Electromechanical materials applications

Choi SW, Shrout TR, Jang SJ, Bhalla AS (1989) Dielectric and pyroelectric properties in the Pb(Mgi/3Nb2/3)03-PbTi03 system. Ferroelectrics 100 29-38 Cross LE (1996) Ferroelectric materials for electromechanical transducer applications. Mater ChemPhys43 108-115... 

This chapter presents a brief overview on sensor and transducer applications of piezoelectric and electrostrictive polymers. Piezoelectric and electrostrictive polymers are smart electromechanical materials which have already found commercial applications in various transducer configurations. Novel applications may arise in the emerging fields of autonomous robots, electronic skin, and flexible energy generators. This chapter focuses on recent device demonstrations of piezoelectric and electrostrictive polymers in these novel fields of research to stimulate and to facilitate the exchange of ideas between disciplines. The applications considered include piezoelectric sensors for electronic skin, piezoelectric loudspeakers and transducers for mechanically flexible energy harvesters, as well as electrostrictive transducers for haptic feedback in displays. 

In most electromechanical materials, dopants are used to tailor the properties for specific applications. Isovalent substitutions are often used to modify the dielectric properties of these materials—for instance, Ba or Sr " substitution for Pb in perovskite and tungsten-bronze structures or Sn for Zr in PZT. The perovskite and tungsten-bionze structures will allow significant substitution with isovalent ions of similar size. 

Lu, F., Lee, H.P., Lim, S.P., 2004. Modelling and analysis of micro piezoelectric power generators for micro-electromechanical-systems applications. Smart Materials and Structures... 

The major piezoelectric applications are sensors (pickups, keyboards, microphones, etc.), electromechanical transducers (actuators, vibrators, etc ), signal devices, and surface acoustic wave devices (resonators, traps, filters, etc ). Typical materials are ZnO, AIN, PbTiOg, LiTaOg, and Pb(Zr.Ti)03 (PZT). 

There are more issues and complexity to be considered if various micro-electromechanical (MEMS)-type devices are included in the macroelectronics tool kit. As described previously, the materials and devices required for TFTs and circuits can provide adequate electromagnetic (visible and RF) sensitivity for many image-type applications. These materials may also provide satisfactory performance in pressure and strain sensors. Nanotube/nanowire-based devices look promising for various chem-bio sensors.85 However, there is little that is known about the ability to integrate printed microfluidic devices (and other such devices with moving parts) into a roll-to-roll-type process. 

Percussion is a repetitive solid body impact, such as experienced by print hammers in high-speed electromechanical applications and high asperities of the surfaces in a gas bearing. Repeated impacts result in progressive loss of solid material. Percussive wear occurs by hybrid wear mechanisms, which combine several of the following mechanisms adhesive, abrasive, surface fatigue, fracture, and tribochemical wear.75... 

For low frequency electromechanical applications in which the acoustic wavelength is much larger than the scale of component phases, some of the ceramic-polymer composites have piezoelectric voltage coefficients orders of magnitude larger than solid PZT. Such materials have obvious applications in hydrophones and other listening devices. 

Selected classes of asymmetric crystal structures exhibit the property of piezoelectricity. With the application of a mechanical strain, piezoelectric materials develop an electrical potential difference across them conversely, when a potential difference is applied to these materials, a displacement occurs. The efficiency of the conversion between mechanical energy and electrical energy is described by the electromechanical coupling constant, which practically ranges to values as high as 0.7 a value of 1 would imply complete conversion between mechanical and electrical energy. 

Carbon nanotubes are responsible for spawning the age of nanotechnology, and creating a paradigm shift in our views on materials and their apphcations. In the field of MEMS and NEMS, CNTs have fonnd applications as electromechanical switches or as pliable nano-actuators, among others. The high elastic modnlns of... 

Winding machinery comprises (1) a drive mechanism to provide means for imparting simultaneous rotary and linear motion to support structures in a continuous manner, (2) membrane and backing material feeder cartridges, (3) a sealant applicator assembly, (4) electromechanical controls, (5) cut off/separation tooling, and... 

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