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40 The PCB Magazine • August 2014 raised in these materials, the hysteresis loop be- comes narrower. When a point called the Curie temperature is reached, the hysteresis loop clos- es and the material becomes paraelec- tric. Please refer to the Figure 2. New ferroelectric materials are a hot area of research cur- rently. Beyond the research materials, PZT, barium tita- nate, lead titanate, and PVDF are all ferroelectric materi- als that are commonly used in today's devices. One of the main ways this property is used in printed electron- ic devices is for rewritable memory. PVDF is typically used in conjunction with another polymer. The PVDF forms rigid crystalline struc- tures, while the function of the copolymer is to act as flexible chains between the crystalline structures. When an electrical field is applied to regions of the film, the PVDF polarity orientates in relation to the field. The orientation of the crystalline regions' po- larization can then be read as a "1" while the default polar- ization crystalline regions' polar- ization can be read as a "0," thereby creating a binary code for the printed memory. Please keep in mind that this is a simplified explanation and that suppliers of ferroelectric materials can give significantly more detail into the mechanism behind printed memory. Multifunctionality The nature of ferroelectric, pyroelectric and piezoelectric materials makes them very useful for multifunctional devices. One such example is the use of array of ferroelectric capacitors in infrared cameras. Such an array makes infrared cameras sensitive enough to detect temperature variations as little as 1/1000000 of a degree Cel- sius. They can also be used in heat and vibra- tional sensors, or in printed sensors for item- level purchases.. There are some devices on the market that utilize ferroelectric materials: gift cards, toys, and RFID tags that are readable by your smartphone or a scanner. The multifunc- tional properties of these materials are also useful in energy harvest- ing, where these materials are incorporated into solar cells and panels. Vibration caused by wind or changes in tem- perature can cause the mate- rials to produce an electrical current that can be harvested in addition to the power gen- erated by the solar cells. An- other recent experiment test- ed these materials by incorpo- rating them into the matting of a playground structure. As children played on the play- ground, the piezoelectric and pyroelectric properties helped to generate electricity. As the sun set, the energy stored dur- ing the day was used to pow- er the lighting for the play- ground. Piezoelectric, pyroelec- tric, and ferroelectric mate- rials have been studied and used for quite a long time. Their relatively low cost, ease of use, and multifunctional ca- pabilities have made them the topic of research for use in various electronic devices, for over a century now. This group of materials is a prime example of how PE can utilize well established materials in next-generation de- vices. As our research advances in this field and the deposition methods improve, we can expect to see more of these multifunctional materials used in our conventional and dispos- able electronics. PCB Josh goldberg is a marketing specialist at taiyo america Inc. Another recent experiment tested these materials by incorporating them into the matting of a playground structure. As children played on the playground, the piezoelectric and pyroelectric properties helped to generate electricity. As the sun set, the energy stored during the day was used to power the lighting for the playground. " " PIEzOELECTRIC, PyROELECTRIC, AND FERROELECTRIC MATERIALS continues