Featured Research

from universities, journals, and other organizations

Self-Assembly Of New Microstructured Material Defies Textbook Physics

Date:
July 19, 1999
Source:
University Of Pennsylvania Medical Center
Summary:
Physicists from the Institute for Medicine and Engineering (IME) at the University of Pennsylvania have found a new class of materials that self-assemble into flat, two-dimensional "crystallites" made from tiny plastic beads the size of bacteria.

Physicists from the Institute for Medicine and Engineering (IME) at the University of Pennsylvania have found a new class of materials that self-assemble into flat, two-dimensional "crystallites" made from tiny plastic beads the size of bacteria. Laurence Ramos, PhD, a postdoctoral fellow in the physics department, and her colleagues at IME and the University of Delaware used membranes similar to soap bubbles as templates to direct the assembly of clusters of the beads into an intriguing new microstructured material. Along the way, the team uncovered a surprise: Under the right conditions, their beads seemed to defy the basic physical principle that oppositely charged objects attract. Their findings appear in this week's issue of Science.

Electrostatic self-assembly of objects onto membranes is a relatively new technique with such potential biological applications as DNA and protein chips, gene-delivery vehicles, and industrial catalysts. The researchers had long-studied the components of their new structures separately, but nothing in their experience prepared them for the highly organized structures Ramos saw when the two were mixed. "The controlled manufacture of these microarrays could mimic and exploit the remarkable organization seen in many natural biomaterials," says coauthor Philip Nelson, PhD, a professor of physics at Penn.

The membrane portion of the material is essentially a thin, positively charged soaplike bubble. The surface of the bubble serves as a temporary template on which the raft of negatively charged spheres assembles. In many cases, the positively charged membrane attracted only a few dozen negatively charged spheres, then repelled all others. "At this point there was a lot of head-scratching, to put it mildly," says Nelson. "Every high-school student is taught that oppositely charged objects attract -- so how could the membrane switch from attracting to repelling the beads?" The key to the puzzle, say the researchers, is to remember that objects in water, such as the plastic beads, are surrounded by an invisible cloud of ions. Under the experiment's conditions, these ions spontaneously migrate in such a way as to overwhelm the membrane's own positive charge, and effectively reverse it in the region not covered by beads. The raft of attached beads then has a definite size, determined ultimately by the membrane's chemical composition. Far from being just an obscure footnote, the fact that the particle arrays can be self-limiting in this way seems to be crucial for the ultimate formation of the "crystallites."

More generally, understanding the basic strategies of self-assembly holds out the promise of far-reaching consequences in the design of future microstructured materials, for example in biosensors, drug carriers, and smart materials that respond to their environment.

Coauthors on the paper are Yi Chen, Tom C. Lubensky, and David A. Weitz from Penn, and Nily Dan and Helim Aranda-Espinoza from the University of Delaware. (Ramos now works at the Universite de Montpellier, France). The research was supported in part by grants from the National Science Foundation.


Story Source:

The above story is based on materials provided by University Of Pennsylvania Medical Center. Note: Materials may be edited for content and length.


Cite This Page:

University Of Pennsylvania Medical Center. "Self-Assembly Of New Microstructured Material Defies Textbook Physics." ScienceDaily. ScienceDaily, 19 July 1999. <www.sciencedaily.com/releases/1999/07/990719081526.htm>.
University Of Pennsylvania Medical Center. (1999, July 19). Self-Assembly Of New Microstructured Material Defies Textbook Physics. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/1999/07/990719081526.htm
University Of Pennsylvania Medical Center. "Self-Assembly Of New Microstructured Material Defies Textbook Physics." ScienceDaily. www.sciencedaily.com/releases/1999/07/990719081526.htm (accessed July 25, 2014).

Share This




More Matter & Energy News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

TSA Administrator on Politics and Flight Bans

TSA Administrator on Politics and Flight Bans

AP (July 24, 2014) TSA administrator, John Pistole's took part in the Aspen Security Forum 2014, where he answered questions on lifting of the ban on flights into Israel's Tel Aviv airport and whether politics played a role in lifting the ban. (July 24) Video provided by AP
Powered by NewsLook.com
Creative Makeovers for Ugly Cellphone Towers

Creative Makeovers for Ugly Cellphone Towers

AP (July 24, 2014) Mobile phone companies and communities across the country are going to new lengths to disguise those unsightly cellphone towers. From a church bell tower to a flagpole, even a pencil, some towers are trying to make a point. (July 24) Video provided by AP
Powered by NewsLook.com
Algonquin Power Goes Activist on Its Target Gas Natural

Algonquin Power Goes Activist on Its Target Gas Natural

TheStreet (July 23, 2014) When The Deal's Amanda Levin exclusively reported that Gas Natural had been talking to potential suitors, the Ohio company responded with a flat denial, claiming its board had not talked to anyone about a possible sale. Lo and behold, Canadian utility Algonquin Power and Utilities not only had approached the company, but it did it three times. Its last offer was for $13 per share as Gas Natural's was trading at a 60-day moving average of about $12.50 per share. Now Algonquin, which has a 4.9% stake in Gas Natural, has taken its case to shareholders, calling on them to back its proposals or, possibly, a change in the target's board. Video provided by TheStreet
Powered by NewsLook.com
Robot Parking Valet Creates Stress-Free Travel

Robot Parking Valet Creates Stress-Free Travel

AP (July 23, 2014) 'Ray' the robotic parking valet at Dusseldorf Airport in Germany lets travelers to avoid the hassle of finding a parking spot before heading to the check-in desk. (July 23) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

    Health News

      Environment News

        Technology News



          Save/Print:
          Share:

          Free Subscriptions


          Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

          Get Social & Mobile


          Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

          Have Feedback?


          Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
          Mobile: iPhone Android Web
          Follow: Facebook Twitter Google+
          Subscribe: RSS Feeds Email Newsletters
          Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins