Researchers control the assembly of nanobristles into helical clusters

January 8, 2009
Illustration of the adhesive and particle trapping potential of the helically assembling bristle. Shown: Low-magnification SEM showing the capture of the 2.5-mm polystyrene spheres. Scale bar, 10 mm. Courtesy of Aizenberg lab at the Harvard School of Engineering and Applied Sciences

(PhysOrg.com) -- From the structure of DNA to nautical rope to distant spiral galaxies, helical forms are as abundant as they are useful in nature and manufacturing alike. Researchers at the Harvard School of Engineering and Applied Sciences (SEAS) have discovered a way to synthesize and control the formation of nanobristles, akin to tiny hairs, into helical clusters and have further demonstrated the fabrication of such highly ordered clusters, built from similar coiled building blocks, over multiple scales and areas.

The finding has potential use in energy and information storage, photonics, adhesion, capture and release systems, and as an enhancement for the mixing and transport of particles. Lead authors Joanna Aizenberg, Gordon McKay Professor of Materials Science at SEAS and the Susan S. and Kenneth L. Wallach Professor at the Radcliffe Institute for Advanced Study, and L Mahadevan, Lola England de Valpine Professor of Applied Mathematics at SEAS, reported the research in the January 9 issue of Science.

"We demonstrated a fascinating phenomenon: How a nanobristle immersed in an evaporating liquid self-assembles into an ordered array of helical bundles. This is akin to the way wet, curly hair clumps together and coils to form dreadlocks—but on a scale 1000 times smaller," said Aizenberg.

Bristles hugging a polystyrene sphere. Courtesy of Aizenberg lab at the Harvard School of Engineering and Applied Sciences

To achieve the "clumping" effect, the scientists used an evaporating liquid on a series of upright individual pillars arrayed like stiff threads on a needlepoint canvas. The resulting capillary forces—the wicking action or the ability of one substance to draw another substance into it—caused the individual strands to deform and to adhere to one another like braided hair, forming nanobristles.

"Our development of a simple theory allowed us to further characterize the combination of geometry and material properties that favor the adhesive, coiled self-organization of bundles and enabled us to quantify the conditions for self-assembly into structures with uniform, periodic patterns," said Mahadevan.

By carefully designing the specific geometry of the bristle, the researchers were able to control the twist direction (or handedness) of the wrapping of two or more strands. More broadly, Aizenberg and Mahadevan, who are both core members of the recently established Wyss Institute for Biologically Inspired Engineering at Harvard, expect such work will help further define the emerging science and engineering of functional self-assembly and pattern formation over large spatial scales.

Potential applications of the technique include the ability to store elastic energy and information embodied in adhesive patterns that can be created at will. This has implications for photonics in a similar way to how the chirally-ordered and circularly-polarizing elytral filaments in a beetle define its unique optical properties.

The finding also represents a critical step towards the development of an efficient adhesive or capture and release system for drug delivery and may be used to induce chiral flow patterns to enhance the mixing and transport of various particles at the micron- and submicron sale.

"We have teased apart and replicated a ubiquitous form in nature by introducing greater control over a technique increasingly used in manufacturing while also creating a micro-physical manifestation of the terrifying braids of the mythical Medusa," said Mahadevan.

"Indeed, our helical patterns are so amazingly aesthetic that often we would stop the scientific discussion and argue about mythology, modern dreadlocks, alien creatures, or sculptures," added Aizenberg.

Provided by Harvard University

Explore further: Why we need computational models in biology

Related Stories

Why we need computational models in biology

August 1, 2016

Many researchers begin the scientific process by making observations of the natural world and collecting data. They then try to extract patterns from these observations and data using statistical analysis. However, defining ...

Liquid crystals open new route to planar optical elements

June 16, 2016

Researchers at Osaka University developed a technology to control the light wavefront reflected from a cholesteric liquid crystal - a liquid crystal phase with a helical structure. Although known for their ability to Bragg-reflect ...

Fusion instabilities lessened by unexpected effect

January 9, 2014

(Phys.org) —A surprising effect created by a 19th century device called a Helmholz coil offers clues about how to achieve controlled nuclear fusion at Sandia National Laboratories' powerful Z machine.

Conjecture on the lateral growth of Type I collagen fibrils

September 12, 2014

Whatever the origin and condition of extraction of type I collagen fibrils, in vitro as well as in vivo, the radii of their circular circular cross sections stay distributed in a range going from 50 to 100 nm for the most ...

Turning viruses into molecular Legos

October 19, 2011

Researchers at the University of California, Berkeley, have turned a benign virus into an engineering tool for assembling structures that mimic collagen, one of the most important structural proteins in nature. The process ...

Recommended for you

Nanovesicles in predictable shapes

August 25, 2016

Beads, disks, bowls and rods: scientists at Radboud University have demonstrated the first methodological approach to control the shapes of nanovesicles. This opens doors for the use of nanovesicles in biomedical applications, ...

Designing ultrasound tools with Lego-like proteins

August 25, 2016

Ultrasound imaging is used around the world to help visualize developing babies and diagnose disease. Sound waves bounce off the tissues, revealing their different densities and shapes. The next step in ultrasound technology ...

Graphene under pressure

August 25, 2016

Small balloons made from one-atom-thick material graphene can withstand enormous pressures, much higher than those at the bottom of the deepest ocean, scientists at the University of Manchester report.

Neuromorphic computing mimics important brain feature

August 18, 2016

(Phys.org)—When you hear a sound, only some of the neurons in the auditory cortex of your brain are activated. This is because every auditory neuron is tuned to a certain range of sound, so that each neuron is more sensitive ...

'Artificial atom' created in graphene

August 22, 2016

In a tiny quantum prison, electrons behave quite differently as compared to their counterparts in free space. They can only occupy discrete energy levels, much like the electrons in an atom - for this reason, such electron ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

KBK
not rated yet Jan 08, 2009
The place the situation falls down in communication of idea or concept as a named metaphor, is to call the wicking effect separate from the quantum atomic function that creates it. This effectively creates a barrier to understanding the phenomena itself in the context of all atomic or quantum phenomena at such levels. Yes it is a macro function that is outlined here, but understanding the effect in the greater context is ill served by it's separate naming -alone.

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.