A monthly column of technology rambling, rumination and reality

By: Jud Early, Corporate Vice President, Research, [TC]²

September 2003

Fractals, Fabrics, and Coherent Light

Sitting atop a structural steel framework, tubular in shape, and the size of a railroad tank car, it is a monument to a national defense initiative sometimes derisively referred to as Star Wars, and in a not too subtle manner, to the error of an engineer who misplaced a decimal point. The huge cylinder, with pipes, wiring harnesses, and expensive looking brackets and fittings is identified by an engraved plaque and a pictorial story board as one of the first extremely high powered lasers intended to vaporize enemy missiles and military satellites in a time of attack. Now sitting between two buildings in a section of Los Alamos National Laboratory that is away from the more trafficked areas, it is in the process of decay and is weathering to ruin. As one who has personally seen the huge element, and heard the story of the design error that committed the subject structure to scrap, I'm still awed by the scale and size of the intended laser. POOF! A cold war era weapon vaporizes the weapon of an enemy country, using only an intense pulse of coherent light. The image from television news programs of the era is etched into the minds of millions of Americans, who see lasers as only destructive.

With no poof, and with an invisible beam of energy, the failing eyesight of another patient is restored to normal. The laser, in one of its most humane uses, performs this feat daily, with the guidance of a skilled surgeon. Two lasers, two uses.

As we go about our daily lives, we are oblivious to the many lasers that we encounter on a routine basis. Insert a music CD into the audio system of your car, a laser reads the pattern of dots on the disk, resulting in music to our ears. Stopping by Blockbuster on the way home, you probably don't think of the laser that will be used to read the movie data that you will be viewing from DVD. And, of course, we all use computers now, don't we? The drive in your computer for CD-ROM or DVD also uses laser energy to read and present the patterns of ones and zeros to circuitry that makes sense of this data.

Are lasers harmful, or helpful? They can be harmful to the eye, but also can be used to preserve sight. They can be helpful in reading media, but harmful to dyes used to color fabrics. This discovery, now several years old, brings us to the next part of our story.

Before we go there, a discussion of fractals is in order. What is a fractal? I don't see many hands raised out there. Maybe a little education is in order.

A fractal is a geometric shape that has symmetry of scale. No matter how many times you zoom in on it, it will look the same. Nature produces fractals, but the computer can generate fractals using both real and complex numbers. To visualize a simple example, picture an equilateral triangle. Now, subdivide the triangle into smaller triangles. The shape is the same, but the size is smaller. Keep dividing the triangles into smaller triangles. The shape does not change, just the scale. This is a simple fractal example.

IMAGE COURTESY OF UNIVERSITY OF MINNESOTA

Fractals can also be non-regular. This obviously is harder to visualize, but when a shape is created that can be divided into a number of smaller shapes, and divided again and again, well, you get the picture. A number of snowflake like designs are available from public sources. The design of mathematically based fractal models is beyond the scope of this article, but for the curious, you can model your own with help from sources on the World Wide Web.

IMAGE COURTESY OF UNIVERSITY OF MINNESOTA

As a boy, my jeans had only enough life to develop four holes. The first two holes came through the original fabric as a knee-first dive onto high friction grass caused the already worn denim to tear. The second holes occurred in much the same way, to the patch that my mother had ironed onto the knees to extend the life of the jeans. By the time they were broken in well enough to be really comfortable, the hems were above my ankles, and retirement of the well-worn jeans was inevitable. The bad thing about the patch was that it was always much darker than the graying denim of the original jeans, inviting taunts, or worse. Today, as I pull on a favorite pair of jeans, worn almost through, not at the knee, but at the bottom of the front pocket, I enjoy the soft feel and the comfort of the wonderful, aging fabric. How delicious they feel as I work around the house, taking care not to overstress the fabric. No way to repair if they tear, so handle with care.

In the 1980s, obtaining the worn look became fashionable. Now the worn jeans, subject of childhood taunts that led to schoolyard shoving and shouting, was in vogue. How can this now be done on a production scale?

More than fifteen years ago, stone washing was brought into use to provide the aged look, and the worn feel for new jeans. Entire businesses were set up just to provide laundering and stone washing of denim. This process was quite hard on the products, with numerous seam failures and the production of seconds from what would otherwise be first quality goods. Rocks, sand, and gravel remaining in the pockets testified to the stone washed heritage, but often fell onto clean floors at home as the jeans were first worn and removed.

Enzyme washing, ice washing, and less damaging processes were tried, but eventually, these processes were displaced by hand abrasion and carefully made cuts in the top ply of fibers that provided a place for fraying and holes to begin as the garments were laundered. The "shotgun look", and many other processes were applied, but all had the negative attribute of damage to the fabric in a way that was uncontrolled. What was needed was a way in which the fabrics could be made to look old, but which would not weaken the fabric structure, and which could be controlled in a manufacturing process.

This is where the convergence of fabrics and lasers began, later encompassing fractals.

A PAIR OF FRACTAL™ JEANS	CLOSE-UP OF FRACTAL IMAGE

Click each image for larger view

In an effort to replace the labor intensive sand blasting, and hand sanding of denim to achieve the worn, used look, researchers at Technolinear, working with CO2 lasers, began to produce fabric treatments that provide the appearance of aged denim, but without the fiber damaging abrasion. The success of their laser scribing to create that worn appearance has led the principals of Technolinear to create additional businesses to deal with licensing of the technology on a royalty basis, and to build a proprietary jeans brand, Fractal Jeans™. A number of patents have been granted, and the technology base has proven to be very robust. Reserving the jeans business for their own, the process has been applied to numerous fabrics and leathers to produce unique patterns, or individual personalization of individual products.

The laser beam removes the dyes that are used to color the fibers comprising the base material. Directed by computer, the scanning beam sweeps across the material, leaving behind a cloud of vaporized dyestuff, a dramatic demonstration of the use of lasers for beneficial treatment. Designs, ranging from plain old plaid to exotic fractal images are scribed quickly. Individual leather patches for designer jeans can be produced with a unique laser-etched serial number to identify each pair. Automotive interiors, as well as home fashions are displayed in the Cleveland Ohio headquarters of this innovative company. Goods are processed in sixty-inch width rolls, and are re-rolled, ready for cutting. A system that utilizes a flexible form mounted on a transport system is used to hold finished jeans while the scribing takes place. Fixturing in this way ensures proper registration of the image to the garment. Prototyping can be done with little tooling, by careful placement of the item into the working field of a scanning beam industrial laser.

PLAID PATTERN ON POLAR FLEECE	HERRINGBONE PATTERN ON SUEDE

Unique combinations of substrate and pattern are not only possible; the process enables innovation and creativity in a manner that is not possible with other methods. For the new product developer, the use of laser scribing hold promise for a new brand icon, or simply a fabric that is unique in selected areas.

Is it cost effective? This is a difficult question; one must consider the cost of alternatives, or the cost of lost opportunity in failing to introducing a product because no other means is available. In taking a ten-dollar pair of jeans, the conversion to a one hundred twenty-five dollar pair with laser scribing or personalization seems almost a no-brainer. Get me a system, now! In this hypothetical example, is the price differential possible because of the laser scribed treatment, or the strength of the brand? It's probably a combination of the two, along with skillful marketing and superior aesthetic appeal. What is caché worth? As a replacement for sand blasting and manual abrasion, the cost of labor for processing in the traditional way can be weighed against the cost of new systems and related training, maintenance and operating costs.

Scribed images do not have to be fractal. Resolution of the scribing permits placement of photographic images on the substrate without printing. Of course, the image is a monotone, with the base color providing a field, and the absence of that color in gray scale providing detail.

This interesting technology, which plays upon the convergence of fabrics, photochemistry and laser energy has yet to find broad adoption in apparel. The possibilities are limited only by imagination, and capital investment.

Next month: Notes from the field

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