جستجوی مقالات مرتبط با کلیدواژه "energy harvesting" در نشریات گروه "مهندسی شیمی، نفت و پلیمر"

Implantable medical devices such as pacemakers are designed to treat, diagnose, and prevent different diseases. Lithium batteries are commonly applied to power these devices, but because of their limited capacity and lifetime, patients have to suffer a painful and risky surgical procedure to replace them. Recently, nanogenerators have been emerged and are widely noticed as they can convert very small biomechanical energies such as heartbeats into electrical energy. The purpose of this project is to manufacture a piezoelectric sensor as an energy harvester with proper performance and biocompatibility with improved electrical output. In this research, a hybrid structure of PVDF coupling with polyamide 11 (PA11) was fabricated using conjugate electrospinning to enhance the piezoelectric properties of the intended piezoelectric sensor. The piezoelectric test results showed an acceptable increase of the piezoelectric coefficient of nanofibers from 62.87 mV/N to 75.75 mV/N by adding 25% volumetric PA 11, indicating the synergistic properties of these two compounds. The specimen (75% PVDF/25% PA 11) also has the highest mechanical properties and can therefore be suggested as an optimum sample.

Recently, the supply of electrical energy from sustainable and renewable energies such as mechanical, thermal and solar energy has been expanded. Piezoelectric materials are one of the best alternatives for supplying electrical energy from the mechanical energy available in nature such as mechanical force, vibration and human body movements. The applications for piezoelectric energy harvester include low power electronics or wireless sensing at relatively lower power levels (nW to mW) with an aim to reduce a reliance on batteries or electrical power through cables and realize fully autonomous and self-powered systems. In fact, the piezoelectric property is the property of a special material that enables the conversion of mechanical energy into electrical energy and vice versa. Piezoelectric property was discovered in ceramics for the first time. However, because of the need to piezoelectric materials with large surfaces and high flexibility in many applications, and the relatively low price and simple manufacturing technology of polymers in comparison with ceramics, polymers are used extensively. Poly(vinylidene fluoride) (PVDF) is a semicrystalline polymer with ferroelectric and piezoelectric properties. It has five distinctive configurations. β-phase is a polar phase showing significant piezoelectricity and pyroelectricity due to the highest dipolar moment and spontaneous polarization. In this review, PVDF polymer is introduced and then the different strategies for identification and quantification of PVDF phases are summarized. Finally, various methods including stretching, high pressure, ultra-fast cooling, melt quenching, using polar solvents, poling, copolymerization, polymer blending, electrospinning and filler addition such as carbon nanotube, clay, metals and metal salts, ceramics and etc., have been discussed for β-phase enhancement.