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Multifunctional capability, flexible design, rugged lightweight construction, and self-powered operation are desired attributes for electronics that directly interface with the human body or with advanced robotic systems. For these and related applications, piezoelectric materials, in forms that offer the ability to bend and stretch, are attractive for pressure/force sensors and mechanical energy harvesters. In this paper we introduce a large area, flexible piezoelectric material that consists of sheets of electrospun fibers of the polymer poly[(vinylidenefluoride-co-trifluoroethylene]. The flow and mechanical conditions associated with the spinning process yield free-standing, three-dimensional architectures of aligned arrangements of such fibers, in which the polymer chains adopt strongly preferential orientations. The resulting material offers exceptional piezoelectric characteristics, to enable, as an example, ultra-high sensitivity for measuring pressure, even at exceptionally small values (0.1 Pa). Quantitative analysis provides detailed insights into the pressure sensing mechanisms, and engineering design rules. Applications range from self-powered micro-mechanical elements, to self-balancing robots and sensitive impact detectors.
The intrinsic flexible character of polymeric materials also causes remarkable strain deformations along directions perpendicular to the applied stress. Here the biaxial response in the shear piezoelectricity of polyvinylidenefluoride copolymers is a
High-performance thermoelectric oxides could offer a great energy solution for integrated and embedded applications in sensing and electronics industries. Oxides, however, often suffer from low Seebeck coefficient when compared with other classes of
The linear dispersion relation in graphene[1,2] gives rise to a surprising prediction: the resistivity due to isotropic scatterers (e.g. white-noise disorder[3] or phonons[4-8]) is independent of carrier density n. Here we show that acoustic phonon s
A novel strategy for the large scale and continuous production of aligned carbon nanotube arrays using millimeter-diameter spheres as growth substrates is reported. The present technique is more productive than the conventional process on flat wafers
There is a renewed interest in photovoltaic solar thermal (PVT) hybrid systems, which harvest solar energy for heat and electricity. Typically, a main focus of a PVT system is to cool the photovoltaic (PV) cells to improve the electrical performance,