The history of electronic textiles.
Early electrical and electronic textiles had components added to existing garments. Later functionality was added by incorporating conducting yarns into fabrics to produce sensors, switches and actuators. Over the last century speculative patents started to appear with some early products such as the electric blanket. In the 1990s there was a surge in research interest in the field which has led to the development of a range of electronic textile products, particularly over the last decade. However, many of these still rely on the addition of electronics to existing garments or on the production of speciality products such as arm or chest bands.
In the 19th century, electricity was the wonder of the age and dubious claims for the benefits of the phenomenon were made. An electric corset was marketed that claimed benefits for “ladies in all stations of life” [1]. A patent from 1911 describes an electrically heated glove [2] for “drivers of aeroplanes, automobiles, motor boats and other conveyances which are guided by manually operated steering wheels”. By the 1930s systems were developed for adding heating elements to blankets, quilts and clothing [3]. The Second World War gave added impetus to the technology as a patent for another electrically heated glove for aviators appears [4]. A British patent from 1964 describes a heated baby carriage blanket [5] and a patent from 1968 outlines some electrically heated socks [6].
The adoption of the transistor saw a focus on the addition of transistor-based electronics to textiles. For example, illuminated clothing is described in a patent from 1979 [7]. In the 1980s, heated textiles continued to predominate in the literature. Examples are an electrically heated lining from 1989 [8] and controllably heated clothing from 1983 [9]. In addition, more sophisticated technologies are also proposed. For example, a report for the US Army in 1983 discussed the feasibility of using sensors to monitor living casualties on the battlefield [10].
In the 1990s the Massachusetts Institute of Technology (MIT) was one of the first academic institutions to work in the area [11], as was the Georgia Institute of Technology [12]. Patents started to appear where boxed electronics are added to clothing [13,14] or otherwise attached [15,16]. In addition, systems were proposed where conducting fibres were integrated into fabrics [17]. In 1998 the U.S. Army Soldier and Biological Chemical Command produced a report on the use of interactive textiles by the military [18].
The new millennium saw a surge in related patents and the first commercially available electronic, rather than electrical, textiles began to appear. An early example was the ICD+Jacket [19] developed by Levi and Philips. Deutsche Telekom [20], Infineon [21] Philips [22] and Sennheiser [23] filed patents in the area and, in addition, more sophisticated applications such as energy harvesting [24] started to appear. Clothing+ claims to have produced the first textile sensor product in 2000 in the form of a sensor belt [25].
Gradually we see the integration of functional elements into the structure. The Burton Amp snowboarding jacket [26] was launched in 2002. Here an IPod is controlled using textile switches. This stemmed from a collaboration between Apple and a manufacturer of snowboarding equipment (Burton Snowboards). In 2004 the NuMetrex heart sensing sports bra [27] and cardio shirt, integrated with conductive fibers directly into the garment, was launched by Textronics (Adidas Wearable Sports Electronics).
A paper from 2004 describes the construction of a fabric-mesh transducer for motion and gesture capture together with ECG measurement [28]. A related paper from 2005 describes capacitive fibre-meshed transducers for touch and proximity sensing [29].
In 2006 and 2008 a patent [30] and a paper [31] describe fully integrated textile switches. Other patents by France telecom [32], Daimler Chrysler [33] and Sentrix [34] describe alternative technologies. A patent from 2009 describes a linear electronic fabric transducer for strain measurement [35]. There was seen a need for fuller integration of components and patents start to appear that address the problem [36]. Key patents from 2008 and 2009 [37,38] described the encapsulation of semi-conductor devices within the fibres of yarns.
Fibretronic [39] have been a major player in the field of wearable electronics and continue to market a range of products. International Fashion Machines [40] market soft textile switches. Marktek make conductive textiles [41] that include heating products. Ohmatex [42] has developed textile conductors and sensors. Polar [43] produce wearable monitoring equipment. Smartlife [44] produce physiological measurement devices for healthcare, sports and defence applications.
The European Space Agency (ESA) iGarment project developed an integrated system for management of civil protection units [45,46]. Philips produces illuminated textiles using LED technology [47]. WearIT@work [48] was a project funded by the EC (€14.6million) to investigate wearable computing. The EC funded Stella (Stretchable Electronics for Large Area Applications) project [49] looked at the design of stretchable circuit boards for incorporation into fabrics.
Developments in graphene technology hold much promise for applications in wearable computers. A report by the US Army Research Laboratory from January 2012 [50] discusses the potential of graphene-based nanoelectronics for applications in wearable electronics.
Battery power has always been a potential problem with wearable electronics. However, reports in 2012 indicate that LG Chem have developed highly flexible cable batteries [51].
EXO Technologies have developed heated gloves (Figure 1) for use by skiers, motorcyclists and the military [52]. The heating elements are knitted from novel polymeric yarns.
The Nike+iPOD is a system where signals from a sensor in a running shoe is transmitted to an iPOD to give time, distance, pace, and calories burned [53]. Adidas have a similar technology as part of their “micoach” system [54]. Zephyr supply wearable, wireless physiology monitoring systems for military and sports applications [55].
Some developments in wearable electronics have focussed on non-textile devices attached to the body. An example would be Google Glass [56] or the Apple iPod wrist-watch computer [57].
Companies such as Cutecircuit make illuminated clothing for fashion and theatrical uses [58] as do LUcentury [59].
Recent papers describe the production of flexible embroidered antennas for megahertz frequency communications [60,61].
Research is also reported on the production of SnO2-microtube-assembled cloths to create a flexible photodetector [62]. Recently a team has fabricated flexible asymmetric supercapacitors on a woven carbon substrate [63].
Over the last decade, there has been considerable interest in even more sophisticated technologies. Smart and interactive textiles are a new emerging sector and growth is forecast at 40% annually [64] and to reach US$2.5 billion by 2021 However, the inclusion of electronic components often compromises the textile characteristics of the resultant fabrics.
| 