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Controlled Release of Hormones by Pellet Implants
Published in Emmanuel Opara, Controlled Drug Delivery Systems, 2020
Various materials have been used to manufacture hormone delivery pellets. Polydimethylsiloxane (PDMS) is a silicone-based organic polymer present in silicone capsules and silicone adhesives (Silastic®, Dow corning). It has been proven to be useful in preparing steroid capsules or pellets, because Silastic® allows steroids to pass through its walls, providing a means of chronic administration of the drugs for long periods of time (Dziuk and Cook 1966, Elsaesser et al. 1989) and its chemical inertness avoids inflammatory reactions (Kivisaari and Niinikoski 1973). This component is also present in other low-cost, commercially available adhesives such as FASTIX® (Akapol SA, Argentina). Some manufacturers do not disclose the composition of the matrix in their hormone pellet and consider them as proprietary.
Active Core Optical Fiber Chemical Sensors and Applications
Published in Kevin Yallup, Krzysztof Iniewski, Technologies for Smart Sensors and Sensor Fusion, 2017
AC-OFCS using polydimethylsiloxane (PDMS) polymer optical fibers have also been reported. PDMS has been used in manufacturing organic polymer optical fibers as well as a cladding material for conventional optical fibers that are used by communication industry. PDMS is a hydrophobic polymer and can be made by polymerizing dimethylsiloxane with some cross-linking agents in the existence of special catalysts. The reagent kits for making this polymer are available from commercial sources. Klunder et al. made PDMS fibers by using silicone sealing products, such as RTV-732 and RTV-from department stores. They investigated the application of these polymer fibers for sensing trichloroethene (TCE) in environmental samples.28,32 TCE absorbs NIR light with peak absorption wavelength at around 1.64 μm. A PDMS optical fiber of 10 mm length was connected with conventional optical fibers as a transducer. This sensor was reported for detecting TCE in water samples down to 1.1 ppm.
Fabrication of BioMEMS Devices
Published in Simona Badilescu, Muthukumaran Packirisamy, BioMEMS, 2016
Simona Badilescu, Muthukumaran Packirisamy
The fabrication of microstructures and micropatterns for BioMEMS devices with soft materials such as polymers and gels is sometimes called soft lithography. The term, a collective name for several techniques, was coined in the 1990s by Professor Whitesides and his group at Harvard University.15 They have developed many of the unconventional methods and unconventional materials for microfabrication that will be discussed later in this chapter. Soft polymeric materials possess many attractive properties, such as high toughness, recyclability, excellent biocompatibility, and biodegradability. Polymers are very desirable materials in the microfabrication of devices in contact with biological materials. Due to the variety of polymers, they offer a broad spectrum of physical and chemical properties for the design of biocompatible microsystems. Soft materials have many attributes that make them ideally suited for defining microfluidic, optical, and nanoelectromechanical structures with low-cost replication processes, such as molding and templating. One of the widely used materials for microfabrication of devices is polydimethylsiloxane (PDMS). PDMS is a silicone elastomer with properties that make it attractive for biomedical applications. It is thermally stable, permeable to gases with good optical and mechanical properties, in addition to being biocompatible, and it can be implanted in vivo. In addition, PDMS is not hygroscopic; that is, it does not swell with water and it shows little autofluorescence. Due to its very good sealing and bonding properties, PDMS has become the material of choice for microfluidics. It is also a cheap and commercially available material and has good elastic properties, allowing the fabrication of nonplanar structures.
Pervaporation separation of ethylacetate-ethanol mixtures using zeolite 13X-filled poly(dimethylsiloxane) membrane
Published in Chemical Engineering Communications, 2022
Sebnem Senol, Buket Kaya, Inci Salt, Berk Tirnakci, Yavuz Salt
Polydimethylsiloxane (PDMS) is a hydrophobic and nontoxic organic polymer having a flexible (Si–O) backbone (Lötters et al. 1997; Kausar 2020), and it has a higher free volume than glassy polymers, which allows them to exhibit better diffusion properties. PDMS can be used in many fields such as coatings, sensors, electronics, adhesives, membranes, biomedical applications, cosmetics, food industry, and lubricants (Vlassov et al. 2018; Kausar 2020). PDMS is an important membrane material in separating organic mixtures, and it offers advantages such as hydrophobicity, high thermal stability, low surface tension, biocompatibility and commercial availability (Lai et al. 2012; Liu et al. 2015; Vopicka et al. 2015; Wang et al. 2016). However, PDMS has poor mechanical properties due to its high chain mobility, and also, PDMS membranes generally exhibit high flux but low selectivity as a consequence of high free volume in the polymer network. Huang et al. (2006) reported that membrane performance improves with zeolite incorporation into the polymeric structure.
Efficient tunability and circuit model of nested-U nanoresonators in optical metasurfaces
Published in Journal of Modern Optics, 2018
Mojtaba Dehghani, Tavakol Pakizeh
Figure 1 indicates the schematics of array and unit cell of the proposed U-shaped resonators-based metasurfaces which are made of a flexible substrate. As shown in Figure 1, the NDU resonators are arranged on a periodic rectangular stretchable polydimethylsiloxane (PDMS) lattice (Px = 2 μm and Py = 1.5 μm). The thickness of patterned Au arrays is t = 100 nm. The PDMS is a highly flexible polymer with excellent mechanical durability, low dielectric loss and low thermal conductance (3,21). These features make it a usable substrate for tuning in metasurfaces and metamaterials by mechanical deformations (stretch). The geometric parameters of the NDU-resonator are shown in Figure 1. There, U-leg length l = 800 nm, lateral width d = 500 nm, line width w = 100 nm and the space between the tip of one U-shaped nano-element and horizontal arm of another U-element y = 100 nm, while the distance between two U-shaped elements is various. This distance is x = 100 nm in steady state.
Emerging applications of microfluidic techniques for in vitro toxicity studies of atmospheric particulate matter
Published in Aerosol Science and Technology, 2021
Fobang Liu, Nga Lee Ng, Hang Lu
While PDMS is the material that is mostly used for the fabrication of microfluidic devices because of its gas permeability, optical transparency, and biocompatibility, PDMS can absorb small hydrophobic organic compounds (Regehr et al. 2009; Toepke and Beebe 2006). This can be an issue for PM toxicity evaluation, since there are considerable amounts of hydrophobic organic components in PM and some of them (such as polycyclic aromatic hydrocarbons) are highly toxic (Jiang, Xu et al. 2019). Further research may be needed on biocompatible, optically transparent, economical, and easy-to-fabricate materials that are also resistant to absorption of small organic molecules (Berthier et al. 2019; Bhatia and Ingber 2014; Domansky et al. 2013; Sackmann, Fulton, and Beebe 2014).