{"id":4610,"date":"2015-06-07T05:04:55","date_gmt":"2015-06-07T05:04:55","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=4610"},"modified":"2015-06-07T05:04:55","modified_gmt":"2015-06-07T05:04:55","slug":"unlocking-nanofibers-potential","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/unlocking-nanofibers-potential\/","title":{"rendered":"Unlocking nanofibers\u2019 potential"},"content":{"rendered":"

Prototype boosts production of versatile fibers fourfold, while cutting energy consumption by 92 percent.<\/em><\/strong><\/span><\/p>\n

\"A<\/a>
A scanning electron micrograph of the new microfiber emitters, showing the arrays of rectangular columns etched into their sides.
Courtesy of the researchers<\/figcaption><\/figure>\n

CAMBRIDGE, Mass. —\u00a0Nanofibers \u2014 polymer filaments only a couple of hundred nanometers in diameter \u2014 have a huge range of potential applications, from solar cells to water filtration to fuel cells. But so far, their high cost of manufacture has relegated them to just a few niche industries.<\/span><\/p>\n

In the latest issue of the journal\u00a0Nanotechnology<\/em>, MIT researchers describe a new technique for producing nanofibers that increases the rate of production fourfold while reducing energy consumption by more than 90 percent, holding out the prospect of cheap, efficient nanofiber production.<\/span><\/p>\n

\u201cWe have demonstrated a systematic way to produce nanofibers through electrospinning that surpasses the state of the art,\u201d says Luis Fernando Vel\u00e1squez-Garc\u00eda, a principal research scientist in MIT\u2019s Microsystems Technology Laboratories, who led the new work. \u201cBut the way that it\u2019s done opens a very interesting possibility. Our group and many other groups are working to push 3-D printing further, to make it possible to print components that transduce, that actuate, that exchange energy between different domains, like solar to electrical or mechanical. We have something that naturally fits into that picture. We have an array of emitters that can be thought of as a dot-matrix printer, where you would be able to individually control each emitter to print deposits of nanofibers.\u201d<\/span><\/p>\n

Tangled tale<\/strong><\/span><\/p>\n

Nanofibers are useful for any application that benefits from a high ratio of surface area to volume \u2014 solar cells, for instance, which try to maximize exposure to sunlight, or fuel cell electrodes, which catalyze reactions at their surfaces. Nanofibers can also yield materials that are permeable only at very small scales, like water filters, or that are remarkably tough for their weight, like body armor.<\/span><\/p>\n

The standard technique for manufacturing nanofibers is called electrospinning, and it comes in two varieties. In the first, a polymer solution is pumped through a small nozzle, and then a strong electric field stretches it out. \u00a0The process is slow, however, and the number of nozzles per unit area is limited by the size of the pump hydraulics.<\/span><\/p>\n

The other approach is to apply a voltage between a rotating drum covered by metal cones and a collector electrode. The cones are dipped in a polymer solution, and the electric field causes the solution to travel to the top of the cones, where it\u2019s emitted toward the electrode as a fiber. That approach is erratic, however, and produces fibers of uneven lengths; it also requires voltages as high as 100,000 volts.<\/span><\/p>\n

Thinking small<\/strong><\/span><\/p>\n

Vel\u00e1squez-Garc\u00eda and his co-authors \u2014 Philip Ponce de Leon, a former master\u2019s student in mechanical engineering; Frances Hill, a former postdoc in Vel\u00e1squez-Garc\u00eda\u2019s group who\u2019s now at KLA-Tencor; and Eric Heubel, a current postdoc \u2014 adapt the second approach, but on a much smaller scale, using techniques common in the manufacture of microelectromechanical systems to produce dense arrays of tiny emitters. The emitters\u2019 small size reduces the voltage necessary to drive them and allows more of them to be packed together, increasing production rate.<\/span><\/p>\n

At the same time, a nubbly texture etched into the emitters\u2019 sides regulates the rate at which fluid flows toward their tips, yielding uniform fibers even at high manufacturing rates. \u201cWe did all kinds of experiments, and all of them show that the emission is uniform,\u201d Vel\u00e1squez-Garc\u00eda says.<\/span><\/p>\n

To build their emitters, Vel\u00e1squez-Garc\u00eda and his colleagues use a technique called deep reactive-ion etching. On either face of a silicon wafer, they etch dense arrays of tiny rectangular columns \u2014 tens of micrometers across \u2014 which will regulate the flow of fluid up the sides of the emitters. Then they cut sawtooth patterns out of the wafer. The sawteeth are mounted vertically, and their bases are immersed in a solution of deionized water, ethanol, and a dissolved polymer.<\/span><\/p>\n

When an electrode is mounted opposite the sawteeth and a voltage applied between them, the water-ethanol mixture streams upward, dragging chains of polymer with it. The water and ethanol quickly dissolve, leaving a tangle of polymer filaments opposite each emitter, on the electrode.<\/span><\/p>\n

The researchers were able to pack 225 emitters, several millimeters long, on a square chip about 35 millimeters on a side. At the relatively low voltage of 8,000 volts, that device yielded four times as much fiber per unit area as the best commercial electrospinning devices.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

Prototype boosts production of versatile fibers fourfold, while cutting energy consumption by 92 percent. CAMBRIDGE, Mass. —\u00a0Nanofibers \u2014 polymer filaments only a couple of hundred nanometers in diameter \u2014 have a huge range of potential applications, from solar cells to water filtration to fuel cells. But so far, their high cost of manufacture has relegated […]<\/p>\n","protected":false},"author":6,"featured_media":4611,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-4610","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-ElectroSpin-1.jpg",639,426,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-ElectroSpin-1-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-ElectroSpin-1-300x200.jpg",300,200,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-ElectroSpin-1.jpg",639,426,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-ElectroSpin-1.jpg",639,426,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-ElectroSpin-1.jpg",639,426,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-ElectroSpin-1.jpg",639,426,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-ElectroSpin-1.jpg",639,426,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-ElectroSpin-1.jpg",639,426,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-ElectroSpin-1.jpg",600,400,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-ElectroSpin-1.jpg",600,400,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-ElectroSpin-1.jpg",639,426,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-ElectroSpin-1.jpg",540,360,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-ElectroSpin-1.jpg",95,63,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-ElectroSpin-1.jpg",639,426,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-ElectroSpin-1.jpg",96,64,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-ElectroSpin-1.jpg",150,100,false]},"author_info":{"info":["Amrita Tuladhar"]},"category_info":"Research<\/a>","tag_info":"Research","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/4610","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=4610"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/4610\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/4611"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=4610"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=4610"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=4610"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}