Posted on 08/25/2004 2:18:47 PM PDT by LibWhacker
Much discussed among computer circles is the so-called end of Moore's Law and its predictions of ever-smaller, faster circuits. Less known is a challenge facing the next generation of hard disk drives: lubricant coatings that can hold up to faster speeds and denser data.
Perfluoropolyethers (PFPEs), the current industry standard, are running up against the polymer's limits in protecting hard drives against daily wear and tear. So University of Illinois PhD candidate Wei Xiao developed an entirely new lubricant, based on inexpensive and abundant polyester.
She presented her work today for the first time at the 228th national meeting of the American Chemical Society, the world's largest scientific society.
In short, the lubricant, called SHP - sterically hindered polyester - "acts like a solid when cast as very thin films," says Xiao. "And it has very good adhesion properties."
Both qualities are important for lubricant design. A computer's hard drive is polished to a mirror finish to create as perfect a surface as possible on which to record, retrieve and erase thousands of hours' worth of data over its lifetime. A lubricant coating shields the disk from damage during contact with the head, which can fly back and forth across the disk dozens of times per second.
As a magnetic recording device, the head itself relies on a magnetic field rather than physical contact to read or write to the disk. But at rest, tiny arms called sliders drop down to the disk surface to protect the head.
"The lubricant needs to be solid enough that the sliders don't sink. But it needs to be liquid enough so that any debris from contact between the head and surface would sink back in," says Xiao's advisor James Economy, PhD, a professor with the school's department of material science and engineering. He came to Illinois after 14 years of heading up polymer research at IBM.
The sliders do sink into PFPEs, however, and the attractive forces of 'stiction,' short for static friction, can keep them from retracting quickly enough when the disk begins to spin again. That 'stickiness' can damage the disk or even snap off the head when the disk starts spinning again.
Two other problems have arisen as disk drives spin ever faster to speed performance, he notes. At the 10,000-plus revolutions per minute now typical of computer hard drives, centrifugal forces can ripple the lubricant like a washboard. The uneven surface can hamper reading and writing, and can leave some tracks less protected from slider strikes.
Secondly, PFPE lubricants "can also spin off entirely," says Economy. To prevent that, researchers "often try to chemically bond it to the disk surface. That's a disadvantage because you've got to figure out the chemistry to do that."
"In our approach, the polymer is very polar," Xiao explains. "So it bonds to the surface on its own." The result is a simpler and less expensive solution, the Illinois researchers believe.
To make their lubricant more stable, Xiao used polyester building blocks containing offshoots of bulky organic molecules. As they polymerize, the bulky groups surround and protect the ester bonds. The effect, called steric hindrance, also helped the team achieve the balance of solid and liquid characteristics they wanted.
Their data also suggest the SHP lubricant is more resistant to corrosion than PFPEs.
"Solving the problems [with PFPE] forced us to make a completely new kind of polyester," Economy says. "I don't think any other [research] group has tried to design new materials in this area."
Indeed, the Illinois team believes their invention may have far broader application, such as the mining industry, for example, or metals manufacturing; perhaps even automobile engines. "Any place where there are wear surfaces," says Economy.
Xiao has sent samples of SHP to the Center for Magnetic Recording Research, an industry-sponsored facility at the University of California, San Diego, which can conduct real-world testing.
There was a lot of 70s polyester that deserved to be hindered -- by whatever means available...
Yep
Thanks Cliff
Salivating tulips...
Myth Busters mounted a CD on a shaper, and I think they had to boost the speed to get it to shatter. Around 30K RPM, iirc.
Routers, and plain old CD drives just wouldn't do it.
That's gotta hurt.
Jackin' the Beanstalk
But a CD is a simple plastic disk, only modestly balanced.
A hard is machined aluminimm, much srtonger, thicker, and balanced. Surface is smoother too -> less vibration.
Muttly hopes it will stand up better than whatever they currently use to his monthly "dip the computer and t.v. in Bleach" policy.
You never can be too sure these days.
Next time, however, Muttly intends to un-plug the t.v. first. Well...the new t.v. It did seem to fix the problem though...
Agreed. Dress it up all you want, but really a hard drive nothing more than an elaborate tape recorder.
A bit more, but yes, I doubt it was designed for the desired speeds (xfer rates) nowadays.
BTW, last time I disassembled a hard drive, probably a 3.2GB, the disks were less than half the thickness of a CD, iirc.
That is an interesting link, but it is a bit outdated. The newest generations of drives have the heads flying one tenth the distance quoted. The current generation flies around 10 nanometers from the disk or 0.4 millionths of an inch. To put that number in perspective, a nanometer is the equivalent of 10 atomic radii, so the current generation heads are flying around only about 50 atoms above the disk.
Even worse, I've noticed recently on programs like "Engineering the Impossible" that terrorism has become a major obstacle to people investing in daring new technologies. There is no way a Europe-Africa bridge or a space elevator is going to be built if some yahoo can blow them up whenever they like.
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