Piezo fabrics

Soin et al. (2014) have produced a 3D-knitted spacer piezo fabric. Melt-spun PVDF yams as spacer yams are incorporated between two knitted faces made of silver-coated polyamide yams. They claim the piezo fabric that can produce a power output density of 1.10-5.10 pW cm at applied impact pressures in the range of 0.02-0.10 MPa. 

Further work will continue to enhance the dielectric constants of materials used for piezo fabrics improvements in fabric architecture and the easy integration of these piezo fibres with other flexible conductors, as well as sensing and actuating fibres. These developments can lead to a whole new generation of smart fabrics which could ultimately reduce the need to carry parasitic batteries, especially for on-person, low-power devices. 

With the aid of a particular class of materials (thin-film piezoelectrics), incorporation of AW devices and conventional integrated circuit components on the same silicon substrate is in fact possible. Under the proper conditions, a number of piezoelectric materials can be deposited in thin-film form, typically by RF sputtering, and retain their piezoelectric nature. For this to occur, the crystallites that grow during deposition must be predominantly oriented in a single, piezo-electrically active crystallographic direction. Two such materials are 2 0 and AIN the former has been used as an overlayer on Si wafers to fabricate all of the FPW devices studied for sensor applications to date, and also for SAW resonators. Because extremely thin piezoelectric films are readily fabricated, both ZnO and AIN have been used to make bulk resonators that operate at much higher... 

Mechanical engineers have used polarized light to detect stress patterns for many years and more recently a number of workers [3-6] have explored the possibilities of photoelasticity for the fabrication of polarization modulators. The systems have been given several names, photoacoustic modulators, photoelastic modulators and stress modulators, the term photoelastic modulator will be used in this chapter. There are basically two types of photoelastic modulator, composite resonators and matched element resonators. Diagrams of the composite resonator and matched element resonator are shown in figures 6 and 7 respectively. The original piezo-optical devices [7] were composite resonators composed of a central block of optical... 

Two key issues in SECM are speed and resolution. These are tied to the nature of the available tips and the techniques used to move them in the vicinity of the sample. One approach to greater speed is the use of multiple tips. There are a number of approaches to the fabrication of an array of tips. A problem with these arrays is alignment of the array with the sample so that all of the tips are at the same or a known distance from the sample. This can be accomplished by having each tip on its own controllable positioning device, such as an array of cantilevers with individual piezoelectric control (32,33). For example, 50 cantilevers with a 200-/xm period (to cover a span of 1 cm) were fabricated with integrated piezo sensors and zinc oxide actuators. Such an array provided 35 A resolution and a 20 kHz bandwidth. A difficulty with such arrays is the complexity of the instrumentation needed to use them. Each sensor in the array essentially needs its own driver and potentiostat. An alternative would be an array of individually addressable tips on a single chip that all move in the x, y, and z directions in unison. This would require some additional means to orient and align the array chip... 

Any type of acoustic transducer, such as quartz crystal microbalance (QCM) or surface acoustic wave device (SAW), is fundamentally based on the piezoelectric effect. This was first described in 1880 by Jacques and Pierre Curie as a property of crystalline materials that do not have an inversion centre. When such a material is subjected to physical stress, a measurable voltage occurs on the crystal surfaces. Naturally, the opposite effect can also be observed, i.e. applying an electrical charge on a piezoelectric material leads to mechanical distortion, the so-called inverse piezo effect. These phenomena can be used to transfrom an electrical signal to a mechanical one and back, which actually happens in QCM and SAW. Different materials are ap-pHed for device fabrication, such as quartz, Hthium tantalate, lithium titanate... 

Piezo inkjet printing has dominated OFET fabrication using printing techniques due to its excellent chemical compatibility and the availability of sophisticated printheads to the development community. 

De Rossi et al. (2003) coated yams and fabrics with carbon-loaded mbber to create piezo-resistive fabric strips positioned at the thoracic and abdominal level. They... 

The more commonly used approach for microarray fabrication is the deposition of pre-synthesized molecules by a microarray printer onto substrate, the so-called contact and nmi-contact microarray printing (Fig. 3a, b). Contact arrayers use different-shaped steel pins for direct deposition of droplets onto the substrate by touching the surface with the pins. Nrai-contact arrayers are similar to commercial piezo-driven ink-jet printers and deposit a droplet onto the substrate without coming into contact with the substrate surface. Microarrayers which use other technical approaches are also commercially available and will also be discussed. 

For the future work, elastomer tunable optofluidic devices are expected to extend into the nano-optics or nanofluidic fields. Several tunable nano-optical antenna devices fabricated on a stretchable PDMS substrate have been demonstrated recently. Combining elastomer-based micro/nano-devices with nanoplasmonic elements can be interesting for molecule-level imaging and spectroscopy. A tunable elastic nanofluidic channel was demonstrated recently on a PDMS chip for nanoparticle separation and molecule trapping [12]. One of the challenges of PDMS-based tunable nano-devices is to realize the high accuracy in control. High-precision control of PDMS-based tunable structures could be realized by very fine pneumatic actuation or connection to a piezo-actuator. 

A possible procedure for synthetic jet fabrication has been shown in Fig. 3. The first step in the fabrication process is the wet etching of the silicon wafer using KOH to form a cavity. The cavity is filled with electroplated nickel in the second step. A polyimide membrane is deposited over the silicon wafer using spin coating in the third step. The back side of the silicon substrate is etched using KOH to obtain the orifice hole. The orifice hole extends till the filled nickel inside the cavity and the nickel material are also etched away. The piezo-ceramic material is deposited on top of the membrane for actuation. In case of electrostatic-based actuation, aluminum electrode is deposited on the membrane. 

The truly wearable sensing inter ces must be easy to use and customised for patient requirements of age, body size and posture, state of mobility etc. The mechanical processing of integrating sensors must be done using industrially viable techniques which neither affects the durability nor the function of smart fabrics. Many sensors can be used to measure the strain and deformation in materials such as piezoelectric sensors, piezo-resitive sensors, and fibre optic sensors. 

Wijshoff,H.,2010. The dynamicsofthe piezo inkjetprintheadopera1ion.Phys.Rep.491 (4-5),77 177. Williams, K.M., Clarino, T.N., 2001. Apparatus and method for fabric printing of nested. Available at https //www.google.com/patents/US6173211 (accessed 20.05.14). 

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