Elastic Modulus Of Membrane Research Articles

The forewing of a black cicada Cryptotympana atrata (Hemiptera, Homoptera: Cicadidae): Microscopic structures and mechanical properties.

Insects in nature flap their wings to generate lift force and driving torque to adjust their attitude and control stability. An insect wing is a biomaterial composed of flexible membranes and tough veins. In this paper, we study the microscopic structures and mechanical properties of the forewing of the black cicada, Cryptotympana atrata. The thickness of the wing membranes and the diameter of veins varied from the wing root to the tip. The thickness of the wing membranes ranged from 6.0 to 29.9μm, and the diameter of the wing veins decreased in a gradient from the wing root to the tip, demonstrating that the forewing of the black cicada is a nonuniform biomaterial. The elastic modulus of the membrane near the wing root ranged from 4.45 to 5.03 GPa, which is comparable to that of some industrial membranes. The microstructure of the wing vein exhibited a hollow tubular structure with flocculent structure inside. The "fresh" sample stored more water than the "dry" sample, resulting in a significant difference in the elastic modulus between the fresh and dried veins. The different membrane thicknesses and elastic moduli of the wing veins near the root and tip resulted in varied degrees of deformation on both sides of the flexion line of the forewing during twisting. The measurements of the forewing of the cicada may serve as a guide for selecting airfoil materials for the bionic flapping-wing aircraft and promote the design and manufacture of more durable bionic wings in the future. RESEARCH HIGHLIGHTS: The distribution of the wing vein diameter and the wing membrane thickness indicated that the forewing of Cryptotympana atrata is composed of heterogeneous materials. The wing membrane and the outer wall of the wing vein are the layered structure with multilayer fibers, which has a great significance for improving the ability of the forewing to sustain aerodynamic loads. The elastic modulus of the wing membrane near the wing root is in the range of 4.45-5.03GPa, which is comparable to that of membranes manufactured by industries. This is a suitable reference for selecting materials for making bionic aircraft wings. We proved that the elastic moduli of the "fresh" and "dry" wing veins differ greatly compared with those of the wing membrane. Because the wing vein microstructure exhibits an internal hollow tubular structure with flocculent structure inside, the "fresh" sample stores more water than the "dry" sample. The wing membrane near the wing root is thicker and reinforced by the main wing vein with a high elastic modulus. This renders the region near the wing root difficult to deform. The membrane far from the wing root is thinner and the elastic modulus of the nearby wing veins is smaller, making them more flexible.

Preparation and properties of poly(ε-caprolactone)/bioactive glass nanofibre membranes for skin tissue engineering

Poly(ε-caprolactone) composite nanofibres for skin tissue engineering and regeneration applications were prepared via electrospinning of poly(ε-caprolactone) nanofibres with bioactive glass nanoparticles at bioactive glass contents of 0, 2, 4, 6 and 8 wt%. The surface properties, water absorptivities, porosities, mechanical properties and biocompatibilities of the composite electrospun nanofibres were characterised in detail. Addition of bioactive glass improved the hydrophilicity and elastic modulus of membranes. The fibre diameter of the neat poly(ε-caprolactone) nanofibres was only 700 nm, but reinforcement with 2, 4, 6 and 8 wt% bioactive glass nanofibres increased the diameter to 1000, 1100, 900 and 800 nm, respectively. The minimum elongation at break of the bioactive glass–reinforced poly(ε-caprolactone) exceeded 100%, which indicated that the composite nanofibres had good mechanical properties. The porosities of the various nanofibres containing different mass loadings of bioactive glass all exceeded 90%. The best performance in terms of cell proliferation and adhesion was found when the bioactive glass mass percent reached 6 wt%. However, higher loadings were unfavourable for cell growth. These preliminary results indicate that poly(ε-caprolactone)/bioactive glass composite nanofibres have promise for skin tissue engineering applications.

The Effect of Bending Rigidity on Measuring the Adhesion Work of Membrane

A theoretical model is developed to examine the effect of bending rigidity on measuring the adhesion work between a flat punch and a flexible membrane by pull-off test. The validity of this model is certified by the theoretical analysis. It can be used in the future experiments to analyze the experimental data when the bending rigidity of the membrane cannot be ignored. From our quantitative analysis, the effect is remarkable and sensitive to the bending rigidity. The effect of bending rigidity should not be neglected unless the membrane is very soft or the membrane is very thin. The elastic modulus of membrane should be less than 1.6MPa when the thickness of the membrane is less than 10μm. Moreover, it is obviously that the thickness plays a key role in the bending rigidity.

Correlations between the form fluctuation modes of flaccid quasispherical lipid vesicles and their role in the calculation of the curvature elastic modulus of the vesicle membrane. Numerical results

It is shown in this paper that the existing theories of the form fluctuations of quasispherical lipid vesicle give a too mean stretching energy of its membrane. A more precise theory taking into account the area conservation of the membrane is proposed. The relation between the amplitudes of the form fluctuations and the curvature elastic modulus of the membrane is obtained numerically by means of a suitable Monte Carlo simulation.