The piezoelectric effect has been studied in wet and dry human bones using a piezoresponse force microscope (PFM). It allowed to measure piezoelectric response with nanometer scale resolution directly in a collagen matrix and to obtain a piezoresponse image near the Haversian channel. Dielectric response and dc conductivity have been measured. Theoretical calculations taking into account the inhomogeneity of the electric field under the PFM tip apex and its screening in highly conductive bone samples were performed for obtaining the piezoelectric coefficient in the bone collagen.

Piezoelectric Effect in Human Bones Studied in Nanometer Scale

In recent years, there is a growing interest in studying the dielectric behavior of biopolymer composites due to their potential application as a dielectric material in various electronic devices such as microchips, transformers, and circuit boards. Conducting electroactive polymer composites have also been investigated for various potential applications which include biological, biomedical, flexible electrodes, display devices, biosensors, and cells for tissue engineering. In this chapter, the preparation and dielectric behavior of various biopolymer composites is presented. These biopolymer composites generally consist of nanoscale metal nanoparticles and carbon-based nanofillers such as carbon nanotubes, graphene, graphene oxide (GO), etc., dispersed into the polymer matrix. The physical and chemical properties of these fillers and their interactions with polymers have a significant effect on the microstructure and the final properties of nanocomposites. The biopolymer composites with excellent dielectric properties show great promise as an energy storage dielectric layer in high-performance capacitor applications such as embedded capacitors. This chapter highlights some of the examples of such biopolymer composites; their processing and dielectric behavior will be discussed in detail.

Biopolymer Composites With High Dielectric Performance: Interface Engineering

An intense search for new renewable sources to produce natural polymers for edible and biodegradable packaging is observed as they offer lower environmental costs. The objective of this work is to investigate the use of hybrid carrageenan, extracted from Mastocarpus stellatus seaweeds, as an alternative to commercial kappa carrageenan in new edible film formulations. To this end, the production and characterization of biodegradable films obtained with mixtures of rice starch and hybrid carrageenan or commercial kappa carrageenan were carried out. Thin, flexible, and transparent films with attractive functional properties were obtained from rice starch–carrageenan mixtures. Films forming solutions produced with hybrid carrageenan showed rheological properties comparable to commercial kappa carrageenan-based solutions. Films formulated with hybrid carrageenan show significantly enhanced UV barrier, oxygen barrier, and hydrophobic properties. Thus, hybrid carrageenan proved to be a promising material for the production of edible coatings and biodegradable films and a good alternative to kappa carrageenan for such application. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42263.

Hybrid carrageenan‐based formulations for edible film preparation: Benchmarking with kappa carrageenan

Publisher Summary “Pyroelectricity” is defined as the manifestation of the temperature dependence of the spontaneous polarization of certain anisotropic solids. The chapter contains a brief presentation of the two-and-a-half-millennium history of pyroelectricity, a detailed discussion of the fundamentals of the phenomenon, and a description of many of its applications. The pyroelectric effect is closely related to piezoelectricity and is the basis for ferroelectricity. Despite many years of research, there are undoubtedly more pyroelectric phenomena and more pyroelectric materials to be discovered. Biological pyroelectricity may be a particularly fruitful area for future research. Up to the present time, the applications of pyroelectricity have been principally in the area of infrared detection with a strong emphasis on security uses. The current emphasis on infrared imaging is largely directed toward the consumer market, and this may have a very strong impact on the daily lives of people. It can be safely predicted that the future holds many exciting developments in the fundamentals and applications of pyroelectricity.

Pyroelectricity: Fundamentals and applications

BiFeO3 (BFO) ceramics were prepared by a modified solid-state-reaction method which adopts a higher heating/cooling rate during the sintering process than usually used. It was found that the calcination temperature T
 cal (from 400 to 750°C) does not influence the BFO phase formation, while the sintering temperature T
 sin (from 815 to 845°C) dominates the phase purity. The optimum sintering temperature was in the range from 825 to 835°C. The optimized samples exhibit saturated ferroelectric hysteresis loops with a remnant polarization of 13.2 μC/cm2. The measured piezoelectric coefficient d
 33 was 45 pC/N. No remnant magnetization was observed in all of the samples. The pyroelectric properties were studied as a function of temperature and frequency. A pyroelectric coefficient as high as 90 μC/m2 K was obtained at room temperature in the optimized sample. An abrupt decrease of the pyroelectric coefficient was observed at temperatures between 70 and 80°C. On the basis of our results, BFO may have the potential for pyroelectric applications.

Pyroelectric properties of BiFeO3 ceramics prepared by a modified solid-state-reaction method

Triglycine sulfate-gelatin (TGS-gelatin) films were grown by evaporation of the water from a solution containing gelatin and TGS. The pyroelectric and dielectric properties of the films were highly dependent on their water content. Moist films had higher pyroelectric coefficients and lower coercive fields than dry films. The dielectric permittivity increased strongly with an increase of water content and had a fractional power frequency dependence. The results are explained using a model of the TGS-gelatin film structure in which the gelatin phase is a superionic conductor or solid electrolyte. Absorption of water causes the formation of electric double layers at the electrode film and TGS crystallite-gelatin phase interfaces.

Very strong influence of moisture on pyroelectric and dielectric properties of triglycine sulfate-gelatin films

The pyroelectric effect has been studied in a number of biological materials. We observed that an extremely large pyroelectric effect could be induced in moist bone by means of a small bias electric field. When the bias field was removed, this effect was reversed in sign and then decayed very slowly. In the absence of a bias field, the pyroelectric effect in moist bone was two order of magnitude greater than in dry bone. The large magnitude of the pyroelectric effect in moist bone suggests that it may have a much greater physiological significance than previously considered.

V. E. Khutorsky

Papers

Very strong influence of moisture on pyroelectric and dielectric properties of triglycine sulfate-gelatin films

Extremely large electric-field-induced pyroelectric effect in bone