Transparent Silicone Rubber Research Articles

A robust and transparent nanosilica-filled silicone rubber coating with synergistically enhanced mechanical properties and barrier performance

Implantable electronic devices (IEDs) are widely used by human beings to achieve medical treatment and diagnosis nowadays. However, ideal encapsulation of IEDs is still far from perfect as full prevention of body fluid diffusion into the coating remains unsolved. Herein, we develop a high-performance composite coating for IED encapsulation by introducing SiO2 nanoparticles into silicone rubber, which synergistically enhances mechanical properties and improves barrier performance. By fabricating composite coatings with different nanosilica contents, 3% nanosilica is proved to be an optimal additive content with an excellent combination of improved fracture strength (from 2.5 MPa to 4.5 MPa), increased coating resistance (from 104 to 109 Ω cm2) and ideal coating uniformity. Mechanical and electrochemical characterizations subsequently confirm substantially enhanced mechanical properties and barrier performance of the composite coating, which effectively resist crack propagation and impede penetrations of water and chloride ions through the coating. Theoretical calculations further uncover that modified SiO2 particles with enriched methyl groups endow a strong bridging effect to interact with silicone rubber monomer, which, together with anti-agglomeration property of methyl groups, contributes to a pronounced improvement in mechanical performance of nanosilica-filled silicone rubber. Benefitting from the enhanced mechanical and barrier properties, the as-fabricated nanosilica-filled silicone rubber demonstrates superior protection for the encapsulated circuits with a significantly improved lifetime (709.1 h) compared to that of circuits coated by pure silicone rubber (472.8 h) and bare circuit boards (1 h), which offers great values for packaging material design in future IED encapsulation.

Elucidation of frictional properties between rubber and flooring using a laser microscope with wide field of view

We investigate the measurement of real contact area, denoted by Ar, between various floor materials and rubber. Observation of Ar plays an important role for better understanding of frictional force. The Ar between them, however, has yet to be observed over regions wider than what an optical microscope can cover. Current optical microscopy techniques are limited by the measurement time required to observe the whole apparent contact area. Further, it is difficult to reproduce actual contact situations between the rubber and the floor materials because at least one of the contacting specimens must be transparent. Usually, glass plates much harder than rubber are used as counter specimens. In this study, we observed the Ar between a transparent silicone rubber and the various floor materials by using a laser microscope with a wide field of view, allowing us to observe the whole apparent contact area of 9 mm × 7 mm for a very short time. By using transparent rubber, we were able to reproduce the actual contact situations of the rubber-floor specimens, which is impossible with glass plates. The measurement of Ar when the apparent contact area was too small suffered from large fluctuations in measurement values due to waviness of the floor specimen. We investigated the apparent contact area required to accurately understand the relationship between frictional force and Ar and clarified the influence of waviness of the floor materials on the distribution of Ar.

Transparent and Mechanically High-Performance Soft Materials Consisting of Colloidal Building Blocks

ConspectusSoft materials, which are optically transparent and exhibit high mechanical performance, will be key materials in important research areas in our future lives, such as highly advanced medicine, soft robotics, and wearable displays. When soft materials are transparent, objects underneath the soft material can be observed by the naked eye. Additionally, because they allow light to pass through, such materials can be used in optical applications such as lenses and displays. Therefore, transparent materials make it possible to transmit light information. Such transparent soft materials have been widely used in our daily life, but their applications will be directed to higher value-added products in the future.One example of a great transparent and flexible soft material is transparent silicone rubber, but even this material is not without drawbacks. Silicone rubber has the property of not adhering to most materials. This feature can be an advantage, but it can also be a disadvantage in some applications. Moreover, its tensile strength, tear strength, and friction resistance are not always strong. The ability to develop transparent soft materials whose surface and mechanical properties differ from those of silicone rubber will lead to the development of various technologies that will enrich our lives.By use of colloid-sized molecules and materials as building blocks to form soft materials, the properties and functions of the resulting soft materials are expected to reflect those of the building blocks. In addition, if the soft material is formed such that the building blocks have a characteristic order, the physical properties derived from the ordered structure can be manifested in the soft material. If the size of the order is as large as the wavelength of light, it is possible to develop materials that can manipulate light. The authors have been working for many years on soft materials in which building blocks of various colloidal sizes are obtained in an ordered state. As a result, we have reported that we can obtain soft materials that are optically transparent and exhibit a variety of mechanical properties. In this Account, we introduce our various works on optically transparent soft materials consisting of colloidal building blocks that exhibit high mechanical performance. To help you understand our research, a basic description of the optical transparency of the materials and the mechanical properties of the materials is given in the Supporting Information, which you are invited to read if necessary.

Patient-specific brain arteries molded as a flexible phantom model using 3D printed water-soluble resin

Visualizing medical images from patients as physical 3D models (phantom models) have many roles in the medical field, from education to preclinical preparation and clinical research. However, current phantom models are generally generic, expensive, and time-consuming to fabricate. Thus, there is a need for a cost- and time-efficient pipeline from medical imaging to patient-specific phantom models. In this work, we present a method for creating complex 3D sacrificial molds using an off-the-shelf water-soluble resin and a low-cost desktop 3D printer. This enables us to recreate parts of the cerebral arterial tree as a full-scale phantom model (10times 6times 4 cm) in transparent silicone rubber (polydimethylsiloxane, PDMS) from computed tomography angiography images (CTA). We analyzed the model with magnetic resonance imaging (MRI) and compared it with the patient data. The results show good agreement and smooth surfaces for the arteries. We also evaluate our method by looking at its capability to reproduce 1 mm channels and sharp corners. We found that round shapes are well reproduced, whereas sharp features show some divergence. Our method can fabricate a patient-specific phantom model with less than 2 h of total labor time and at a low fabrication cost.

Shear, Torsion and Pressure Tactile Sensor via Plastic Optofiber Guided Imaging

Object manipulation performed by robots refers to the art of controlling the shape and location of an object through force constraints with robot end-effectors, both robot hands, and grippers. The success of task execution is usually guaranteed by the sense of touch. In this work, we present an optical tactile sensor incorporating plastic optical fibers, transparent silicone rubber, and an off-the-shelf color camera that can detect: translational and rotational shear forces, and contact location and its normal force. Contact localization is possible thanks to the shear strain. Specifically, one of the layers stretches so that its thickness decreases. The decrease in the thickness results in the color change at the point of contact. Elastic behavior of the sensing media provides a robust rotational and translational shear detection mechanism when torque and planar force, respectively, are applied onto the sensing surface. Thanks to the plastic optofibers, signal processing electronics are placed away from the sensing surface making the sensor immune to hazardous environments. Machine learning techniques were used to benchmark the sensing performance of the sensor. By implementing a multi-output CNN model, the contact type was classified into normal and shear or torsional deformation and their corresponding continuous contact features were estimated.

"Barbed snore surgery" simulator: a low-cost surgical model.

"Barbed snore surgery" (BSS) represents one of the last innovation for obstructive sleep apnea syndrome (OSAS) surgical management. Although this technique represents an effective and minimally invasive surgery, it is not still widespread in many ENT centers. The aim of our study was to develop an inexpensive surgical simulator useful to expedite the surgical learning curve for BSS in untrained ENT surgeons. The simulator is a simple model composed of a manually shaped silicone palate (3 × 4 × 1cm) fixed on a resin skeleton (21 × 16 × 12cm) using a transparent silicon rubber. The mandible is fixed bilaterally with the aid of two screws allowing for modular inter-incisive distance. Barbed anterior pharyngoplasty (BAPh) was readily performed on the simulator to show the feasibility of this BSS model. All surgical steps were carried out determining a lift and a shortening of the palate as in real surgery. This is the first surgical model that provides a realistic, easily repeatable training in the performance of BSS. Our BSS surgical model is very inexpensive with a cost of approximately 19.25$ dollars and it is manufactured to facilitate a worldwide diffusion of this promising palatal surgery for OSAS.

Patient Specific Diagnostics for cardiovascular diseases based on diagnostic imaging: an application to the aneurism of the ascending aorta

In the framework of a collaboration between clinicians and engineers (namely, the Department of Radiology of the Brotzu Hospital in Cagliari and the group of experimental hydraulics at DICAAR - University of Cagliari), methodologies for the application of the in vitro study of the cardiovascular fluid mechanics to the support of the physical interpretation of the diagnostic imaging data are being tested. To this aim, we set up a mock-loop able to reproduce the physiologic pulsatile flow and designed to host a replica of aortic root made of transparent silicon rubber. Then, we developed a procedure to obtain a transparent and compliant replica of a patient specific ascending aorta from diagnostic images. The patient specific aorta model can be inserted in the mock-loop to study the fluid dynamics by means of particle image velocimetry techniques. We compared the flow in three cases, corresponding to physiological conditions, mild and severe aortic root dilation, observing significant differences in the redirection of the transvalvular jet and vortex evolution in the aortic flow. The observed fluid dynamics differences may have relevant implications on the thromboembolism and vascular tissue damage potential.

Marangoni interface self-assembly hybrid carbon nano-network for transparent conductive silicone rubber

Inspired by compact one-dimensional (1D) and two-dimensional (2D) hybrid network like natural thrombosis and beaver’s dam, we use Marangoni interface self-assembly hybrid 1D carbon nanotube and 2D graphene (CNT+G) as continuously connected nano-network onto the surface of silicone ink coated silicone rubber. Both good optical transmittance and electrical conductivity demonstrated in the transparent conductive silicone rubber (TCSR). Besides, the TCSR also have excellent mechanical adhesion between the (CNT+G) film and silicone ink coated silicone rubber.

Real-Time Sensing of TET2-Mediated DNA Demethylation In Vitro by Metal-Organic Framework-Based Oxygen Sensor for Mechanism Analysis and Stem-Cell Behavior Prediction.

Active DNA demethylation, mediated by O2-dependent ten-eleventranslocation (TET) enzymes, has essential roles in regulating gene expression. TET kinetics assay is vital for revealing mechanisms of demethylation process. Here, by a metal-organic framework (MOF)-based optical O2 sensor, we present the first demonstration on real-time TET2 kinetics assay in vitro. A series of luminescent Cu(I) dialkyl-1,2,4-triazolate MOFs were synthesized, which were noble-metal-free and able to intuitively response to dissolved O2 in a wide range from cellular hypoxia (≤15 μM) to ambient condition (∼257 μM). By further immobilization of the MOFs onto transparent silicon rubber (MOF@SR) to construct O2 film sensors, and real-time monitoring of O2 consumption on MOF@SR over the reaction time, the complete TET2-mediated 5-methylcytosine (5mC) oxidation process were achieved. The method overcomes the limitations of the current off-line methods by considerably shortening the analytical time from 0.5-18 h to 10 min, and remarkably reducing the relative standard deviation from 10%-68% to 0.68%-4.2%. As a result, the Michaelis-Menten constant ( Km) values of TET2 for 5mC and O2 in ascorbic acid-free (AA-) condition were precisely evaluated to be 24 ± 1 and 43.8 ± 0.3 μM, respectively. By comparative study on AA-containing (AA+) conditions, and further establishing kinetics models, the stem-cell behavior of TETs was successfully predicted, and the effects of key factors (AA, O2, Fe2+) on TETs were revealed, which were fully verified in mouse embryonic stem (mES) cells. The method is promising in wide application in kinetics analysis and cell behavior prediction of other important O2-related enzymes.

The Preparation of Transparent Silicone Rubber with Rapid Vulcanization and Ultraviolet Absorbing Effect

Silicone materials have excellent weathering resistance, high and low temperature resistance, anti-yellowing and a series of excellent properties over other materials. In this study vinyl silicone oil as the base polymer, hydrogen silicone oil as a cross-linking agent, vinyl silicone resin and ultraviolet absorber as additives, platinum complex as a catalyst, were used to make ultraviolet absorption of highly transparent silicone rubber. Different structures of silicone resin with vinyl group have different effects on the curing speed of the products. The silicone resin with MM^ViQ can help achieve rapid curing speed. Due to polarity difference for polysiloxane system and ultraviolet absorber, when necessary a suitable organic solvent may be introduced to increase the compatibility of the ultraviolet absorber with the silicone composition to prepare transparent products. Considering that the addition of organic solvents may have effects such as volatiles and properties, the amount of solvent introduced should be as low as possible. In addition, regarding the amount of the ultraviolet absorber added, too little ultraviolet absorber may not achieve a satisfactory ultraviolet absorption effect, but too much would lead to an increase in the amount of solvent introduced. Different ultraviolet absorber could induce different ultraviolet absorption effect and aging resistance.

Injection moulding of high precision optics for light-emitting diodes made of liquid silicone rubber

In the market of lighting technologies, light-emitting diodes (LEDs) gradually substitute conventional light sources. Because of their high energy efficiency and long lifetime, they are increasingly used in consumer products, interior and exterior lighting applications in the home and mobility sector as well as in industrial applications. The material properties in the surrounding area of the light-emitting semiconductor chip are crucial to the performance of LED. Although the energy efficiency of LED is higher compared to conventional light sources, temperatures exceed about 150°C close to the semiconductor chip. Especially in combination with high amounts of blue ultraviolet (UV) radiation, the materials for encapsulation cannot meet the requirements and reduce the lifetime of an LED significantly. Contrary to conventional materials, high transparent liquid silicone rubber (LSR) can resist high temperatures as well as UV radiation and offer a great freedom in design. This enables the combination of the encapsulation (primary optics) and the secondary optics in one component. The objective of an ongoing joint research project with various partners from the industry is the development of an innovative injection moulding process for high precision optics in LED applications made of LSR, which is analysed at the Institute of Plastics Processing (IKV), Aachen, Germany. Therefore, the LED board is placed in the injection mould and overmoulded with LSR. The goal is a highly integrated process with major emphasis on the reduction of components, mounting steps and costs. Furthermore, the combination of primary and secondary optics promises an improved effectiveness because losses in light power due to the transition of the primary and secondary optics are reduced.

Biomaterial characteristics and application of silicone rubber and PVA hydrogels mimicked in organ groups for prostate brachytherapy

It is definite that transparent material with similar structural characteristics and mechanical properties to human tissue is favorable for experimental study of prostate brachytherapy. In this paper, a kind of transparent polyvinyl alcohol (PVA) hydrogel and silicone rubber are developed as suitable substitutions for human soft tissue. Segmentation and 3D reconstruction of medical image are performed to manufacture the mould of organ groups through rapid prototyping technology. Micro-structure observation, force test and CCD deformation test have been conducted to investigate the structure and mechanical properties of PVA hydrogel used in organ group mockup. Scanning electron microscope (SEM) image comparison results show that PVA hydrogel consisting of 3g PVA, 17g de-ionized water, 80g dimethyl-sulfoxide (DMSO), 4g NaCl, 1.5g NaOH, 3g epichlorohydrin (ECH) and 7 freeze/thaw cycles reveals similar micro-structure to human prostate tissue. Through the insertion force comparison between organ group mockup and clinical prostate brachytherapy, PVA hydrogel and silicone rubber are found to have the same mechanical properties as prostate tissue and muscle. CCD deformation test results show that insertion force suffers a sharp decrease and a relaxation of tissue deformation appears when needle punctures the capsule of prostate model. The results exhibit that organ group mockup consisting of PVA hydrogel, silicone rubber, membrane and agarose satisfies the needs of prostate brachytherapy simulation in general and can be used to mimic the soft tissues in pelvic structure.

Influence of molar ratio of Si–H to Si–CH=CH2 on mechanical and optical properties of silicone rubber

High-strength and optically transparent silicone rubber was prepared using vinyl-MQ silicone resin as base gum. Influence of molar ratio of Si–H to Si–Vi (A value) on curing process as well as mechanical and optical properties were studied. The results show that the curing time and curing temperature decreases, while storage modulus after curing increases, as the A value increases. The optimal mechanical and optical properties can be obtained when the A value is 1.8, leading to the formation of an ultraviolet (UV) transparent silicone rubber with tensile strength of 8.03 MPa and UV transmittance up to 95.8% at 350 nm.

Design and testing of an underwater acoustic Fresnel zone plate diffractive lens

Fresnel zone plate (FZP) lenses offer a means of focusing sound based on diffraction in cases where the thickness of conventional lenses may be impractical. A binary-profile FZP for underwater use featuring a center acoustically opaque disk with alternating transparent and opaque annular regions was fabricated to operate nominally at 200 kHz. The overall diameter of the lens was 13 in. and consisted of 13 opaque annuli. The opaque regions were 3 mm thick and made from silicone rubber with a high concentration of gas voids. These regions were bonded to an acoustically transparent silicone rubber substrate film that was 1 mm thick. The FZP was situated in a frame and tested in a 5 x 4 x 4 cu. ft. ultrasonic tank using a piston source for insonification. The measured focal distance for normal incidence of 12.5 cm agreed with finite-element predictions taking into account the wavefront curvature of the incident field which had to be included given the finite dimensions of tank. The focal gain was measured to be 20 dB. The radius to the first null at the focal plane was approximately 4 mm, which agreed with theoretical resolution predictions. [Work sponsored by the Office of Naval Research.]

Application and nursing of indirect bonding in correction of dento-maxillofacial deformities by using Dreve transparent silicone rubber

Objective To evaluate the application and nursing of indirect bonding in correction of dento-maxillofacial deformities by using Dreve transparent silicone rubber. Methods Fifteen patients who needed to be treated by fixed appliance technology were selected, and all of them received the indirect bonding with Dreve transparent silicone rubber, single pallet transfer method, four - hand operation. And the effects of indirect bonding were evaluated. Results By using the new indirect bonding techniques, the brackets achieved accurate location and the errors were very small; the chairside operating time was greatly shortened, with average operating time about （13.11 ± 1.27） mins; the procedure of dental laboratories became convenient and took less time （the operating time was about 38 mins） ; the bonding strength of brackets increased, with the shedding rates of 4.4%. Conclusions The indirect bonding with transparent silicone rubber is a simple and effective way to correct dento-maxillofacial deformities, which can provide the basis for the clinical use of indirect bonding. Key words: Oral cavity malformation; Nursing; Indirect bonding; Dento-maxillofacial deformities

Experimental insights into flow impingement in cerebral aneurysm by stereoscopic particle image velocimetry: transition from a laminar regime

This study experimentally investigated the instability of flow impingement in a cerebral aneurysm, which was speculated to promote the degradation of aneurysmal wall. A patient-specific, full-scale and elastic-wall replica of cerebral artery was fabricated from transparent silicone rubber. The geometry of the aneurysm corresponded to that found at 9 days before rupture. The flow in a replica was analysed by quantitative flow visualization (stereoscopic particle image velocimetry) in a three-dimensional, high-resolution and time-resolved manner. The mid-systolic and late-diastolic flows with a Reynolds number of 450 and 230 were compared. The temporal and spatial variations of near-wall velocity at flow impingement delineated its inherent instability at a low Reynolds number. Wall shear stress (WSS) at that site exhibited a combination of temporal fluctuation and spatial divergence. The frequency range of fluctuation was found to exceed significantly that of the heart rate. The high-frequency-fluctuating WSS appeared only during mid-systole and disappeared during late diastole. These results suggested that the flow impingement induced a transition from a laminar regime. This study demonstrated that the hydrodynamic instability of shear layer could not be neglected even at a low Reynolds number. No assumption was found to justify treating the aneurysmal haemodynamics as a fully viscous laminar flow.

157 透明半球シリコーンゴムを用いた生体部位計測用探り棒の研究開発(機械力学・計測制御,一般講演)

157 透明半球シリコーンゴムを用いた生体部位計測用探り棒の研究開発(機械力学・計測制御,一般講演)

Microscale electrodialysis: Concentration profiling and vortex visualization

In this paper, the microscale experimental model system for studying electrodialysis (ED) process is described, which is used for visualizing in situ fluid flow and concentration profile over a wide range of applied voltages (0–100V). On the transparent silicone rubber, polydimethylsiloxane (PDMS), microscale channels (width~1mm, height~200μm) were fabricated between ion exchange membranes, while allowing microscopic visualization of fluid flow and concentration changes within the ED unit cell. This ED platform was then operated on the commercial microscope with 10mM NaCl solution. Cationic fluorescence dyes (Rhodamine 6G) were added for flow and salt concentration tracer. Concentration and fluid flow profiles within the ED cell exhibit distinct behaviors in Ohmic, limiting, and overliming regimes, respectively. Although such dynamic behaviors have been predicted previously, to the best of our knowledge, this is the first time that they were clearly visualized in a realistic ED model. Based on visualized fluid flows and concentration profiles, one can elucidate many important factors that affect ion transport (salt removal) efficiency, such as the expansion of boundary layer and vortex instability. This model system would be instrumental to test and optimize ED system parameters, and can be applicable to the study of other desalination processes such as capacitance deionization.

On key parameters influencing cavitation damage upon fast decompression in a hydrogen saturated elastomer

A transparent silicone rubber (vinyltrimetoxysilane) has been exposed to pressurized hydrogen from 0.1 to 27 MPa, saturated and submitted to gas decompression over a wide range of controlled rates of pressure (between 0.2 and 90 MPa/min).A spatial and temporal follow up of the development of damage during and after decompression has been conducted. The pressure level and the decompression rate are both needed to predict if blister fracture will occur and, if it does, at what level of pressure in the chamber. Using these two parameters, it is possible in some cases to predict the onset of damage.

Bionics in textiles: flexible and translucent thermal insulations for solar thermal applications

Solar thermal collectors used at present consist of rigid and heavy materials, which are the reasons for their immobility. Based on the solar function of polar bear fur and skin, new collector systems are in development, which are flexible and mobile. The developed transparent heat insulation material consists of a spacer textile based on translucent polymer fibres coated with transparent silicone rubber. For incident light of the visible spectrum the system is translucent, but impermeable for ultraviolet radiation. Owing to its structure it shows a reduced heat loss by convection. Heat loss by the emission of long-wave radiation can be prevented by a suitable low-emission coating. Suitable treatment of the silicone surface protects it against soiling. In combination with further insulation materials and flow systems, complete flexible solar collector systems are in development.