Search

The JKR (Johnson–Kendall–Roberts) method of contact mechanics has been widely utilized for measuring adhesion properties between a deformable elastomeric lens and various materials. Such measurements are normally performed in air. We attempted to verify whether the JKR technique could be practical for evaluating adhesion properties under water. After modifying the common JKR apparatus to be suitable for underwater studies, two types of hydrophobic coating systems, silicone/silicone and silicone/silanized silicon wafer, were used. The work of adhesion ( W A ) values obtained from loading measurements and under zero load were found to be slightly smaller than the values estimated using surface energies and contact angles of water formed on the surfaces of these coatings. One possible cause for the slightly smaller values could be contamination/alteration of the coating surface properties upon immersion in water. The results suggested that, with proper control of experimental conditions, the JKR technique could be extended to evaluate adhesion properties under water. [ABSTRACT FROM AUTHOR]

Abstract: Silicone elastomers are widely used in implantable devices, including silicone breast implants. These rubbers are generally formed/cured using platinum-catalyzed hydrosilylation. The current scientific literature on the chemistry of platinum is reviewed, as it applies to the use of platinum catalysts for cure of silicone elastomers destined for use in silicone breast implants. These discussions serve as a basis to examine the recent literature describing release of platinum into tissues adjacent to silicone breast implants, the chemical nature of the platinum present in breast implants and the possible association between platinum and clinical outcomes. [Copyright &y& Elsevier]

The integration of more and more functionality into smaller and smaller form factor electronic products, drives the need for denser chip to substrate interconnect systems. As the number of I/O pins increases, the use of area array chips or packages becomes inevitable. Metal patterned elastomer chip sockets have now been improved to work with contact densities as high as 80 000 contacts/cm² corresponding to a pitch of 36 μm. Sockets with 10 000 contacts and a 72-μm pitch have survived more than 400 cycles in air-to-air thermal cycling chambers as well as freezing shocks caused by dipping into liquid nitrogen. Although the daisy chain test circuits breaks for temperatures lower than -50 °C and higher than 90 °C, they always return to the initial resistance values when entering the normal temperature range. The combination of a gold-to-gold contact interface and the elastic features of the contact bumps makes this socket an ideal compliance layer between bare chips and different types of carrier substrates, reducing the problems caused by thermomechanical mismatch between the substrate and the chip. Bad dies can easily be replaced, since the chip is not soldered or glued to the socket. The size and the possibility to control the geometry of the contacts provides means to maintain a good high-frequency characteristic impedance matching all the way to the chip pad. [ABSTRACT FROM AUTHOR]

Abstract: Instead of conventional method such as thermal cross-linking method, γ-irradiation is used to improve the properties of polydimethylsiloxane (PDMS) as a matrix containing progesterone. The thermal cross-linking of PDMS monolithic systems containing drug is deleterious to the drug. Usually, all drugs are unstable both at high vulcanizing temperature and in the presence of peroxide catalysts. This novel method is found to be effective for the stability of the controlled drug delivery systems. The PDMS (three medical grades) matrices were exposed to γ-irradiation in ambient conditions with total doses of 50, 75 and 100kGy. The mechanical properties confirmed that the samples are cross-linked. It is found that the progesterone release rate is affected by irradiation treatment. It is deduced, however that there is no significant difference in the release profile of progesterone by increasing the irradiation dose from 50 to 100kGy. [Copyright &y& Elsevier]

Abstract: The enzyme α-chymotrypsin, a model for catalytic proteins, was entrapped in different silicone elastomers that were formed via the condensation-cure room temperature vulcanization (CC-RTV) of silanol terminated poly(dimethylsiloxane) with tetraethyl orthosilicate as a crosslinker, in the presence of different poly(ethylene oxide) oligomers that were functionalized with triethoxysilyl groups. The effects of various chemical factors on both the activity and entrapping efficiency of proteins (leaching) were studied using a 2-level fractional factorial design—a chemometrics approach. The factors studied include the concentration and chain length of poly(ethylene oxide), enzyme content, and crosslinker (TEOS) concentration. The study indicated that poly(ethylene oxide) can stabilize the entrapped α-chymotrypsin in silicone rubber: the specific activity can be maximized by incorporating a relatively high content of short chain, functional PEO. Increased enzyme concentration was found to adversely affect the specific activity. The effect of TEOS was found to be insignificant when PEO was present in the elastomer, however, it does affect the activity positively in the case of simple elastomers. [Copyright &y& Elsevier]

Abstract: Lipase Candida rugosa was entrapped in silicone rubber via condensation-cure room temperature vulcanization of silanol-terminated poly(dimethylsiloxane) with tetraethyl orthosilicate as a crosslinker, to give a highly active silicone-enzyme elastomer. The effect on enzyme activity of addition of water and hydrophilic polymeric moieties based on poly(ethylene oxide) 2 was examined, as were crosslinker concentration, enzyme concentration, and elastomer thickness. It was demonstrated that lipase is most active in silicone elastomers and more active in silicone oils than simple hydrocarbons. Crosslink density in these elastomers was not an important factor in the reactivity of the rubber. However, the addition of hydrophilic species prior to elastomer formation decreased the efficiency both of the dispersion of the enzyme and the resulting activity of the elastomer. This effect could be moderated by prior exposure of the lipase to silicone oil. Thus, hydrophobic silicones play a protective/activating role for lipase. [Copyright &y& Elsevier]

Abstract: Two new types of passive samplers were designed and tested on semivolatile organic compounds. The first type (a spiral-rod sampler) consists of a low-density polyethylene membrane acting as a permeation film and a silicone elastomer as the receiving material; the second (a stir-bar sampler) has the same membrane material but a polydimethylsiloxane-coated stir bar acting as the collector phase and installed radially symmetrically in the sampler. The advantages of the new samplers are their simple design, low costs, and their easy processing via thermodesorption coupled with capillary gas chromatography and mass selective detection. In both samplers, the uptake of selected analytes was integrative over exposure periods of up to 384h. The sampling rates calculated from a laboratory calibration study using the chlorinated semivolatiles hexachlorobenzene, hexachlorocyclohexane isomers and polychlorinated biphenyls ranged from 88.1mlh−1 for δ-hexachlorocyclohexane to 3443mlh−1 for 2,2′,5,5′-tetrachlorobiphenyl. A field trial at a hazardous waste dump near Bitterfeld, Germany, for up to 21days combined with periodical determinations of air concentrations using low-volume sampling indicated that the new samplers can in principle be used in the field, although the sampling rates derived from the field results differed considerably from the laboratory findings. Nevertheless the preliminary results suggest that the new sampler types are promising for the long-term air monitoring of semivolatiles. [Copyright &y& Elsevier]

Recent demands for non-toxic antifouling technologies have led to increased interest in coatings based on silicone elastomers that 'release' macrofouling organisms when hydrodynamic conditions are sufficiently robust. However, these types of coatings accumulate diatom slimes, which are not released even from vessels operating at high speeds ( > 30 knots). In this study, adhesion strength and motility of three common fouling diatoms ( Amphora coffeaeformis var. perpusilla (Grunow) Cleve, Craspedostauros australis Cox and Navicula perminuta Grunow) were measured on a polydimethylsiloxane elastomer (PDMSE) and acid-washed glass. Adhesion of the three species was stronger to PDMSE than to glass but the adhesion strengths varied. The wall shear stress required to remove 50% of cells from PDMSE was 17 Pa for Craspedostauros , 24 Pa for Amphora and >> 53 Pa for Navicula ; the corresponding values for glass were 3, 10 and 25 Pa. In contrast, the motility of the three species showed little or no correlation between the two surfaces. Craspedostauros moved equally well on glass and PDMSE, Amphora moved more on glass initially before movement ceased and Navicula moved more on PDMSE before movement ceased. The results show that fouling diatoms adhere more strongly to a hydrophobic PDMSE surface, and this feature may contribute to their successful colonization of low surface energy, foul-release coatings. The results also indicate that diatom motility is not related to adhesion strength, and motility does not appear to be a useful indicator of surface preference by diatoms. [ABSTRACT FROM AUTHOR]

A technique is discussed for producing a robust ultrasound (US)-compatible flow phantom that consists of a thin-walled silicone-elastomer vessel with a lumen of arbitrary geometry, embedded in an agar-based tissue-mimicking material (TMM). The TMM has an acoustic attenuation of 0.56 dB cm-1 MHz-1 at 5 MHz, with nearly linear frequency-dependence and acoustic velocity of 1539 ± 4 m s-1. The vessel-mimicking material (VMM) has an acoustic attenuation of 3.5 dB cm-1 MHz-1 with linear frequency-dependence and an acoustic velocity of 1020 ± 20 m s-1. Scattering particles, which are added to the VMM to increase echogenicity and add speckle texture, lead to higher attenuation, depending on particle concentration and frequency. The VMM is stable over time, with a Young’s elastic modulus of 1.3 to 1.7 MPa for strains of up to 10%, which mimics human arteries under typical physiological conditions. The phantom is sealed to prevent TMM exposure to air or water, to avoid changes to the acoustic velocity. [Copyright &y& Elsevier]

The long-term fixation of cemented femoral components may be jeopardised by the presence of a fibrous tissue layer at the bone–cement interface. This study used both experimental and finite element (FE) methods to investigate the load transfer characteristics of two types of cemented hip replacements (Lubinus SPII and Mu¨ller-Curved) with a fibrous tissue layer.The experimental part investigated six stems of each type, where these were implanted in composite femurs with a specially selected silicone elastomer modelling the soft interfacial layer. Two fibrous tissue conditions were examined: a layer covering the full cement mantle, representing a revision condition; and a layer covering the proximal portion of the cement mantle, representing a non-revised implant with partial debonding and fibrous tissue formation. The FE method was used to model the full fibrous tissue layer condition, for both implants. The layer was modelled as a homogeneous, linearly isotropic material. A cross-comparison was performed of the experimental and FE findings.Agreement between experimental and FE models was verified to be within 15%. Varying the stiffness parameter of the FE soft tissue layer had little influence on the cortical bone strains, though had considerable effect on the cement strains. Stress shielding occurred for both stems under both fibrous tissue conditions, with the greatest reduction around the calcar. However, the cortical bone strains were generally larger than those for the equivalent well-fixed stems. The fibrous tissue layer was not found to increase the general strain pattern of the cement mantle, though localised regions of high stress were detected. [Copyright &y& Elsevier]

Oxybutynin, a drug of choice in the treatment of urinary incontinence, has low oral bioavailability due to extensive first-pass metabolism. A toxic metabolite, N-desethyloxybutynin, has been linked to adverse reactions to oral oxybutynin. This study, therefore, reports on the design of an oxybutynin intravaginal ring (IVR) of reservoir design, comprising an oxybutynin silicone elastomer core encased in a non-medicated silicone sheath, manufactured by reaction injection moulding at 50 °C. An unusually high initial burst release of oxybutynin (42.7 mg in 24 h) was observed in vitro with a full length core (100 mg drug loading), with subsequent non-zero order drug release. Use of fractional segment cores substantially reduced the burst effect, yielding linear cumulative drug release versus time plots from days 2 to 14. Thus, a 1/8 fractional segment core gave a 24 h burst of 11.28 mg oxybutynin and, thereafter, zero order release at the target dose of 5 mg/day over 14 days. Two oxybutynin cores, each 1/16 of full length, gave a greater release than a single 1/8 core, due to core segment end effects resulting in an increased surface area for release. The burst release was investigated by determining drug solubilities in the propan-1-ol product of elastomer condensation cure (390 mg/ml) and in the elastomer itself (13.9–20.21 mg/ml, by direct extraction and indirect thermal methods). These high oxybutynin solubilities were considered the major contributors to the burst effect. It was concluded that use of a fractional segment core would allow development of a suitable oxybutynin reservoir IVR. [Copyright &y& Elsevier]

Through 97 patients over 9 years, the authors present a surgical treatment for “funnel chest” using custom-made silicone elastomer prothesis which are deeply placed, behind muscle and aponevroses. They justify the choice of this simple and non invasive technique, by the fact that this deformation is only morphological in most cases or even only inaesthetic with exceptionnal cardiac or pulmonary consequences. Patient’s motivation being mainly due to psychological disconfort, the non invasive aspect of the technique leads them to choose surgery, particularly as results are good and complications seldom. [Copyright &y& Elsevier]

Composite materials, specifically ceramic–polymer composites and metal–polymer composites have received increased interest in a number of engineering applications, from impact protection, microelectronics to tribology. The characteristics of Nd:YAG laser ablation of a B4C:polysiloxane mixture have been studied with the use of time-integrated spectroscopy, laser surface profiling and microscopic analysis. The removal process for a variety of pulse widths and pulse energies have been interpreted using Beer–Lambert analysis. The spectroscopy results show no discernible B4C contribution to the plasma emissions. The polymer on its own and the composite mixture produced mostly a thermal background emission spectrum. These results are supported by high speed imaging. The polymer material acts as a binder matrix in the system and is instantly dissociated by the laser irradiation. In general, the ablation of this composite material can be attributed mainly to a thermal process. [Copyright &y& Elsevier]

In this study, we prepared a series of binary and ternary silicate/silicone elastomer dielectric composites with excellent actuation and energy storage performance by incorporating talc (Tl), wollastonite (Wl) and halloysite nanotube (HNT) into methyl vinyl silicone rubber (MVSR). Tl or Wl can act as physical barriers to prohibit HNT from aggregating to obtain uniform dispersion, which eliminates the step of surface modification and simplifies the preparation process. In this composite system, Tl and Wl effectively improve the breakdown strength of MVSR, while HNT significantly increases the dielectric constant of MVSR. It is worth noting that the addition of Tl reduces the elastic modulus of Tl/MVSR composites. The 40 wt%Tl/MVSR composite obtains the maximum actuated strain of 8.79% under low electric field of 35.96 kV/mm, which is 43.6% higher than pure MVSR (6.12% under an electric field of 47.1 kV/mm). The 10 wt%Wl/MVSR composite obtains the maximum actuated strain of 12.76% because of high breakdown strength. The ternary composite Tl-HNT/MVSR and Wl-HNT/MVSR play a synergistic effect in improving the dielectric and electromechanical properties due to the simultaneous increase in dielectric constant and breakdown strength. The 10 wt%Wl-10 wt%HNT/MVSR composite obtains the maximum actuated strain of 16.22% and energy storage density of 54.19 kJ/m3, which is 165% and 76.3% higher than pure MVSR (6.12% and 30.74 kJ/m3), respectively. This work establishes a simple and effective method for high performance dielectric elastomer composites. [Display omitted] • Binary and ternary silicate/silicon elastomer dielectric composites are prepared. • The elastic modulus of MVSR is decreased by adding Tl. • The dispersion of HNT is improved by using Tl or Wl as physical barriers. • HNT increases dielectric constant while Tl and Wl improve breakdown strenghth. • Ternary composites obtain high actuated strain and energy storage density. [ABSTRACT FROM AUTHOR]

Anatomical models for research and education are often made of artificial materials that attempt to mimic biological tissues in terms of their mechanical properties. Recent developments in additive manufacturing allow tuning mechanical properties with microstructural designs. We propose a strategy for designing material microstructures to mimic soft tissue viscoelastic behaviour, based on a micromechanical Mori–Tanaka model. The model was applied to predict homogenised viscoelastic properties of materials, exhibiting a matrix-inclusion microstructure with varying inclusion volume fractions. The input properties were thereby obtained from compression relaxation tests on silicone elastomers. Validation of the model was done with experimental results for composite samples. Finally, different combinations of silicones were compared to mechanical properties of soft tissues (hepatic, myocardial, adipose, cervical, and prostate tissue), found in literature, in order to design microstructures for replicating these tissues in terms of viscoelasticity. The viscoelastic Mori–Tanaka model showed good agreement with the corresponding experimental results for low inclusion volume fractions, while high fractions lead to underestimation of the complex modulus by the model. Predictions for the loss tangent were reasonably accurate, even for higher inclusion volume fractions. Based on the model, designs for 3D printed microstructures can be extracted in order to replicate the viscoelastic properties of soft tissues. [ABSTRACT FROM AUTHOR]

The effect of multiwall carbon nanotubes (MWCNTs) and magnesium oxide (MgO) on the thermal conductivity of MWCNTs and MgO-reinforced silicone rubber was studied. The increment of thermal conductivity was found to be linear with respect to increased loading of MgO. In order to improve the thermal transportation of phonons 0.3 wt % and 0.5 wt % of MWCNTs were added as filler to MgO-reinforced silicone rubber. The MWCNTs were functionalized by hydrogen peroxide (H2O2) to activate organic groups onto the surface of MWCNTs. These functional groups improved the compatibility and adhesion and act as bridging agents between MWCNTs and silicone elastomer, resulting in the formation of active conductive pathways between MgO and MWCNTs in the silicone elastomer. The surface functionalization was confirmed with XRD and FTIR spectroscopy. Raman spectroscopy confirms the pristine structure of MWCNTs after oxidation with H2O2. The thermal conductivity is improved to 1 W/m·K with the addition of 20 vol% with 0.5 wt % of MWCNTs, which is an ~8-fold increment in comparison to neat elastomer. Improved thermal conductive properties of MgO-MWCNTs elastomer composite will be a potential replacement for conventional thermal interface materials. [ABSTRACT FROM AUTHOR]

When grasping objects with uneven or varying shapes, accurate pressure measurement on robot fingers is critical for precise robotic gripping operations. However, measuring the pressure from the sides of the fingertips remains challenging owing to the poor omnidirectionality of the pressure sensor. In this study, we propose an omnidirectional sensitive pressure sensor using a cone-shaped magnet slider and Hall sensor embedded in a flexible elastomer, which guarantees taking pressure measurements from any side of the fingertip. The experimental results indicate that the proposed pressure sensor has a high sensitivity (61.34 mV/kPa) in a wide sensing range (4–90 kPa) without blind spots on the fingertip, which shows promising application prospects in robotics. [ABSTRACT FROM AUTHOR]

Commercial conductive polysiloxane composites are usually unrecyclable and suffer from inherent poor mechanical properties. Herein, mechanically strong, healable, and reprocessable conductive carbon black (CB)/polysiloxane nanocomposites were prepared through incorporating dual crosslinks of imine bonds and Zn(II)-amino coordination bonds in elastomer networks. Following the energy-dissipating mechanisms of sacrificial bonds, the integration of coordination bonds led to the remarkable improvement of strength, stretchability, and toughness without compromising the self-healing ability or reprocessability. Furthermore, the sacrificial and reversible manner of coordination bonds in nanocomposites was studied in detail. In addition to enhancing the electrical conductivity of nanocomposites (i.e., 6.48 S/m at CB content of 12 wt%), the incorporation of CB could promote the rupture of sacrificial bonds and improve the energy-dissipating efficiency significantly. [ABSTRACT FROM AUTHOR]

Reconstruction of bone defects and contour irregularities in the craniofacial region is difficult and often requires complex solutions. This study investigated the tissue response, vascularization and bone ingrowth, in hydroxyapatite, porous polyethylene and silicone elastomer when used as bone graft substitutes. 24 albino rabbits (8 rabbits for each implant) were used in this investigation. Hydroxyapatite 500 particles, silicone rubber and porous high-density polyethylene were placed in the cavities formed with a drill in the rabbit frontal bones. As a part of a prospective study the vascularization rates of all implant materials were analyzed 10 days and 2 months after surgery using 99mTechnetium-MDP (Methylene diphosphonate) scintigraphy of the skull. The scintigraphic studies were performed 2 hours after intravenous injection of 4 mCi (148 MBq) 99mTc-MDP. The frontal bone was excised on the 10th and 60th days. All tissue specimens were placed first in 10% formalin and then in 10% nitric acid solution for decalcification. The vascularization, connective tissue ingrowth, foreign body reaction and bone regeneration around the implant were evaluated. Results of this study suggested that hydroxyapatite and porous polyethylene were stabilized in bone while as expected silicone was mobile, also hydroxyapatite implants are vascularized better and are more biocompatible than porous polyethylene. [ABSTRACT FROM AUTHOR]

Not much is known about the specific pathophysiologic mechanisms of soiling. Although the causes of soiling may vary, it is mostly associated with anorectal disorders that can deform the contour of the anus and anal canal. In most cases, this disorder can be treated successfully by medical or surgical therapy. If this appropriate treatment is not available or fails, reconstruction of the contour deformity of the anus by perianal (submucosal) injection of soft tissue bulking agents may be successful.The main purpose of this pilot study was to evaluate locoregional reaction and distant migration after local perianal injection of solid polydimethylsiloxane elastomer particles (Bioplastique™ implants).Twelve Lewis rats received a local perianal injection of Bioplastique™ implants. Six of them received an additional perianal injection of gentamicin. Six weeks after injection, the rats were euthanized.Microscopically, the local tissue reaction was that of a quiescent foreign body reacting with encapsulation. Microscopic examinations could not reveal any migration to locoregional lymph nodes, liver, spleen, lungs, or brain.We conclude that, because of minimum local reaction and lack of evidence of distant migration, polydimethylsiloxane elastomer particle paste (Bioplastique™ implants) seems to be a potentially safe substance for local perianal injection. [ABSTRACT FROM AUTHOR]

Shunt infections after implantation or revision of a shunt for CSF drainage in hydrocephalic patients are serious complications. In view of their frequency, this study investigated the efficacy of prophylactic administration of a single dose of the antibiotic cefazedone in reducting in the post-operative infection rate. Fifty children of up to 14 years of age suffering from hydrocephalus of various etiologies were treated prophylactically and compared with a similar untreated group. The diagnosis of infection was based mainly on microbiological and clinical observations and investigations. Classical infection parameters were also recorded and evaluated, but played only a secondary role in establishing the diagnosis as they can change post-operatively without an infection being present. The infection rates observed were 6% in the group of patients who received antibiotic treatment prophylactically and 14% in the untreated control group. [ABSTRACT FROM AUTHOR]

The absence of an ear is a considerable aesthetic problem which affects the patient's psychology and social behaviour. We are describing a case of 25-year-old male reporting to the Department of Prosthodontics, with a chief complaint of deficient left auricular tissue. This can be corrected surgically, prosthetically or through a combination of these approaches; but the choice of treatment depends on patient. The patient chose prosthetic rehabilitation over surgical procedures & retention becomes a critical issue in this approach. Out of many types of retentive methods, we selectively incorporated new materials and used the latest technology to ensure the highest quality prosthesis. Creative approach for each patient with a focus on their individual needs was considered as it gives more satisfaction to the patient. This article describes a new, simple and cost effective technique by embedding Bluetooth-headset device into the silicone elastomer of a mechanically-retained auricular prosthesis. [ABSTRACT FROM AUTHOR]

Patients with acquired defects often had severe trauma which leads to psychological instability, functional loss and poor aesthetics. Digital defects threaten the integrity of one's self esteem and also leads to a reduced and compromised function. A well fitted and colour matched finger prosthesis can make a patient feel a capable person and not a handicap. This article describes a technique for fabrication of custom made finger prosthesis with a silicone elastomer. The customization of the prosthesis leads to a better fit and retention. An excellent shade matching is achieved by the use of intrinsic colours. The other advantages of using silicone as a material of choice for prosthesis fabrication are also discussed. [ABSTRACT FROM AUTHOR]

Majority of nosocomial infections are associated with biofilms growing on indwelling medical devices. These biofilms are nourished by a continuous flow of body fluids and subjected to shear stress forces. Cells dispersed from C. albicans biofilms are highly virulent and developmentally distinct from their parent biofilms. To study biofilm dispersed cells, it becomes imperative to isolate newly dispersed cells using a flow biofilm model. In this chapter, we detail the methods underlying assembly and workings of a simple flow biofilm model using materials commonly available in most microbiological laboratories. Biofilms developed using this system are robust and particularly suitable for studies requiring large amounts of biofilm (dispersed) cells for downstream analyses. Importantly, this apparatus mimics in vivo flow conditions, thereby making it a physiologically relevant model., (© 2022. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

The diversity and dynamics of the microbial species populating the human vagina are increasingly understood to play a pivotal role in vaginal health. However, our knowledge about the potential interactions between the vaginal microbiota and vaginally administered drug delivery systems is still rather limited. Several drug-releasing vaginal ring products are currently marketed for hormonal contraception and estrogen replacement therapy, and many others are in preclinical and clinical development for these and other clinical indications. As with all implantable polymeric devices, drug-releasing vaginal rings are subject to surface bacterial adherence and biofilm formation, mostly associated with endogenous microorganisms present in the vagina. Despite more than 50 years since the vaginal ring concept was first described, there has been only limited study and reporting around bacterial adherence and biofilm formation on rings. With increasing interest in the vaginal microbiome and vaginal ring technology, this timely review article provides an overview of: (i) the vaginal microbiota, (ii) biofilm formation in the human vagina and its potential role in vaginal dysbiosis, (iii) mechanistic aspects of biofilm formation on polymeric surfaces, (iv) polymeric materials used in the manufacture of vaginal rings, (v) surface morphology characteristics of rings, (vi) biomass accumulation and biofilm formation on vaginal rings, and (vii) regulatory considerations. [ABSTRACT FROM AUTHOR]

Precise thermomechanical positioning has been demonstrated in an actuator device based on a silicone elastomer with a high thermal expansion coefficient. The actuator performance has been characterized using optical microscopy, and the actuator has been deployed in an optical coupling experiment to demonstrate the precise positioning of a ball lens between two single-mode fibers. Tuning of the coupling efficiency has been achieved in excellent agreement with calculated values and precise positioning (better than 200 nm) over a range of 20 mum has been achieved with low power dissipation and temperature control of plusmn0.2 degC. The actuation is linear with temperature over the entire range of motion. This linearity was achieved while amplifying the thermally induced expansion of the elastomer along the alignment axis by a factor of 2.1 over its nominal isotropic expansion value by physically constraining the material in the device. The device performance gives favorable implications for the use of such actuators in optical packaging applications [ABSTRACT FROM PUBLISHER]

• Hydrophilic sponges are made from standard precursors in a simple 4-step process. • Our sponges have extraordinary high water absorbing capacity of 1600%. • Hydrophilic sponges may find use as dewatering agents for many nonpolar liquids. Separation of water from non-polar liquid mixtures (dewatering) is a challenging, yet an important problem in such fields as petroleum industry and power coolants. We describe a method of fabrication and properties of a high-capacity hydrophilic sponge based on polydimethylsiloxane (PDMS). The sponge is obtained by addition of 1-octanol and incorporating zinc chloride powder template in the precursor PDMS liquid followed by heat curing at 115 °C with subsequent elution of the template. The produced PDMS sponges have water absorbing capacity reaching approx. 1600%, which is two times higher than typically known for dewatering sorbents. Those high-capacity sponges may find use as dewatering agents for oils, hydrocarbons and other nonpolar liquids. [ABSTRACT FROM AUTHOR]

• Industrial primer formulations were used to bond silicone elastomers on metals. • One formulation comprising PMHS, vinyl-PDMS and Pt catalyst but no silanes. • Strong adhesion of the primer with mixture of silanes and reactive PDMSs. • Fumed silica filler promotes adhesion in the PDMSs based primers. The aim of this study was to explore the chemistry and adhesive properties of industrial primer formulations used for bonding silicone elastomers on AA6061 aluminum alloy. The composition of different primer formulations was determined using conventional chemical analyses. Adhesion strength was measured using 90° peel test. The formulation comprising partially condensed vinyltrimethoxysilane (VTMS) and tetrapropoxysilane (TPOS) and titanium tetrabutoxide (TTB) catalyst showed a strong adhesion to metal but a low adhesive strength of the primer-elastomer interface. 29Si NMR spectroscopy results have shown that exchange reactions of alkoxy groups of VTMS, TPOS and TTB has occurred in the formulation. Surprisingly, one formulation was free of silane and consisted of a one-component addition curing system comprising a SiH oligosiloxane, a vinyl-PDMS with a Pt catalyst and silica filler. This formulation enabled high cohesive strength of the primer and primer-elastomer interphase but it showed low adhesion to the metal. The more complex formulation containing a mixture of silanes (vinyltriethoxysilane, methyltriethoxysilane and tetraethoxysilane), a vinyl silicone gum, a hydroxy-terminated PDMS and silica filler resulted in the highest adhesive strength with 100 % cohesive failure in the elastomer. We found that the reinforcement effect of silica filler plays an important role in the promotion of adhesion. [ABSTRACT FROM AUTHOR]

Abstract: The present work uses nanoindentation method to measure the hardness of silicone elastomer annealed at 80 °C, 120 °C, 200 °C, 300 °C, and 350 °C for 60 min, respectively. Based on the apparent surface analysis, a linear relationship is found between the hardness and the reciprocal of the penetration depth. It is found that hardness of the polymer sample obviously decreases after annealing at 80 °C, which is due to the removal of any potential surface residual stresses under the initial annealing process. If the annealing temperature is larger than 300 °C, the hardness increased a lot. Therefore, from the characterization of surface hardness, what kind of (delete) temperature ever reached in the device made of silicone elastomer in the biology field can be deduced. [Copyright &y& Elsevier]

Multimode polymeric waveguides and 45° micromirrors have been fabricated using deep X-ray lithography. Polymethylmetacrylate was used as a core layer and silica and silicone elastomer as a lower and upper cladding layer, respectively. The propagation loss of the waveguide was 0.54 dB/cm at 830 nm and the loss of micromirrors was less than 0.43 dB at the wavelength. The X-ray lithography technique offers the controllability of mirror angles to 45° and -45° so that it gives flexibility to the system architecture of optical interconnections. [ABSTRACT FROM PUBLISHER]