Energy Harvesting Materials for Smart Fabrics and Interactive Textiles

Smart fabrics and interactive textiles (SFIT) are defined as textiles that are able to sense stimuli from the environment and react or adapt to them in a predetermined way. For example, smart textiles/garments can incorporate sensors/actuators, processing and communications for use in applications such as health monitoring, consumer products and in the automotive sector. Smart fabrics and interactive textiles represent the next generation of fabrics and the potential opportunities for exploiting them are enormous. During recent involvement with the textiles community and talking in particular to developers of smart fabrics and intelligent clothing, it has become clear that a major obstacle towards integrating electronic functionality into fabrics is the portable power supply required. For example, whilst conductive tracks can be printed onto, or conductive yarns woven into, a fabric, the power supply for any integrated device is presently a standard battery. This requires conventional connection and must be repeatedly replaced and removed during washing. No matter how integrated the functionality of the fabric becomes, at present there is no alternative to powering the system using discrete batteries. Energy harvesting (also known as energy scavenging) is concerned with the conversion of ambient energy present in the environment into electricity. Energy Harvesting is now a significant research topic with conferences such as PowerMEMS, IEEE MEMS, Transducers, DTIP and Eurosensors featuring at least one session on the subject. Energy harvesters do not have the energy density (energy stored for a given volume) of a battery but offer the attraction of an integrated power supply that will last the lifetime of the application and will not require recharging or replacement. This project will focus on harvesting energy from two sources: kinetic and thermal energy all of which have been identified as promising approaches for powering mobile electronics. - Kinetic Energy Harvesting - For example, there is a large amount of kinetic energy available from human motion. Human motion characterised by large amplitude, low frequency movements that can also exert large forces. It has been estimated that 67W of energy are available in each step . - Thermal Energy Harvesting - Harvesting of energy from heat sources (such as the human body) can be achieved by the conversion of thermal gradients to electrical energy using the Seebeck effect. There has been interest in the generation of power from body heat as a means to power wearable devices. For example Seiko have produced a wrist watch powered by body heat. Reported results for power densities achieved from micro-fabricated devices are 0.14 microW/mm^2 from a 700 mm^2 device for a temperature difference of 5 K, which is typically achievable for wearable applications. The proposal involves using rapid printing processes and active printed inks to achieve energy harvesting fabrics. This will result in a low cost, easy to design, flexible and rapid way to realise energy harvesting textiles/garments. Both inkjet and screen printed are fully accepted processes widely used in the textile industry for depositing patterns. The proposed screen and inkjet printing processes have many benefits including low-cost, repeatability, flexibility, suitability for small/medium series and mass production, short development time, compatibility with a wide range of textiles and the capability of depositing a wide range of materials. The inks and associated printing parameters will be researched to enable the bespoke design and layout of the energy harvesting films in the application being addressed. The research will provide a toolbox of materials and processes suitable for a range of different fabrics that enable a user to develop the energy harvesting fabric best suited to their requirements.

The beneficiaries of the research are: the textiles industry, application areas of SFIT (medical and assisted living, protective work wear, fitness and consumer), the environment and research staff Substantial benefits for the textile industry and SFIT applications will occur in the medium to long term due as SFIT technology matures. Europe has a significant textiles based industry (147,407 companies, 2.3 million workers, annual turnover of 197,810 Billion Euro). The development of Smart Fabrics and Interactive Textiles (SFIT) is one way in which the long-term competitiveness of this industry can be ensured and there is therefore significant research effort to this end. The research will overcome a key obstacle towards SFIT integration leading to higher product quality, reliability and lifetime, increased functionality and user acceptability. Application areas that will benefit include medical and assisted living. Garment based body sensors for use in health monitoring and preventative care are being widely researched but the aspect of powering these systems has been overlooked. Remote health monitoring has great potential for improving the public health. Similarly, protective work wear (e.g. electroluminescent fabrics for improved visibility and integrated sensors for monitoring the environment) and fitness/consumer applications (e.g. heart rate monitoring) all require some form of power supply. Textiles encompass a much broader range of applications than just clothing. Textiles are used in home furnishings, bags and luggage, automotive trim, tents/marquees, sails, architectural structures, floor coverings, industrial applications and agriculture. It is clear the range of applications for SFIT is considerable with great potential for an energy harvesting fabric in many of these. The research will have a modest impact on the environment. It is estimated that over 170,000 tonnes of batteries of all types are disposed of every year in UK. This project will provide other opportunities for energy harvesting that have not yet been considered and will provide an alternative to using batteries in SFIT applications. Regarding research staff, the project will deliver highly skilled people. The Research Fellows and PhD students will gain valuable research skills in a multidisciplinary area. In addition to practical expertise, they will gain experience of disseminating results by being actively involved in all aspects of communications and engagement. To achieve this impact, it is essential that the project results are widely disseminated across a range of forums to raise awareness amongst researchers from a broad range of disciplines. The main research outputs will be in high quality peer reviewed academic journals (Sensors and Actutors, Smart Materials and Structures, Journal of Intelligent Material Systems and Structures and IEEE Sensors). Results will also be disseminated at conferences and events that specifically target beneficiaries. The SFIT community will be addressed at the Smart Fabrics conferences and Euratex events. The energy harvesting community will be accessed through the Energy Harvesting Network co-ordinated by the PI and attendance at PowerMEMS. Wider dissemination through conferences such as Tranducers and Eurosensors and other events that specifically target end users and systems integrators such as the Energy Harvesting and Storage and Printed Electronics conferences run by IDTechEx. More general communications to the wider media will be done with the assistance of the School's Marketing and Communications Manager, Joyce Lewis. ECS issues around 80 news releases each year to international and national media and receives outstanding coverage. High quality media training of researchers is recognized as being an essential part of our success in public engagement. The PI has experience of media activities including radio interviews, general press and web based dissemination.