °C. Adding nickel powder to the PDMS mold makes the hardness 2.29 times higher than that of pure PDMS and can withstand a pressure of 7 kg cm−2, which is very conducive to hot embossing. This study used a self-designed five-sided cladding iron block base and a PDMS mold with ferromagnetic metal powder for hot embossing. This heating apparatus can quickly raise the PDMS surface temperature and emboss deep V-groove microstructures on the polycarbonate (PC) film; the replication performance can reach more than 97%.
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Wang, Chaonan, Meifeng Xu, Tian Xu, and Yonglong Jin. "Fabrication of Ag/PDMS Substrate of High-Density Hot Spots and Its Application in in situ Detection." Nano 16, no. 06 (May 20, 2021): 2150064. http://dx.doi.org/10.1142/s1793292021500648.
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Through a replacement reaction approach, Ag nanostructure was easily prepared on economical digital video disc (DVD) and polydimethysiloxane (PDMS) with surface structure duplicating from the former. Distinct nanoscale morphology was observed, featuring intersecting Ag nanoplates with abundant hot spots on the DVD and spherical Ag nanoparticles on the PDMS. Surface-enhanced Raman scattering (SERS) spectra, using crystal violet as a probe, revealed a superior enhancement effect in Ag/DVD versus that in Ag/PDMS. Considering the desirable flexibility and transparency of PDMS for in situ detection, we further developed a protocol to introduce intersecting Ag nanoplates onto the PDMS surface. The resulting Ag/PDMS substrate was endowed with remarkable sensitivity, excellent uniformity and good stability under mechanical bending. Furthermore, effective in situ detection of malachite green on fish was demonstrated, highlighting the great potential of our approach for the in situ detection of target molecules on a curved surface.
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Joshi, Shivani, Antonie van Loon, Angel Savov, and Ronald Dekker. "Adhesion Improvement of Polyimide/PDMS Interface by Polyimide Surface Modification." MRS Advances 1, no. 1 (2016): 33–38. http://dx.doi.org/10.1557/adv.2016.56.
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ABSTRACTSilicon wafers coated with a 5μm thick layer of polyimide were treated with different surface modification techniques such as chemical adhesion promoters, oxygen plasma and an Ar+ sputter etch. After surface modification, the wafers were molded with a 1mm thick layer of PDMS. The adhesion of the PDMS was tested by peel testing and by using a Nordson DAGE wedge shear tester. It was found that commercially available chemical adhesion promoters and oxygen plasma treatment resulted in a very poor PI/PDMS adhesion, whereas the Ar+ sputter etch resulted in an adhesion so strong that the PDMS could not be delaminated from the PI surface without the failure of the material.
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Feng, Xiaoming, Huiying Guan, Ze Wang, Shichao Niu, and Zhiwu Han. "Biomimetic Slippery PDMS Film with Papillae-Like Microstructures for Antifogging and Self-Cleaning." Coatings 11, no. 2 (February 17, 2021): 238. http://dx.doi.org/10.3390/coatings11020238.
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Transparent materials with antifogging and self-cleaning ability are of extreme significance for utilization in outdoor solar cell devices to alleviate the performance loss and maintenance costs. Herein, with inspiration from the anti-wetting surfaces in nature, regular papillae-like microstructure arrays (PMAs) inspired by lotus leaves were designed via a common UV lithography combined with a soft replication. Subsequently, the biomimetic slippery polydimethylsiloxane (PDMS) film (BSPF) inspired by the pitcher plant was fabricated successfully by infusing with hydrophobic liquid lubricant. The resultant surface has hydrophobic surface chemistry, a slippery interface, PMAs structure. The wettability, optical characteristic, antifogging property and self-cleaning ability of the PMAs-based BSPF were characterized experimentally. The film displays excellent optical transmittance, antireflection, antifogging, and self-cleaning properties, which is superior to the flat PDMS film (FPF). Remarkably, an average reflection of ∼11.3% in the FPF was reduced to ∼8.9% of the BSPF. In addition, after gradient spray test for 120 s, the antifogging efficiency was close to 100% for the BSPF surface in comparison with the flat PDMS film (FPF), biomimetic PDMS film (BPF) and flat slippery PDMS film (FSPF) (35%, 70% and 85%). Furthermore, we also discovered that the BSPF surface exhibited a better self-cleaning performance toward a variety of liquids than solid dust.
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Baek, Ju Yeoul, Gu Han Kwon, Jeong Yun Kim, Jin Ho Cho, Seung Ha Lee, Kyung Sun, and Sang Hoon Lee. "Stable Deposition and Patterning of Metal Layers on the PDMS Substrate and Characterization for the Development of the Flexible and Implantable Micro Electrode." Solid State Phenomena 124-126 (June 2007): 165–68. http://dx.doi.org/10.4028/www.scientific.net/ssp.124-126.165.
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PDMS(polydimethylsiloxane) is a flexible and biocompatible material and is widely used in bio- or medical-related fields. Recently, PDMS has been used as a substrate of implantable electrodes but has exhibited limits in stable metal layer deposition and patterning. In this paper, we have developed processes for both the stable metallization of PDMS surface and the selective patterning of conductive elements. The surface treatment via the oxygen plasma ions significantly affects the adhesion of metal layers to the PDMS surface, while the other factors exhibited no significant relations. On the basis of our procedure resulted in the effective production of the stable and fine (line width: 20 ) electrode patterns on the PDMS substrate. Finally, we fabricated PDMS-based flexible and implantable micro electrode for the subretinal prosthesis.
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binti Din, Nurnadia Nadira, and Khairol Amali bin Ahmad. "Tropical Climate Adaptation via Biomimicry and Surface Functionalization for Electronic Circuitry." Key Engineering Materials 908 (January 28, 2022): 605–11. http://dx.doi.org/10.4028/p-u196g3.
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Surface functionalization has diverse applications from tropicalization, superhydrophobicity to chemical bonding and biomolecular applications. Tropical climate adaptability is necessary in order to successfully carry out the equipment’s functionality in extreme climate. Temperature gradient can lead to internal damage and humidity also leads to the surface’s degradation, thus lead to circuits’ shortcuts. Hence this research aimed to fabricate and characterize polydimethylsiloxane (PDMS) based biomimicry and surface functionalization for hydrophobic, fungus free and stable layer against tropical climate. Another nanoparticle that needs to be used to optimize the required criteria is polytetrafluoroethylene (PTFE). Varying the ratio of PDMS/PTFE mixture affects the resulting performance. The composite was layered onto taro leaves using soft-lithography technique. Several of the conventional method limitations were addressed such as water contact angle (WCA) and light transmittance. The overall average WCA of a PDMS/PTFE template obtained was between 92° until 108° whereas for a negatively replicated PDMS/PTFE template was between 121° until 131°. The plain PDMS template shows the average transmittance of 62.28% whereas the PDMS/PTFE template shows the average of less than 7.49% transmittance. The negatively replicated leaf PDMS/PTFE template shows the average transmittance percentage of 15.772% and a minimum of less than 2%. The obtained WCA results had proven that the soft-lithography technique is able to increase the surface wettability of equipment.
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Basiron, Norfatehah, Srimala Sreekantan, Khairul Arifah Saharudin, Zainal Arifin Ahmad, and Vignesh Kumaravel. "Improved Adhesion of Nonfluorinated ZnO Nanotriangle Superhydrophobic Layer on Glass Surface by Spray-Coating Method." Journal of Nanomaterials 2018 (October 21, 2018): 1–11. http://dx.doi.org/10.1155/2018/7824827.
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In this present work, a superhydrophobic glass surface comprising zinc oxide nanotriangles (ZnO-nt) and nontoxic silylating agent was developed via a cost-effective spray-coating technology. ZnO-nt was synthesized by a hydrothermal method. Poly(dimethylsiloxane) (PDMS) and dimethyldiethoxysilane (DMDEOS) were used as nontoxic (nonfluoro) silylating agents. The morphology and crystallinity of ZnO-nt were studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. ZnO-nt with polymeric silane (PDMS) exhibited maximum wettability as compared to nonpolymeric silane (DMDEOS). The water contact angle (WCA), sliding angle (SA), and surface roughness of ZnO-nt/PDMS-coated glass substrate under UV treatment were 165 ± 1°, 3 ± 1°, and 791 nm, respectively. The WCA of ZnO-nt/PDMS was higher (165°) than that of commercial ZnO/PDMS (ZnO-C/PDMS). ZnO-nt/PDMS was strongly attached to the glass substrate with good stability and adhesion. The reasons for improved hydrophobicity, adhesion, and mechanism of hierarchical microstructure formation on the glass substrate were explained in detail. PDMS was attached to the glass substrate via hydrogen bonds from solvated zinc acetate.
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Røn, Troels, Irakli Javakhishvili, Søren Hvilsted, Katja Jankova, and Seunghwan Lee. "Self-restoring polymer brushes under tribological stress and the biomedical applications." MRS Advances 1, no. 27 (2016): 1971–76. http://dx.doi.org/10.1557/adv.2016.345.
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ABSTRACTFor biological and mechanical systems involving moving parts, surface slipperiness is often a critical attribute for their optimal functions. Surface grafting with hydrophilic polymers is a powerful means to render materials slippery in aqueous environment. In “inverted grafting-to approach”, the hydrophilic polymer chains of amphiphilic diblock copolymers dispersed within a poly(dimethylsiloxane) (PDMS) network are selectively segregated upon exposure to aqueous solution. This allows formation of extremely stable brush-like polymer layers. Tribological application of inverted grafting-to approach was successfully demonstrated with PDMS-block-poly(acrylic acid) (PDMS-b-PAA) dispersed within thin PDMS films on PDMS blocks by showing friction coefficients (µ) of ca 10-2 to 10-3, depending on the load, pH and buffer salinity in the absence of other external re-supply of PAA chains. Further manipulations of the thin PDMS film incorporating PDMS-b-PAA to optimize the tribological properties are presented. Lastly, first trials to employ PAA-grafted PDMS surface to generate in-vitro mucosae model are also presented and discussed.
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Lee, Sung-Jun, Gang-Min Kim, and Chang-Lae Kim. "Effect of Glass Bubbles on Friction and Wear Characteristics of PDMS-Based Composites." Coatings 11, no. 5 (May 19, 2021): 603. http://dx.doi.org/10.3390/coatings11050603.
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The purpose of this study is to improve the mechanical durability and surface frictional characteristics of polymer/ceramic-based composite materials. Polydimethylsiloxane (PDMS)/glass bubble (GB) composite specimens are prepared at various weight ratios (PDMS:GB) by varying the amount of micro-sized GBs added to the PDMS. The surface, mechanical, and tribological characteristics of the PDMS/GB composites are evaluated according to the added ratios of GBs. The changes in internal stress according to the indentation depth after contacting with a steel ball tip to the bare PDMS and PDMS/GB composites having different GB densities are compared through finite element analysis simulation. The elastic modulus is proportional to the GB content, while the friction coefficient generally decreases as the GB content increases. A smaller amount of GB in the PDMS/GB composite results in more surface damage than the bare PDMS, but a significant reduction in wear rate is achieved when the ratio of PDMS:GB is greater than 100:5.
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Hamid, Intan Sue Liana Abdul, Beh Khi Khim, Mohammad Faiz Mohamed Omar, Khairu Anuar Mohamad Zain, Nuha Abd Rhaffor, Sofiyah Sal Hamid, and Asrulnizam Abd Manaf. "Three-Dimensional Soft Material Micropatterning via Grayscale Photolithography for Improved Hydrophobicity of Polydimethylsiloxane (PDMS)." Micromachines 13, no. 1 (January 1, 2022): 78. http://dx.doi.org/10.3390/mi13010078.
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In this present work, we aim to improve the hydrophobicity of a polydimethylsiloxane (PDMS) surface. Various heights of 3D PDMS micropillars were fabricated via grayscale photolithography, and improved wettability was investigated. Two approaches of PDMS replication were demonstrated, both using a single master mold to obtain the micropillar arrays. The different heights of fabricated PDMS micropillars were characterized by scanning electron microscopy (SEM) and a surface profiler. The surface hydrophobicity was characterized by measuring the water contact angles. The fabrication of PDMS micropillar arrays was shown to be effective in modifying the contact angles of pure water droplets with the highest 157.3-degree water contact angle achieved by implementing a single mask grayscale lithography technique.
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Chen, Weiqiang, Raymond H. W. Lam, and Jianping Fu. "Photolithographic surface micromachining of polydimethylsiloxane (PDMS)." Lab Chip 12, no. 2 (2012): 391–95. http://dx.doi.org/10.1039/c1lc20721k.
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Xia, Yong, Nan Zhu, Ying Zhao, Jiehui Zhu, Huajie Chen, Liyun Xu, and Lirong Yao. "Construction of Durable Self-Cleaning PDMS Film on Polyester Fabric Surface." Materials 16, no. 1 (December 21, 2022): 52. http://dx.doi.org/10.3390/ma16010052.
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The superhydrophobic surface can be prepared by two methods; one is by reducing the surface energy, and the other is by constructing a micro-nano rough structure. To achieve high superhydrophobic performance in terms of durability, the firm combination of hydrophobic coating and substrate is particularly important. Here, we use polydimethylsiloxane (PDMS) as a low surface energy monomer, water-borne polyurethane (WPU) as a dispersing aid, and use high-power ultrasound to disperse PDMS in water to make emulsion. The polyester matrix is etched by atmospheric plasma, dipped in PDMS emulsion, dried, and finally baked to induce PDMS on the surface of polyester fiber to cross-link into film. A series of tests on the self-cleaning polyester fabric prepared by this method show that when the concentration of PDMS is 8 g/L and the mass ratio of PDMS to WPU is 20:1, the water contact angle (WCA) reaches the maximum value of 148.2°, which decreases to 141.5° after 200 times of washing and 138.6° after 5000 times of rubbing. Before and after PDMS coating, the tensile strength of polyester fabric increases from 489.4 N to 536.4 N, and the water vapor transmission decreases from 13,535.7 g/(m2·d) to 12,224.3 g/(m2·d). This research is helpful to the large-scale production of self-cleaning polyester fabric. In the future, on the basis of this research, we will add functional powder to endow self-cleaning polyester fabric with higher hydrophobicity and other properties.
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Jankauskaitė, Virginija, Pranas Narmontas, and Algirdas Lazauskas. "Control of Polydimethylsiloxane Surface Hydrophobicity by Plasma Polymerized Hexamethyldisilazane Deposition." Coatings 9, no. 1 (January 11, 2019): 36. http://dx.doi.org/10.3390/coatings9010036.
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The properties of a polydimethylsiloxane (PDMS) surface were modified by a one-step deposition of plasma polymerized hexamethyldisilazane (pp-HMDS) by the arc discharge method. Scanning electron microscopy, atomic force microscopy, and Fourier-transform infrared spectroscopy analytical techniques were employed for morphological, structural, and chemical characterization of the pp-HMDS modified PDMS surface. The changes in PDMS substrate wetting properties were evaluated by means of contact angle measurements. The unmodified PDMS surface is hydrophobic with a contact angle of 122°, while, after pp-HMDS film deposition, a dual-scale roughness PDMS surface with contact angle values as high as 170° was obtained. It was found that the value of the contact angle depends on the plasma processing time. Chemically, the pp-HMDS presents methyl moieties, rendering it hydrophobic and making it an attractive material for creating a superhydrophobic surface, and eliminating the need for complex chemical routes. The presented approach may open up new avenues in design and fabrication of superhydrophobic and flexible organosilicon materials with a self-cleaning function.
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Yang, Da Hyun, Sangyong Jung, Jae Young Kim, and Nae Yoon Lee. "Fabrication of a Cell-Friendly Poly(dimethylsiloxane) Culture Surface via Polydopamine Coating." Micromachines 13, no. 7 (July 15, 2022): 1122. http://dx.doi.org/10.3390/mi13071122.
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In this study, we fabricated a poly(dimethylsiloxane) (PDMS) surface coated with polydopamine (PDA) to enhance cell adhesion. PDA is well known for improving surface adhesion on various surfaces due to the abundant reactions enabled by the phenyl, amine, and catechol groups contained within it. To confirm the successful surface coating with PDA, the water contact angle and X-ray photoelectron spectroscopy were analyzed. Human umbilical vein endothelial cells (HUVECs) and human-bone-marrow-derived mesenchymal stem cells (MSCs) were cultured on the PDA-coated PDMS surface to evaluate potential improvements in cell adhesion and proliferation. HUVECs were also cultured inside a cylindrical PDMS microchannel, which was constructed to mimic a human blood vessel, and their growth and performance were compared to those of cells grown inside a rectangular microchannel. This study provides a helpful perspective for building a platform that mimics in vivo environments in a more realistic manner.
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Lin, Quan Kui, Xiao Jie Huang, Jun Mei Tang, and Hao Chen. "Facile and Efficient Anti-Fouling Surface Construction on Poly(dimethylsiloxane) via Mussel-Inspired Chemistry." Advanced Materials Research 749 (August 2013): 344–49. http://dx.doi.org/10.4028/www.scientific.net/amr.749.344.
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Poly (dimethylsiloxane) (PDMS) silicones have found many applications in biomedical devices, such as catheters and intraocular lenses. But their hydrophobicity makes the possibility of the unexpected bioadhesion. In this paper, we reported a facile and efficient anti-fouling surface modification method on PDMS via self-polymerization of dopamine and the followed hyaluronic acid immobilization. Dopamine, commonly used as a neurotransmitter, is also a small molecule mimic of the adhesive proteins of mussels. Self-polymerization of dopamine can produce a thin polydopamine (PDA) layer on PDMS surface. Subsequently, thiol group functionalized hyaluronic acid (denoted as HA-SH) was immobilized covalently onto the resultant surface by the coupling between thiol group and reactive polydopamine layer. Then, the in vitro adhesion behaviors of the lens epithelial cells (LECs) and macrophage were investigated for evalution the anti-fouling effect of the hyaluronic acid modified PDMS surface. The results indicated that the cellular adhesion on PDMS were greatly decreased after hyaluronic acid modification, which suggested the potential application of such hyaluronic acid modified PDMS in biomedical applications.
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Sousa-Cardoso, Francisca, Rita Teixeira-Santos, Ana Francisca Campos, Marta Lima, Luciana C. Gomes, Olívia S. G. P. Soares, and Filipe J. Mergulhão. "Graphene-Based Coating to Mitigate Biofilm Development in Marine Environments." Nanomaterials 13, no. 3 (January 18, 2023): 381. http://dx.doi.org/10.3390/nano13030381.
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Due to its several economic and ecological consequences, biofouling is a widely recognized concern in the marine sector. The search for non-biocide-release antifouling coatings has been on the rise, with carbon-nanocoated surfaces showing promising activity. This work aimed to study the impact of pristine graphene nanoplatelets (GNP) on biofilm development through the representative marine bacteria Cobetia marina and to investigate the antibacterial mechanisms of action of this material. For this purpose, a flow cytometric analysis was performed and a GNP/polydimethylsiloxane (PDMS) surface containing 5 wt% GNP (G5/PDMS) was produced, characterized, and assessed regarding its biofilm mitigation potential over 42 days in controlled hydrodynamic conditions that mimic marine environments. Flow cytometry revealed membrane damage, greater metabolic activity, and endogenous reactive oxygen species (ROS) production by C. marina when exposed to GNP 5% (w/v) for 24 h. In addition, C. marina biofilms formed on G5/PDMS showed consistently lower cell count and thickness (up to 43% reductions) than PDMS. Biofilm architecture analysis indicated that mature biofilms developed on the graphene-based surface had fewer empty spaces (34% reduction) and reduced biovolume (25% reduction) compared to PDMS. Overall, the GNP-based surface inhibited C. marina biofilm development, showing promising potential as a marine antifouling coating.
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Whulanza, Yudan, Hanif Nadhif, Jos Istiyanto, Sugeng Supriadi, and Boy Bachtiar. "PDMS Surface Modification Using Biomachining Method for Biomedical Application." Journal of Biomimetics, Biomaterials and Biomedical Engineering 26 (February 2016): 66–72. http://dx.doi.org/10.4028/www.scientific.net/jbbbe.26.66.
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Engineering a cell-friendly material in a form of lab-on-chip is the main goal of this study. The chip was made of polydimethyl siloxane (PDMS) with a surface modification to realize a groovy structure on its surface. This groovy surface was naturally and randomly designed via biomachining process. This measure was aimed to improve the cell attachment on the PDMS surface that always known as hydrophobic surface. The biomachined surface of mold and also products were characterized as surface roughness and wettability. The result shows that the biomachining process were able to be characterized in three classes of roughness on the surface of PDMS.
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Dabaghi, Mohammadhossein, Shadi Shahriari, Neda Saraei, Kevin Da, Abiram Chandiramohan, Ponnambalam Ravi Selvaganapathy, and Jeremy A. Hirota. "Surface Modification of PDMS-Based Microfluidic Devices with Collagen Using Polydopamine as a Spacer to Enhance Primary Human Bronchial Epithelial Cell Adhesion." Micromachines 12, no. 2 (January 26, 2021): 132. http://dx.doi.org/10.3390/mi12020132.
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Polydimethylsiloxane (PDMS) is a silicone-based synthetic material used in various biomedical applications due to its properties, including transparency, flexibility, permeability to gases, and ease of use. Though PDMS facilitates and assists the fabrication of complicated geometries at micro- and nano-scales, it does not optimally interact with cells for adherence and proliferation. Various strategies have been proposed to render PDMS to enhance cell attachment. The majority of these surface modification techniques have been offered for a static cell culture system. However, dynamic cell culture systems such as organ-on-a-chip devices are demanding platforms that recapitulate a living tissue microenvironment’s complexity. In organ-on-a-chip platforms, PDMS surfaces are usually coated by extracellular matrix (ECM) proteins, which occur as a result of a physical and weak bonding between PDMS and ECM proteins, and this binding can be degraded when it is exposed to shear stresses. This work reports static and dynamic coating methods to covalently bind collagen within a PDMS-based microfluidic device using polydopamine (PDA). These coating methods were evaluated using water contact angle measurement and atomic force microscopy (AFM) to optimize coating conditions. The biocompatibility of collagen-coated PDMS devices was assessed by culturing primary human bronchial epithelial cells (HBECs) in microfluidic devices. It was shown that both PDA coating methods could be used to bind collagen, thereby improving cell adhesion (approximately three times higher) without showing any discernible difference in cell attachment between these two methods. These results suggested that such a surface modification can help coat extracellular matrix protein onto PDMS-based microfluidic devices.
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Martinez, Miguel Angel, Juana Abenojar, and Sara Lopez de Armentia. "Environmentally Friendly Plasma Activation of Acrylonitrile–Butadiene–Styrene and Polydimethylsiloxane Surfaces to Improve Paint Adhesion." Coatings 8, no. 12 (November 26, 2018): 428. http://dx.doi.org/10.3390/coatings8120428.
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Generally, polymeric materials present an issue related to their low surface energy: low painting ability. The main aim of this work is to improve the adhesion between polymeric surfaces (polydimethylsiloxane (PDMS), and acrylonitrile-butadiene-styrene (ABS)) and paints (epoxy (EP), and polyurethane (PU)-based). In order to increase adhesion, hydrophilic modification of surfaces by atmospheric pressure plasma torch treatment (APPT) was proposed. Furthermore, it can permit dissimilar joints, i.e., ABS with a metal joined by a silicone (based PDMS), to be painted. The surface modifications were characterized by measurements of surface energy and roughness. In addition, the effectiveness of the pre-treatment on improving paint adhesion was confirmed by scratch, cross-cut, and adhesion tests. Results showed the possibility of coating both ABS and PDMS with a PU-based paint when treated with plasma. As a novel result, polymer and metal panels joined by silicone were able to be painted with the PU paint.
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Zhang, Qiushu, Bei Peng, Mengqi Chu, Pan Wen, Song Wang, and Jintao Xu. "Curved Film Microstructure Arrays Fabricated via Mechanical Stretching." Micromachines 12, no. 11 (October 20, 2021): 1281. http://dx.doi.org/10.3390/mi12111281.
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We report on curved film microstructure arrays fabricated through polydimethylsiloxane (PDMS) film buckling induced by mechanical stretching. In the process of the microstructure preparation, a PDMA film is glued on a bidirectionally prestretched PDMS sheet that has a square distributed hole array on its surface. After releasing the prestrain, the film microstructure array is created spontaneously. The fabricated microstructures possess a spherical surface and demonstrate very good uniformity. The film microstructure arrays can serve as microlens arrays with a focal length of 1010 μm. The microstructure formation mechanism is investigated via theoretical analysis and numerical simulation. The simulation results agree well with the experimental results. The prestrain applied by mechanical stretching during the fabrication has an important effect on the shape of the resulting film microstructures. The microstructure geometry can be easily tuned through controlling the applied prestrain.
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Wang, Juanjuan, Lele Li, Enping Liu, Xue Han, and Conghua Lu. "Ultrasonic-Assisted Deposition Method for Creating Conductive Wrinkles on PDMS Surfaces." Coatings 12, no. 7 (July 6, 2022): 955. http://dx.doi.org/10.3390/coatings12070955.
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Harnessing surface wrinkle surfaces in various functional devices has been a hot topic. However, rapidly creating wrinkled surfaces on elastomers of arbitrary shape (especially curved surfaces) is still a great challenge. In this work, an ultrasonic-assisted deposition method has been proposed to achieve nanomodification of the robust layer (e.g., carbon nanotubes (CNTs)) with a labyrinth wrinkle pattern on polydimethylsiloxane (PDMS) fiber, sheet, and porous sponge. It is found that the swelling effect of the dispersion and the ultrasonic treatment play vital roles in the surface wrinkling. As a demonstration, the conductive wrinkled CNTs@PDMS fibers were assembled as stretchable strain sensors. The initial conductivity and the strain-sensing performances could be well tuned by simply adjusting the ultrasonic treatment time. The wrinkled CNTs@PDMS fiber strain sensor exhibited remarkable stretchability (ca. 300%) and good sensitivity, which can be applied in various human motion detection, voice recognition, and air-flow monitoring. It is also expected that the facile ultrasonic-assisted deposition method for surface wrinkling can be extended to fabricate various smart devices with promoted performances.
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Duo, Shu Wang, Mi Mi Song, Ting Zhi Li, Ying Luo, and Mei Shuan Li. "Polyhedral Oligomeric Silsesquioxane/PDMS Hybrid Coating Protecting Polyimide from Atomic Oxygen Erosion." Advanced Materials Research 189-193 (February 2011): 336–39. http://dx.doi.org/10.4028/www.scientific.net/amr.189-193.336.
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Hybrid inorganic/organic polymers have been prepared by copolymerizing a silanol terminated polydimethylsiloxane (PDMS) with an Octa(aminophenyl) -silsesquioxane (POSS). The AO resistance of these POSS/PDMS hybrid films was tested in the ground-based AO simulation facility. Exposed and unexposed surfaces have been characterized by X-ray photoelectron spectroscopy. The XPS data indicate that the carbon content of the near-surface region is decreased from 65.3 to 18.9 at% after AO exposure. The oxygen and silicon concentrations in the near-surface region increase after AO exposure. The data reveal the formation of a passive inorganic SiO2 layer on the POSS/PDMS hybrid films during the AO exposure, which serves as a protective barrier preventing further degradation of the underlying polymer with increased exposure to the AO flux. The erosion yield of the POSS/PDMS (20 wt%) hybrid film was 1.7×10-26 cm3/atom, decreased by two orders of magnitude compared with the value of 3.0×10-24 cm3/atom of the polyimide film.
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Choi, Young, Sang Hyun Park, Sung Min Park, Gyung Mok Nam, Seung Pyo Woo, Sang Heon Park, Won Young Uhm, and Sang Hee Yoon. "Effects of GnF Concentration on the Mechanoelectrical Properties and Surface Morphology of GnF/PDMS Composites." Key Engineering Materials 765 (March 2018): 65–69. http://dx.doi.org/10.4028/www.scientific.net/kem.765.65.
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The graphite nanoflake (GnF)-reinforced polydimethylsiloxane (PDMS) composites (GnF/PDMS composites) are developed as new polymer matrix composites (PMCs) with controllable mechanoelectrical properties. Here, we investigate the effect of GnF concentration on the mechanoelectrical properties (i.e., elastic modulus, fracture strain, and conductivity) of GnF/PDMS composites; the change in the surface morphology of GnF/PDMS composites caused by a variation in GnF concentration is also explored. The mechanoelectrical properties are measured by performing tensile tests on the GnF/PDMS composite specimens with different GnF concentrations of 5.0, 10.0, 12.5, 15.0, 20.0, and 25.0 wt.%. The surface morphology is analyzed in terms of internal void formation and surface roughness. The elastic modulus is measured to be in the range of 1.62 to 13.8 MPa which is proportional to GnF concentration, while the fracture strain and electrical conductivity are respectively characterized to be in ranges of 0.09 to 2.09 and 0.3 to 221.0 S/m which are in inverse proportion to GnF concentration. An increase in GnF concentration leads to increases in internal voids’ amount and surface roughness. The GnF/PDMS composites can be used as sensing materials for detecting both small and large deformations in a variety of engineering applications.
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Hashemzadeh, Hadi, Abdollah Allahverdi, Mosslim Sedghi, Zahra Vaezi, Tahereh Tohidi Moghadam, Mario Rothbauer, Michael Bernhard Fischer, Peter Ertl, and Hossein Naderi-Manesh. "PDMS Nano-Modified Scaffolds for Improvement of Stem Cells Proliferation and Differentiation in Microfluidic Platform." Nanomaterials 10, no. 4 (April 2, 2020): 668. http://dx.doi.org/10.3390/nano10040668.
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Microfluidics cell-based assays require strong cell-substrate adhesion for cell viability, proliferation, and differentiation. The intrinsic properties of PDMS, a commonly used polymer in microfluidics systems, regarding cell-substrate interactions have limited its application for microfluidics cell-based assays. Various attempts by previous researchers, such as chemical modification, plasma-treatment, and protein-coating of PDMS revealed some improvements. These strategies are often reversible, time-consuming, short-lived with either cell aggregates formation, not cost-effective as well as not user- and eco-friendly too. To address these challenges, cell-surface interaction has been tuned by the modification of PDMS doped with different biocompatible nanomaterials. Gold nanowires (AuNWs), superparamagnetic iron oxide nanoparticles (SPIONs), graphene oxide sheets (GO), and graphene quantum dot (GQD) have already been coupled to PDMS as an alternative biomaterial enabling easy and straightforward integration during microfluidic fabrication. The synthesized nanoparticles were characterized by corresponding methods. Physical cues of the nanostructured substrates such as Young’s modulus, surface roughness, and nanotopology have been carried out using atomic force microscopy (AFM). Initial biocompatibility assessment of the nanocomposites using human amniotic mesenchymal stem cells (hAMSCs) showed comparable cell viabilities among all nanostructured PDMS composites. Finally, osteogenic stem cell differentiation demonstrated an improved differentiation rate inside microfluidic devices. The results revealed that the presence of nanomaterials affected a 5- to 10-fold increase in surface roughness. In addition, the results showed enhancement of cell proliferation from 30% (pristine PDMS) to 85% (nano-modified scaffolds containing AuNWs and SPIONs), calcification from 60% (pristine PDMS) to 95% (PDMS/AuNWs), and cell surface marker expression from 40% in PDMS to 77% in SPION- and AuNWs-PDMS scaffolds at 14 day. Our results suggest that nanostructured composites have a very high potential for stem cell studies and future therapies.
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DONG, L. M., G. X. LIAO, C. LIU, S. S. YANG, and X. G. JIAN. "SYNTHESIS AND CHARACTERIZATION OF POLY(PHTHALAZINONE ETHER NITRILE) COPOLYMERS WITH HYDROPHOBIC SURFACE." Surface Review and Letters 15, no. 05 (October 2008): 705–9. http://dx.doi.org/10.1142/s0218625x08011731.
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Poly(phthalazinone ether nitrile) (PPEN) block copolymers containing polysiloxane were prepared so as to create a strongly hydrophobic polymer surface. The copolymers were synthesized from eugenol end-capped polydimethylsiloxane (PDMS) and fluoro-terminated PPEN oligomers by the aromatic nucleophilic substitution polycondensation in the presence of dimethyl sulfoxide/o-dichlorobenzene and K 2 CO 3 as solvents and catalyst, respectively. The resultant copolymers were characterized by FTIR, 1 H NMR, and gel permeation chromatography. XPS analysis results indicated that the copolymer film had a very rich PDMS segment surface. Atomic force microscopy further showed that there existed a continuous PDMS phase on the copolymer surface and PPEN as the dispersive particles was dispersed at diameters between 0.1 and 0.3 nm. The enrichment of PDMS in the copolymer surface could be responsible for an increase of surface water repellency (113.4°).
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Gokaltun, Aslihan, Martin L. Yarmush, Ayse Asatekin, and O. Berk Usta. "Recent advances in nonbiofouling PDMS surface modification strategies applicable to microfluidic technology." TECHNOLOGY 05, no. 01 (March 2017): 1–12. http://dx.doi.org/10.1142/s2339547817300013.
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In the last decade microfabrication processes including rapid prototyping techniques have advanced rapidly and achieved a fairly mature stage. These advances have encouraged and enabled the use of microfluidic devices by a wider range of users with applications in biological separations and cell and organoid cultures. Accordingly, a significant current challenge in the field is controlling biomolecular interactions at interfaces and the development of novel biomaterials to satisfy the unique needs of the biomedical applications. Poly(dimethylsiloxane) (PDMS) is one of the most widely used materials in the fabrication of microfluidic devices. The popularity of this material is the result of its low cost, simple fabrication allowing rapid prototyping, high optical transparency, and gas permeability. However, a major drawback of PDMS is its hydrophobicity and fast hydrophobic recovery after surface hydrophilization. This results in significant nonspecific adsorption of proteins as well as small hydrophobic molecules such as therapeutic drugs limiting the utility of PDMS in biomedical microfluidic circuitry. Accordingly, here, we focus on recent advances in surface molecular treatments to prevent fouling of PDMS surfaces towards improving its utility and expanding its use cases in biomedical applications.
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Kopeć, Kamil, Michał Żuk, and Tomasz Ciach. "HYDROGEL ANTIBACTERIAL COATING FOR SILICONE MEDICAL DEVICES." Progress on Chemistry and Application of Chitin and its Derivatives 26 (September 30, 2021): 135–47. http://dx.doi.org/10.15259/pcacd.26.012.
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Effective antibacterial coatings are in demand in medicine, especially for urological medical devices such as catheters and stents. We propose the production method of an antibacterial hydrogel coating on polydimethylsiloxane (PDMS, silicone), a popular surface for medical materials. The coating process consists of the following steps: PDMS surface activation (introduction of hydroxyl groups), silanisation (introduction of amine groups) and application of chitosan/alginate hydrogel with the addition of lysozyme as an antibacterial agent using the layer-by-layer method. We investigated the effect of polyion concentration on the coating mass, swelling ratio and stability. We analysed the adsorption of Micrococcus luteus, Escherichia coli and Proteus rettgeri on a PDMS surface using confocal laser scanning microscopy. The chitosan/alginate hydrogel coating with immobilised lysozyme protected the PDMS surface against adhesion for all three tested bacterial strains.