1,721,142 research outputs found
Novel photopolymers and innovative technologies for the fabrication of microfluidic devices
No full textMicrofluidic devices can process and manipulate small amounts of fluids (nanoliters), using channels with a diameter of tens to hundreds of micrometers. One can effectively scale down chemical and analytical reactions to a microscopic size, reduce the quantities of reagents involved, increase the selectivity, efficiency and speed of the process, and minimize the involved costs. Therefore microfluidics represents an emerging technology in many areas of chemistry and biotechnology. Microelectronics provided the technologies suitable for the fabrication of the first microfluidic devices made of silicon and glass, but these materials have soon been displaced by polymers. However, some problems still exist regarding fabrication process, integration of microcomponents, and compatibility toward the reaction media. Consequently, the development of new materials or modification of existing polymers is still a key issue to guarantee the full success of microfluidic devices and their spreading on the market. Moreover an important aspect for the widespread availability of microfluidics is the optimization of new technologies for manufacturing devices. Only fabrication methods that guarantee a mass production of chips at low cost and that can be easily applied to different materials allow microfluidic devices to become versatile tools. It is therefore essential to explore new polymeric materials with properties suitable for specific applications in microfluidics and to develop rapid and low cost microfabrication technologies that do not limit the achievable features. Testing new polymeric materials and developing innovative fabrication technologies can certainly widen the application field of microfluidics. The research work carried out concerns the development of novel polymers suitable for the fabrication of microfluidic devices via innovative methodologies based on photopolymerization. First we prepared different UV cured polymers by photopolymerization of radical reactive systems, and some of them were selected (depending on their physico-chemical properties) for manufacturing microfluidic devices. For the fabrication of microfluidic devices, photopolymerization was coupled with lithographic techniques in order to develop direct or replicating methods. The different technologies based on UV curing we optimized allowed the fabrication of microfluidic devices in short times, without using solvents, and at room temperature. The obtained devices were then tested for chemical and biological microfluidic application
Photopolymerization of acrylic oligomers and photolithographic processes for the fabrication of microfluidic devices
No full textUndercuring and oxygen inhibition as strategies for bonding and patterning fluorinated photopolymers
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A novel disulfide-containing monomer for photoinitiator-free self-healable photocured coatings
Full text linkIn recent years, UV-curable coatings have slowly replaced solvent-based ones, mainly due to their sustainable features such as low energy consumption and fast curing process. Crosslinked photocured networks containing linear disulfides have attracted a lot of attention due to the peculiar properties and responsiveness of S-S bonds[1], which make them suitable for several applications, chief among them self-healable materials[2,3]. Indeed disulfide bonds are recognized for their sensitivity to several stimuli, and cleavage of disulfide with the formation of thiyl radicals could be easily achieved.
Based on these distinctive features, herein a novel photocurable diacrylated polyurethane monomer containing disulfide bonds (DSPDA)[4] was synthesized through a one-step process without the need for further purification. The photopolymerization kinetics of the monomer was studied through real-time FTIR, highlighting a fast and complete conversion. High acrylate conversions were reached even in the absence of a photoinitiator, thus demonstrating the self-initiating capabilities of the synthesized monomer thanks to disulfide cleavage and thiyl radicals generation upon UV light exposure. Clear coatings were produced using DSPDA monomer and disulfide dynamicity was exploited to obtain self-healing of surface scratches after heat application
A novel disulfide-containing monomer for photoinitiator-free self-healable photocured coatings
Full text linkDisulfide-containing coatings are gaining importance due to the peculiar properties and responsiveness of S-S bonds, which make them suitable for several applications, first among them self-healable materials. Herein, a novel UV-curable diacrylated polyurethane monomer containing disulfide bonds (DSPDA) was synthesized through a one-step process without the need for further purification, as assessed by NMR and HPLC analyses. The photopolymerization kinetics of the monomer was studied through real-time FTIR, highlighting a fast and complete conversion even in the absence of a photoinitiator, thus demonstrating the self-initiating capabilities of the synthesized monomer based on the disulfide cleavage upon UV light exposure. Clear coatings having a Tg = 72 °C were obtained. The self-healing ability of the films was assessed: thanks to the presence of disulfide bonds in the cured coating, a recovery of the damage was obtained in only 10 min by heating at 100 °C
Novel disulfide-containing monomers for dynamic UV-cured inks and coatings
Full text linkDynamically crosslinked networks containing linear disulfides have attracted a lot of interest due to the high responsiveness of disulfide bonds to plenty of external stimuli, like pH, light, temperature, and redox conditions. The introduction of this type of bonds into acrylic networks allows obtaining a triggerable material that could be used for designing new coatings with tailored properties, such as self-healing and deinking capabilities. In this work, novel acrylic monomers containing disulfide bonds are synthesized and UV-cured, obtaining transparent coatings. The reactivity of the systems is studied by rt-FTIR, demonstrating that the photocleavage of the disulfide bonds can be used as an innovative way to start the photopolymerization reaction, leading to a self-initiated mechanism and avoiding the use of photoinitiators
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