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Web Date: May 10, 2016

Micropillars are gentle dust busters

New technique to remove sub-micrometer dust particles could be useful for electronics, aerospace, and art
Department: Science & Technology
News Channels: Materials SCENE, Organic SCENE
Keywords: materials, art & artifacts, microscopic dust, dust, contaminants, art conservation, micropillars, PDMS, electrostatic forces
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A scanning electron micrograph shows 50-µm-wide polydimethylsiloxane pillars (green) that can remove 7.75-µm-diameter silica particles (purple) electrostatically from a poly(methyl methacrylate) film. When the pillars contact another dusty patch, particles roll off the pillar tops and up the sides, making space for new ones.
Credit: Hadi Izadi
Scanning electron micrograph of micropillars with silica particles stuck to them.
 
A scanning electron micrograph shows 50-µm-wide polydimethylsiloxane pillars (green) that can remove 7.75-µm-diameter silica particles (purple) electrostatically from a poly(methyl methacrylate) film. When the pillars contact another dusty patch, particles roll off the pillar tops and up the sides, making space for new ones.
Credit: Hadi Izadi

Most of us fight a battle with dust every day. But for art conservators and those in the electronics industry, microscopic dust can be calamitous, diminishing beauty and value, and rendering devices unusable. Particles larger than 10 µm can be blown off using air jets. But known methods to get rid of smaller specks—such as solvents, ultrasonic waves, and lasers—can damage surfaces while cleaning.

T. Kyle Vanderlick and her colleagues at Yale University have come up with a simple, nondestructive tool to eradicate this invisible enemy (ACS Appl. Mater. Interfaces 2016, DOI: 10.1021/acsami.5b09154). They made polydimethylsiloxane (PDMS) sheets covered with an array of microscopic cylindrical pillars 2–50 µm in diameter. They used this material to lift spherical silica particles with diameters of 0.26–7.75 μm from thin poly(methyl methacrylate) (PMMA) films, which serve as a proxy for dust particles on delicate acrylic paint films.

When the researchers gently touch the film with the material, the PDMS interacts minimally with the PMMA, but strong electrostatic forces transfer the silica particles to the pillars’ flat tips. The method should work to remove dust from any rigid surface, says Hadi Izadi, a postdoctoral associate in Vanderlick’s group.

When the material is brought down on another dusty spot, new silica particles push away the ones already stuck on the pillar tips. Those previously attached particles roll up the sides of the pillars, leaving clean PDMS pillar tips to grab new particles. To ensure this self-cleaning, the pillars cannot be more than eight times wider than the particles.

That’s the critical advantage of the micropillar material over a flat PDMS sheet, which also attracts dust, Izadi says. Dust particles have nowhere to go on a flat sheet, so they accumulate and cause tiny dents when pressed repeatedly on the PMMA surface. Flat sheets also do not work on sub-micrometer particles, for reasons the researchers don’t fully understand.

Instead, by repeatedly tapping the micropillar material on the film, the researchers could eliminate all the dust from the surface. The researchers estimate that the micropillar material can clean a surface nine times its size covered in a monolayer of dust.

 
Chemical & Engineering News
ISSN 0009-2347
Copyright © American Chemical Society

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