Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers simplify tiny structures' construction drip by drip

12.11.2018

Popping the top on house paint usually draws people to look inside the can. But Princeton researchers have turned their gaze upward, to the underside of the lid, where it turns out that pattern of droplets could inspire new ways to make microscopically small structures.

The trick comes in controlling the droplets, which form under competing influences like gravity and surface tension. A new study, published Oct. 26 in the journal Nature Communications, explains how a deeper understanding of these highly dynamic, sometimes unstable forces can be harnessed to cheaply and quickly fabricate objects that normally require a more expensive and time-consuming process.


Shown are three lab samples in descending size. The rings were cured in a centrifuge using acceleration to control the length scale of the droplet structures, which can be used to create biomimetic devices like artificial compound eyes or ciliary carpets.

Credit: Pierre-Thomas Brun

"We've done away with the molds," said Pierre-Thomas Brun, assistant professor of chemical and biological engineering at Princeton and the principal investigator for the study. "We don't need a clean room or any fancy equipment, so engineers have much more freedom in the design process."

Using a silicone common in medical devices, the team poured a thin liquid film over the surface of a plate, about the size of a compact disc, which they then flipped upside down for several minutes while the film cured.

Without intervention, the liquid silicone congeals into an irregular array of droplets -- much like the paint under a lid. But by etching the plate with mathematical precision, using lasers to cut the marks, the researchers "seeded" the droplets into a lattice of perfect hexagons, each with a uniform dimension.

"Gravity wants to pull the fluid down," said Joel Marthelot, postdoctoral research associate at Princeton and lead author on the paper.

"Capillary forces want the surface to deform minimally. So there is a competition between these two forces, which gives rise to the length scale of the structure."

More sophisticated versions of the experiment used a centrifuge in place of gravity, which allowed the team to vary the size of the drops with an indefinite range. Instead of plates, in this version they used plastic cylinders that look like clear hockey pucks.

The excess fluid spun off and left their predictable pattern of cured drops. The technique worked down to the limit of their machinery, which produced a lattice of structures that were each around 10 microns, a fraction of the width of a human hair. The structures, which are prototypes, simulate the kinds of soft lenses that are a common part in smartphones.

"The faster it spins, the smaller the drops," Marthelot said, noting that they could make structures even smaller than what they had achieved so far. "We don't really know the limit of our technique. Only the limit of our centrifuge."

According to Brun, the kinds of mechanical instabilities that cause this behavior are usually regarded by engineers as a kind of nemesis. They are the physical thresholds that determine weight loads or heat capacities. "In this case," he said, "we took advantage of something that is normally seen as bad. We tamed it and made it functional by turning it into a pathway to fabrication."

The technique can be easily expanded to large-scale manufacturing, the researchers said. As their methods evolve, they plan to create biomimetic devices, like an inflatable compound lens that mimics the eye of an insect, or soft robots that can be used in medical technologies.

"One can envision a wide range of potential future application," said Jörn Dunkel, associate professor of mathematics at the Massachusetts Institute of Technology, "from drag-reducing or superhydrophobic surfaces to micro-lenses and artificial ciliary carpets."

###

In addition to Brun and Marthelot, two other researchers contributed to the study: Elizabeth Strong, formerly a student at MIT and now a Ph.D. candidate at the University of Colorado, Boulder; and Pedro M. Reis of the Ecole Polytechnique Fédérale de Lausanne.

Scott Lyon | EurekAlert!
Further information:
https://engineering.princeton.edu/news/2018/11/07/researchers-simplify-tiny-structures-construction-drip-drip
http://dx.doi.org/10.1038/s41467-018-06984-7

More articles from Studies and Analyses:

nachricht Virtual "moonwalk" for science reveals distortions in spatial memory
18.11.2019 | Max-Planck-Institut für Kognitions- und Neurowissenschaften

nachricht Autonomous Agriculture in 2045?
15.11.2019 | Fraunhofer-Institut für Experimentelles Software Engineering IESE

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

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

Im Focus: Images from NJIT's big bear solar observatory peel away layers of a stellar mystery

An international team of scientists, including three researchers from New Jersey Institute of Technology (NJIT), has shed new light on one of the central mysteries of solar physics: how energy from the Sun is transferred to the star's upper atmosphere, heating it to 1 million degrees Fahrenheit and higher in some regions, temperatures that are vastly hotter than the Sun's surface.

With new images from NJIT's Big Bear Solar Observatory (BBSO), the researchers have revealed in groundbreaking, granular detail what appears to be a likely...

Im Focus: New opportunities in additive manufacturing presented

Fraunhofer IFAM Dresden demonstrates manufacturing of copper components

The Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM in Dresden has succeeded in using Selective Electron Beam Melting (SEBM) to...

Im Focus: New Pitt research finds carbon nanotubes show a love/hate relationship with water

Carbon nanotubes (CNTs) are valuable for a wide variety of applications. Made of graphene sheets rolled into tubes 10,000 times smaller than a human hair, CNTs have an exceptional strength-to-mass ratio and excellent thermal and electrical properties. These features make them ideal for a range of applications, including supercapacitors, interconnects, adhesives, particle trapping and structural color.

New research reveals even more potential for CNTs: as a coating, they can both repel and hold water in place, a useful property for applications like printing,...

Im Focus: Magnets for the second dimension

If you've ever tried to put several really strong, small cube magnets right next to each other on a magnetic board, you'll know that you just can't do it. What happens is that the magnets always arrange themselves in a column sticking out vertically from the magnetic board. Moreover, it's almost impossible to join several rows of these magnets together to form a flat surface. That's because magnets are dipolar. Equal poles repel each other, with the north pole of one magnet always attaching itself to the south pole of another and vice versa. This explains why they form a column with all the magnets aligned the same way.

Now, scientists at ETH Zurich have managed to create magnetic building blocks in the shape of cubes that - for the first time ever - can be joined together to...

Im Focus: A new quantum data classification protocol brings us nearer to a future 'quantum internet'

The algorithm represents a first step in the automated learning of quantum information networks

Quantum-based communication and computation technologies promise unprecedented applications, such as unconditionally secure communications, ultra-precise...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

First International Conference on Agrophotovoltaics in August 2020

15.11.2019 | Event News

Laser Symposium on Electromobility in Aachen: trends for the mobility revolution

15.11.2019 | Event News

High entropy alloys for hot turbines and tireless metal-forming presses

05.11.2019 | Event News

 
Latest News

Volcanoes under pressure

18.11.2019 | Earth Sciences

Scientists discover how the molecule-sorting station in our cells is formed and maintained

18.11.2019 | Life Sciences

Hot electrons harvested without tricks

18.11.2019 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>