Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Just add water: 3-D silicon shapes fold themselves when wetted by microscopic droplets

03.06.2014

Tiny self-assembling tools could one day deliver drugs to targeted areas of the body or even perform autonomous microsurgery

Researchers from the University of Twente in the Netherlands have taken the precise art of origami down to the microscopic scale. Using only a drop of water, the scientists have folded flat sheets of silicon nitride into cubes, pyramids, half soccer-ball-shaped bowls and long triangular structures that resemble Toblerone chocolate bars – an omnium-gatherum of geometric objects, which are almost too tiny to see with the naked eye.


This video shows how a flat design folds into a cube with the addition of water. The researchers can fold and unfold the cube multiple times without wear, as long at the structure remains wet.

Credit: Journal of Applied Physics/A. Legrain, et. al, University of Twente

"While making 3-D structures is natural in everyday life, it has always been extremely difficult to do so in microfabrication, especially if you want to build a large number of structures cheaply," said Antoine Legrain, a graduate student at the MESA+ Institute for Nanotechnology at the University of Twente. To help solve the challenge of building in miniature, researchers have turned to the technique of self-assembly, in which natural forces such as magnetism or surface tension trigger a shape change.

In the 1990s self-assembly became a way to help cram even more computing power into shrinking electronic devices. So-called solder assembly used the surface tension of melting solder to fold silicon, the electronic industry's standard semiconductor material, into 3-D shapes that more efficiently filled a small space with electrical components.

The University of Twente team also created silicon-based shapes, but they used a more ubiquitous liquid – water – to activate and control the folding. They describe their water-based folding system in a paper in the Journal of Applied Physics, from AIP Publishing.

"Water is everywhere, is biocompatible, cheap, and easy to apply," said Legrain. Using water instead of solder also speeds up the folding of each individual structure. If the water-based process is further developed to fold multiple structures at once, it could become cheaper than current self-folding approaches, said Legrain.

To create their menagerie of 3-D shapes, the researchers used a custom software program to first design the flat starting pattern. They then "printed" the design onto silicon wafers. To create hinges, the researchers etched away material just before depositing a thinner layer.

"Possible shapes are in principle limitless," said Legrain, "as long as they can first be made on a flat surface."

To fold the designs, the researchers pumped a small amount of water through a channel they had left in the silicon wafer. The capillary forces created by water molecules sticking to each other and to the silicon pulled the flat surfaces together to form fully three-dimensional creations.

The team also discovered that the final structures, which are about the size of a grain of sand, can be opened and closed up to 60 times without signs of wear, as long as they remain wet.

The ability to unfold and refold the structures could be useful in biomedical applications. For example, self-folding tools could deliver drugs exactly where they are needed in the body or grab a tiny amount of tissue for a micro-biopsy.

This is not the first time the researchers demonstrated the ability to fold silicon with water droplets, but it is the first time they devised a precise way to control the size of the droplets by pumping water through a channel located beneath the flat design. Previous efforts, which involved placing the water droplets by hand, were hard to control and resulted in structures that could only be folded once.

Watching through a microscope as the new system folded and unfolded shapes in front of his eyes was an exciting experience, said Legrain. "Cleanroom fabrication at research level can be long, tricky and frustrating. It is a good feeling when we obtain such nice results out of it," he said.

For now, creating the soccer ball and Toblerone shapes are fun ways for the researchers to test their system and understand its capabilities. Going forward, the team is working toward making conductive hinges and creating 3-D sensors with their new technique.

###

The article "Controllable elastocapillary folding of three-dimensional micro-objects through-wafer filling" is authored by A. Legrain, T. G. Janson, J. W. Berenschot, L. Abelmann and N. R. Tas. It will be published in the Journal of Applied Physics on June 3, 2014 (DOI: 10.1063/1.4878460). After that date, it may be accessed at: http://scitation.aip.org/content/aip/journal/jap/115/21/10.1063/1.4878460

ABOUT THE JOURNAL

Journal of Applied Physics is an influential international journal publishing significant new experimental and theoretical results of applied physics research. See: http://jap.aip.org

Jason Socrates Bardi | Eurek Alert!

Further reports about: ability droplets microscopic self-assembly structures technique tiny

More articles from Physics and Astronomy:

nachricht Researchers find the macroscopic Brownian motion phenomena of self-powered liquid metal motors
02.07.2015 | Science China Press

nachricht Liquids on Fibers - Slipping or Flowing?
01.07.2015 | Universität des Saarlandes

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Viaducts with wind turbines, the new renewable energy source

Wind turbines could be installed under some of the biggest bridges on the road network to produce electricity. So it is confirmed by calculations carried out by a European researchers team, that have taken a viaduct in the Canary Islands as a reference. This concept could be applied in heavily built-up territories or natural areas with new constructions limitations.

The Juncal Viaduct, in Gran Canaria, has served as a reference for Spanish and British researchers to verify that the wind blowing between the pillars on this...

Im Focus: X-rays and electrons join forces to map catalytic reactions in real-time

New technique combines electron microscopy and synchrotron X-rays to track chemical reactions under real operating conditions

A new technique pioneered at the U.S. Department of Energy's Brookhaven National Laboratory reveals atomic-scale changes during catalytic reactions in real...

Im Focus: Iron: A biological element?

Think of an object made of iron: An I-beam, a car frame, a nail. Now imagine that half of the iron in that object owes its existence to bacteria living two and a half billion years ago.

Think of an object made of iron: An I-beam, a car frame, a nail. Now imagine that half of the iron in that object owes its existence to bacteria living two and...

Im Focus: Thousands of Droplets for Diagnostics

Researchers develop new method enabling DNA molecules to be counted in just 30 minutes

A team of scientists including PhD student Friedrich Schuler from the Laboratory of MEMS Applications at the Department of Microsystems Engineering (IMTEK) of...

Im Focus: Bionic eye clinical trial results show long-term safety, efficacy vision-restoring implant

Patients using Argus II experienced significant improvement in visual function and quality of life

The three-year clinical trial results of the retinal implant popularly known as the "bionic eye," have proven the long-term efficacy, safety and reliability of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

World Conference on Regenerative Medicine in Leipzig: Last chance to submit abstracts until 2 July

25.06.2015 | Event News

World Conference on Regenerative Medicine: Abstract Submission has been extended to 24 June

16.06.2015 | Event News

MUSE hosting Europe’s largest science communication conference

11.06.2015 | Event News

 
Latest News

Siemens acquires leading UK enforcement provider Zenco Systems

02.07.2015 | Press release

Viaducts with wind turbines, the new renewable energy source

02.07.2015 | Power and Electrical Engineering

NASA sees heavy rain in Tropical Cyclone Chan-Hom

02.07.2015 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>