Magnetic Cube Microbots

Janus cubes, polymer microparticles coated with metal on one side, self-assemble into various structures under the influence of a magnetic field, and manipulating the magnetic field turns the structures into microbots for use in drug delivery, in cell measurement, or as miniature actuators. Orlin Velev, a chemical engineer at North Carolina State University, outlined his group’s work. The researchers use photolithography to create polymer cubes about 10 µm across, then coat one side with a 10-nm layer of chromium topped by a 100-nm layer of cobalt. Placing the cubes between two electromagnets causes them to align and form a chain that stays connected after the field is turned off. Oriented one way (trans), the north-south poles of adjoining magnets align into a stiff connection. In the other orientation (cis), they can flip back and forth, so the chains fold and unfold when a magnetic field is applied. The group has made the chain fold around a cell and applied a magnetic gradient to move the captured cell. Another group at Swiss Federal Institute of Technology (ETH), Zurich, has shown it can control the microbots inside a rabbit eye as a possible microsurgical tool. Velev is studying if by squeezing a cell to measure its stiffness, he can determine whether it is healthy or infected with a virus. A related application involves contracting and expanding the chains to act as microactuators and tiny muscles.

New MPI Review

An new MPI review titled "Magnetic particle imaging: tracer development and the biomedical applications of a radiationfree, sensitive, and quantitative imaging modality" was just published by Stanley Harvey-Smith, Le Duc Thang and Nguyen Thanh in the journal "Nanoscale". The whole area is very nicely covered. The main feature is a presentation on the up-to-date literature for the development of SPIONs tailored for improved imaging performance, and developments in the current and promising biomedical applications of this emerging technique, with a specific focus on theranostics, cell tracking and perfusion imaging. The area of the superparamagnetic particles that are ideal for use with MPI is clearly the expertise of the authors. 

Check it out, the article is freely available at https://pubs.rsc.org/en/content/articlepdf/2022/nr/d1nr05670k.

New Review About Ferrofluids and Bio-Ferrofluids: Looking Back and Stepping Forward

Several of our colleagues under the guidance of Ladislau Vekas have just published the largest review about ferrofluids that I have come across - 101 pages of it! They start out with some early relevant results from around 50 years ago, and then get into a comprehensive description of recent achievements in ferrofluid synthesis, advanced characterization, as well as the governing equations of ferrohydrodynamics, the most important interfacial phenomena and the flow properties. Finally, it provides an overview of recent advances in tunable and adaptive multifunctional materials derived from ferrofluids and a detailed presentation of the recent progress of applications in the field of sensors and actuators, ferrofluid-driven assembly and manipulation, droplet technology, including droplet generation and control, mechanical actuation, liquid computing and robotics.

Check it out here: 
Socoliuc V, Avdeev MV, Kuncser V, Turcu R, Tombácz E, Vékás L (2022). Ferrofluids and bio-ferrofluids: looking back and stepping forward. Nanoscale, in print.

Record-Breaking Molecular Magnet

By coupling a pair of lanthanide ions within the same compound, researchers have created what they believe are the most magnetic molecules ever made. 

“By all the traditional metrics of single-molecule magnets, they’re the best,” Nicholas Chilton says of the new molecules. Chilton, who’s based at the University of Manchester, collaborated on the work with Jeffrey Long at the University of California, Berkeley, and Benjamin Harvey at the US Naval Air Warfare Center Weapons Division. Although the molecules’ magnetism reveals itself only at low temperatures, Chilton hopes that these dilanthanide complexes might pave the way for new types of powerful yet lightweight permanent magnets.

Lanthanides such as neodymium and samarium partner with transition metals in the strongest rare earth magnets, which are used in some electric vehicle motors and wind turbines. In rare earth magnets, metal-metal bonds help align unpaired electrons in the lanthanides and their transition-metal partners, boosting the overall magnetism. Coupling two lanthanides in this way should lead to even greater magnetism, but it has proved difficult to forge bonds between them.

Although lanthanides have previously bonded together inside fullerenes, Chilton says, “as far as I’m aware, these are the first conventional molecular lanthanide-lanthanide bonds.” The new complexes contain a pair of lanthanide ions—terbium or dysprosium, for example—bridged by three iodide anions and capped by bulky aromatic ligands. A single, shared electron sits in a bonding orbital between the two ions, and this helps align all the unpaired electrons on both ions.

For more details, check the article here:  https://www.science.org/doi/10.1126/science.abl5470.

Magnetic Guiding with Permanent Magnets

Peter Blümler from the University of Mainz published a very nice review about the basics of magnet systems that can be used to guide magnetic particles against viscous forces. Halbach arrays are very nicely explained, with all the formulas, and then put to action.

What's included in this paper: The equations of magnetic fields and forces as well as velocities are derived in detail and physical limits are discussed. The special hydrodynamics of nanoparticle dispersions under these circumstances is reviewed and related to technical constraints.The possibility of 3D guiding and magnetic imaging techniques are discussed. Finally, the first results in guiding macroscopic objects, superparamagnetic nanoparticles, and cells with incorporated nanoparticles are presented. The constructed magnet systems allow for orientation, movement, and acceleration of magnetic objects and, in principle, can be scaled up to human size.

Check out this interesting article here.

European Inventor Price 2021 Goes to Two of Our Own

The European Patent Office honours Robert Grass and Wendelin Stark, professors of chemical engineering for their research in DNA encapsulation. Their invention enables the storage of digital data for thousands of years and product tracing throughout supply chains.

"DNA has a really high storage capacity," says Robert Grass. "A whole library can be stored in a really tiny amount of DNA for a millennia." Grass, professor and chemical engineer and Professor Wendelin Stark, who heads up the Functional Materials Engineering Lab at ETH Zurich are pioneers of DNA encapsulation. Masterfully combining nature with patented technology, their invention provides a novel method for synthesizing digital data into artificial DNA. The process even includes coding for error-correction contributed by fellow ETH Zurich engineer and data scientist, at the time, Reinhard Heckel. The team also achieved error-free data recovery, even after environmental exposure tests that simulate the equivalent of thousands of years of storage.

Developing nanometer-sized glass beads with diameters 10,000 times thinner than a sheet of paper, the beads protect the DNA from the corrosive forces of nature in much the same way that amber protects fossilized insects. Their invention enables digital DNA storage for thousands of years, meeting challenging data storage needs as technology accelerates at an exponential rate.

Eager to demonstrate the vast potential applications of their novel technology, Grass and Stark partnered up with English band, Massive Attack to commemorate the 20^th anniversary of their Mezzanine album by encoding it in DNA. The album’s DNA was also incorporated into spray paint used to create an artwork with literally thousands of DNA copies of the album embedded in the paint on canvas work. They also encoded in DNA the premiere season of the Netflix television series, Biohackers demonstrating the versatility of the technology.

The glass-encapsulated DNA storage method that the professors and their research team have been developing since 2012 has also been commercialised by the former doctoral students Michela Puddu and Gediminas Mikutis with the ETH spin-off, Haelixa AG which they co-founded in 2016. At Haelixa, DNA is being used to label products such as precious stones, gold, and even organic cotton, to ensure that product origins or working conditions - are traceable throughout the supply chain. Grass and Stark have also co-founded several other companies including ETH spin-offs TurboBeads LLC and hemotune AG.

Microvehicles to Navigate Blood Vessels Upstream

Researchers led by ETH Zurich Professors Daniel Ahmed and Brad Nelson recently developed microvehicles that are small enough to navigate our blood vessels and can be propelled against a fluid flow using ultrasound. To achieve this, the researchers used magnetic beads made of iron oxide and a polymer with a diameter of 3 micrometers, and studied their behavior in a thin glasstube, which was similar in size to blood vessels in a tumor. The team then employed a magnetic field to induce the particles to cluster into a swarm, before using ultrasound to guide the cluster close to the wall of the tube. Finally, the researchers switched to a rotating magnetic field to propel the microbeads against the flow. Future applications include microsurgery, precisely delivering cancer drugs to tumors and transferring drugs from blood vessels into the tissues of the brain.

Check out the details here, with movie:  https://www.nature.com/articles/s42256-020-00275-x

Ultrafast Terahertz Magnetometry Could Enable Heat-Free Magnetism Control

Physicists have precisely measured the ultrafast change in a magnetic state in materials by observing the emission of terahertz (THz) radiation that accompanies such a change in magnetization. An international research team that included scientists from Bielefeld University, Uppsala University, the University of Strasbourg, the University of Shanghai for Science and Technology, Max Planck Institute for Polymer Research, ETH Zürich, and the Free University Berlin developed and tested the ultrafast magnetometry method.

The work could pave the way for spintronic research and technologies based on a purely acoustic and, where possible, heat-free, ultrafast control of magnetism. 

This principle states that a change in the magnetization of a material must result in an emission of electromagnetic radiation that will contain complete information on this change. If the magnetization in a material changes on a picosecond timescale, the emitted radiation will belong to the THz frequency range. This radiation, known as magnetic dipole emission, is weak and can be easily obscured by light emission that has originated elsewhere.

For more information, go here.