A Review of Piezoelectric Footwear Energy Harvesters: Principles, Methods, and Applications.

Over the last couple of decades, numerous piezoelectric footwear energy harvesters (PFEHs) have been reported in the literature. This paper reviews the principles, methods, and applications of PFEH technologies. First, the popular piezoelectric materials used and their properties for PEEHs are summarized. Then, the force interaction with the ground and dynamic energy distribution on the footprint as well as accelerations are analyzed and summarized to provide the baseline, constraints, potential, and limitations for PFEH design. Furthermore, the energy flow from human walking to the usable energy by the PFEHs and the methods to improve the energy conversion efficiency are presented. The energy flow is divided into four processing steps: (i) how to capture mechanical energy into a deformed footwear, (ii) how to transfer the elastic energy from a deformed shoes into piezoelectric material, (iii) how to convert elastic deformation energy of piezoelectric materials to electrical energy in the piezoelectric structure, and (iv) how to deliver the generated electric energy in piezoelectric structure to external resistive loads or electrical circuits. Moreover, the major PFEH structures and working mechanisms on how the PFEHs capture mechanical energy and convert to electrical energy from human walking are summarized. Those piezoelectric structures for capturing mechanical energy from human walking are also reviewed and classified into four categories: flat plate, curved, cantilever, and flextensional structures. The fundamentals of piezoelectric energy harvesters, the configurations and mechanisms of the PFEHs, as well as the generated power, etc., are discussed and compared. The advantages and disadvantages of typical PFEHs are addressed. The power outputs of PFEHs vary in ranging from nanowatts to tens of milliwatts. Finally, applications and future perspectives are summarized and discussed.

Identification and immune responses of thrombocytes in bacterial and viral infections in grass carp (Ctenopharyngodon idella).

Thrombocytes are an important component in peripheral blood cells and play a crucial role in immune regulation. CD41 is one of the biomarkers of thrombocytes. In this study, grass carp (Ctenopharyngodon idella) CD41 protein was expressed in Escherichia coli and purified by affinity chromatography. Subsequently, New Zealand rabbits were immunized with this protein via subcutaneous injection. The antibody titer examined by enzyme linked immunosorbent assay was 1:12800. The concentration of rabbit polyclonal antibody purified by HiTrap-rprotein-AFF affinity chromatography column was 1.9 mg/mL. The specificity was identified by SDS-PAGE, Western blot, flow cytometry, and indirect immunofluorescence assays. The purified antibody was used to screen grass carp thrombocytes, and CD41+ cells were 14.13%. CD41+ cells were further verified by Giemsa staining, transmission electron microscopy and RT-PCR. mRNA expression of CD41 in thrombocytes was not affected by viral or bacterial challenge in vitro, while CD41 transcripts were remarkably induced post pathogenic infections in vivo, which results from the immature hematopoietic stem cells and thrombocytes. Indirect immunofluorescence assay revealed that grass carp reovirus (GCRV) could not invade thrombocytes; however, mRNA expressions of some representative innate immune genes (IFN1, IL-1ß, TNFα and Mx2) were significantly up-regulated post GCRV challenge. Meanwhile, the transcripts of some innate immune genes (IL-6 and TNFα) were swiftly increased post bacterial infection. These results indicated that the rabbit anti-CD41 polyclonal antibody possesses good specificity and can effectively bind to the CD41 protein on the surface of grass carp thrombocytes. Grass carp thrombocytes participate in immune regulation in viral and bacterial infections.

Pattern recognition receptors in grass carp Ctenopharyngodon idella: II. Organization and expression analysis of NOD-like receptors.

Nucleotide-binding domain and leucine-rich repeat containing receptors (NLRs) are a pivotal intracellular pattern recognition receptor family. However, studies on NLR genes in important economic fish grass carp (Ctenopharyngodon idella) are sporadic. The accumulations of genomic resource and transcriptomic sequences make it feasible to conduct a systematic analysis of these genes. In this study, we systematically conducted the genome-wide study of C. idella NLR genes and characterized their phylogeny, gene structure, conserved domain, evolutionary mechanism, and expression profiles post viral or bacterial challenge. A total of 65 NLR genes were identified and clustered into five subfamilies based on structural and phylogenetic features, including eight NODs (NLR-A), five NLRP-like receptors (NLR-B), forty-seven teleost-specific NLRs (NLR-C), two members with a B30.2 domain at the C-terminal (NLR-B30.2), and three additional NLRs (other NLRs). Gene structure analysis showed that NLRs were significantly different, with exon numbers from 3 to 31. Conserved domain analysis showed that most members of C. idella NLRs had additional domains besides the typical NLR domains. Gene duplication analysis indicated that the evolution of the NLR gene family was mainly related to segment duplication. mRNA expression analysis indicated that many members were differently expressed in multiple tissues post grass carp reovirus (GCRV) or Aeromonas hydrophila infection. The expression was particularly enhanced in liver post GCRV infection, and obviously lower post A. hydrophila infection than that post GCRV infection in spleen. These results provide systematic basic data for further functional studies of NLR, and insight into the immune responses of piscine fish NLRs to pathogen infections.

Design, fabrication, and performance of a flextensional transducer based on electrostrictive polyvinylidene fluoride-trifluoroethylene copolymer.

Taking advantage of the high electrostrictive strain and high elastic energy density of a newly developed electrostrictive polymer, modified poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] based polymers, a flex-tensional transducer was designed, and its performance was investigated. The flextensional transducer consists of a multilayer stack made of electrostrictive P(VDF-TrFE) polymer films and two flextensional shells fixed at the ends to the multilayer stack. Because of the large transverse strain level achievable in the electrostrictive polymer and the displacement amplification of the flextensional shells, a device of a few millimeters thick and lateral dimension about 30 mm x 25 mm can generate an axial displacement output of more than 1 mm. The unique flextensional configuration and the high elastic energy density of the active polymer also enable the device to offer high-load capability. As an underwater transducer, the device can be operated at frequencies below 1 kHz and still exhibit relatively high transmitting voltage response (TVR), very high source level (SL), and low mechanical quality factor (Qm).