A material-based model for the simulation and control of soft robot actuator

An innovative material-based model is described for a three-pneumatic channel, soft robot actuator and implemented in simulations and control. Two types of material models are investigated: a soft, hyperelastic material model and a novel visco-hyperelastic material model are presented and evaluated in simulations of one-channel operation. The advanced visco-hyperelastic model is further demonstrated in control under multi-channel actuation. Finally, a soft linear elastic material model was used in finite element analysis of the soft three-pneumatic channel actuator within SOFA, moving inside a pipe and interacting with its rigid wall or with a soft hemispherical object attached to that wall. A collision model was used for these interactions and the simulations yielded “virtual haptic” 3d-force profiles at monitored nodes at the free- and fixed-end of the actuator

Protection against renal ischemia reperfusion injury by CD44 disruption

Inflammation contributes to renal ischemia reperfusion (I/R) injury, potentially causing renal dysfunction. The inflammatory infiltrate mainly consists of neutrophils, which are deleterious for the renal tissue. Because CD44 is expressed by neutrophils and is rapidly upregulated by capillary endothelial cells after I/R injury, it was hypothesized that CD44 might play an important role in the development of I/R injury. This study showed that rapid CD44 upregulation on renal capillary endothelial cells mediates neutrophil recruitment to the postischemic tissue. Hence, CD44 deficiency led to decreased influx of neutrophils regardless of comparable levels in chemotactic factors expressed in the kidney. The reduced influx of neutrophils was associated with preserved renal function and morphology. Adoptive transfer experiments of labeled neutrophils revealed that endothelial CD44 rather than neutrophil CD44 mediates neutrophil migration. Activation of neutrophils increased cell-surface expression of hyaluronic acid (HA). Altogether, a novel mechanism in the recruitment of neutrophils that involves interaction of endothelial CD44 and neutrophil HA was found. Either blocking endothelial CD44 or removal of neutrophil HA decreased rolling and adhesion of neutrophils. Administration of anti-CD44 to mice reduced the influx of neutrophils into the postischemic tissue, associated with renal function preservation. Therefore, anti-CD44-based therapies may contribute to prevent or reduce renal I/R injur

3D Constitutive model of the rat large intestine: estimation of the material parameters of the single layers

Several functions of the large intestine depend on its morphology and biomechanical properties. Since some classes of soft tissues have non-linear mechanical behavior, they may be modeled as hyperelastic materials applying the strain energy function. Moreover, as the arterial walls, the colonic walls are composed by collagen fibers characterized by an anisotropic behavior. It is known a mechanical model of artery that considered its walls composed of two cylindrical layers reinforced with fibers of collagen suitably oriented. Afterwards, it has been proposed a structure-based mathematical model for mechanical passive behavior of the rat colon, fitted to data obtained from inflation/extension tests that doesn’t subdivide the walls into layers. However, the wall of the rat large intestine is composed by four distinct layers, i.e. mucosa, submucosa, muscle layer and serosa. Thus, the aim of this paper is to identify a method for estimating the parameters of a computational model that considers each layer of the colonic walls. We use the Nelder-Mead nonlinear regression technique for minimizing the residual sum of squares between experimental data reported in literature and the outcomes of the proposed model. The estimated material parameters (k1,k2,c) are used to develop a 3D finite element model. Furthermore, we computed the components of the Cauchy stress over the colonic wall across each layer for different values of internal pressure and axial stretch