Their advance, published in the Jan. 20 issue of Nature, utilizes a new class of self-assembling materials that they developed. The team demonstrated that they can produce a large, complex structure – an intricate lattice – from tiny colloidal particles called triblock Janus spheres.
“This is a big step forward in showing how to make non-trivial, non-obvious structures from a very simple thing,” said Steve Granick, Founder Professor of Engineering at the University of Illinois and a professor of materials science and engineering, chemistry, and physics. “People know a lot about how to do it with molecules – soaps for example – but scientists and engineers know very little about how to make it happen with particles. Particles are very different from molecules: They’re big, they’re nonflexible, and they have lots of critically different materials properties.”
Much of the work to date in making complicated structures from colloidal particles has been done through computer simulation. Researchers model complicated designs built of highly complicated particles.
However, creating complicated building blocks for experimental use is difficult. By contrast, the triblock Janus spheres’ elegant simplicity makes them ideal for real-world manufacture.
“It was conceptually challenging to fabricate a complex porous material from a simple design, especially in the field of colloidal particles,” said graduate student Qian Chen, a co-author of the paper. “Here, we achieve that with really easy designs that we can use in experiments.”
Granick’s group is well-known for its work with Janus particles. Named for the dual-natured Roman god, Janus particles have two sides or segments of different surface chemistry. Having explored spheres with two different-natured halves, Chen had the idea to make spheres with three “stripes” of reactivity, dubbed triblock Janus spheres. The center band is charged, while the poles are hydrophobic, or water-adverse.
“After many experiments with Janus particles, I wanted to see if adding one more segment would introduce more surprises,” Chen said. “Usually in colloid science people use particles that have a uniform surface chemistry. But for this particle, it’s like a block polymer. It has three segments of chemistry.”
In a salt-water solution, the hydrophobic poles are drawn together, while the charged equators repel one another. As a result, the spheres form a complex lattice where only the poles are in contact with one another. The hydrophobic polar caps are large enough to come into contact with two other spheres. This causes the spheres to arrange into a formation like a six-pointed star, creating a sheet of delicate lace.
Such porous sheets of schizoid particles, hydrophobic and hydrophilic at the same time, could have applications as specialized filters.
“It’s like a better soap,” Granick said. “Just as soap is very good at dissolving both fats and water-soluble things, our new lacy lattice can also filter out both water-soluble and oil-soluble matter. We have this wonderful self-produced lacy structure that’s oil-loving and water-loving at different parts in a periodic array.”
The team could apply their simple particle design to fabricate other planar laces. Adjusting the size of the spheres or the proportion of the bands could lead to other lattice patterns or tuned pore sizes. In addition, further exploration of triblock spheres and other Janus particles could open doors to a broad area of self-assembly of complex structures from simple materials.
“Someday maybe we could have a soup of different components, remove some of it, and there would be a microelectronic chip,” Granick said. “It’s a brand new area. The materials are so different that the structures that they form will be different.”
Research scientist Sung Chul Bae also was a co-author of the paper. The U.S. Department of Energy sponsored this work through the Frederick Seitz Materials Research Laboratory at the U. of I.
Liz Ahlberg | University of Illinois
Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously
17.01.2017 | Sonderforschungsbereich 668
Manchester scientists tie the tightest knot ever achieved
13.01.2017 | University of Manchester
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
17.01.2017 | Earth Sciences
17.01.2017 | Materials Sciences
17.01.2017 | Architecture and Construction