Energy & Green Tech

Keeping refrigerants flowing steadily in HVAC units

Oak Ridge National Laboratory researchers have demonstrated that microchannel heat exchangers in heating, ventilation and air conditioning units can keep refrigerants evenly and continually distributed through the insertion ...

Electronics & Semiconductors

Tiny devices pave way for self-charging smart tech

Self-charging smartwatches and health trackers could be a step closer following the development of tiny mechanical devices powered by movement, a study suggests.

Electronics & Semiconductors

Impaired-driver sensor could pave the way for safer vehicles

The bipartisan infrastructure bill recently signed into law by President Joe Biden includes a requirement for automakers to install driver monitoring systems that detect intoxicated or impaired drivers. Current systems rely ...

Electronics & Semiconductors

A new flexible piezoelectric composite for 3-D printing

Researchers at Peking University, Southern University of Science and Technology and the University of Jinan in China have recently designed a ceramic-polymer composite that can be used to print complex 3-D grid architectures. ...

Engineering

A battery-free sensor for underwater exploration

To investigate the vastly unexplored oceans covering most our planet, researchers aim to build a submerged network of interconnected sensors that send data to the surface—an underwater "internet of things." But how to supply ...

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Piezoelectricity

Piezoelectricity ( /piˌeɪzoʊˌilɛkˈtrɪsɪti/) is the charge which accumulates in certain solid materials (notably crystals, certain ceramics, and biological matter such as bone, DNA and various proteins) in response to applied mechanical stress. The word piezoelectricity means electricity resulting from pressure. It is derived from the Greek piezo or piezein (πιέζειν), which means to squeeze or press, and electric or electron (ήλεκτρον), which stands for amber, an ancient source of electric charge. Piezoelectricity is the direct result of the piezoelectric effect.

The piezoelectric effect is understood as the linear electromechanical interaction between the mechanical and the electrical state in crystalline materials with no inversion symmetry. The piezoelectric effect is a reversible process in that materials exhibiting the direct piezoelectric effect (the internal generation of electrical charge resulting from an applied mechanical force) also exhibit the reverse piezoelectric effect (the internal generation of a mechanical strain resulting from an applied electrical field). For example, lead zirconate titanate crystals will generate measurable piezoelectricity when their static structure is deformed by about 0.1% of the original dimension. Conversely, those same crystals will change about 0.1% of their static dimension when an external electric field is applied to the material.

Piezoelectricity is found in useful applications such as the production and detection of sound, generation of high voltages, electronic frequency generation, microbalances, and ultrafine focusing of optical assemblies. It is also the basis of a number of scientific instrumental techniques with atomic resolution, the scanning probe microscopies such as STM, AFM, MTA, SNOM, etc., and everyday uses such as acting as the ignition source for cigarette lighters and push-start propane barbecues.

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