107 research outputs found

    Screen Printed PZT Thick Films Using Composite Film Technology

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    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

    Development of a cantilever beam generator employing vibration energy harvesting

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    This paper details the development of a generator based upon a cantilever beam inertial mass system which harvests energy from ambient environmental vibrations. The paper compares the predicted results from Finite Element Analysis (FEA) of the mechanical behaviour and magnetic field simulations and experimental results from a generator. Several design changes were implemented to maximise the conversion of magnetic energy into generated power and a maximum power output of 17.8µW was achieved at a resonant frequency of 56.6Hz and an applied acceleration of 60mg (g = 9.81ms-2)

    An improved thick-film piezoelectric material by powder blending and enhanced processing parameters

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    Reliable UHF long-range textile-integrated RFID tag based on a compact flexible antenna filament

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    This paper details the design, fabrication and testing of flexible textile-concealed RFID tags 1 for wearable applications in a smart city/ smart building environment. The proposed tag designs aim 2 to reduce the overall footprint, enabling textile integration whilst maintaining the read range. The 3 proposed RFID filament is less than 3.5 mm in width and 100 mm in length. The tag is based on an 4 electrically small (0.0033λ 2) high-impedance planar dipole antenna with a tuning loop, maintaining a 5 reflection coefficient less than −21 dB at 915 MHz, when matched to a commercial RFID chip mounted 6 alongside the antenna. The antenna strip and the RFID chip are then encapsulated and integrated in 7 a standard woven textile for wearable applications. The flexible antenna filament demonstrates a 1.8 8 dBi gain which shows a close agreement with the analytically calculated and numerically simulated 9 gains. The range of the fabricated tags has been measured and a maximum read range of 8.2 m was 10 recorded at 868 MHz. Moreover, the tag's maximum calculated range at 915 MHz is 18 m, which 11 is much longer than the commercially available laundry tags of larger length and width, such as 12 Invengo RFID tags. The reliability of the proposed RFID tags has been investigated using a series 13 of tests replicating textile-based use case scenarios which demonstrates its suitability for practical 14 deployment. Washing tests have shown that the textile-integrated encapsulated tags can be read after 15 over 32 washing cycles, and that multiple tags can be read simultaneously while being washed

    Dispenser printing of electrochromic display on textiles for creative applications

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    For the first time, the design, fabrication and testing of a dispenser-printed electrochromic (EC) display on fabric using Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) as the EC material are reported. The entire display is based on a lateral structural design in which the electrodes are located adjacent to each other in the same plane. The display is directly printed onto a, polyvinyl chloride (PVC)-coated, 100% polyester woven fabric which is commonly used in the creative industries. Each layer was cured below 130°C to ensure no thermal damage to the fabric. Each display pixel, consisting of the colour changing and counter electrodes, was separately driven at two voltage direct currents (VDCs). The colour change between pale blue and dark blue was controlled by switching the polarity using a microcontroller. Two demonstrators, a 3 × 3 pixel matrix display and a seven segment display, were achieved with an average switching speed of 5 s

    Laser curing of screen and inkjet printed conductors on flexible substrates

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    Copper nanoparticle (NP) inks offer lower cost conductors compared with the more common silver conductors used for flexible electronics applications. However, oxidation occurs during conventional oven-curing limiting their use. This paper reports screen/inkjet printed copper conductors, cured using a laser, on flexible Kapton (Polyimide), PET (Polyethylene terephthalate), paper and polyester/cotton fabric in ambient air. The results show that copper NP inks can be laser sintered without oxidation or damage to these flexible substrates

    Dispenser printed proximity sensor on fabric for creative smart fabric applications

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    This paper reports, for the first time, a dispenser printed proximity sensor on fabric for wearable creative applications. The entire proximity sensor is dispenser printed onto a woven polyester/cotton fabric which is the predominant fabric used for clothing. Dispenser printing of electronic functions on fabric allows for significantly greater design freedom compared to weaving or knitting. In addition, it is a digital printing process and therefore does not require additional masks or screens compared with more traditional screen or gravure printing techniques. The printed proximity sensors are tested using an Arduino micro-controller, used throughout the smart fabrics industry, and the results show that the printed sensors detect the proximity of a human hand or limb and can therefore be used for, or integrated within, existing smart fabrics allowing interactivity

    Fully spray-coated organic solar cells on woven polyester cotton fabric for wearable energy harvesting applications

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    This paper presents the novel use of spray coating to fabricate organic solar cells on fabrics for wearable energy harvesting applications. The surface roughness of standard woven 65/35 polyester cotton fabric used in this work is of the order of 150 µm and this is reduced to few microns by a screen printed interface layer. This pre-treated fabric substrate with reduced surface roughness was used as the target substrate for the spray coated fabric organic solar cells that contains multiple layers of electrodes and active materials. A fully spray coated photovoltaic (PV) devices fabricated on fabric substrates has been successfully demonstrated with comparable power conversion efficiency to the glass based counterparts. All PV devices are characterised under simulated AM 1.5 conditions. Device morphologies were examined by scanning electron microscopy (SEM). This approach is potentially suitable for the low cost integration of PV devices into clothing and other decorative textilesThis work was supported by Sensor Platform for HEalthcare in a Residential Environment (SPHERE) project (EP/K031910/1). Professor S. P. Beeby acknowledges EPSRC support through his Fellowship ‘Energy Harvesting Materials for Smart Fabrics and Interactive Textiles’ (EP/I005323/1). Professor P. J. Skabara thanks the Royal Society for a Wolfson Research Merit Award

    Dispenser printed capacitive proximity sensor on fabric for applications in the creative industries

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    This paper reports a planar capacitive proximity sensor fully dispenser printed on a standard polyester woven fabric using conductive ink. Dispenser printing is a new digital printing technique offering the advantages of complete geometric design flexibility and the ability to direct write multilayer devices without requiring bespoke tooling. A dispenser printer is also capable of printing a wide range of ink viscosities encompassing those of inkjet and screen printable inks. Previous research has demonstrated the principle of using proximity sensors for human interaction but none of them are fabricated directly on fabric. In this research, the proximity sensor is dispenser printed directly onto the fabric with an optimised loop electrode design which uses 76% less conductive ink while still offering 90% of the detection range when compared with a standard filled electrode design. The loop design also has the highest detection coefficient (maximum detection distance versus the conductive area of the sensor) of 0.23 compared with 0.06 and 0.1 for the investigated filled and spiral designs, respectively. In addition, the ratio of the track width to the width of the entire sensor is investigated showing 1/16 as being the most suitable ratio for the proximity sensor printed on fabric. Proximity sensors with loop widths ranging from 10 mm to 400 mm are evaluated. The maximum detection distance is 400 mm when the largest sensor is used and the linearity of the sensing circuit is 0.79