Folding silicone: building on the microscale

April 25, 2007 By Miranda Marquit, Phys.org feature
Folding silicone: building on the microscale
Image credit: Charlotte Py

“With classical tools, it is hard to manipulate something so tiny as on the microscale or the nanoscale,” Charlotte Py tells PhysOrg.com. “But here we show how you can use a small drop of water as a micro-wrench to bend planar templates into three-dimensional structures.”

Py is a scientist currently at the University of Paris 7, but the work on capillary folding of elastic sheets was carried out as a collaboration between Physique et Mécanique des Milieux Hétérogènes (PMMH), ESPCI and the Laboratoire d’Hydrodynamique at École Polytechnique. The results are published on Physical Review Letters in a piece titled “Capillary Origami: Spontaneous Wrapping of a Droplet with an Elastic Sheet.”

Folding silicone: building on the microscale
Image credit: Charles Baroud

Py and her coauthors, Paul Reverdy and Charles Baroud at École Polytechnique, and Lionel Doppler, José Bico, and Benoît Roman at PMMH-ESPCI, performed experiments showing how capillary forces can be used to create shapes on the microscale. Capillary forces describe the ability of a substance (in this case water) to draw another substance to it. “This is the first time capillary forces have been used to bend planar templates into something that’s three dimensional. Until now, capillary forces have mainly been used to assemble objects in 2D, for instance at the surface of water.”

The experiment makes use of silicone rubber, which is flexible. “We make thin sheets of silicone,” Py explains, “and we cut them into different shapes, such as flowers, triangles or squares, depending on what we want to build. Then we add a drop of water. Water droplets tend to minimize contact with air, so the drop immediately starts to wrap itself in the sheet.” As the droplet begins to evaporate at room temperature, the wrapping becomes tighter and tighter, until the structure is formed. “Because this happens spontaneously, there is no need to manipulate the process after putting the water on the sheet.”

Py points out the additional results of this work: “One funny thing is that action of capillary forces on small structures was well known. But it has been seen as a problem because it can cause damage. Microstructures such as microcantilevers used in air bag sensors sometimes collapse due to moisture. Now we are showing how to build something using capillary forces. What was once seen only as an inconvenience appears now to have a benefit.”

“Additionally,” Py continues, “this is interesting from a fundamental point of view. The way you fold a two dimensional sheet into three-dimensional objects raises questions of differential geometry. For instance, wrapping a sphere with a sheet is impossible without crumpling, tearing or stretching the sheet.” (Py points out that this is the essence of Gauss’ classical theorema egregium.)

Ultimately, Py and her colleagues hope that this process can be used in microscale mass production. “This can be used to produce very, very small objects,” she says. “We performed the experiment at a one or two millimeter size, but it is based on techniques that are easy to downscale to even smaller sizes.” Applications of this wrapping technology have the potential to enhance the ability to build microstructures, as well as be included in some systems, such as components in electromechanical devices.

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

Explore further: Using crumpled graphene balls to make better batteries

Related Stories

Using crumpled graphene balls to make better batteries

January 18, 2018

Lithium metal-based batteries have the potential to turn the battery industry upside down. With the theoretically ultra-high capacity of lithium metal used by itself, this new type of battery could power everything from personal ...

Recommended for you

On the rebound

January 22, 2018

Our bodies have a remarkable ability to heal from broken ankles or dislocated wrists. Now, a new study has shown that some nanoparticles can also "self-heal" after experiencing intense strain, once that strain is removed.

Nanoparticle gel controls twisted light with magnetism

January 22, 2018

"Help me, Obi Wan Kenobi. You're my only hope." For many of those around at the release of Star Wars in 1977, that scene was a first introduction to holograms—a real technology that had been around for roughly 15 years.

Information engine operates with nearly perfect efficiency

January 19, 2018

Physicists have experimentally demonstrated an information engine—a device that converts information into work—with an efficiency that exceeds the conventional second law of thermodynamics. Instead, the engine's efficiency ...

0 comments

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.