# NIST Calculations May Improve Temperature Measures for Microfluidics

##### Sep 08, 2009

(PhysOrg.com) -- If you wanted to know if your child had a fever or be certain that the roast in the oven was thoroughly cooked, you would, of course, use a thermometer that you trusted to give accurate readings at any temperature within its range. However, it isn’t that simple for researchers who need to measure temperatures in microfluidic systems—tiny, channel-lined devices used in medical diagnostics, DNA forensics and “lab-on-a-chip” chemical analyzers—as their current “thermometer” can only be precisely calibrated for one reference temperature. Now, researchers at the National Institute of Standards and Technology have proposed a mathematical solution that enables researchers to calibrate the “thermometer” for microfluidic systems so that all temperatures are covered.

Reactions taking place in microfluidic systems often require heating, meaning that users must accurately monitor temperature changes in fluid volumes ranging from a few microliters (a droplet approximately 1 millimeter in diameter) to sub-nanoliters (a droplet approximately 1/10 of millimeter in diameter). A common technique, for example, depends heavily on precise temperature cycling. Ordinary thermometers or other temperature probes are useless at such tiny dimensions, so some groups have turned to temperature-sensitive fluorescent dyes, particularly rhodamine B. The intensity of the dye’s fluorescence decreases with increasing temperature. The idea is that the dye can be used as a noninvasive way to map the range of temperatures occurring within a microfluidic system during heating and, in turn, provide a means of calibrating that system for experiments.

However, the technique currently requires the user to base all readings on the fluorescence at a single reference temperature. Previous groups have developed “calibration curves” that relate temperature to rhodmaine B fluorescent intensity based on a reference temperature of about 23 degrees Celsius (a technique first proposed by NIST researchers David Ross, Michael Gaitan and Laurie Locascio in 2001*). But it turns out that the curves are only good for that one temperature. In an upcoming paper in Analytical Chemistry**, the NIST team—Jayna J. Shah, Michael Gaitan and Jon Geist—reports that changing the reference point, such as the higher temperature when a microfluidic system is first heated, introduces errors when a dye intensity-to-temperature calculation is done using current methods.

“Our analysis shows that a simple linear correction for a 40 degrees Celsius reference temperature identified errors between minus 3 to 8 degrees Celsius for three previously published sets of calibration equations derived at approximately 23 degrees Celsius,” says lead researcher Shah.

To address the problem, the NIST team developed mathematical methods to correct for the shift experienced when the reference temperature changes. This allowed the researchers to create generalized calibration equations that can be applied to any reference temperature.

Microfluidic DNA amplification (production of numerous copies of DNA from a tiny sample) by the polymerase chain reaction (PCR) is one procedure that could benefit from the new NIST calculations, Shah says. “PCR requires a microfluidic device to be cycled through temperatures at three different zones starting around 65 degrees Celsius, so a useful dye intensity-to-temperature ratio would have to be based on that temperature and not a reference point of 23 degrees Celsius,” she explains.

* D. Ross, M. Gaitan and L.E. Locascio. Temperature measurement in microfluidic systems using a temperature-dependent fluorescent dye. Analytical Chemistry, Vol. 73, No. 17, pages 4117-4123, Sept. 1, 2001.

** J.J. Shah, M. Gaitan and J. Geist. Generalized temperature measurement equations for rhodamine B dye solution and its application to microfluidics. , Vol. 81, No. 19, Oct. 1, 2009 (published online Sept. 1, 2009).

Provided by National Institute of Standards and Technology (news : web)

## Related Stories

#### Micro Microwave Does Pinpoint Cooking for Miniaturized Labs

Nov 08, 2007

Researchers at the National Institute of Standards and Technology and George Mason University have demonstrated what is probably the world’s smallest microwave oven, a tiny mechanism that can heat a pinhead-sized ...

#### Novel temperature calibration improves NIST microhotplate technology

Aug 11, 2009

Researchers at the National Institute of Standards and Technology have developed a new calibration technique that will improve the reliability and stability of one of NIST's most versatile technologies, the ...

#### NIST Micro Sensor and Micro Fridge Make Cool Pair

Apr 15, 2008

Researchers at the National Institute of Standards and Technology have combined two tiny but powerful NIST inventions on a single microchip, a cryogenic sensor and a microrefrigerator. The combination offers ...

#### Low-cost microfluidics can be a sticky problem

May 12, 2006

A deceptively simple approach to bonding thermoplastic microchannel plates together with solvent could be used for low-cost, high-volume production of disposable "lab-on-a-chip" devices, according to researchers from the ...

#### Driving water droplets uphill

Apr 02, 2008

Lab-on-a-chip technology could soon simplify a host of applications, thanks to a new way to move droplets up vertical surfaces on flexible chips.

#### Novel 'noise thermometry' may help redefine international unit of temperature

Jun 03, 2008

After seven years of work, researchers at the National Institute of Standards and Technology have built a system that relies on the "noise" of jiggling electrons as a basis for measuring temperatures with ...

## Recommended for you

#### New biosensor will guard water supplies from toxic threats

9 hours ago

Supported by a \$953,958 grant from the Defense Advanced Research Projects Agency (DARPA), researchers at the University of California San Diego will develop a sophisticated new biosensor that can protect the nation's water ...

#### Microbial detection array detects plague in ancient human remains

Mar 07, 2014

(Phys.org) —Scientists who study past pandemics, such as the 14th century Black Death that devastated much of Europe, might soon be turning to an innovative biological detection technology for some extra ...

#### In situ chemical imaging at the sub-biofilm-scale now possible

Mar 06, 2014

(Phys.org) —Catching biofilm chemistry with images has always been a cold or dry affair. Now, a multidisciplinary team at Pacific Northwest National Laboratory is the first to demonstrate imaging of a biofilm's ...

#### A complete medical check-up on a chip

Mar 04, 2014

(Phys.org) —About the size of a stapler, this new handheld device developed at EFPL is able to test a large number of proteins in our body all at once-a subtle combination of optical science and engineering.

#### Using hydrogen exchange mass spec­trom­etry to confirm biopharmaceuticals

Mar 04, 2014

Biopharmaceuticals, also known as biologics, are the fastest growing sector of the pharmaceutical industry and most people living today will probably take a biopharmaceutical or know someone who takes one. ...

## More news stories

#### Scientists 'herd' cells in new approach to tissue engineering

Sometimes it only takes a quick jolt of electricity to get a swarm of cells moving in the right direction.

#### Researchers closer to improving safety, effectiveness of lithium therapy

Lithium, one of the oldest and most widely used drugs to treat neuropsychiatric illnesses, such as bipolar disorder, has a serious drawback – toxicity. In a continued effort to find a safer form of lithium, ...

#### New biosensor will guard water supplies from toxic threats

Supported by a \$953,958 grant from the Defense Advanced Research Projects Agency (DARPA), researchers at the University of California San Diego will develop a sophisticated new biosensor that can protect the nation's water ...

#### Turing's theory of chemical morphogenesis validated 60 years after his death

Alan Turing's accomplishments in computer science are well known, but lesser known is his impact on biology and chemistry. In his only paper on biology, Turing proposed a theory of morphogenesis, or how identical ...

#### Scents and sustainability: Renewable sources for artificial scents and flavors

Fresh banana, a waft of flowers, blueberry: the scents in Shota Atsumi's laboratory in the UC Davis Department of Chemistry are a little sweeter than most. That's because Atsumi and his team are engineering ...

#### World's first 3-D acoustic cloaking device hides objects from sound

(Phys.org) —Using little more than a few perforated sheets of plastic and a staggering amount of number crunching, Duke engineers have demonstrated the world's first three-dimensional acoustic cloak. The ...

#### London launches hi-tech trial for pedestrian safety

(Phys.org) —London is trying out intelligent pedestrian technology to make crossing the road easier and safer. Announced earlier this month, the technology is said to be the first scheme of its kind in ...

#### At tech fest: 3D printers, bitcoin and 'Titanfall'

Bitcoin, 3-D printed candy and George Takei, the Star Trek-actor-turned-Facebook-phenomenon, are among the attractions this week at the South By Southwest festival in Austin, Texas, where the geek set is ...

#### Long-term warming likely to be significant despite recent slowdown

A new NASA study shows Earth's climate likely will continue to warm during this century on track with previous estimates, despite the recent slowdown in the rate of global warming.

#### Lignin breakthroughs serve as GPS for plant research

Researchers at North Carolina State University have developed the equivalent of GPS directions for future plant scientists to understand how plants adapt to the environment and to improve plants' productivity ...