Nanotechnology Now







Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > Penn Researchers Show New Way of Assembling Particles Into Complex Structures

Kathleen J. Stebe
Kathleen J. Stebe

Abstract:
Many recent advances in microtechnology and nanotechnology depend on microscopic spherical particles self-assembling into large-scale aggregates to form a relatively limited range of crystalline structures. Directed assembly is a new branch of this field, where scientists figure out how to make particles assemble to form a broad range of structures at given locations.

Penn Researchers Show New Way of Assembling Particles Into Complex Structures

Philadelphia, PA | Posted on August 5th, 2012

Current techniques for directed assembly typically use an applied field, such as an electric or magnetic field, to move particles and to assemble them into well-defined structures. Now, researchers at the University of Pennsylvania have identified a simple new method to direct particle assembly based only on surface tension and particle shape.

The research, led by Kathleen J. Stebe, professor in the Department of Chemical and Biomolecular Engineering and the school's Deputy Dean for Research, was performed by a team of researchers in her laboratory, Marcello Cavallaro Jr., Lorenzo Botto, Eric P. Lewandowski and Marisa Wang. It was published in the Proceedings of the National Academy of Sciences.

Their results rely on the simple fact that a liquid surface will tend to minimize its surface area.

"It's the same reason that surface tension makes a drop of water want to be a sphere," Stebe said. "But we can tune that phenomenon to do astonishing things."

Self-assembling spherical particles have been used to make new materials with unique optical and mechanical properties, but non-spherical, or anisotropic, particles may hold even greater promise. By having a definable directionality, the properties of the materials the particles make up can be altered based on their orientations.

In the study, Stebe's lab used cylindrical particles made out of a common polymer. When placed on the surface of a thin film of water, the cylinders produce a saddle-shaped deformation: the water's surface dips at each end of a particle and rises up along their sides.

The Stebe lab had previously demonstrated that this saddle-shape can be used to orient two cylindrical particles end-to-end. As the depressions at their ends come in contact, surface tension causes the area of the space between them to contract, bringing the ends together.

In the new study, instead of two particles interacting, particles interact with a stationary post. The post pokes through the water's surface, causing the surface to curve upward around it. The interaction between a particle's deformation and this curve is governed by the same phenomenon of surface tension shown in the earlier study; the particles move so as to make the surface area as small as possible.

"This means that as soon as the particles hit the surface of the water, they change their alignment and start moving rapidly uphill toward the post," Cavallaro said. "We were also able to predict the lines they would travel for three different post shapes."

By changing the cross-sectional shape of the posts, the researchers were able to show fine control over how the particles moved and oriented. A circular post attracted particles in straight lines, whereas an elliptical post drew particles to the elongated ends. A square post produced the most complex behavior, drawing particles strongly to the corners, leaving the sides open.

The lab's choice of particle shape and material was only to help the researchers observe the particles' orientation and position; any non-spherical particle, on any liquid-liquid or liquid-vapor surface, would be governed by the same principles and produce the same type of deformation. This makes this research particularly powerful: it does not depend on the particle having a certain shape or being made from a certain material.

Surfaces studded with strategically placed and shaped posts could direct and orient particles into almost any configuration. And because the mechanism behind the particles' movement is simply the surface curvature, their movement could be "programmed" by changing the arrangement of the posts or the shape of the interface.

"I could go in with needle, for example, and dynamically pull the surface up at different locations, or over different times," Stebe said.

"Very often when we think about using micro- or nanotechnology, we're not thinking about properties on that tiny scale: It's going to be the organized structure made from micro- or nanoparticles that's going to be useful, perhaps as a lens or a smart surface," she said. "This phenomenon could be used to make new structures by sending particles to certain locations. We could define paths and say ‘here's a docking site: go there' or ‘here's a spot where we want nothing; don't go there.'

"This is a clear demonstration of directed assembly. Like self-assembly, things come together from the bottom up, but here they come together exactly where we want them to."

The research was supported by the National Science Foundation.

####

For more information, please click here

Contacts:
Evan Lerner

215-573-6604

Copyright © University of Pennsylvania

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

UC research partnership explores how to best harness solar power March 2nd, 2015

Researchers turn unzipped nanotubes into possible alternative for platinum: Aerogel catalyst shows promise for fuel cells March 2nd, 2015

Important step towards quantum computing: Metals at atomic scale March 2nd, 2015

New Hopes for Treatment of Intestine Cancer by Edible Nanodrug March 2nd, 2015

Videos/Movies

Maximum Precision in 3D Printing: New complete solution makes additive manufacturing standard for microfabrication February 26th, 2015

Simulating superconducting materials with ultracold atoms: Rice physicists build superconductor analog, observe antiferromagnetic order February 23rd, 2015

Waterloo invention advances quantum computing research: New device, which will be used in labs around the world to develop quantum technologies, produces fragile entangled photons in a more efficient way February 16th, 2015

Los Alamos Develops New Technique for Growing High-Efficiency Perovskite Solar Cells: Researchers’ crystal-production insights resolve manufacturing difficulty January 29th, 2015

Govt.-Legislation/Regulation/Funding/Policy

Researchers turn unzipped nanotubes into possible alternative for platinum: Aerogel catalyst shows promise for fuel cells March 2nd, 2015

First detailed microscopy evidence of bacteria at the lower size limit of life: Berkeley Lab research provides comprehensive description of ultra-small bacteria February 28th, 2015

Warming up the world of superconductors: Clusters of aluminum metal atoms become superconductive at surprisingly high temperatures February 25th, 2015

SUNY Poly CNSE Researchers and Corporate Partners to Present Forty Papers at Globally Recognized Lithography Conference: SUNY Poly CNSE Research Group Awarded Both ‘Best Research Paper’ and ‘Best Research Poster’ at SPIE Advanced Lithography 2015 forum February 25th, 2015

Molecular Machines

Monitoring the real-time deformation of carbon nanocoils under axial loading February 18th, 2015

Stomach acid-powered micromotors get their first test in a living animal January 27th, 2015

Nanoshuttle wear and tear: It's the mileage, not the age January 26th, 2015

Mysteries of ‘Molecular Machines’ Revealed: Phenix software uses X-ray diffraction spots to produce 3-D image December 22nd, 2014

Molecular Nanotechnology

Monitoring the real-time deformation of carbon nanocoils under axial loading February 18th, 2015

Nanotechnology: Better measurements of single molecule circuits February 18th, 2015

Half spheres for molecular circuits: Corannulene shows promising electronic properties February 17th, 2015

Tiny robotic 'hands' could improve cancer diagnostics, drug delivery February 4th, 2015

Self Assembly

Nanotubes self-organize and wiggle: Evolution of a nonequilibrium system demonstrates MEPP February 10th, 2015

Engineering self-assembling amyloid fibers January 26th, 2015

Revealed: How bacteria drill into our cells and kill them December 2nd, 2014

Live Images from the Nano-cosmos: Researchers watch layers of football molecules grow November 5th, 2014

Discoveries

UC research partnership explores how to best harness solar power March 2nd, 2015

Researchers turn unzipped nanotubes into possible alternative for platinum: Aerogel catalyst shows promise for fuel cells March 2nd, 2015

Important step towards quantum computing: Metals at atomic scale March 2nd, 2015

New Hopes for Treatment of Intestine Cancer by Edible Nanodrug March 2nd, 2015

Announcements

UC research partnership explores how to best harness solar power March 2nd, 2015

Researchers turn unzipped nanotubes into possible alternative for platinum: Aerogel catalyst shows promise for fuel cells March 2nd, 2015

Important step towards quantum computing: Metals at atomic scale March 2nd, 2015

New Hopes for Treatment of Intestine Cancer by Edible Nanodrug March 2nd, 2015

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More










ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







© Copyright 1999-2015 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE