ABSTRACT
Bioinspired soft robotics aims at reproducing the complex hierarchy and architecture of biological tissues within artificial systems to achieve the typical motility and adaptability of living organisms. The development of suitable fabrication approaches to produce monolithic bodies provided with embedded variable morphological and mechanical properties, typically encountered in nature, is still a technological challenge. Here we report on a novel manufacturing approach to produce three-dimensional functionally graded hydrogels (3D-FGHs) provided with a controlled porosity gradient conferring them variable stiffness. 3D-FGHs are fabricated by means of a custom-designed liquid foam templating (LFT) technique, which relies on the inclusion of air bubbles generated by a blowing agent into the monomer-based template solution during ultraviolet-induced photopolymerization. The 3D-FGHs' apparent Young's modulus ranges from 0.37 MPa (bulky hydrogel region) to 0.09 MPa (highest porosity region). A fish-shaped soft swimmer is fabricated to demonstrate the feasibility of the LFT technique to produce bioinspired robots. Mobility tests show a significant improvement in terms of swimming speed when the robot is provided with a graded body. The proposed manufacturing approach constitutes an enabling solution for the development of macroscopic functionally graded hydrogel-based structures usable in biomimetic underwater soft robotics applications.
Subject(s)
Robotics , Animals , Biomimetics/methods , Hydrogels/chemistry , Porosity , Robotics/methods , SwimmingABSTRACT
The aim of this work was to analyze the influence of fibers on the mechanical behavior of fiber-reinforced elastomers under cyclic loading. Thus, the focus was on the characterization of structure-property interactions, in particular the dynamic mechanical and viscoelastic behavior. Endless twill-woven glass fibers were chosen as the reinforcement, along with silicone as the matrix material. For the characterization of the flexible composites, a novel testing device was developed. Apart from the conventional dynamic mechanical analysis, in which the effect of the fiber orientation was also considered, modified step cycle tests were conducted under tensile loading. The material viscoelastic behavior was studied, evaluating both the stress relaxation response and the capability of the material to dissipate energy under straining. The effects of the displacement rate of the strain level, the amplitude of the strain applied in the loading-unloading step cycle test, and the number of the applied cycles were evaluated. The results revealed that an optimized fiber orientation leads to 30-fold enhanced stiffness, along with 10 times higher bearable stress. The findings demonstrated that tailored reinforced elastomers with endless fibers have a strong influence on the mechanical performance, affecting the structural properties significantly.
ABSTRACT
El presente trabajo describe una metodologia analitica destinada a estudiar la cinetica de transferencia de piroxicam(I) y ranitidina(II) desde el tracto gastrointestinal de rata. Las sustancias liberadas hacia ambos lados de la membrana, sitio serosal y mucosal dificultan la determinacion de los principios activos por espectroscopia ultravioleta convencional. Las determinaciones de I y II se realizaron empleando espectroscopia derivativa de primer orden; para el primer case se efectuaron las mediciones en medio acido y el maximo de la derivada primera se registro a 354 nm y para II a pH 7.4 a 337 nm. Se encontro buena correlacion entre los valores obtenidos en solucion Krebs y solucion Krebs incubada durante 90 minutos con trozos intestinales (r=0.9999 y r=0.9908 para I y II respectivamente). Se realizaron los ensayos de recuperacion correspondientes estableciendose asi la confiabilidad del metodo analitico seleccionado
