Magnetic attraction: NIST/CU microchip demonstrates concept of 'MRAM for biomolecules'

October 19, 2011

Researchers from the National Institute of Standards and Technology (NIST) and University of Colorado Boulder (CU) have developed a low-power microchip that uses a combination of microfluidics and magnetic switches to trap and transport magnetic beads. The novel transport chip may have applications in biotechnology and medical diagnostics.

A key innovation in the new chip is the use of magnetic switches like those in a computer random access memory. As described in a new paper,* the NIST/CU team used the chip to trap, release and transport magnetic beads that potentially could be used as transport vehicles for biomolecules such as DNA.

Conventional microfluidics systems use pumps and valves to move particles and liquids through channels. Magnetic particle transport microchips offer a new approach to microfluidics but generally require continuous power and in some cases cooling to avoid sample damage from excessive heating. The NIST/CU technology eliminates these drawbacks while offering the possibility for random access two-dimensional control and a memory that lasts even with the power off.

The demo chip features two adjacent lines of 12 thin-film magnet switches called spin valves, commonly used as magnetic sensors in read heads of high-density computer disk drives. In this case, however, the spin valves have been optimized for magnetic trapping. Pulses of electric current are used to switch individual spin valve magnets "on" to trap a bead, or "off" to release it, and thereby move the bead down a ladder formed by the two lines (see video clip). The beads start out suspended in salt water above the valves before being trapped in the array.

"It's a whole new way of thinking about microfluidics," says NIST physicist John Moreland. "The cool thing is it's a switchable permanent magnet--after it's turned on it requires no power. You beat heat by switching things quickly, so you only need power for less than a microsecond."

NIST researchers previously demonstrated that spin valves could be used to trap and rotate particles** and recently were awarded two patents related to the idea of a magnetic chip. ***

Magnetic tags are used in bioassays such as protein and DNA purification and cell breakdown and separation. The chip demonstration provides a conceptual foundation for a more complex magnetic random access memory (MRAM) for molecular and cellular manipulation. For example, programmable microfluidic MRAM chips might simultaneously control a large number of beads, and the attached molecules or cells, to assemble "smart" tags with specified properties, such as an affinity for a given protein at a specific position in the array. NIST is also interested in developing cellular and molecular tags for magnetic resonance imaging (MRI) studies in which individual cells, such as cancer cells or stem cells, would be tagged with a smart magnetic biomarker that can be tracked remotely in an MRI scanner, Moreland says. Automated spin valve chips might also be used in portable instruments for rapid medical diagnosis or DNA sequencing.
The lead author of the new paper, Wendy Altman, did the research at NIST as a CU graduate student working on her doctoral thesis. Another author, Bruce Han, was a CU student in NIST's Summer Undergraduate Research Fellowship (SURF) program.

* W.R. Altman, J. Moreland, S.E. Russek, B.W. Han and V. M. Bright. 2011. Controlled transport of superparamagnetic beads with spin-valves. Applied Physics Letters, Vol. 99, Issue 14, Oct. 3.

** See 2007 Tech Beat article, "Magnetic Computer Sensors May Help Study Biomolecules," at

*** U.S. Patent 7,981,696 B2, awarded July 19, 2011, and U.S. Patent 7,985,599 B2, awarded July 26, 2011. Inventors John Moreland, Elizabeth Mirowski, and Stephen Russek. Microfluidic platform of arrayed switchable spin-valve elements for high-throughput sorting and manipulation of magnetic particles and biomolecules.

Watch the microfluidic chip at work on YouTube:

National Institute of Standards and Technology (NIST)

Related Memory Articles from Brightsurf:

Memory of the Venus flytrap
In a study to be published in Nature Plants, a graduate student Mr.

Memory protein
When UC Santa Barbara materials scientist Omar Saleh and graduate student Ian Morgan sought to understand the mechanical behaviors of disordered proteins in the lab, they expected that after being stretched, one particular model protein would snap back instantaneously, like a rubber band.

Previously claimed memory boosting font 'Sans Forgetica' does not actually boost memory
It was previously claimed that the font Sans Forgetica could enhance people's memory for information, however researchers from the University of Warwick and the University of Waikato, New Zealand, have found after carrying out numerous experiments that the font does not enhance memory.

Memory boost with just one look
HRL Laboratories, LLC, researchers have published results showing that targeted transcranial electrical stimulation during slow-wave sleep can improve metamemories of specific episodes by 20% after only one viewing of the episode, compared to controls.

VR is not suited to visual memory?!
Toyohashi university of technology researcher and a research team at Tokyo Denki University have found that virtual reality (VR) may interfere with visual memory.

The genetic signature of memory
Despite their importance in memory, the human cortex and subcortex display a distinct collection of 'gene signatures.' The work recently published in eNeuro increases our understanding of how the brain creates memories and identifies potential genes for further investigation.

How long does memory last? For shape memory alloys, the longer the better
Scientists captured live action details of the phase transitions of shape memory alloys, giving them a better idea how to improve their properties for applications.

A NEAT discovery about memory
UAB researchers say over expression of NEAT1, an noncoding RNA, appears to diminish the ability of older brains to form memories.

Molecular memory can be used to increase the memory capacity of hard disks
Researchers at the University of Jyväskylä have taken part in an international British-Finnish-Chinese collaboration where the first molecule capable of remembering the direction of a magnetic above liquid nitrogen temperatures has been prepared and characterized.

Memory transferred between snails
Memories can be transferred between organisms by extracting ribonucleic acid (RNA) from a trained animal and injecting it into an untrained animal, as demonstrated in a study of sea snails published in eNeuro.

Read More: Memory News and Memory Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to