Polymer ferroelectret based on polypropylene foam: piezoelectric properties prediction using dynamic mechanical analysis

Biomedical Applications of Electrets: Recent Advance and Future Perspectives

Recently, electrical stimulation, as a non-pharmacological physical stimulus, has been widely exploited in biomedical and clinical applications due to its ability to significantly enhance cell proliferation and differentiation. As a kind of dielectric material with permanent polarization characteristics, electrets have demonstrated tremendous potential in this field owing to their merits of low cost, stable performance, and excellent biocompatibility. This review provides a comprehensive summary of the recent advances in electrets and their biomedical applications. We first provide a brief introduction to the development of electrets, as well as typical materials and fabrication methods. Subsequently, we systematically describe the recent advances of electrets in biomedical applications, including bone regeneration, wound healing, nerve regeneration, drug delivery, and wearable electronics. Finally, the present challenges and opportunities have also been discussed in this emerging field. This review is anticipated to provide state-of-the-art insights on the electrical stimulation-related applications of electrets.

The intrinsic piezoelectric properties of materials - a review with a focus on biological materials

Piezoelectricity, a linear electromechanical coupling, is of great interest due to its extensive applications including energy harvesters, biomedical, sensors, and automobiles. A growing amount of research has been done to investigate the energy harvesting potential of this phenomenon. Traditional piezoelectric inorganics show high piezoelectric outputs but are often brittle, inflexible and may contain toxic compounds such as lead. On the other hand, biological piezoelectric materials are biodegradable, biocompatible, abundant, low in toxicity and are easy to fabricate. Thus, they are useful for many applications such as tissue engineering, biomedical and energy harvesting. This paper attempts to explain the basis of piezoelectricity in biological and non-biological materials and research involved in those materials as well as applications and limitations of each type of piezoelectric material.

Piezoelectricity, a linear electromechanical coupling, is of great interest due to its extensive applications including energy harvesters, biomedical, sensors, and automobiles.

Piezoelectric Polymer and Paper Substrates: A Review

Polymers and papers, which exhibit piezoelectricity, find a wide range of applications in the industry. Ever since the discovery of PVDF, piezo polymers and papers have been widely used for sensor and actuator design. The direct piezoelectric effect has been used for sensor design, whereas the inverse piezoelectric effect has been applied for actuator design. Piezo polymers and papers have the advantages of mechanical flexibility, lower fabrication cost and faster processing over commonly used piezoelectric materials, such as PZT, BaTiO₃. In addition, many polymer and paper materials are considered biocompatible and can be used in bio applications. In the last 20 years, heterostructural materials, such as polymer composites and hybrid paper, have received a lot of attention since they combine the flexibility of polymer or paper, and excellent pyroelectric and piezoelectric properties of ceramics. This paper gives an overview of piezoelectric polymers and papers based on their operating principle. Main categories of piezoelectric polymers and papers are discussed with a focus on their materials and fabrication techniques. Applications of piezoelectric polymers and papers in different areas are also presented.

Rotomolding of Foamed and Unfoamed GTR-LLDPE Blends: Mechanical, Morphological and Physical Properties

In this work, a simple method is presented to produce ground tire rubber (GTR) -linear low density polyethylene (LLDPE) compounds and foams via rotational molding. In particular, different GTR concentrations (0 to 50% wt.) were dry-blended with different chemical blowing agent (CBA) content (0 to 1% wt.). From the samples produced, a complete set of characterization was performed in terms of mechanical properties (tensile, flexural and impact), density and morphological properties. The results show that increasing GTR content or CBA content not only decreased both tensile and flexural moduli, but decreased ultimate strength and strain at break. As expected, increasing blowing agent content decreased density. Besides, with respect to impact strength, the value of all samples decreased with the addition of GTR or CBA except for 0.2% wt. CBA of GTR-LLDPE composite foams, which nearly remain at the same level.

Soft and Flexible Bilayer Thermoplastic Polyurethane Foam for Development of Bioinspired Artificial Skin

Inspired by the epidermis-dermis composition of human skin, here we have simply developed a lightweight, robust, flexible, and biocompatible single-electrode triboelectric nanogenerator (S-TENG)-based prototype of bilayer artificial skin, by attaching one induction electrode with unfoamed skin layer of microcellular thermoplastic polyurethane (TPU) foam, which shows high-performance object manipulation [by responding differently toward different objects, viz., aluminum foil, balloon, cotton glove, human finger, glass, rubber glove, artificial leather, polyimide, poly(tetrafluoroethylene) (PTFE), paper, and wood], due to electrification and electrostatic induction during contact with the objects having different chemical functionalities. Comparative foaming behavior of ecofriendly supercritical fluids, viz., CO₂ over N₂ under variable temperatures (e.g., 130 and 150 °C) and constant pressure (15 MPa), have been examined here to pursue the soft and flexible triboelectric TPU foam. The foam derived by CO₂ foaming at 150 °C has been prioritized for development of S-TENG. Foam derived by CO₂ foaming at 130 °C did not respond as well due to the smaller cell size, higher hardness, and thicker skin. Inflexible N₂-derived foam was not considered for S-TENG fabrication. Object manipulation performance has been visualized by principal component analysis (PCA), which shows good discrimination among responses to different objects.

Analytical prediction of the piezoelectric d33 response of fluoropolymer arrays with tubular air channels

The present study is focused on tubular multi-channel arrays composed of commercial fluoropolymer (FEP) tubes with different wall thickness. After proper charging in a high electric field, such tubular structures exhibit a large piezoelectric [Formula: see text] coefficient significantly exceeding the values of classical polymer ferroelectrics and being even comparable to conventional lead-free piezoceramics. The quasistatic piezoelectric [Formula: see text] coefficient was theoretically derived and its upper limits were evaluated considering charging and mechanical properties of the arrays. In order to optimize the [Formula: see text] coefficient the remanent polarization and the mechanical properties were taken into account, both being strongly dependent on the air channel geometry as well as on the wall thickness of the FEP tubes. The model predictions are compared with experimental d₃₃ coefficients for two particular arrays with equal air gaps of 250 μm, but with different wall thickness of utilized FEP tubes of 50 μm and 120 μm, respectively. Analytical modeling allows for the prediction that arrays made of FEP tubes with a wall thickness of 10 μm are foreseen to exhibit a superb piezoelectric response of up to 600 pC/N if the height of stadium-like shaped air channels is reduced down to 50 μm, making them potentially interesting for application as highly sensitive sensors and energy harvesting.