Extrusion of poly(vinylidene fluoride) filaments: effect of the processing conditions and conductive inner core on the electroactive phase content and mechanical properties

Electrospun piezoelectric scaffolds for cardiac tissue engineering

The use of smart materials in tissue engineering is becoming increasingly appealing to provide additional functionalities and control over cell fate. The stages of tissue development and regeneration often require various electrical and electromechanical cues supported by the extracellular matrix, which is often neglected in most tissue engineering approaches. Particularly, in cardiac cells, electrical signals modulate cell activity and are responsible for the maintenance of the excitation-contraction coupling. Addition of electroconductive and topographical cues improves the biomimicry of cardiac tissues and plays an important role in driving cells towards the desired phenotype. Current platforms used to apply electrical stimulation to cells in vitro often require large external equipment and wires and electrodes immersed in the culture media, limiting the scalability and applicability of this process. Piezoelectric materials represent a shift in paradigm in materials and methods aimed at providing electrical stimulation to cardiac cells since they can produce and deliver electrical signals to cells and tissues by mechanoelectrical transduction. Despite the ability of piezoelectric materials to mimic the mechanoelectrical transduction of the heart, the use of these materials is limited in cardiac tissue engineering and methods to characterise piezoelectricity are often built in-house, which poses an additional difficulty when comparing results from the literature. In this work, we aim at providing an overview of the main challenges in cardiac tissue engineering and how piezoelectric materials could offer a solution to them. A revision on the existing literature in electrospun piezoelectric materials applied to cardiac tissue engineering is performed for the first time, as electrospinning plays an important role in the manufacturing of scaffolds with enhanced piezoelectricity and extracellular matrix native-like morphology. Finally, an overview of the current techniques used to evaluate piezoelectricity and their limitations is provided.

Polyvinylidene fluoride - Hydroxyapatite 0-3 biocomposite filaments processed by twin-screw extrusion

Polyvinylidene fluoride - hydroxyapatite composite filaments were processed by twin-screw extrusion at different processing angular velocities and characterized by scanning electron and atomic force microscopies, differential scanning calorimetry and tensile tests. Polymer-ceramic composites with a 0-3 connectivity were successfully obtained. Regardless of the used processing parameters, all composite filaments present very similar melting (∼152°C) and solidification (∼139°C) points and elastic moduli (∼1.0 GPa) for hydroxyapatite as dispersed phase in the composite with concentrations up to 25 wt%, indicating that they are adequate for twin-screw extrusion and 3D printing. However, the yield strength (∼29 MPa), ultimate tensile strength (∼36 MPa) and tensile point (∼29 MPa) parameters are similar only for hydroxyapatite concentrations up to 15 wt%, once higher concentrations of hydroxyapatite as dispersed phase result in fragile samples (∼50% lower for each studied property).

Piezoelectric Materials for Energy Harvesting and Sensing Applications: Roadmap for Future Smart Materials

Piezoelectric materials are widely referred to as "smart" materials because they can transduce mechanical pressure acting on them to electrical signals and vice versa. They are extensively utilized in harvesting mechanical energy from vibrations, human motion, mechanical loads, etc., and converting them into electrical energy for low power devices. Piezoelectric transduction offers high scalability, simple device designs, and high-power densities compared to electro-magnetic/static and triboelectric transducers. This review aims to give a holistic overview of recent developments in piezoelectric nanostructured materials, polymers, polymer nanocomposites, and piezoelectric films for implementation in energy harvesting. The progress in fabrication techniques, morphology, piezoelectric properties, energy harvesting performance, and underpinning fundamental mechanisms for each class of materials, including polymer nanocomposites using conducting, non-conducting, and hybrid fillers are discussed. The emergent application horizon of piezoelectric energy harvesters particularly for wireless devices and self-powered sensors is highlighted, and the current challenges and future prospects are critically discussed.

Real-Time Early Warning System for Sustainable and Intelligent Plastic Film Manufacturing

In this study, real-time preventive measures were formulated for a crusher process that is impossible to automate, due to the impossibility of installing sensors during the production of plastic films, and a real-time early warning system for semi-automated processes subsequently developed. First, the flow of a typical film process was ascertained. Second, a sustainable plan for real-time forecasting in a process that cannot be automated was developed using the semi-automation method flexible structure production control (FSPC). Third, statistical early selection of the process variables that are most probably responsible for failure was performed during data preprocessing. Then, a new, unified dataset was created using the link reordering method to transform the time sequence of the continuous process into one time zone. Fourth, a sustainable prediction algorithm was developed using the association rule method along with traditional statistical techniques, and verified using actual data. Finally, the overall developed logic was applied to new production process data to verify its prediction accuracy. The developed real-time early warning system for semi-automated processes contributes significantly to the smart manufacturing process both theoretically and practically.