'Bumpy' glass could lead to self-cleaning windows, slick micromachines

Date: 20 January 2005
Source: Ohio State University
Ohio State University engineers are designing super-slick, water-repellent surfaces that mimic the texture of lotus leaves.

The patent-pending technology could lead to self-cleaning glass, and could also reduce friction between the tiny moving parts inside microdevices.
Scientists have long known that the lotus, or water lily, makes a good model for a water-repellent surface, explained Bharat Bhushan, Ohio Eminent Scholar and the Howard D. Winbigler Professor of mechanical engineering at Ohio State. The leaf is waxy and covered with tiny bumps, so water rolls off.

In studying the lotus leaf, Bhushan realized that the same texture could be exploited to reduce friction between moving parts on machines. Small machines, such as those under development in the fields of micro- and nanotechnology, can’t be lubricated by normal means, and would especially benefit from the technology.

“In general, what’s good for water-repellency is good for fighting friction,” Bhushan said.

But when it comes to designing high-tech surfaces -- for instance, a water-repellent car windshield or a low-friction joint on a micromachine -- just copying a lotus leaf isn’t enough. Bumpy, waxy surfaces can actually become sticky under some circumstances.

“What people don’t know is what kind of surface is optimal,” he said.

So he and his colleagues have built the first computer model that calculates the best bumpy surface for different materials and applications.

With the right kind of texture, manufacturers could make self-cleaning windows. Because the bumps would measure only a few nanometers (millionths of a meter) high, and would be made of a transparent material, the window would look like any other but still repel water and dirt. That would mean less window cleaning in homes and businesses.

So far, Bhushan’s team has focused on modeling bumps of different sizes and shapes. All the bumps included in the model aid water repellency by keeping water droplets from directly touching the surface.

Because the bumps are so much smaller than a droplet and so close together, they can’t puncture the droplet. In fact, if the droplet were perfectly balanced, it would just lie on the bumps the way a person can safely lie on a bed of nails. Bhushan’s model calculates how and where to place the bumps so that the droplet will contact the surface in just the right way to roll off.

In automobiles, water-repellent glass would improve safety by helping drivers see better, especially during inclement weather.

Right now, drivers can spray coatings on car windows to accomplish much the same thing, but those coatings wear off. Because the new technology builds water-repellency into the surface of the window, it would continue to work for the lifetime of the window.

Though drivers may rejoice at the idea of less window cleaning, Bhushan is most excited about what his technology could do for microelectronics. In 2001, his team developed the first direct method for measuring the friction between moving parts inside micromachines, and he has since been working on methods to reduce that friction.

Some of Bhushan’s industrial partners are building light-based electronics in which tiny mirrors move to reflect light in different directions. Others are working on very small sensors that detect and process chemical samples. Both kinds of devices are too small to use traditional lubricants on the moving parts.

One way to eliminate the need for lubricant is to build slick surfaces onto each individual part. Bhushan suspects his lotus-leaf surfaces might do the job. Manufacturers would just have to use his model to figure out what size and shape bumps are best for their application.

Bhushan has been supporting this work with his own internal laboratory funds, and he’ll need an industrial partner to carry the work further. He wants to fabricate some very high-quality textured materials for scientific study, so he’ll have to buy time in a clean room facility -- the kind computer chip manufacturers use.

600450 'Bumpy' glass could lead to self-cleaning windows, slick micromachines glassonweb.com
Date: 20 January 2005
Source: Ohio State University

See more news about:

Others also read

Emirates Glass, a Dubai Investment subsidiary, has won a major contract to supply 140,000 square meters of its premium glass to the prestigious development on the Palm Jumeirah, reaffirming its already established reputation as the single most prominent company in the entire regional glass industry.The deal was announced during the company's participation in the prestigious Big 5 show, the largest annual venue for the entire Middle-East glass contracting industry.
Isra Vision Systems AG supplier of machine vision systems, has successfully improved its market position in display glass inspection with a major order totalling 1.8 Mio Euro.
Packagers such as the UK's Rexam and private equity firms are set to vie for pump-sprayer business Calmar, which France's Saint-Gobain (SGOB.
The National Lime & Stone Co. will discontinue production of calcined lime early next month at its Carey plant, the company CEO announced Thursday.
Jain Scientific Glass Works, manufacturers of glassware for laboratories, is importing glass as raw material from China, which was much cheaper than the local product and abundantly available.
Japan 1 2 1 S. Korea 6 6 3 Southern Taiwan 4 2 0 Central Taiwan 0 4 2 AGC Japan 0 1 1 Taiwan (Yunlin) 1 1 1 Source: PIDA (Photonic Industry & Technology Development Association) Taiwan TFT-LCD Panel Makers Happy to See Substrate-price Falls in 2006 Taipei, Dec. 27, 2005 (CENS)--Both of the world's top-two glass-substrate makers are actively expanding their production capacity in Taiwan, which is expected to cut substrate transportation time and cost for local thin film transistor-liquid crystal display (TFT-LCD) panel makers and boost production efficiency, according to Michael Wang, project manager and senior analyst of Taiwan's PIDA (Photonic Industry & Technology Development Association).According to Wang, Asahi Glass Co. (AGC) of Japan has solved problems in lowering the defect-free rate for the production of fifth- and sixth-generation (5G, 6G) glass substrates, and is expected to tap the market with products with higher price competitiveness in 2006 to grab more market share in the 6G substrate businessIn addition, Wang added, the aggressive capacity added by both Corning of the U.S., the world's No. 1 substrate supplier, and AGC, the No. 2, will lead to price drops for glass substrates and will especially benefit TV panel makers such as AU Optronics Corp. (AUO) and Chi Mei Optoelectronics Corp. (CMO) in TaiwanCurrently, Wang pointed out, a 6G substrate is priced at about 27,000 to 30,000 Japanese yen, about 1,000 to 2,000 yen lower than in the third quarter of 2005.

Add new comment