'Application of Digital Textile Printing Technology to Integrate Photovoltaic Thin Film Cells into Wearables'

Consumer electronics are typically designed with a battery power source and are carried in light limited pockets or bags. The marriage of electronic devices and wearables provides the opportunity to utilize surfaces exposed to the sun to generate energy to power the electronic devices. Photovoltaic flexible thin film converts solar energy into electrical energy. This photovoltaic thin film has a similar thickness to paper and has material properties much like those of camera film. The photovoltaic flexible modules come in various sizes ranging from 2x4in to 8.5x11in sheets. They can be rolled into a three inch diameter without physical damage and continue to function if scratched or punctured. The durability and efficiency of these photovoltaic flexible thin film modules have improved to a point where they are a viable option for incorporation into wearables. Ultimately, these thin film photovoltaic cells can reduce the amount of battery storage engineered into electronic devices and eliminate maintenance related to replacing batteries. Devices such as the Burton Shield iPOD Jacket, Menswear Fall Sensing Shirt, and Shimadzu DataGlass 2/A are examples of smart garments where battery maintenance or battery weight could be reduced by using photovoltaic flexible thin film for charging.

The successful integration of photovoltaic thin film cells into wearables is tightly tied to the consumer concept of fashion. In the consumer market, smart clothing must remain visually attractive and complement or enhance the wearer's appearance; otherwise it will not be commercially successful. In order maximize energy collection, it is necessary to place the photovoltaic film in visibly prominent areas on the wearable. These solar cells are graphically strong and as a result need to be more visually integrated into the garment structure.

Digital textile printing enables the designer to incorporate unusual components into a design by printing fabric that matches the pattern of the component. Direct digital textile printing technologies typically employ the use of ink jet printing to allow the user to print designs directly from the computer to fabric. For this paper, digital textile printing technologies refers to a number of integrated software and hardware components that are typically used to create digitally printed fabrics. These include off-the-shelf software packages (such as Adobe Photoshop and Illustrator), industry specific design and patternmaking software (PAD patternmaking system, Pointcarr), wide-format ink jet printers for direct textile printing (Encad 1500TX, Colorspan Fabrijet), RIP software used for processing the image files into information that is useful for the printer, and other support hardware. The wide variety of wearables to which photovoltaic thin film cells can be applied requires wide variety of fabrics to make these garments which eliminates the possibility of utilizing a large order of fabric. Digital textile printing makes it possible to do small scale production on a variety of fabrics. (Ross, 2005)