Finite element analysis of biomechanical interactions of a subcutaneous suspension suture and human face soft-tissue: a cadaver study.

In order to study the local interactions between facial soft-tissues and a Silhouette Soft® suspension suture, a CE marked medical device designed for the repositioning of soft tissues in the face and the neck, Finite element simulations were run, in which a model of the suture was embedded in a three-layer Finite Element structure that accounts for the local mechanical organization of human facial soft tissues. A 2D axisymmetric model of the local interactions was designed in ANSYS, in which the geometry of the tissue, the boundary conditions and the applied loadings were considered to locally mimic those of human face soft tissue constrained by the suture in facial tissue repositioning. The Silhouette Soft suture is composed of a knotted thread and sliding cones that are anchored in the tissue. Hence, simulating these interactions requires special attention for an accurate modelling of contact mechanics. As tissue is modelled as a hyper-elastic material, the displacement of the facial soft tissue changes in a nonlinear way with the intensity of stress induced by the suture and the number of the cones. Our simulations show that for a 4-cone suture a displacement of 4.35 mm for a 2.0 N external loading and of 7.6 mm for 4.0 N. Increasing the number of cones led to the decrease in the equivalent local strain (around 20%) and stress (around 60%) applied to the tissue. The simulated displacements are in general agreement with experimental observations.

Impact of drinking water supplementation of a blend of peppermint, coneflower (Echinacea purpurea), thyme, propolis, and prebiotic on performance, serum constituents, and immunocompetence of broiler chickens.

Essential oils, extracts, their components, and other non-antibiotic beneficial additives are becoming increasingly popular as naturally occurring immunomodulatory agents. A study was conducted to evaluate the effects of a blend (hereafter refers to as ImmunoMax (IMX)) of peppermint, coneflower, thyme, propolis, and prebiotic on performance, immune response, hematological indices, and serum biochemistry of broiler chickens. A total of 300 day-old broiler male chicks were randomly assigned to 4 treatments: control (A) (not treated), 0.25 mL/L (B), 0.5 mL/L (C), and 1 mL/L (D) supplementing drinking water with IMX on alternate days, starting at day 21. The results demonstrated a higher body weight gain (BWG) and feed intake (FI) in groups B, C, and D (P < 0.05) with no significant difference in FCR. The results also revealed a superior immune response to NDV, IB, and IBD (P < 0.05), albeit no constant linear response. The largest portion of the heterophil, the smallest amount of the lymphocyte, and therefore the highest heterophil-to-lymphocyte ratio (H:L) were observed in the control group, while the lowest ratio belonged to groups B and C (P < 0.05). Hemoglobin content, hematocrit, total number of red blood cells (RBC), and white blood cells (WBC) were also affected by IMX, showing a significant rise compared to the control group (P < 0.05). Administering 0.25 mL/L of IMX resulted a higher thigh and breast yield as well as the smallest amount of abdominal fat (P < 0.05). The serum content of total protein (TP) and albumin (ALB) was superior in groups receiving 0.25 and 0.5 mL/L of IMX; these treatments also yielded an inferior content of glucose (GLU), triglycerides (TG), cholesterol (CHOL), LDL, and VLDL, in addition to causing the highest content of HDL (P < 0.05). The results obtained in this study revealed the immunomodulatory efficacy of a standardized natural multidrug, IMX, thereby improving the performance and carcass yield of modern broiler chickens with the optimal dosages of 0.25 and 0.5 mL/L.

Highly Sensitive Porous PDMS-Based Capacitive Pressure Sensors Fabricated on Fabric Platform for Wearable Applications.

A novel porous polydimethylsiloxane (PDMS)-based capacitive pressure sensor was fabricated by optimizing the dielectric layer porosity for wide-range pressure sensing applications in the sports field. The pressure sensor consists of a porous PDMS dielectric layer and two fabric-based conductive electrodes. The porous PDMS dielectric layer was fabricated by introducing nitric acid (HNO3) into a mixture of PDMS and sodium hydrogen bicarbonate (NaHCO3) to facilitate the liberation of carbon dioxide (CO2) gas, which induces the creation of porous microstructures within the PDMS dielectric layer. Nine different pressure sensors (PS1, PS2,..., PS9) were fabricated in which the porosity (pore size, thickness) and dielectric constant of the PDMS dielectric layers were varied by changing the curing temperature, the mixing proportions of the HNO3/PDMS concentration, and the PDMS mixing ratio. The response of the fabricated pressure sensors was investigated for the applied pressures ranging from 0 to 1000 kPa. A relative capacitance change of ∼100, ∼323, and ∼485% was obtained by increasing the curing temperature from 110 to 140 to 170 °C, respectively. Similarly, a relative capacitance change of ∼170, ∼282, and ∼323% was obtained by increasing the HNO3/PDMS concentration from 10 to 15 to 20%, respectively. In addition, a relative capacitance change of ∼94, ∼323, and ∼460% was obtained by increasing the PDMS elastomer base/curing agent ratio from 5:1 to 10:1 to 15:1, respectively. PS9 exhibited the highest sensitivity over a wide pressure sensing range (low-pressure ranges (<50 Pa), 0.3 kPa-1; high-pressure ranges (0.2-1 MPa), 3.2 MPa-1). From the results, it was observed that the pressure sensors with dielectric layers prepared at relatively higher curing temperatures, higher HNO3 concentrations, and higher PDMS ratios resulted in increased porosity and provided the highest sensitivity. As an application demonstrator, a wearable fit cap was developed using an array of 16 pressure sensors for measuring and mapping the applied pressures on a player's head while wearing a helmet. The pressure mapping aids in observing and understanding the proper fit of the helmet in sports applications.

A new model of passive muscle tissue integrating Collagen Fibers: Consequences for muscle behavior analysis.

Mechanical properties of muscle tissue are crucial in biomechanical modeling of the human body. Muscle tissue is a combination of Muscle Fibers (MFs) and connective tissue including collagen and elastin fibers. There are a lot of passive muscle models in the literature but most of them do not consider any distinction between Collagen Fibers (CFs) and MFs, or at least do not consider the mechanical effects of the CFs on the Three-Dimensional (3-D) behavior of tissue. As a consequence, unfortunately, they cannot describe the observed stress-stretch behavior in tissue in which the reinforced direction is not parallel to the MF direction. In this research, a new passive muscle model is presented, in which the CFs are separately considered in the formulation: they are distributed along the MFs in a cross-shaped arrangement. Thanks to this new architecture, a mechanical reinforced direction can be proposed, in addition to the muscle main fiber direction. The passive biomechanical properties of the genioglossus muscle of a bovine tongue have been measured under uniaxial tensile tests. To characterize the 3-D response of the tissue, tests have been performed in different directions with respect to the MF direction. Moreover, a Constitutive Law (CL) has been proposed for modeling this behavior. In addition to our measurements on the bovine genioglossus muscle, results published in the literature on experimental data from the longissimus dorsi of pigs and the chicken pectoralis muscle were used to appraise the applicability of the proposed model. It is demonstrated that the proposed passive muscle model provides an accurate description of the fiber-oriented nature of muscle tissue. Also, it has been shown that using Finite Element Analysis (FEA) it might be possible to predict the angle θ between CFs and MF.

A visco-hyperelastic constitutive model and its application in bovine tongue tissue.

Material properties of the human tongue tissue have a significant role in understanding its function in speech, respiration, suckling, and swallowing. Tongue as a combination of various muscles is surrounded by the mucous membrane and is a complicated architecture to study. As a first step before the quantitative mechanical characterization of human tongue tissues, the passive biomechanical properties in the superior longitudinal muscle (SLM) and the mucous tissues of a bovine tongue have been measured. Since the rate of loading has a sizeable contribution to the resultant stress of soft tissues, the rate dependent behavior of tongue tissues has been investigated via uniaxial tension tests (UTTs). A method to determine the mechanical properties of transversely isotropic tissues using UTTs and inverse finite element (FE) method has been proposed. Assuming the strain energy as a general nonlinear relationship with respect to the stretch and the rate of stretch, two visco-hyperelastic constitutive laws (CLs) have been proposed for isotropic and transversely isotropic soft tissues to model their stress-stretch behavior. Both of them have been implemented in ABAQUS explicit through coding a user-defined material subroutine called VUMAT and the experimental stress-stretch points have been well tracked by the results of FE analyses. It has been demonstrated that the proposed laws make a good description of the viscous nature of tongue tissues. Reliability of the proposed models has been compared with similar nonlinear visco-hyperelastic CLs.