Screen Printed PZT Thick Films Using Composite Film Technology

A spin coating composite sol gel technique for producing lead zirconate titanate (PZT) thick films has been modified for use with screen printing techniques. The resulting screen printing technique can be used to produce 10 ?m thick films in a single print. The resultant films are porous but the density can be increased through the use of repeated sol infiltration/pyrolysis treatments to yield a high density film. When fired at 710°C the composite screen printed films have dielectric and piezoelectric properties comparable to, or exceeding, those of films produced using a 'conventional' powder/glass frit/oil ink and fired at 890°C

Clamping effect on the piezoelectric responses of screen-printed low temperature PZT/Polymer films on flexible substrates

This paper introduces a new flexible lead zirconate titanate (PZT)/polymer composite material that can be screen-printed onto fabrics and flexible substrates, and investigates the clamping effect of these substrates on the characterization of the piezoelectric material. Experimental results showed that the optimum blend of PZT/polymer binder with a weight ratio of 12:1 provides a dielectric constant of 146. The measured value of the piezoelectric coefficient d33 was found to depend on the substrate used. Measured d33clp values of 70, 40, 36 pC N−1 were obtained from the optimum formulation printed on Polyester–cotton with an interface layer, Kapton and alumina substrates, respectively. The variation in the measured d33clp values occurs because of the effect of the mechanical boundary conditions of the substrate. The piezoelectric film is mechanically bonded to the surface of the substrate and this constrains the film in the plane of the substrate (the 1-direction). This constraint means that the perpendicular forces (applied in the 3-direction) used to measure d33 introduce a strain in the 1-direction that produces a charge of the opposite polarity to that induced by the d33 effect. This is due to the negative sign of the d31 coefficient and has the effect of reducing the measured d33 value. Theoretical and experimental investigations confirm a reduction of 13%, 50% and 55% in the estimated freestanding d33fs values (80 pC N−1) on Polyester–cotton, Kapton and alumina substrates, respectively. These results demonstrate the effect of the boundary conditions of the substrate/PZT interface on the piezoelectric response of the PZT/polymer film and in particular the reduced effect of fabric substrates due to their lowered stiffness

Dispenser-printed sound-emitting fabrics for applications in the creative fashion and smart architecture industry

This paper presents a printing technology for the design and manufacture of interactive planar speakers. With this technology, sound emission can be easily integrated into various textiles at the design stage with minimal assembly after printing. This paper reports direct-write dispenser-printed sound-emitting smart fabrics, aimed at creative fashion and smart architecture applications opening up new opportunities in product design. Planar spiral speakers generate a membrane vibration and so emit sound when driven from an a.c. audio source if a magnet is in close proximity to the spiral. These speakers can be integrated on fabrics to form the basis of clothing in fashion applications. The speaker designs were printed on woven polyester fabric and produced a measured peak sound output level of 85 dB with a wide frequency response from 20 Hz to 20 kHz. This research demonstrates a straightforward fabrication method, based on dispenser printing, to achieve sound emission from a fabric. The fabrication process requires a processing temperature of 130 °C for 10 min which is compatible with the majority of fabrics which are used in fashion and architecture industries. This paper reports on the theory and the manufacturing technology to achieve direct-write dispenser-printed planar spiral speakers on fabrics

An automated process for inclusion of package dies and circuitry within a textile yarn

The integration of small electronic components into textile fabrics, without compromising the textile qualities such as flexibility and conformability, is necessary in ensuring wider adoption of electronic textiles. A solution is to use flexible, electronic yarns that incorporate electronic components within the fibers of the yarn. The production of these novel yarns was initially a craft skill, with inclusion of electronics within each section of yarn taking 60–90 minutes. A prototype, automated production process was developed to speed up the manufacturing process to 6 minutes. This paper describes the process, using machinery and methods from both electronics and textiles applications

A micro electromagnetic generator for vibration energy harvesting

Vibration energy harvesting is receiving a considerable amount of interest as a means for powering wireless sensor nodes. This paper presents a small (component volume 0.1 cm3, practical volume 0.15 cm3) electromagnetic generator utilizing discrete components and optimized for a low ambient vibration level based upon real application data. The generator uses four magnets arranged on an etched cantilever with a wound coil located within the moving magnetic field. Magnet size and coil properties were optimized, with the final device producing 46 µW in a resistive load of 4 k? from just 0.59 m s-2 acceleration levels at its resonant frequency of 52 Hz. A voltage of 428 mVrms was obtained from the generator with a 2300 turn coil which has proved sufficient for subsequent rectification and voltage step-up circuitry. The generator delivers 30% of the power supplied from the environment to useful electrical power in the load. This generator compares very favourably with other demonstrated examples in the literature, both in terms of normalized power density and efficiency

Enabling platform technology for smart fabric design and printing

A hardware and software platform is presented enabling the design, and realisation via printing, of smart fabrics. The cultural and creative industries are an important economic area within which designers frequently utilise fabrics. Smart fabrics offer further creative opportunities to the cultural and creative industries, but designers often lack the required specialist knowledge, in electronics, software and materials, to produce smart fabrics. The software platform offers the ability to perform design, layout and visualisation of a smart fabric using a library of standard smart fabric functions (e.g. electroluminescence) so specialist expertise is not needed. Operation of the smart fabric can be simulated, and parameters can be set for smart fabric control electronics, which consists of standard circuit board modules. The software also provides driver code for the hardware platform to print the smart fabric. The hardware platform consists of a bespoke dispenser printer; functional inks are deposited via a pneumatic syringe controlled by the driver software, allowing bespoke rapid prototyped smart fabrics to be printed. Operation of the software and hardware system is demonstrated by the realisation of an interactive smart fabric consisting of electroluminescent lamps controlled by a proximity sensor. The modular electronics are used to control the smart fabric operation using embedded code generated by the software platform. For example, the blink rate of the electroluminescent lamp can be adjusted by the proximity of a hand. This control is achieved by the use of intuitive drop-down menus and input/output selections by the creative user. At present, the platform allows the design, print and implementation of smart fabrics incorporating the functions of colour change, electroluminescence, sound emission and proximity sensing. The platform can be expanded to add additional functions in the future and the printer will be compatible with new inks developed for screen and inkjet printing

Development of user-friendly wearable electronic textiles for healthcare applications

This paper presents research into a user-friendly electronic sleeve (e-sleeve) with integrated electrodes in an array for wearable healthcare. The electrode array was directly printed onto an everyday clothing fabric using screen printing. The fabric properties and designed structures of the e-sleeve were assessed and refined through interaction with end users. Different electrode array layouts were fabricated to optimize the user experience in terms of comfort, effectivity and ease of use. The e-sleeve uses dry electrodes to facilitate ease of use and the electrode array can survive bending a sufficient number of times to ensure an acceptable usage lifetime. Different cleaning methods (washing and wiping) have been identified to enable reuse of the e-sleeve after contamination during use. The application of the e-sleeve has been demonstrated via muscle stimulation on the upper limb to achieve functional tasks (e.g., hand opening, pointing) for eight stroke survivors