Wearable technology is quickly becoming commonplace in our everyday life - fit-ness and health monitors, smart watches, and Google Glass, just to name a few. Itudis very clear that in near future the wearable technology will only grow. One of theudbiggest wearable fields is the E-textiles. E-textiles empower clothes with new functionality by enhancing fabrics with electronics and interconnects. The main obstacleudto the development of E-textile field is the relative difficulty and large tolerance inudits manufacturing as compared to the standard circuit production. Current methods such as the application of conductive foils, embroidering of conductive wires andudtreatment with conductive coatings do not possess efficient, fast and reliable massudproduction traits inherent to the electronic industry. On the other hand, the methodudof conductive printing on textile has the potential to unlock the efficiency similar toudPCB production, due to its roll-to-roll and reel-to-reel printing capabilities. Further-more, printing on textiles is a common practice to realize graphics, artwork, etc. andudthus adaptability to conductive ink printing will be relatively easier. Even thoughudconductive printing is a fully additive process, the end circuit layout is very similarudto the one produced via PCB manufacture. However, due to high surface roughnessudand porosity of textiles, efficient and reliable printing on textile has remained elusive. Direct conductive printing on textile is possible but only on specialized denseudand tightly interwoven fabrics. Such fabrics are usually uncommon and expensive.udAnother option is to employ an interface layer that udflattens the textile surface, thusudallowing printing on it. The interface layer method can be used with a variety ofudtextiles such as polyester/cotton that can be found in any store, making this methodudpromising for wearable electronics. Very few examples and that too of simple structures such as a line, square patch or electrode have been reported which utilize anudinterface layer [1{13]. No sophisticated circuit or a system level design involving integration of components on textile has been demonstrated in this medium before. Thisudwork, for the first time, demonstrates a complete system printed on a polyester/cotton T-shirt, that helps in tracking the person who is wearing that T-shirt through audsmart phone or any Internet enabled device. A low cost dielectric material (CreativeudMaterials 116-20 Dielectric ink) is used to print the interface layer through manualudscreen printing method. The circuit layout and antenna have been ink-jet printedudwith silver nano-particles based conductive ink. Utilizing WiFi technology, this wearable tracking system can locate the position of lost children, senior citizens, patientsudor people in uniforms, lab coats, hospital gowns, etc. The device is small enoughud(55 mm x 45 mm) and light weight (10.5g w/o battery) for people to comfortablyudwear it and can be easily concealed in case discretion is required. Field tests haveudrevealed that a person can be localized with up to 8 meters accuracy and the deviceudcan wirelessly communicate with a hand-held receiver placed 55 meters away. Future development of the method with techniques such as automated screen printing,udpick and place components, and digital ink-jet printing can pave the way for massudproduction.
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