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Keeping samples cold, very cold: extremely low temperatures enhance storage and various research projects.

Late in May 2011, a freezer failed at McLean Hospital just outside of Boston. This freezer contained brains provided by Autism Speaks for research conducted by the Harvard Brain Tissue Resource Center. For some reason, the typically -80 C temperatures climbed to about 7 C, which damaged at least 54 samples. This accident raised awareness in the public and the scientific world about the value of keeping samples frozen.

Very low temperatures can be used to experiment with new and exotic materials, develop instruments, or store samples such as cell lines. The technology that creates such low-temperature environments includes various types of freezers. For example, so-called ultralow temperature freezers can keep samples at temperatures below -80 C. Moreover, millikelvin (mK) cryostats can keep materials just a few hundredths of a degree above absolute zero (-273 C).

"These freezers get used in labs, repositories, pharmaceutical companies, and biobanks that store thousands of samples," says Deepak Mistry, senior manager, strategic development and marketing at Panasonic Healthcare Company of North America (Secaucus, N.J.). "This can include stem cells, cord blood, T cells, and a variety of all different cell types." Also, the storage can be short- or long-term. For long-term, says Joe LaPorte, senior product manager at Panasonic, "It can be up to 25 years, even longer in some cases."

Creations from cryostats

High Precision Devices (Boulder, Colo.) offers a range of cryostats, which maintain so-called cryogenic temperatures or below -150 C. Joshua T. West, staff physicist at the company, says, "People are often using [our cryostats] when working on superconducting detectors or quantum computing."

This company's millikelvin cryostats provide temperatures within 0.05 of a degree of absolute zero. Instead of relying on liquid cryogens, such as liquid helium or nitrogen, these cryostats cool their payload in two stages, first using an acoustic refrigeration technique to get to within a few degrees of absolute zero, then employing magnetic refrigeration to reach the final temperature--all with no moving parts.

The technology for this approach to refrigeration came from the National Institute of Standards and Technology (NIST). "We licensed part of the design from them," West says. "Now, they use some of our technology for many things, such as nuclear forensics, which develops a nuclear fingerprint to determine the levels of enrichment in a nuclear sample. That's often required in the verification of nuclear treaties."

In addition, engineers at High Precision Devices are using their cryogenics knowledge to collaborate with John Clarke of the University of California, Berkeley, and his colleagues to develop a low-field magnetic resonance imaging (MRI) device based on ultrasensitive superconducting quantum interference devices (SQuIDSs). A conventional MRI uses a very large magnet, so it cannot be used close to any metal, such as a titanium screw, in a patient. "The low-field MRI can be used around metals, but it is not as sensitive," says West. In addition, the low-field approach to MRI promises other advances, including improved imaging of prostate cancer.

A collection of cryos

From Oxfordshire, U.K., Oxford Instruments Nanoscience offers a range of cryostats, including devices that operate above 1 K to the Triton Dilution refrigerators that provide a temperature below 10 mKs. David Haynes, sales and marketing director of Oxford Instruments Nanoscience, says, "Our benchtop systems can be integrated into spectroscopy or microscopy systems." He adds, "The Triton systems get used in applications in quantum computing and characterization of materials at low temperature."

Haynes points out that more than 50% of his company's sales involve Cryofree technology, or platforms that do not use cryogens. "In addition to removing the need for expensive liquid cryogens," Haynes says, "the development of Cryofree solutions has opened up new opportunities in system design allowing a much larger sample space that can be used to accommodate a researcher's experiment or a quantum-computing processor and associated electronics."

Oxford Instruments also strives to make its systems easier to use. For example, Haynes says that the systems include "advanced sample loading through the top and/or bottom of the system, user-friendly control systems, and advanced interfacing that allows the end user to easily integrate the equipment with their system." He adds, "We are also able to supply superconducting-magnet solutions that can be fully integrated with our low temperature environments."

Avoiding accidents

To prevent the kinds of problems that the Harvard brain bank experienced, Panasonic offers freezers with backup systems. "Our new -86 C Twin Guard series has a dual independent autocascade cooling system, which means there's a built-in backup compressor," says Mistry. "If one compressor goes down, the other one can still keep the samples at -65 C." And one freezer can hold many samples. Panasonic's largest -86 C freezer is 26 [ft.sup.3]. "It can hold 57,600 two-inch vials in one freezer," says Mistry.

As LaPorte explains, "The goal is to run for years without any major warm up." Given that crucial goal, he points out that the interface should be as simple as possible. "This is not a product that people change," he says. "You set it once, adjust the high and low alarms, and then leave it."

To also ensure that stability, LaPorte points out, "Panasonic uses vertical integration. We manufacture or design most of the components in our systems." He adds, "It makes our time-to-market longer, but lots of it is related to stress testing before we hit the market."

In the wake of losing precious brain samples because of a freezer malfunction, researchers and institutions will look more carefully at this technology. Moreover, low-temperature freezers must constantly improve. "Compared to freezers produced 10 years ago," LaPorte says, "our freezers use 30 to 40% less energy, and we do that with a new patent-pending, heat-exchange design."

It's well worth saving energy to run these freezers, but it's even more important to protect the contents inside them. One freezer can protect decades' worth of work, where the value of the contents verges on priceless.

--Mike May

Contributing Editor
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Title Annotation:MATERIALS SCIENCE
Comment:Keeping samples cold, very cold: extremely low temperatures enhance storage and various research projects.(MATERIALS SCIENCE)
Author:May, Mike
Publication:R & D
Geographic Code:1USA
Date:Aug 1, 2012
Words:990
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