Simple Method Yields Complex Micro- and Nanoparticle Shapes

July 26, 2007 By Laura Mgrdichian feature
Simple Method Yields Complex Micro- and Nanoparticle Shapes
A collection of scanning electron microscope images (color added) of the particle shapes, including capsules (C), “tacos” (E), and lenses (R). Photo courtesy of Samir Mitragotri.

In applications from drug delivery to electronics, polymer particles several billionths to millionths of a meter in size could play key roles. But before many of these uses can be realized, scientists must thoroughly understand how these particles behave – behaviors that are strongly linked to the particles' precise shapes, which so far have been difficult to produce on demand and in variation. Recently, however, scientists from the University of California at Santa Barbara (UCSB) found a way to widen this bottleneck.

“There is a shortage of methods to produce non-spherically shaped polymer particles. We have developed a method that addresses this challenge,” said UCSB engineer Samir Mitragotri, the study's corresponding scientist, to

The method is fairly simple, low cost, and can produce substantial quantities of particles (from billions to trillions) of more than 20 widely varying shapes. These include rods, various disks, bullets, barrels, and lenses.

The particles are made of polystyrene, a polymer most commonly used to make foam packaging materials. The pre-shaped particles are spherical and have diameters between 60 nanometers (billionths of a meter) and 10 micrometers (millionths of a meter).

The particles are first suspended in a polymer solution, cast into films of varying thicknesses, and mixed with the compound glycerol to plasticize the films. The films were then dried. From there, the researchers used two approaches, dubbed A and B, and then a combination of the two, to engineer the full array of shapes.

In approach A, the particles were melted using either a solvent or heat and then the entire film was stretched on an apparatus custom built for the task. By stretching the film in one, two, or both directions, the particles were pulled into various shapes. Different shapes resulted from the use of solvent versus heat, and the thickness of the film also produced new geometries. Among the shapes yielded by approach A were circular disks, rectangular disks, “flying saucers,” rods, and worms.

In approach B, the films were stretched before melting, which produced a different set of shapes than A, most more complex, including pulley wheels, barrels, bullets, and capsules.

Combining approaches A and B resulted in yet another set of shapes, many rather unusual. These included ribbon-like particles with curled ends, elongated hexagonal disks, and even “ravioli” and “tacos.”

Most of the shapes produced were a few micrometers in size, but the scientists were able to produce nanoparticles, which greatly increases the particles' potential applications. The group says that particles made of polymers other than polystyrene could be produced using their method, and that the method is scalable to produce even greater numbers of them.

Added Mitragotri, “There is already evidence supporting the importance of particle shape in various applications, such as the design of new carriers for drug delivery. We believe that the availability of a simple method to make these particles will lead to many new discoveries and technologies.”

Citation: Julie A. Champion, Yogesh K. Katare, and Samir Mitragotri (2007) Proc Natl Acad Sci USA 104:11901-11904

Copyright 2007
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of

Explore further: Neil deGrasse Tyson weighs in on New Horizons' Pluto discoveries

Related Stories

New 3-D printing method creates complex micro objects

November 3, 2015

Bioengineers from the UCLA Henry Samueli School of Engineering and Applied Science have developed a new method of 3-D printing that allows production of complex micro-scale objects smaller than the width of a human hair. ...

'Bubble piano' plays bubbles in sync with Beethoven symphony

November 3, 2015

(—Calling it an "Ode to Bubbles," MIT researchers have produced bubbling in sync with Beethoven's Symphony No. 9: Ode to Joy on a surface resembling a piano keyboard. The performance demonstrates the researchers' ...

Results of the Rosetta mission before perihelion

October 30, 2015

Astronomy & Astrophysics is publishing a special feature of 46 articles that present the results obtained by the Rosetta mission before the comet 67P/Churyumov-Gerasimenko reached its perihelion.

Sensing small molecules may revolutionize drug design

October 23, 2015

Most pharmaceutical drugs consist of tiny molecules, which target a class of proteins found on the surfaces of cell membranes. Studying these subtle interactions is essential for the design of effective drugs, but the task ...

Recommended for you

Physicists develop new technique to fathom 'smart' materials

November 26, 2015

Physicists from the FOM Foundation and Leiden University have found a way to better understand the properties of manmade 'smart' materials. Their method reveals how stacked layers in such a material work together to bring ...

Mathematicians identify limits to heat flow at the nanoscale

November 24, 2015

How much heat can two bodies exchange without touching? For over a century, scientists have been able to answer this question for virtually any pair of objects in the macroscopic world, from the rate at which a campfire can ...

New sensor sends electronic signal when estrogen is detected

November 24, 2015

Estrogen is a tiny molecule, but it can have big effects on humans and other animals. Estrogen is one of the main hormones that regulates the female reproductive system - it can be monitored to track human fertility and is ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.