emit light. Emissive OLED displays do not require backlighting and are viewable at oblique angles. They are also transparent; red, green, and blue layers can be stacked such that a full-color (RGB) pixel is a fully color-mixed single pixel with depth, rather than a closely spaced planar cluster of pixels as in traditional CRT and LCD displays.

OLEDs are commercially available today in a mass market of smaller displays (such as in car stereos, MP3 players, and cell phones). More innovative use of the technology awaits the streamlining of manufacturing methods; for example, flexible display screens are being developed using plastic substrates (such as thin polyester films and bendable metallic foils). Technology demonstrations by a number of companies, including Polymer Vision ( polymervision.com), feature devices with rollable displays (see Figure 1). Taking the concept a step further, we anticipate development of large, flexible display interfaces that bend, flex, and conform to many surfaces.

OLED technology is also a focus of interest as a path to energy-efficient solid-state lighting. Since organic polymer layers can be manufactured as large-area active elements, it is possible to combine area color, shape, and flexibility to create novel interactive objects and interfaces. For instance, researchers at General Electric Global Research ( www.ge.com/ research/) anticipate light-emissive curtains and wallpapers.

Electrophoretic displays (EPDs), often associated with the brand name E-Ink ( www.eink.com/), are marketed as alternatives to traditional flexible paper. One type of particle display, “electronic ink,” consists of thousands of microcapsules deposited onto a substrate. Each microcapsule contains positively charged white particles and negatively charged black particles suspended in a clear fluid. When a negative electric field is applied, the white particles move to the top of the microcapsule, causing that “pixel” to appear white and vice versa (see Figure 1). The microcapsules are bi-stable, meaning that once configured as black or white, no further energy is required to maintain their state. As with OLED, flexibility is achieved through the use of flexible substrates (plastic) and conductors (metal foil or printed conductive traces).

Applications of E-Ink are primarily as a paper substitute in traditionally monochrome paper-based media (such as signage and e-books) but also include irregularly shaped and flexible displays. For example, the Seiko Watch Corporation ( www.seikowatches.

com) has produced a limited run of unique watches based on a small, flexible E-Ink display. E-Ink also prototyped various color displays and demonstrated multicolor EPDs using color filters [ 2].

In addition to even newer technologies still being developed and refined, existing technologies offer some of their benefits in the form of displays or light-emitting materials. For example, electroluminescent lighting (EL) is a technology through which thin, flexible lamps are produced via an industrial printing process. A layer of phosphor is sandwiched between two conductive layers, illuminating when an alternating electrical current is applied across the layers. EL is widely used in backlighting applications for portable electronics, as well as for large-surface-area applications. Manufactured EL panels can be cut into irregular shapes, as well as printed onto, lending themselves to advertising and signage.

At www.aeolab.com, we have applied the materials and processes used in the manufacturing of commercial electroluminescent panels to hand-print custom-designed light panels on paper and fabric within a studio environment. The Puddlejumper raincoat ( www.mintymonkey.com/puddlejumper _p1.html) developed by Elise Co features EL panels silk-screened onto flexible fabric and activated via water-droplet sensors printed with conductive inks (see Figure 2).

In addition to flat panels, EL lamps are also manufactured as wire elements and packaged in clear plastic tubing of varying diameters. In this form, the material is well-suited to creative manipulation as a fiber, combined with other materials or integrated directly into textiles with either a woven or knitted structure. Artists and designers have used EL wire to make light-emitting artifacts ranging from garments to lamps to spatial installations (such as Loop’s Sonumbra ( www.loop.ph), a net-like illuminated canopy.

Optical fiber is another product that can be used creatively as a material for lighting and display. Specially treated “side-emitting” fibers (with outer coatings that diffuse light along the length of the strand rather than reflecting it perfectly within the interior core) are produced in thicknesses of up to a quarter of an inch. Strands of such fiber are woven into fabric and embedded into other materials, then coupled with light sources at the fiber ends to create unique textile and flexible-display surfaces. These integra-