Anyone who has ever worked in a laboratory has seen them: magnetic stirrers that rotate magnetic stir bars in liquids to mix them. The stir bars come in many different forms—now including nanometer-sized.
In the journal Angewandte Chemie, researchers from Singapore have now introduced chains made of 40 nm iron oxide particles that act as the world’s smallest magnetic stir bars, effectively stirring picoliter-sized drops of emulsion with a commercial magnetic stirrer.
Effective stirring is essential in chemical and biological experiments. This is usually achieved with magnetic stirrers and stir bars. However, this does not work in the tiny channels and droplets used in lab-on-a-chip applications and for microliter-scale experiments in the biosciences.
Inexpensive stir bars that are small enough but still able to absorb external magnetic energy and efficiently translate it to stir tiny volumes are thus high on the wish list.The problem lies in the tiny size of previous micrometer-sized stir bars: They are too big to remain suspended because they are pulled to the bottom of the vessel by both gravity and magnetic attraction. At the same time, they are too small to completely stir the solution when they are on the bottom, which works for macroscopic stir bars. The majority of the liquid remains unmixed.
A team led by Hongyu Chen at the Nanyang Technological University in Singapore has now found a solution to this problem: tiny silicon dioxide coated rods made of lined-up iron oxide nanoparticles.
They are even easy to make. Magnetic iron oxide particles with diameters of 40nm are stabilized with oleic acid, modified with citric acid to make them water-soluble, and dispersed in a water/propanol mixture. After addition of an organosilicon compound and ammonia, the reaction vessel is simply left to stand near a magnet overnight. The stir bars can then simply be collected by centrifugation.
The thickness of the silicon layer can be controlled, allowing for the production of stir bars with diameters ranging from 75 nm to 1.4 µm. Their length can reach up to 17 µm. The bars are thus so small that they remain suspended in solution. Addition of a large number of stir bars ensures that all of the liquid is stirred. In the magnetic field of a conventional magnetic stir plate, the individual stir bars move independently. It is thus possible to thoroughly mix droplets of just a few picoliters.
The nanoscale stir bars can be easily removed by adding the droplets on top of a strong magnet wrapped in a layer of plastic film. The magnetic field gradually pulls the stir bars to the bottom of the droplets, and the droplets can then simply be picked up with a pipette.About the Author
Author: Hongyu Chen, Nanyang Technological University, Singapore (Singapore), http://www.ntu.edu.sg/home/hongyuchen/
Title: Stirring in Suspension: Nanometer-Sized Magnetic Stir Bars
Angewandte Chemie International Edition, Permalink to the article: http://dx.doi.org/10.1002/anie.20130324
Hongyu Chen | Angewandte Chemie
Asian dust providing key nutrients for California's giant sequoias
28.03.2017 | University of California - Riverside
Chlamydia: How bacteria take over control
28.03.2017 | Julius-Maximilians-Universität Würzburg
The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.
To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
28.03.2017 | Physics and Astronomy
28.03.2017 | Health and Medicine
28.03.2017 | Life Sciences