David Kirkpatrick

August 5, 2010

Separating and sizing nanoparticles

Filed under: Science — Tags: , , , — David Kirkpatrick @ 2:12 pm

A useful nanotech development.

The release:

NIST nanofluidic ‘multi-tool’ separates and sizes nanoparticles

IMAGE: A 3-D nanofluidic “staircase ” channel with many depths was used to separate and measure a mixture of different-sized fluorescent nanoparticles. Larger (brighter) and smaller (dimmer) particles were forced toward the…

Click here for more information.

A wrench or a screwdriver of a single size is useful for some jobs, but for a more complicated project, you need a set of tools of different sizes. Following this guiding principle, researchers at the National Institute of Standards and Technology (NIST) have engineered a nanoscale fluidic device that functions as a miniature “multi-tool” for working with nanoparticles—objects whose dimensions are measured in nanometers, or billionths of a meter.

First introduced in March 2009 (see “NIST-Cornell Team Builds World’s First Nanofluidic Device with Complex 3-D Surfaces”, the device consists of a chamber with a cascading “staircase” of 30 nanofluidic channels ranging in depth from about 80 nanometers at the top to about 620 nanometers (slightly smaller than an average bacterium) at the bottom. Each of the many “steps” of the staircase provides another “tool” of a different size to manipulate nanoparticles in a method that is similar to how a coin sorter separates nickels, dimes and quarters.

In a new article in the journal Lab on a Chip*, the NIST research team demonstrates that the device can successfully perform the first of a planned suite of nanoscale tasks—separating and measuring a mixture of spherical nanoparticles of different sizes (ranging from about 80 to 250 nanometers in diameter) dispersed in a solution. The researchers used electrophoresis—the method of moving charged particles through a solution by forcing them forward with an applied electric field—to drive the nanoparticles from the deep end of the chamber across the device into the progressively shallower channels. The nanoparticles were labeled with fluorescent dye so that their movements could be tracked with a microscope.

As expected, the larger particles stopped when they reached the steps of the staircase with depths that matched their diameters of around 220 nanometers. The smaller particles moved on until they, too, were restricted from moving into shallower channels at depths of around 110 nanometers. Because the particles were visible as fluorescent points of light, the position in the chamber where each individual particle was stopped could be mapped to the corresponding channel depth. This allowed the researchers to measure the distribution of nanoparticle sizes and validate the usefulness of the device as both a separation tool and reference material. Integrated into a microchip, the device could enable the sorting of complex nanoparticle mixtures, without observation, for subsequent application. This approach could prove to be faster and more economical than conventional methods of nanoparticle sample preparation and characterization.

The NIST team plans to engineer nanofluidic devices optimized for different nanoparticle sorting applications. These devices could be fabricated with tailored resolution (by increasing or decreasing the step size of the channels), over a particular range of particle sizes (by increasing or decreasing the maximum and minimum channel depths), and for select materials (by conforming the surface chemistry of the channels to optimize interaction with a specific substance). The researchers are also interested in determining if their technique could be used to separate mixtures of nanoparticles with similar sizes but different shapes—for example, mixtures of tubes and spheres.


* S.M. Stavis, J. Geist and M. Gaitan. Separation and metrology of nanoparticles by nanofluidic size exclusion. Lab on a Chip, forthcoming, August 2010

February 12, 2009

February 2009 media tips from Oak Ridge National Laboratory

The release:

February 2009 Story Tips

(Story Tips Archive)

Story ideas from the Department of Energy’s Oak Ridge National Laboratory. To arrange for an interview with a researcher, please contact the Communications and External Relations staff member identified at the end of each tip.

MICROSCOPY—-STEM in liquid . . . . . .

Researchers at ORNL and Vanderbilt University have unveiled a new technique for imaging whole cells in liquid using a scanning transmission electron microscope. Electron microscopy is the most important tool for imaging objects at the nano-scale–the size of molecules and objects in cells. But electron microscopy requires a high vacuum, which has prevented imaging of samples in liquid, such as biological cells.” The new technique – liquid STEM – uses a micro-fluidic device with electron transparent windows to enable the imaging of cells in liquid. A team led by Niels de Jonge imaged individual molecules in a cell, with significantly improved resolution and speed compared with existing imaging methods. “Liquid STEM has the potential to become a versatile tool for imaging cellular processes on the nanometer scale,” said de Jonge. “It will potentially be of great relevance for the development of molecular probes and for the understanding of the interaction of viruses with cells.” The work was recently described in the on-line Proceedings of the National Academy of Sciences.

BIOLOGY—-Time-saving tool . . . . . .

Scientists studying human health, agriculture and the environment have a powerful new tool to help them better understand microbial processes and how they relate to ecosystems. The GeoChip consolidates into one analysis something that using traditional methods would require dozens of tests and take possibly years to complete, according to co-developer Chris Schadt of ORNL’s Biosciences Division. This lab on a chip features more than 24,000 gene probes that target more than 150 functional gene groups involved in biochemical, ecological and environmental processes. The GeoChip is especially useful for bioremediation of sediments and soils, determining the role of microbes in soil and learning how microbial processes are connected to ecosystem responses to human-induced environmental changes such as temperature, moisture and carbon dioxide. This research was funded by the Department of Energy’s Office of Biological and Environmental Research.


CYBERSPACE—-Thwarting threats . . . . . .

Colonies of cyber robots with unique missions can in near real time detect network intruders on computers that support U.S. infrastructure. These “cybots” created for an ORNL software program called UNTAME (Ubiquitous Network Transient Autonomous Mission Entities) may be especially useful for helping government agencies deter, defend, protect against and defeat cyber-attacks. “What scares us the most isn’t what we can see, but rather what we can’t see,” said Joe Trien of the lab’s Computational Sciences & Engineering Division. “A coordinated cyber attack could disrupt one or more of U.S. critical infrastructures, and these attacks can reach across the world at the speed of light.” Trien led a team of researchers that developed UNTAME.


COMPUTING—-First petascale projects . . . . . .

The National Center for Computational Sciences at Oak Ridge National Laboratory has granted early access to a number of projects to test Jaguar, which has peak performance of 1.6 petaflops and is the most powerful computer in the world for open science. The “Petascale Early Science” period will run approximately 6 months and consist initially of 20 projects, said NCCS Director of Science Doug Kothe. The early phase period seeks to deliver high-impact science results and advancements; harden the system for production; and embrace a broad user community to use the system, Kothe said. Proposals include: modeling to better understand climate change; energy storage and battery technology; cellulose conversion to ethanol; combustion research for more efficient automobile engines; and high-temperature superconductors for more efficient transmission of electricity. Fusion, nuclear energy, materials science, nuclear physics, astrophysics, and carbon sequestration also will be explored. “These early simulations on Jaguar will also help us harden the system for a broader collection of projects later in the year,” said Kothe.

September 21, 2008

DNA testing in the field

Filed under: Science, Technology — Tags: , , , , — David Kirkpatrick @ 11:47 am

From the release/media placement:

Landers Lab Micro-Sizes Genetics Testing

September 18, 2008 — Using new “lab on a chip” technology, James Landers hopes to create a hand-held device that may eventually allow physicians, crime scene investigators, pharmacists, even the general public, to quickly and inexpensively conduct DNA tests from almost anywhere, without need for a complex and expensive central laboratory.

“We are simplifying and miniaturizing the analytical processes so we can do this work in the field, away from traditional laboratories, with very fast analysis times, and at a greatly reduced cost,” said Landers, a University of Virginia professor of chemistry and mechanical engineering and associate professor of pathology.

Landers published a review this month of his research and the emerging field of lab-on-a-chip technology in the journal Analytical Chemistry.

“This area of research has matured enough during the last five years to allow us to seriously consider future possibilities for devices that would allow sample-in, answer-out capabilities from almost anywhere,” he said.

Landers and a team of researchers at U.Va., including mechanical and electrical engineers, with input from pathologists and physicians, are designing a hand-held device  — based on a unit the size of a microscope slide — that houses many of the analytical tools of an entire laboratory, in extreme miniature. The unit can test, for example, a pin-prick-size droplet of blood, and within an hour provide a DNA analysis.

“In creating these automated micro-fluidic devices, we can now begin to do macro-chemistry at the microscale,” Landers said.

Such a device could be used in a doctor’s office, for example, to quickly test for an array of infectious diseases, such as anthrax, avian flu or HIV, as well as for cancer or genetic defects. Because of the quick turnaround time, a patient would be able to wait only a short time onsite for a diagnosis. Appropriate treatment, if needed, could begin immediately.

Currently, test tube-size fluid samples are sent to external labs for analysis, usually requiring a 24- to 48-hour wait for a result.

“Time is of the essence when dealing with an infectious disease such as meningitis,” Landers said. “We can greatly reduce that test time, and reduce the anxiety a patient experiences while waiting.”

Landers said the research also dovetails with the trend toward “personalized medicine,” in which medical care increasingly is tailored to the specific genetic profile of a patient. Such highly specialized personalized care can allow physicians to develop specific therapies for patients who might be susceptible to, for example, particular types of cancers.

Simplifying genetic testing, and reducing the costs of such tests, could help pave the way toward routine delivery of such personalized care based on an individual’s genetic profile.

Hand-held micro labs also would be useful to crime scene investigators who could collect and analyze even a tiny sample of blood or semen on the scene, enter the finding into a genetic database, and possibly identify the perpetrator very shortly after a crime has occurred.

Likewise, agricultural biotechnologists could do very rapid genetic analysis on
thousands of hybrid plants that have desirable properties such as drought and disease resistance, Landers said.

“We can now do lab work in volumes that are thousands of times smaller than would normally be used in a regular lab setup, and can do it up to 100 times faster,” he said. “As we improve our techniques and capabilities, the costs of fabricating these micro-analysis devices will drop enough to employ them routinely in a wide variety of settings.”

Landers even envisions home DNA test kits, possibly available for purchase from pharmacies, that would allow individuals to self-test for flu or other diseases.

His colleagues at U.Va. include Mathew Begley, professor of mechanical engineering; Molly Hughes, assistant professor of internal medicine, and Sanford Feldman, director of the Center for Comparative Medicine.

— By Fariss Samarrai