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Macromolecular Rapid Communications Mar 2016Silicone elastomers are promising materials for dielectric elastomer transducers (DETs) due to their superior properties such as high efficiency, reliability and fast... (Review)
Review
Silicone elastomers are promising materials for dielectric elastomer transducers (DETs) due to their superior properties such as high efficiency, reliability and fast response times. DETs consist of thin elastomer films sandwiched between compliant electrodes, and they constitute an interesting class of transducer due to their inherent lightweight and potentially large strains. For the field to progress towards industrial implementation, a leap in material development is required, specifically targeting longer lifetime and higher energy densities to provide more efficient transduction at lower driving voltages. In this review, the current state of silicone elastomers for DETs is summarised and critically discussed, including commercial elastomers, composites, polymer blends, grafted elastomers and complex network structures. For future developments in the field it is essential that all aspects of the elastomer are taken into account, namely dielectric losses, lifetime and the very often ignored polymer network integrity and stability.
Topics: Dimethylpolysiloxanes; Electric Conductivity; Electric Power Supplies; Electrodes; Silicone Elastomers
PubMed: 26773231
DOI: 10.1002/marc.201500576 -
International Journal of Pharmaceutics:... Dec 2021A dapivirine-releasing silicone elastomer vaginal ring for reducing women's risk of HIV acquisition has recently been approved. A next-generation multipurpose vaginal...
A dapivirine-releasing silicone elastomer vaginal ring for reducing women's risk of HIV acquisition has recently been approved. A next-generation multipurpose vaginal ring releasing dapivirine and levonorgestrel is currently in development, offering hormonal contraception and HIV prevention from a single device. Previously, we reported challenges with incorporating levonorgestrel into rings manufactured from addition-cure silicone elastomers due to an irreversible chemical reaction between the levonorgestrel molecule and the hydride-functionalised crosslinker component of the silicone elastomer formulation, leading to low drug content assay, cure inhibition, and reduced ring mechanical properties (which may account for the increased incidence of ring expulsion in vivo). Here, we report on the development and testing of various custom silicone elastomer materials specifically formulated to circumvent these issues. After extensive testing of the custom silicones and subsequent manufacture and testing (Shore M hardness, pot life, content assay, oscillatory rheology, mechanical testing) of rings containing both dapivirine and levonorgestrel, a lead candidate formulation was selected that was amenable to practical ring manufacture via injection molding, exhibited no substantial levonorgestrel binding, and offered suitable mechanical properties.
PubMed: 34977558
DOI: 10.1016/j.ijpx.2021.100091 -
Brain Sciences Jan 2021(1) Background: Cranioplasty is a surgery to repair a skull bone defect after decompressive craniectomy (DC). If the process of dissection of the epidural adhesion...
(1) Background: Cranioplasty is a surgery to repair a skull bone defect after decompressive craniectomy (DC). If the process of dissection of the epidural adhesion tissue is not performed properly, it can cause many complications. We reviewed the effect of a silicone elastomer sheet designed to prevent adhesion. (2) Methods: We retrospectively reviewed 81 consecutive patients who underwent DC and subsequent cranioplasty at our institution between January 2015 and December 2019. We then divided the patients into two groups, one not using the silicone elastomer sheet ( = 50) and the other using the silicone elastomer sheet ( = 31), and compared the surgical outcomes. (3) Results: We found that the use of the sheet shortened the operation time by 24% and reduced the estimated blood loss (EBL) by 43% compared to the control group. Moreover, the complication rate of epidural fluid collection (EFC) in the group using the sheet was 16.7%, which was lower than that in the control group (41.7%, < 0.023). Multivariate logistic regression analysis showed the sheet (OR 0.294, 95% CI 0.093-0.934, = 0.039) to be significantly related to EFC. (4) Conclusions: The technique using the silicone elastomer sheet allows surgeons to easily dissect the surgical plane during cranioplasty, which shortens the operation time, reduces EBL, and minimizes complications of EFC.
PubMed: 33477608
DOI: 10.3390/brainsci11010124 -
Journal of Indian Prosthodontic Society 2020The aim of this systematic review was to evaluate the effect of addition of various nanoparticles into maxillofacial silicone elastomer on color stability and mechanical... (Review)
Review
AIM
The aim of this systematic review was to evaluate the effect of addition of various nanoparticles into maxillofacial silicone elastomer on color stability and mechanical and biological properties of the silicone elastomer.
SETTINGS AND DESIGN
This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines(PRISMA).
MATERIALS AND METHODS
The electronic database search in MEDLINE/PubMed was based on population (silicone elastomer), intervention (nanoparticles), comparison (unreinforced silicone elastomer with nanoparticle-reinforced silicone elastomer), outcome (color stability and mechanical, physical, and biological properties), i.e., PICO framework. The key words used are ("maxillofacial silicone" OR "silicone elastomer" OR "facial silicone") AND ("nanoparticles" OR "Nano-oxides") AND ("colour stability" OR "Hardness," "tensile strength" OR "tear strength" OR "antifungal activity").
RESULTS
The database search resulted in 2099 studies, of which 2066 articles were excluded as they were irrelevant, duplicates, and data were not available. The remaining 33 full-text articles were assessed for eligibility, out of which 2 articles were in Chinese language, 3 articles were thesis documents, and 8 were review articles. A total of 12 articles were excluded and the remaining 20 articles were included. One article was yielded by hand search of references of included studies. A total of 21 studies were included in the present systematic review.
CONCLUSION
With the available evidence in the literature, it can be concluded that addition of nanoparticles at various concentrations may improve the physical and mechanical properties and color stability of the prosthesis made from the silicone elastomers.
PubMed: 33223694
DOI: 10.4103/jips.jips_429_19 -
Swiss Medical Weekly 2012This opinion article has been written on request because of the recent public controversy over silicone breast implants produced by a now-defunct company, Poly Implant... (Review)
Review
This opinion article has been written on request because of the recent public controversy over silicone breast implants produced by a now-defunct company, Poly Implant Prosthese (PIP) in France. More than 300,000 PIP devices have been implanted. The purposes of my article are to (1.) provide a general overview of silicone breast implant materials, (2.) to describe the general safety of these materials as reported to date, and (3.) to summarise current publicly available information about these aspects of the PIP prostheses. The materials covered are the silicone rubber from which the implant shells are made and the silicone gel used to fill the shell. The materials safety issues are biocompatibility (especially of the gel) and biodurability of the shell. The literature reviewed indicates that biocompatibility is not an issue with other current generation implants. However, biodurability is. A rough estimate of implant shell rupture rate is ~10+% at 10 years. Information is still emerging about the PIP implants. Initial regulatory disclosures suggest the PIP implants may have both biocompatibility and biodurability problems. They also suggest that PIP implants may have been produced using silicone materials not certified as medical grade. Governmental health and regulatory agencies are just now in the process of deciding what actions should be taken to protect patients.
Topics: Biocompatible Materials; Breast Implants; Humans; Materials Testing; Prosthesis Failure; Silicone Elastomers; Silicone Gels
PubMed: 22826101
DOI: 10.4414/smw.2012.13614 -
International Journal of Molecular... Sep 2022Novel radar-wave absorption nanocomposites are developed by filling the nanoscaled ferrites of strontium ferroxide (SrFeO) and carbonyl iron (CIP) individually into the...
Novel radar-wave absorption nanocomposites are developed by filling the nanoscaled ferrites of strontium ferroxide (SrFeO) and carbonyl iron (CIP) individually into the highly flexible liquid silicone rubber (LSR) considered as dielectric matrix. Nanofiller dispersivities in SrFeO/LSR and CIP/LSR nanocomposites are characterized by scanning electronic microscopy, and the mechanical properties, electric conductivity, and DC dielectric-breakdown strength are tested to evaluate electrical insulation performances. Radar-wave absorption performances of SrFeO/LSR and CIP/LSR nanocomposites are investigated by measuring electromagnetic response characteristics and radar-wave reflectivity, indicating the high radar-wave absorption is dominantly derived from magnetic losses. Compared with pure LSR, the SrFeO/LSR and CIP/LSR nanocomposites represent acceptable reductions in mechanical tensile and dielectric-breakdown strengths, while rendering a substantial nonlinearity of electric conductivity under high electric fields. SrFeO/LSR nanocomposites provide high radar-wave absorption in the frequency band of 11~18 GHz, achieving a minimum reflection loss of -33 dB at 11 GHz with an effective absorption bandwidth of 10 GHz. In comparison, CIP/LSR nanocomposites realize a minimum reflection loss of -22 dB at 7 GHz and a remarkably larger effective absorption bandwidth of 3.9 GHz in the lower frequency range of 2~8 GHz. Radar-wave transmissions through SrFeO/LSR and CIP/LSR nanocomposites in single- and double-layered structures are analyzed with CST electromagnetic-field simulation software to calculate radar reflectivity for various absorbing-layer thicknesses. Dual-layer absorbing structures are modeled by specifying SrFeO/LSR and CIP/LSR nanocomposites, respectively, as match and loss layers, which are predicted to acquire a significant improvement in radar-wave absorption when the thicknesses of match and loss layers approach 1.75 mm and 0.25 mm, respectively.
Topics: Electricity; Iron; Radar; Silicone Elastomers; Strontium
PubMed: 36142338
DOI: 10.3390/ijms231810424 -
Journal of Prosthodontic Research Jul 2022To assess the bonding between conventional and additively manufactured silicone elastomers and cylindrical retention titanium magnets for anchorage of facial prostheses.
PURPOSE
To assess the bonding between conventional and additively manufactured silicone elastomers and cylindrical retention titanium magnets for anchorage of facial prostheses.
METHODS
The customized titanium retention magnets were embedded in conventional and additively produced silicone blocks without primer application (n = 20) and with two commercially available primers G611 (n = 20) and A304 (n = 20) applied onto the magnet surface. The pull out test was performed in the universal testing machine using 45° and 90° angulation and the pull out strength was measured for each group. Additionally the SEM images of the pulled out magnets' surface were obtained and the amount of residual silicone onto the magnet surface was quantified.
RESULTS
Significantly higher pull out strength values (p < 0.05) were revealed for 90° specimens (0.11 - 0.17 ± 0.01 N/mm) compared to the 45° group (0.03 ± 0.02 N/mm). The pull out test with primer revealed no significant differences between the G 611 and A 304 primers in the additive group. However, significantly (p < 0,05) higher values were observed for conventional specimens in the A304 group (1.10 ± 0.21 N/mm) compared to the G611 group (0.59 ± 0.27 N/mm).
CONCLUSION
The application of both used primers may be an acceptable technical option for the anchorage of retention titanium magnets in silicone facial prostheses, produced additively in a fully digital workflow.
Topics: Magnets; Materials Testing; Maxillofacial Prosthesis; Printing, Three-Dimensional; Silicone Elastomers; Titanium
PubMed: 34545007
DOI: 10.2186/jpr.JPR_D_21_00019 -
Frontiers in Robotics and AI 2021Developing highly sensitive flexible pressure sensors has become crucially urgent due to the increased societal demand for wearable electronic devices capable of...
Developing highly sensitive flexible pressure sensors has become crucially urgent due to the increased societal demand for wearable electronic devices capable of monitoring various human motions. The sensitivity of such sensors has been shown to be significantly enhanced by increasing the relative dielectric permittivity of the dielectric layers used in device construction via compositing with immiscible ionic conductors. Unfortunately, however, the elastomers employed for this purpose possess inhomogeneous morphologies, and thus suffer from poor long-term durability and unstable electrical response. In this study, we developed a novel, flexible, and highly sensitive pressure sensor using an elastomeric dielectric layer with particularly high permittivity and homogeneity due to the addition of synthesized ionic liquid-grafted silicone oil (denoted LMS-EIL). LMS-EIL possesses both a very high relative dielectric permittivity (9.6 × 10 at 10 Hz) and excellent compatibility with silicone elastomers due to the covalently connected structure of conductive ionic liquid (IL) and chloropropyl silicone oil. A silicone elastomer with a relative permittivity of 22 at 10 Hz, Young's modulus of 0.78 MPa, and excellent homogeneity was prepared by incorporating 10 phr (parts per hundreds rubber) of LMS-EIL into an elastomer matrix. The sensitivity of the pressure sensor produced using this optimized silicone elastomer was 0.51 kPa, which is 100 times higher than that of the pristine elastomer. In addition, a high durability illustrated by 100 loading-unloading cycles and a rapid response and recovery time of approximately 60 ms were achieved. The excellent performance of this novel pressure sensor suggests significant potential for use in human interfaces, soft robotics, and electronic skin applications.
PubMed: 34616775
DOI: 10.3389/frobt.2021.737500 -
Sensors (Basel, Switzerland) Mar 2023Wearable electrode arrays can selectively stimulate muscle groups by modulating their shape, size, and position over a targeted region. They can potentially...
Wearable electrode arrays can selectively stimulate muscle groups by modulating their shape, size, and position over a targeted region. They can potentially revolutionize personalized rehabilitation by being noninvasive and allowing easy donning and doffing. Nevertheless, users should feel comfortable using such arrays, as they are typically worn for an extended time period. Additionally, to deliver safe and selective stimulation, these arrays must be tailored to a user's physiology. Fabricating customizable electrode arrays needs a rapid and economical technique that accommodates scalability. By leveraging a multilayer screen-printing technique, this study aims to develop personalizable electrode arrays by embedding conductive materials into silicone-based elastomers. Accordingly, the conductivity of a silicone-based elastomer was altered by adding carbonaceous material. The 1:8 and 1:9 weight ratio percentages of carbon black (CB) to elastomer achieved conductivities between 0.0021-0.0030 S cm and were suitable for transcutaneous stimulation. Moreover, these ratios maintained their stimulation performance after several stretching cycles of up to 200%. Thus, a soft, conformable electrode array with a customizable design was demonstrated. Lastly, the efficacy of the proposed electrode arrays to stimulate hand function tasks was evaluated by in vivo experiments. The demonstration of such arrays encourages the realization of cost-effective, wearable stimulation systems for hand function restoration.
Topics: Electrodes; Elastomers; Silicone Elastomers; Wearable Electronic Devices; Neural Prostheses
PubMed: 36991692
DOI: 10.3390/s23062982 -
Journal of Indian Prosthodontic Society 2021This systematic review aims to identify and interpret results of studies that evaluated the changes in the color stability of maxillofacial prosthetic materials due to... (Meta-Analysis)
Meta-Analysis Review
AIM
This systematic review aims to identify and interpret results of studies that evaluated the changes in the color stability of maxillofacial prosthetic materials due to chemical instability of silicones and pigments and the effect of exposure to environmental conditions and aging factors on the same.
SETTINGS AND DESIGN
This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines (PRISMA).
MATERIALS AND METHODS
Relevant articles written in English only, before November 15, 2019, were identified using an electronic search in the PubMed/Medline conducted to identify pertinent articles. The relevancy of the articles was verified by screening the title, abstract, and full text, if they met the inclusion criteria. A total of 42 articles satisfied the criteria, from which data were extracted for qualitative synthesis. This review protocol was registered in the International Prospective Register of Systematic Reviews (PROSPERO registration number CRD42019124562).
STATISTICAL ANALYSIS USED
Since considerable data heterogenicity was present in all studies except the ones on incorporation of TiO2 for which meta-analysis using random effects model was performed.
RESULTS
The database search resulted in 234 studies, of which 202 articles were excluded due to lack of relevance, duplication, and unavailability of data. The remaining 32 fulltext articles were assessed for eligibility, out of which 2 articles were excluded. Twelve articles were yielded by manual search. A total of 42 studies were included in the present systematic review. Due to heterogeneous data, meta-analysis could be only carried out with the effect of TiO nano particle on color stability.
CONCLUSIONS
Although there has been extensive amount of research in this field, an ideal maxillofacial silicone exhibiting good color stability in various human and environmental aging conditions is yet to be identified. Human and environmental aging conditions have an adverse effect on the color stability and addition of TiO nano particle seems to improve the same.
Topics: Humans; Silicone Elastomers
PubMed: 33938863
DOI: 10.4103/jips.jips_253_19