A review on fibrous scaffolds in cardiovascular tissue engineering

It has been long and widely known that cardiovascular diseases (CVD) are among the leading causes of the death worldwide. Thecurrent treatments have come a long way to reduce mortality and improve life quality of those affected, but they still presentdrawbacks and limitations, and that is why cardiovascular tissue engineering is thought to be the great promise for the future.Fibrous scaffolds have been a trendy topic in tissue engineering (TE) for years now, and several techniques have been developed andoptimized to produce fibers of various biomaterials – a microstructure that is particularly important for valvular and vascular tissuesdue to their unique composition and organization. This review aims to explain the rationale behind the use of fibrous scaffolds incardiovascular TE, the main biomaterials and techniques that have been employed to produce such scaffolds and how close they areto clinical applications...

A FEM-based method to determine the complex material properties of piezoelectric disks.

Numerical simulations allow modeling piezoelectric devices and ultrasonic transducers. However, the accuracy in the results is limited by the precise knowledge of the elastic, dielectric and piezoelectric properties of the piezoelectric material. To introduce the energy losses, these properties can be represented by complex numbers, where the real part of the model essentially determines the resonance frequencies and the imaginary part determines the amplitude of each resonant mode. In this work, a method based on the Finite Element Method (FEM) is modified to obtain the imaginary material properties of piezoelectric disks. The material properties are determined from the electrical impedance curve of the disk, which is measured by an impedance analyzer. The method consists in obtaining the material properties that minimize the error between experimental and numerical impedance curves over a wide range of frequencies. The proposed methodology starts with a sensitivity analysis of each parameter, determining the influence of each parameter over a set of resonant modes. Sensitivity results are used to implement a preliminary algorithm approaching the solution in order to avoid the search to be trapped into a local minimum. The method is applied to determine the material properties of a Pz27 disk sample from Ferroperm. The obtained properties are used to calculate the electrical impedance curve of the disk with a Finite Element algorithm, which is compared with the experimental electrical impedance curve. Additionally, the results were validated by comparing the numerical displacement profile with the displacements measured by a laser Doppler vibrometer. The comparison between the numerical and experimental results shows excellent agreement for both electrical impedance curve and for the displacement profile over the disk surface. The agreement between numerical and experimental displacement profiles shows that, although only the electrical impedance curve is considered in the adjustment procedure, the obtained material properties allow simulating the displacement amplitude accurately.