Experimental and Numerical Analysis of the Deformation Behavior of Adaptive Fiber-Rubber Composites with Integrated Shape Memory Alloys

Fiber-reinforced rubber composites with integrated shape memory alloy (SMA) actuator wires present a promising approach for the creation of soft and highly elastic structures with adaptive functionalities for usage in aerospace, robotic, or biomedical applications. In this work, the flat-knitting technology is used to develop glass-fiber-reinforced fabrics with tailored properties designed for active bending deformations. During the knitting process, the SMA wires are integrated into the textile and positioned with respect to their actuation task. Then, the fabrics are infiltrated with liquid silicone, thus creating actively deformable composites. For dimensioning such structures, a comprehensive understanding of the interactions of all components is required. Therefore, a simulation model is developed that captures the properties of the rubber matrix, fiber reinforcement, and the SMA actuators and that is capable of simulating the active bending deformations of the specimens. After model calibration with experimental four-point-bending data, the SMA-driven bending deformation is simulated. The model is validated with activation experiments of the actively deformable specimens. The simulation results show good agreement with the experimental tests, thus enabling further investigations into the deformation mechanisms of actively deformable fiber-reinforced rubbers.

Effect of Vinyl-Terminated Silicone Oil Chain Length and Reinforcing Agent on the Properties of Silicone Rubber

To solve the problems of low strength and high viscosity of room temperature vulcanized liquid silicone rubber, a series of terminated vinyl silicone oil were designed and synthesized, and low viscosity and high strength silicone rubber were prepared by the mechanical reinforcing agent. the results show that the molecular structure of the vinyl-terminated silicone oil has a significant effect on the mechanical properties and viscosity of the silicone rubber, and the best performance is found when the content of vinyl-terminated silicone oil is 0.16%. The low viscosity and high strength silicone rubber prepared from it was reinforced by vinyl MQ resin and fumed silica, which had a significant effect on improving the performance. Its tensile strength increased to 5.03 MPa, elongation at break to 338.90%, and tear strength to 7.15 kN/m compared to conventional silicone rubber, while the hardness increased to 43°. The viscosity is 34.9 Pa•s. The compression modulus is 7.48 MPa.

High Resolution Ultrasound of Fillers and Their Implications in Aesthetic Medicine: A Study in Human Cadavers

The use of fillers for cosmetic or therapeutic purposes is very common and it’s increasing daily. Although it’s true that in most cases the results are as expected, the use of these substances is not free from the development of complications, even when it’s performed by highly trained medical physicians. On the other hand, these substances can be used indiscriminately by untrained personnel leading to a serious public health complication known as iatrogenic allogenosis, which leads to problems related to malpractice. Most of the time, professionals are consulted for a second opinion regarding the use of these substances, because use of these substances might be unknown due to the patients denying or forgetting the use of these. The presence of a previous unknown filler in aesthetic areas that require treatment may trigger severe or irreversible reactions, especially if non-absorbable fillers were injected. High resolution ultrasound is an extremely useful diagnostic tool for the identification of fillers. In this paper we will describe the ultrasound appearance of hyaluronic acid, calcium hydroxyapatite, liquid silicone, silicone oil, biopolymers, and Polymethylmethacrylate (PPMA) and then we compare it with it’s reported appearance in previous studies. The injection of the substances was carried out in human cadavers with the intention of gathering ultrasound images as similar to the imaging behavior of these substances in vivo. The obtained images can be used as precise references in the ultrasound evaluation, diagnosis, follow-up and behavior of the filler materials in the benefit of a comprehensive approach in the management of patients.

Morphometrical observation on the left atrium in human adults

Aim. To determine the left atrial dimensions, their ratios and relationships that characterize anatomy for left atrium structure in the normal human adult using the model of the atrial end-diastolic phase. Methods. We studied 54 heart specimens of subjects aged 3588 years who died from non-cardiac causes. The atrial end-diastolic phase was modeled by filling a specimen fixed in 1% formalin with liquid silicone. After silicone hardened, we performed morphometric measurements by a caliper. The data were processed by using a cluster, correlation and variance analysis. For pairwise comparison, we used the MannWhitney U-test or a two-sided t-test. Results. The article presents mean, standard deviation, median, 25th percentile and 75th percentile and coefficients of variation for the length, width and sagittal size of the left atrium, as well as the values of the distances between the pulmonary vein orifices, which characterize the dimensions of the left atrium posterior wall. Based on the left atrial size differences and their ratios, the specimens were divided into three clusters. The first (n1=23) and second clusters (n2=10) were represented by hearts with a cubic atrium; the second group differed from the first in the larger size of the left atrium. The third cluster (n3=21) included the hearts in which the largest left atrium size was the width, so the shape of the atria resembled a parallelepiped. The typical number of the pulmonary vein ostia we found in 91% of the specimens. The posterior wall of the left atrium, with a common number and topography of the ostia, were rectangle or an unequal trapezium in shape. We analyzed correlations between the sizes of the heart, left atrium and its posterior wall. We concretized the conceptual apparatus concerning the nomenclature and terminology of the left atrium anatomical structures. Conclusion. Based on the size ratio, two shape variations of the left atrium body can be identified: cubic or parallelepiped; cubic atria can be divided into large and small; the co-directional dimensions of the left atrial body and its posterior wall showed the strongest correlations.

In Vitro Study of the Interaction of Innate Immune Cells with Liquid Silicone Rubber Coated with Zwitterionic Methyl Methacrylate and Thermoplastic Polyurethanes

The biocompatibility of medical devices, such as implants and prostheses, is strongly determined by the host’s immune response to the implanted material. Monocytes and macrophages are main actors of the so-called foreign body reaction. The innate immune system macrophages (M) can be broadly classified into the pro-inflammatory M1-type and the anti-inflammatory, pro-healing M2-type. While a transient inflammatory initial state can be helpful during an infection, persistent inflammation interferes with proper healing and subsequent regeneration. The functional orientation of the immune response, mirrored by monocyte polarization, during interaction with different biomaterials has not yet been sufficiently explored. In implant manufacturing, thermoplastic polyurethane (TPU) represents the state-of-the-art material. The constantly growing areas of application and the associated necessary adaptations make the optimization of these materials indispensable. In the present study, modified liquid silicone rubber (LSR) were compared with two of the most commonly used TPUs, in terms of monocyte adhesion and M1/M2 polarization in vitro. Human monocytes isolated from venous blood were evaluated for their ability to adhere to various biomaterials, their gene expression profile, and their cytokine release. Based on the results, the different polymers exhibit different potential to bias monocytes with respect to early pro-inflammatory cytokine production and gene transcription. Furthermore, none of our test materials showed a clear trend towards M1 or M2 polarization. However, we were able to evaluate the inflammatory potential of the materials, with the classic TPUs appearing to be the most unreactive compared to the silicone-based materials.

Micro injection molding of individualised implants using 3D printed molds manufactured via digital light processing

Here, we demonstrate a manufacturing process for individualised, small-sized implant prototypes. Our process is promising for the manufacturing of drug-releasing (micro)implants to be implanted in the round window niche (RWN-I, solid body, free-form-shaped design, 1.1 x 2.7 x 3.1 mm) and for frontal neo-ostium implants (FO-I, tube-like design, length ~ 7 mm, Ø ~ 2-6 mm) for frontal sinus drainage. Implant prototypes are manufactured using micro injection molding (μIM). We use digital light processing (DLP) as a 3D printing technique for rapid tooling of accurate molds for the μIM process. A common acrylate-based photopolymer for stiff and high-detailed modelling but with low head deflection temperature of HDT = 60.5 °C is used for DLP 3D printing of the molds. The molds were 3D printed with a layer height of 50 μm in about 20 min (RWN-I) and 60 min (FO-I). For μIM investigations, we use liquid silicone rubber (LSR) as a biocompatible and medically relevant material. Micro injection molding of LSR was investigated using mold temperatures between Tmold = 110 °C (long tcuring ~ 2 h) up to Tmold = 160 °C (short tcuring ~ 5 min). As a result, small-sized, complex-shaped implant prototypes of LSR can be successfully manufactured via μIM using high Tmold = 160 °C and short curing time. DLP 3D printing material with relative low HDT = 60.5 °C was suitable for μIM. There is no significant wear of the molds, when used for a low number of μIM cycles (n ~ 8). Design of metal mold housing has to be suitable (perfect fit of mold, no cavities facing the molds surface for prevention of thermal expansion of mold into cavities).