How Fabric Displays Work

There has been some confusion about what, exactly, a fur fabric display is. Philips Electronics filed a patent application with the simple title "Fabric Display," though some science blogs and magazines have referred to it as "furry television." At its most basic level, this fur fabric display relies on a very simple technology. Patches of fur cover an image, and when the fur moves, it reveals the image underneath. It's a simple way to conceal and reveal designs.

The fabric display has three layers. The bottom layer is conductive, which means it can carry electricity from a power source -- like a small battery pack -- to the rest of the fabric to create an electrostatic field across the fur, which gives each strand of fur the same electrical charge.

The next layer in a fur fabric display is the fabric's base color or design. This could be a company logo, a picture or just a particular color. The furry display doesn't change the design on the cloth; it just hides or reveals portions of the design at a given time.

The third layer is the fur. It can be any color, but it must be short enough so that when the user turns on the electrostatic field, the strands stand on end and reveal the design or color of the fabric underneath. For example, in a simple fur fabric display, you could use red fur to cover a blue shirt. When you turn on the power for the conductive layer, the red fur would stand on end, revealing the blue shirt underneath. To a distant observer, it would appear that the shirt had just magically changed colors.

The patent application refers to each small, visible section of the base fabric as a "pixel," which may be why some articles refer to the display as furry television. While it might be possible to approximate primitive animation techniques by printing one image across the fur layer and a slightly adjusted image on the fabric underneath, it's not quite the same as watching television on someone's jacket.

In the next section, we'll learn how some designers use a different form of energy to create fabric displays: heat.

The word "thermochromic" looks a little intimidating at first, but the concept itself is pretty simple. Thermo comes from the Greek word "thermos," which means warm or hot. Chromic comes from "chroma," meaning color. A thermochromic substance changes color as it changes temperature. In fabrics, a special dye acts as the thermochromic agent.

Some thermochromic dyes change from colorful to clear, revealing the color of the fabric underneath. Companies can use thermochromic dyes in shirts that slowly reveal a company slogan or logo as the shirt heats up. When the shirt cools down, the logo seems to disappear.

There are two widely used elements in thermochromic dyes, and both rely on chemical reactions:

Like fur fabric displays, thermochromic fabrics aren't animated -- they can only conceal and reveal designs or colors based on environmental conditions. While that might be enough for some people, others want even more dynamic clothing.

In the next section, we'll look at a technology that turns normal clothes into wearable neon signs -- electroluminescent fabric displays.

If wearing a furry display or heat-sensitive clothing doesn't seem appealing, you might want to look into electroluminescent fabric displays. Electroluminescent substances give off light after being exposed to electricity. For fabric displays, designers use electroluminescent wire (EL wire) to create amazing, vibrant effects.

EL wires have several layers:

EL wire needs a high voltage -- around 100 volts -- to glow brightly. Lower voltages result only in a dull glow. Some EL wires can produce a range of light wavelengths depending on the frequency of applied power. Elwire.com offers an "aqua" EL wire with a color that varies from deep green to deep blue as the user alters the power frequency from 60 hertz (Hz) to 6 Hz. Also, because EL wire needs an AC power system, any outfit that has EL wire will need a battery pack and an inverter -- a device that converts direct current (DC) power to AC power. To learn more about AC and DC power, read our article on How Electricity Works.

Because the core of EL wire is copper, it's flexible but holds its shape. You can bend EL wire into all sorts of designs. When it's turned off, EL wire looks like a colorful plastic tube, but when the power comes on, EL wire looks like thin strands of neon lights. An outfit with EL wire could have several different strands emitting different colors, and might even include a sequencer -- a special circuit board -- connected to the power source that manages each strand's power supply. By alternating power to various strands, the wire can appear to be animated as different strands flash on and off.

Clothes with EL wire require careful maintenance and cleaning procedures. If the wire is permanently affixed to the clothing, the wearer will need to carefully wash it by hand and let it dry on a flat surface, or rely on spot cleaning. Throwing electroluminescent clothes into the washing machine is a good way to ruin a special outfit, and could even damage other clothes or the washing machine itself if the plastic tubing around the copper core tears.

Electroluminescent clothes are bright and vibrant, and with the right equipment they can display lights in patterns and sequences, but they're still fairly static -- you're limited by the shapes into which you've bent the EL wire.

In the next section, we'll learn about LED fabric displays and how they give you more options to express yourself through clothing.

Light emitting diodes (LEDs) are tiny light bulbs designed to fit into electrical circuits. Unlike incandescent bulbs, LEDs don't use a filament to generate light. Instead, light is a byproduct of electron motion within semiconductor material. Electrons move from high energy states to lower ones, releasing photons in the process. LEDs take advantage of this, harnessing and focusing the photons into tiny light bulbs. The gap between the higher and lower states of energy determines the frequency of the photon, which we observe as a specific color of light.

Several companies sell clothes that use LEDs to create special patterns or messages. Most of these companies will alter regular clothing to include LEDs. For instance, if you want to turn your normal jacket into an advertisement for HowStuffWorks, you'd send the jacket and a description of what you wanted to the alteration company. A company employee would cut small holes in the jacket and fit an LED into each hole. Once assembled, the lights spell out your message. On the inside of the jacket, each LED attaches to a circuit board. Most companies cover the circuitry with a thin fabric lining. The employee then attaches a power source, usually a small battery pack that can fit into a jacket, shirt or pants pocket.

Other companies cover the LEDs with a thin fabric so that the plastic bulbs aren't visible. When turned on, the light shines through the thin cloth. Like electroluminescent clothing, clothes using LED technology must be carefully maintained and washed. Otherwise, the delicate circuitry could become damaged.

The circuitry controlling an LED display can be as simple as a power switch, meaning all the LEDs are either turned on or off, or it can include microprocessors, which let the wearer customize how the LEDs light on and off. This means that if a shirt has a block of RGB LED lights (LEDs that can emit any color of light), the wearer can create a program telling each LED when to turn on and off as well as what color it should be. By alternating colors and turning on and off, an LED fabric display can create simple images or messages. Each LED acts as a pixel, but because LEDs are much larger than television pixels, the resolution on an LED display won't be very sharp. Because of the low resolution, clothes with LEDs are best for simple messages or designs.

Using LED displays, you can have a preprogrammed light show on your clothing. But what if you want an even more impressive display? In that case, you'll need to look at technology that can display full moving pictures like television signals.

In the next section, we'll learn more about one of these technologies -- PLEDs.

PLED stands for polymer light emitting diode, which is a technology used in backlighting, illumination and electronic displays. Unlike LEDs, which are small bulbs, a PLED display is a thin, flexible film made of polymers and capable of emitting the full color spectrum of light.

A PLED is constructed of several layers:

When the engineer applies an electric field between the two electrodes, the polymer emits light, much like an LED. Because the polymers in PLED are made of organic molecules, they are also known as OLEDs -- organic light emitting diodes. To learn more about how these diodes can emit light, read our article on How OLEDs Work.

Using a PLED screen, it would be possible to create a fabric television. PLED displays are very thin and relatively light compared to other display technologies. Of course, the screen is just one important element in the overall fabric display -- you would also need a power source, such as a lithium-ion battery, and a signal source. The signal source could be a small computer containing preloaded video clips or even a WiFi-enabled device that could stream audio and video directly to your clothes.

Clothes using PLED displays aren't currently available, though several Web pages list fabric displays as a likely PLED application in the near future.

In the next section, we'll look at how an invention called T-Shirt TV works and the impact it's made on advertising.

In 2004, Brand Marketers introduced Adver-Wear, shirts with built-in 11-inch television screens and a four-speaker sound system. Adam Hollander designed and produced the first Adver-Wear shirts -- also known as T-Shirt TV -- because he felt that static advertisements don't reach younger consumers. In interviews, Hollander said that young people had become so used to television that marketers needed to find new ways to incorporate video and animation in advertising strategies or risk losing customers.

The shirts weigh about six and a half pounds. Because they use flat panel television screens, the shirts are a little bulky. Hollander created the shirts specifically for advertising, with no intention of offering them to the public, so comfort and practicality weren't of much concern in the design process. The components are also too expensive to sell T-Shirt TV clothing to the consumer market.

In addition to the screen and speaker system, the shirts need a portable power source -- usually in the form of a lithium-ion battery. It also needs a video source: a custom-built computer that can store and play digital media efficiently. Brand Marketers can incorporate the system into most types of clothes as well as include interactive features like a handheld touch-screen if clients request it. Currently, the systems can play any length of audio or video files separately or in a loop. Future versions of the shirt will include Bluetooth and WiFi capability, adding more interactive features to the clothing.

The marketing firm Adwalker offers a similar product: A portable, wearable computer system. A padded harness acts as the frame for the system, which includes a portable PC, computer monitor, a handheld touch screen and a printer. Clients can send Adwalker videos, software, logos and other computer files and Adwalker incorporates them into eye-catching presentations. An Adwalker employee wears the harness and interacts with the general public. Using this system, the Adwalker employee can:

The system is bulkier than Adver-Wear, but it's even more interactive and has more functions than T-Shirt TV.

As advertising companies continue to search for new ways to grab our attention, we'll likely see more applications of fabric displays. We may even see applications where entire outfits act like a television screen, with images wrapping around from front to back.

To learn more about fabric displays and related topics, follow the links on the next page.