A self-powered mechanical energy harvester based on CH3NH3PbI3 doped P(VDF-HFP)/PANI composite films

Piezoelectric polymers, particularly poly(vinylidene fluoride) (PVDF) and its copolymers attract attention from researchers due to their stretchability, flexibility, lightweight, and most importantly their biocompatible nature. In this research work, we report on the preparation of polymer composite films as flexible piezoelectric generators (PGs) and their electroactive phase (β- and γ-phase) formation. The piezoelectric properties of copolymer poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) have been enhanced by incorporating polyaniline (PANI) and methylammonium lead iodide (CH3NH3PbI3) into it for a higher yield of the electroactive phases where a traditional electrical poling treatment was avoided. The remarkable enhancement in the piezoelectric phase (i.e., β-phase) of the P(VDF-HFP) copolymer has been reported in this work, and it is found that the overall improvement of the piezoelectric β-phase and the conversion of the degree of crystallinity is governed by the incorporation of the PANI and CH3NH3PbI3 fillers as revealed by the attenuated total reflectance (ATR) and X-ray diffraction (XRD) analysis. The X-ray photoelectron spectroscopy (XPS) analysis further confirmed the interfacial dipole-dipole interaction of PANI with the P(VDF-HFP) copolymer matrix. Piezoelectric generators (PGs) fabricated from the composite films show an open circuit piezoelectric voltage output of 5 volts and an output power of 8.2 nW. The capacitor charging capability by simple repetitive finger touch and release motions (a pressure amplitude of ∼14 kPa) of the flexible PGs promises their applicability as a piezoelectric-based energy harvester where different mechanical vibrations can be utilized.

Sensing of ultraviolet light: a transition from conventional to self-powered photodetector

Clouds in the sky pass almost 80% of ultraviolet (UV) radiation to the earth's surface, which has a significant impact on humankind. Conventional UV photodetectors (PDs) require an external battery, which not only increases the device size but also has a limited life span and maintenance costs can be prohibitively expensive. An alternative and more technically-sound solution would be the use of self-powered UV PDs that can operate independently, eliminating the need for an external source. Although many exciting studies have been done and state-of-the-art research is underway to successfully fabricate self-powered UV PDs, periodic reviews on this topic are deemed essential so that the technology's readiness can be properly evaluated and critical challenges can be addressed in a timely manner. In this article, the key issues and most exciting developments made in recent years on built-in electric field assisted self-powered UV PDs based on p-n homojunctions, p-n heterojunctions, and Schottky junctions followed by energy harvester integrated UV PDs are extensively reviewed. Finally, a summary and comparison of different types of self-powered UV PDs as well as future challenges that need to be addressed are discussed. This review sets a foundation providing essential insights into the present status of self-powered UV PDs with which researchers can engage and deal with the major challenges.

High-Performance Electronic Cloth for Facilitating the Rehabilitation of Human Joints

The concern about easily characterizing the conditions of human joints to facilitate rehabilitation during recovery training has been out of sight, even though it is acknowledged that timely recovering functions of injured joints is a must. To facilitate the situation to be addressed, a stretchable, air-permeable electronic cloth (SApEC) was fabricated by electrostatic spinning and hot-pressing. The SApEC consists of conductive-elastic fabric Ag and composite nanofibrous membrane (CNFM) with components of poly(vinylidene fluoride- co-hexa-fluoropropyiene) and thermoplastic urethane. The electronic cloth not only owns chemical stability and ultralight weight, but scavenges triboelectric signals from joint movements. These characters allow the SApEC to be an easy and convenient indicator to indicate the activity of joints, when users get rehabilitation training in non-hospital places. With the assistance of several electronic components, the SApEC could control alarms, such as a warning lamp. This favorable ability allows the SApEC to make alerts, once users face any accidents again, like sudden fall or heart failure. Given the advantages mentioned above, it is reasonable to believe that the SApEC has a promising prospect in portable and wearable electronics, involving indicating rehabilitation of joints and keeping an eye on users' safety.

Toward High Power Generating Piezoelectric Nanofibers: Influence of Particle Size and Surface Electrostatic Interaction of Ce-Fe2O3 and Ce-Co3O4 on PVDF

Development of flexible piezoelectric nanogenerator (PENG) is a real challenge for the next-generation energy-harvesting applications. In this paper, we report highly flexible PENGs based on poly(vinylidene fluoride) (PVDF)/2 wt % Ce-Fe₂O₃ and PVDF/2 wt % Ce-Co₃O₄ nanocomposite fibers. The incorporation of magnetic Ce-Fe₂O₃ and Ce-Co₃O₄ greatly affects the structural properties of PVDF nanofibers, especially the polymeric β and γ phases. In addition, the new composites enhanced the interfacial compatibility through electrostatic filler-polymer interactions. Both PVDF/Ce-Fe₂O₃ and PVDF/Ce-Co₃O₄ nanofibers-based PENGs, respectively, produce peak-to-peak output voltages of 20 and 15 V, respectively, with the corresponding output currents of 0.010 and 0.005 μA/cm² under the force of 2.5 N. Enhanced output performance of the flexible nanogenerator is correlated with the electroactive polar phases generated within the PVDF, in the presence of the nanomaterials. The designed nanogenerators respond to human wrist movements with the highest output voltage of 0.15 V, for the PVDF/Ce-Fe₂O₃ when subjected to hand movements. The overall piezoelectric power generation is correlated with the nanoparticle size and the existing filler-polymer and ion-dipole interactions.

Enhanced functional properties of soft polymer–ceramic composites by swift heavy ion irradiation

Variations of different physical properties with the fluence (ions per cm²) of Li³⁺ion irradiation.

Natural Sugar-Assisted, Chemically Reinforced, Highly Durable Piezoorganic Nanogenerator with Superior Power Density for Self-Powered Wearable Electronics

Natural piezoelectric materials are of increasing interest, particularly for applications in biocompatible, implantable, and flexible electronic devices. In this paper, we introduce a cost-effective, easily available natural piezoelectric material, that is, sugar in the field of wearable piezoelectric nanogenerators (PNGs) where low electrical output, biocompatibility, and performance durability are still critical issues. We report on a high-performance piezoorganic nanogenerator (PONG) based on the hybridization of sugar-encapsulated polyvinylidene fluoride (PVDF) nanofiber webs (SGNFW). We explore the crucial role of single-crystal sugar having a fascinating structure along with the synergistic enhancement of piezoelectricity during nanoconfinement of sugar-interfaced macromolecular PVDF chains. As a consequence, the SGNFW-based PONG exhibits outstanding electricity generation capability (e.g., ∼100 V under 10 kPa human finger impact and maximum power density of 33 mW/m²) in combination with sensitivity to abundantly available different mechanical sources (such as wind flow, vibration, personal electronics, and acoustic vibration). Consequently, it opens up suitability in multifunctional self-powered wearable sensor designs for realistic implementation. In addition, commercially available capacitors are charged up effectively by the PONG because of its rapid energy storage capability. The high performance of the PONG not only offers "battery-free" energy generation (several portable units of light-emitting diodes and a liquid crystal display screen are powered up without using external storage) but also promises its use in wireless signal transmitting systems, which widens the potential in personal health care monitoring. Furthermore, owing to the geometrical stress confinement effect, the PONG is proven to be a highly durable power-generating device validated by stability test over 10 weeks. Therefore, the organic nanogenerator would be a convenient solution for portable personal electronic devices that are expected to operate in a self-powered manner.