Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New magnetic herding technique proposed to manipulate the very small

21.06.2005


Engineers have introduced a new magnetic shepherding approach for deftly moving or positioning the kinds of tiny floating objects found within organisms, in order to advance potential applications in fields ranging from medicine to nanotechnology.

The authors of a new research article said their method avoids pitfalls of using tiny light beams, electric currents or even a competing magnetic approach to micromanipulate so-called "colloidal" objects. "Biology is composed primarily of colloidal materials, things larger than a few billionths of a meter that are suspended in solution and don’t settle rapidly," said Benjamin Yellen, who developed this "magnetic nanoparticle assembler" technique while obtaining his doctorate at Drexel University.

"They could be cells or large molecules; they are also being investigated for a variety of new devices, such as miniature lasers or semiconducting components," added Yellen, who in September will become an assistant professor of mechanical engineering and materials science at Duke University’s Pratt School of Engineering.



Yellen is first author of a research paper on the method, already available on-line and to be published in print in the Tuesday, June 21, 2005, issue of Proceedings of the National Academy of Sciences (PNAS). His coauthors are Gary Friedman, the Drexel professor of electrical and computer engineering who supervised his Ph.D. work, and Drexel graduate student Ondrej Hovorka.

The research was supported by the National Science Foundation and Department of Defense.

According to the paper, other investigators are currently focusing either on using laser light beams or electric fields to "transport, sort or assemble microscopic objects." But Yellen’s research group contends that "neither technique has demonstrated sufficient flexibility required for widespread adoption."

Yellen, who is a postdoctoral researcher at Children’s Hospital of Philadelphia, said in an interview that while high-intensity lasers -- like fictional Star Trek tractor beams -- can move around tiny objects, they can also destructively overheat biological materials. In addition, micromanipulating large numbers of particles can require confining unmanageable numbers of individual light beams in small spaces.

Meanwhile, using electricity as a micromanipulator requires space-consuming grids of electrical circuitry, he added. And electrical fields can also trigger disruptive chemical reactions. "The big advantage to using magnetism is that very few things in nature are magnetically susceptible," he said.

The PNAS authors’ paper described how they demonstrated their technique by first patterning permanent rectangular and circular "magnetic traps," each with millionths of a meter dimensions, on silicon or glass wafers. Each trap was made of cobalt, an element that, like iron, is magnetic. Over those trap-patterned wafers the authors then added a fluid containing swarms of suspended magnetic iron oxide nanoparticles, with each particle measuring only about 10 billionths of a meter ("nano" means "billionths").

Into this "ferrofluid" (the prefix "ferro" refers to "iron") they then floated non-magnetic microscopic beads of the colloid latex, each bead measuring between 90 and 5,000 nanometers. Finally, the researchers set up an additional switchable external magnetic field that, when switched on, could alter the magnetic field surrounding the permanent magnetic traps.

This arrangement allowed the non-magnetic latex beads to be herded around, even arranged into a variety of complex patterns, by varying how the dueling magnetic fields influenced the shepherding swarms of magnetic iron oxide nanoparticles. Under the direction of changeable magnetic fields, the particle swarms acted collectively like nano-scale tugboats to push and pull the comparatively large beads of colloids. The beads themselves were color-labeled so their movements could be traced under microscopic observation. "In a way, bead movement is analogous to the movement of a train along a railroad track," wrote the authors in their PNAS paper.

While "trap magnetization establishes the track," fields from the switchable external magnet "provide locomotion," they explained. Moreover, the track could be switched to new orientations by adjusting the interplay of fields between the permanent traps and the switchable magnetic source. The authors suggested that the micromotions of this magnetic nanoparticle assembler might be made programmable by modifications of today’s magnetic recording technology.

They listed a number of potential applications, ranging from the speedier assembly of molecules for biosensors or hybridization experiments, to precision arrangements of cells, bacteria and viruses in futuristic medical diagnostic devices, to the assembly of advanced microelectronic components, such as nanowire transistors.

Their paper also noted that a competing magnetic micromanipulation technique already exists that requires pre-bonding to "magnetic particle carriers."

"You have to do a lot of chemical steps along the way, so it’s not so convenient," Yellen said of that competing approach. "It would be much more convenient to just simply mix the nonmagnetic materials with a ferrofluid and have them moved around without having to attach them to a magnetic carrier."

Once he arrives at Duke, Yellen said he plans to apply his magnetic nanoparticle assembler approach to designing advanced biosensors and cell membrane probes.

Monte Basgall | EurekAlert!
Further information:
http://www.duke.edu

More articles from Physics and Astronomy:

nachricht Shape matters when light meets atom
05.12.2016 | Centre for Quantum Technologies at the National University of Singapore

nachricht Climate cycles may explain how running water carved Mars' surface features
02.12.2016 | Penn State

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

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

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

IHP presents the fastest silicon-based transistor in the world

05.12.2016 | Power and Electrical Engineering

InLight study: insights into chemical processes using light

05.12.2016 | Materials Sciences

High-precision magnetic field sensing

05.12.2016 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>