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Objective: To date, no vascular model to analyze frictional forces between stent retriever devices and vessel walls has been designed to be similar to the real human vasculature. We developed a novel in vitro intracranial cerebrovascular model and analyzed frictional forces of three stent retriever devices. Methods: A vascular mold was created based on digital subtraction angiography of a patient's cerebral vessels. The vascular model was constructed using polydimethylsiloxane (PDMS, Dow Corning, Inc.) as a silicone elastomer. The vascular model was coated on its inner surface with a lubricating layer to create a low coefficient of friction (~0.037) to closely approximate the intima. A pulsatile blood pump was used to produce blood flow inside the model to approximate real vascular conditions. The frictional forces of Trevo XP, Solitaire 2, and Eric 4 were analyzed for initial and maximal friction retrieval forces using this vascular model. The total pulling energy generated during the 3 cm movement was also obtained. Results: Results for initial retrieval force were as follows: Trevo, 0.09 ± 0.04 N; Solitaire, 0.25 ± 0.07 N; and Eric, 0.33 ± 0.21 N. Results for maximal retrieval force were as follows: Trevo, 0.36 ± 0.07 N; Solitaire, 0.54 ± 0.06 N; and Eric, 0.80 ± 0.13 N. Total pulling energy (N·cm) was 0.40 ± 0.10 in Trevo, 0.65 ± 0.10 in Solitaire, and 0.87 ± 0.14 in Eric, respectively. Conclusions: Using a realistic vascular model, different stent retriever devices were shown to have statistically different frictional forces. Future studies using a realistic vascular model are warranted to assess SRT devices. [ABSTRACT FROM AUTHOR]

A procedure for 3D printing of silicone elastomers with a direct ink writing (DIW) process has demonstrated great potential in areas as diverse as flexible electronics, medical devices, and soft robotics. In this report, we propose a comprehensive guide for printing highly stretchable silicones in response to material, equipment and process dilemmas. Specifically, we first tested the material properties of Dow Corning 737, then modeled and simulated two commonly used needles to select a suitable needle, followed by parameter optimization experiments using the built DIW printer to find out the appropriate printing speed and layer height with a defined air pressure and needle diameter. Finally, the optimal combination of parameters was obtained. For further demonstration, artificial muscles and structurally complex soft grippers were also printed directly to verify the feasibility of high-precision 3D printing of soft actuators with soft materials. We believe that this work could provide a guide for further work using the DIW process to print soft matter in a wide range of application scenarios. [ABSTRACT FROM AUTHOR]

Optical couplant greases based on polydimethylsiloxane (PDMS) may be employed in devices such as scintillator-based radiation detectors that operate in extreme environmental conditions. The optical transmission of Dow Corning DOWSIL Q2-3067 optical couplant grease was measured at room temperature as a function of wavelength (200–800 nm) and grease thickness (0.13–1 mm). Across the spectral range, transmission decreased with increasing thickness, and the increase was more pronounced at wavelengths < 400 nm. An effective ultraviolet (UV) cutoff wavelength of ~270 nm was found, independent of grease thickness, although a weak transmission feature was observed below this cutoff at 233 nm. The optical transmission spectra exhibited a dependence on temperature, increasing with increasing temperature to 50 °C and decreasing with decreasing temperature to −10 °C. This temperature dependence was more pronounced at wavelengths < 400 nm and for thicker grease layers. Below −10 °C, transmission decreased sharply for all wavelengths. This decrease was correlated with a sharp increase in viscosity, indicating that the grease undergoes a thermal transition at −11 °C ± 1 °C. This thermal transition occurs more slowly with decreasing temperature for thinner layers of grease, but all measured grease thicknesses were reasonably opaque at temperatures below −20 °C. These results will aid in predicting the optical and mechanical performance of optical systems such as radiation detectors exposed to extreme outdoor environmental conditions. [ABSTRACT FROM AUTHOR]

This article investigates the dependency of temperature on electrical resistance (R) change in micro carbon fiber polymer composites (MCFPC), for further development as an Internet of Things sensor from previous research works. Three mixtures were prepared using Dow Corning's Silastic 145 as base polymer and made vary fiber content weight percentages: fiber diameter to length ratio ∅⁄l 0.13 and carbon fiber content of 13%; ∅⁄l:0.66 and carbon fiber contents of 40% and 50%. Composites tested were submitted to temperature loading, with a constant strain of 0.0%, for assessment of R when a change in the composite's temperature occurs. The composite response was observed to follow an Arrhenius function, for temperatures ranging from −10°C to 40°C. The apparent activation energy was calculated to evaluate further differences between carbon fiber contents and the sensitivity factor, S T due to temperature is determined. The specimens were also tested with a constant strain of 2.86% to assess creep. It was found that creep and R, over the period of time in the analysis, best fit a discrete latent variable model. The sensitivity factor change is determined in regard to stress relaxation, S R . The properties of MCFPC investigated here can be used to establish relationships between electrical resistance outputs and environmental loading conditions for this type of composites, enabling the possibility of deployment as part of a management system network for structural monitoring with real-time data acquisition. [ABSTRACT FROM AUTHOR]

Self-humidification is becoming a popular strategy for water management in proton exchange membrane fuel cells (PEMFCs), owing to the advantages of decreased volume, cost, and parasitic power of the hydrogen fuel cell engine. Membrane dehydration is one of the key issues that seriously affect the performance and lifespan of PEMFCs under low humidity conditions. In this work, an electrospinning approach was employed to fabricate gas diffusion layers (e-GDLs) composed of nanosized carbon fibers with a nanoscale pore structure. Further, a vapor deposition of Dow Corning Sylgard 184 was utilized to apply a hydrophobic coating to enhance the hydrophobicity of the e-GDL. The fabricated e-GDL can help alleviate the dehydration of the catalyst-coated membrane by increasing the breakthrough pressure. The breakthrough pressure of the e-GDL is five folds higher than that of the current commercial GDL, owing to the combined effects of the nanostructure and enhanced hydrophobicity. This superior characteristic is expected to effectively alleviate membrane dehydration under low humidity conditions. In addition, the e-GDL has excellent elastic deformability, which can effectively alleviate the irreversible damage caused by the pre-tightening force in the stack assembly process, thus enhancing the durability and lifetime of PEMFCs. [ABSTRACT FROM AUTHOR]

The chemical composition, microstructure, strength, and thermal stability of polymer-derived Sylramic™ SiC fibers fabricated by Dow Corning and COI Ceramics, Inc., and nitrogen-treated Sylramic™ SiC fibers, referred to as Sylramic™-iBN and Super Sylramic™-iBN SiC fibers, were investigated and compared. The baseline Sylramic™ SiC fibers fabricated by both vendors as well as the nitrogen-treated Sylramic™ SiC fibers are composed mostly of β-SiC (∼97 wt%) with small amounts of TiB 2 (∼2 wt%), amorphous carbon (∼1 wt%) and trace amounts of B 4 C. Most of the amorphous carbon is segregated at the core/interior of the fibers. Both baseline and nitrogen-treated Sylramic™ SiC fibers have similar grain size and pore size distribution, except for a thin layer of in-situ grown crystalline BN (30–70 nm) on the surface of Sylramic™-iBN and Super Sylramic™-iBN fibers. Wide variation in strength within a batch as well as between batches is observed in both baseline and nitrogen-treated Sylramic™ SiC fibers but both types of fibers are microstructurally stable at temperatures to 1800 °C in argon and nitrogen environments compared to Nicalon™-S and Tyranno®-SA SiC fibers. Under the same creep condition, Super Sylramic™-iBN fibers show better creep resistance compared to Sylramic™, Sylramic™-iBN, Hi-Nicalon™-S, and Tyranno®-SA fibers. Possible reasons for strength variability and the mechanism of in-situ BN formation on Sylramic™ SiC fibers are discussed. [ABSTRACT FROM AUTHOR]

Gas‐assisted injection molding is a polymer processing technology in which a penetrating gas bubble hollows out a plastic part as it cools and solidifies within a mold. In this study, non‐isothermal gas injection experiments at high capillary number illustrate the effects of delay time in gas injection, tube diameter, capillary number, and temperature‐sensitive fluid viscosity and flow activation energy on coating thickness. Experiments with polybutene H‐300 and Dow Corning silicon oil (DC‐200) in stainless steel tubing (1.27 and 0.635 cm) demonstrated fractional coverage increasing from 0.6 to a maximum in the range of 0.63–0.83 at short delay times, then decaying toward 0.6 at long delay times upon approaching the cooled isothermal state. Further analysis is drawn from simulations based on a simple theoretical model incorporating one‐dimensional heat transfer with convection at the outer surface of the mold, non‐isothermal behavior of the viscous fluid, and radial velocity profiles in the one‐phase fluid flow region. Quantitative agreement is found between experimental and simulated results. Two‐dimensional modeling and simulation methods extend the prior results to illustrate transient axial and radial heat transfer as well as flow behavior with respect to the penetrating gas bubble within the fluid flow region. [ABSTRACT FROM AUTHOR]

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For 20 years, the cold temperature/S10/von Hagens' plastination technique was used to preserve biological specimens without challenge. It became the "gold standard" for preservation of beautiful, dry biological specimens. Near the end of the 21st century, a group from the University of Michigan and environs and Dow Corning™, USA, combined silicone ingredients, similar to the von Hagens' plastination products, however in a different sequence. The new polymer (Cor‐tech) was combined with the cross‐linker to design the "impregnation mix" which would invade the cellular structure of the specimen and yet was stable at room temperature. Later, curing would be by application of the catalyst onto the impregnated specimen. This unique sequencing of products would become the "Room temperature/Dow Corning™/Corcoran—Silicone plastination technique." The results of this room temperature technique provided similar plastinates, beautiful and practical for demonstration, containing no toxic chemical residues and forever preserved. As the name implies, impregnation of this silicone mix could be done at room temperature, without having to be kept cold. Both processes (cold and room temperature) required the same four basic steps for plastination. As well, both processes used similar basic polymers and additives to produce plastinates. However, they were combined in a different sequence. Cold temperature combines polymer and catalyst/chain extender, which is not stable and therefore must be kept colder than −15°C, while room temperature combines polymer with cross‐linker which is stable, and likely forever. [ABSTRACT FROM AUTHOR]

Testicular prosthesis implantation may be used for neoscrotal augmentation in transgender men. Assess the clinical outcomes and risk factors for postoperative complications of this procedure in transgender men. All transgender men who underwent neoscrotal augmentation with testicular implants between January 1992 and December 2018 were retrospectively identified. A retrospective chart study was performed that recorded surgical characteristics and postoperative complications. Risk factors on complications were identified using uni- and multivariate analyses. Surgical outcomes included explantation due to infection, extrusion, discomfort, or leakage. We identified 206 patients, and the following prostheses were placed: Dow Corning (n = 22), Eurosilicone (n = 2), Nagor (n = 205), Polytech (n = 10), Promedon (n = 105) , Prometel (n = 22), Sebbin (n = 44), and unknown (n = 2). The mean clinical follow-up time was 11.5 ± 8.3 years. In 43 patients (20.8%), one or both prostheses were explanted due to infection, extrusion, discomfort, prosthesis leakage, or urethral problems. Currently, scrotoplasty according to Hoebeke is the most frequently performed technique. Our review found that for this technique explantation occurred in 6 of 52 patients (11.5%). A history of smoking was a risk factor for postoperative infections and prosthesis explantation. In earlier years, larger prostheses were immediately placed at scrotal reconstruction; however, a trend can be seen toward smaller and lighter testicular prostheses and delayed implantation. Patients wanting to undergo this procedure can be adequately informed on postoperative outcomes. Strengths of this study include the number of patients, long clinical follow-up time, and completeness of data. Weaknesses of this study include its retrospective nature and the high variability of prostheses and surgical techniques used. Over the years, scrotoplasty techniques and testicular prostheses preferences have changed. Explantation rates have dropped over the last decade. Pigot GLS, Al-Tamimi M, Ronkes B, et al. Surgical Outcomes of Neoscrotal Augmentation with Testicular Prostheses in Transgender Men. J Sex Med 2019;16:1664–1671. [ABSTRACT FROM AUTHOR]

The cause of hysteresis in organic field-effect transistors (OFETs) and its application in organic synaptic transistors are studied. Benefiting from the slow polarization process of dipoles in organosilicone (Dow Corning 1–2577) dielectric, the devices exhibit the desirable synaptic behaviors, including excitatory postsynaptic current (EPSC), memory function, potentiation/depression characteristics, endurance characteristics and spike-amplitude-dependent plasticity. Further, combining the DC 1–2577 dielectric with the polydimethylsiloxane (PDMS) support, a flexible conformable DC 1–2577 dielectric organic synapse transistor is fabricated, which provides a great potential for the wearable and implantable artificial neuromorphic systems for artificial intelligence and new-generation computers. Image 1078 • The hysteresis effect of organic thin-film field-effect transistor is studied. • The DC 1–2577 dielectric transistors exhibit the desirable synaptic behaviors. • The principle is slow polarization process of dipoles in organosilicone dielectric. • The flexible conformable organic synaptic transistor is fabricated on PDMS support. [ABSTRACT FROM AUTHOR]

The ongoing conflict against terrorism has resulted in an escalation of blast-induced traumatic brain injuries (bTBI) caused by improvised explosive devices (IEDs). The destructive IEDs create a blast wave that travels through the atmosphere. Blast-induced traumatic brain injuries, attributed to the blast wave, can cause life-threatening injuries and fatalities. This study aims to find a surrogate brain material for assessing the effectiveness of head protection systems designed to mitigate bTBI. Polydimethylsiloxane (PDMS) is considered as the surrogate brain material. The stiffness of PDMS (Sylgard 184, Dow Corning Corp.) can be controlled by varying the ratio of base and curing agent. Cylindrical PDMS specimen with ratios of 1:10, 1:70, and 1:80 were subjected to unconfined compression experiments at linear rates of 5 mm/min, 50 mm/min, and 500 mm/min. A ramp-hold strain profile was used to simulate a stress relaxation experiment. The fractional Zener viscoelastic model was used to describe the stress relaxation response, after optimization of the material constants for the brain surrogate and shock wave exposure brain tissue. The results show that the low cost PDMS can be used as a surrogate brain material to study the dynamic brain response to blast wave exposure. [ABSTRACT FROM AUTHOR]