ANN ARBOR, Mich.---A nanoscale thermometer that responds to temperature represents a new class of nanoscale assemblies that could lead to more accurate medical testing devices, in addition to applications in homeland security, and micro- and nano-electromechanical system technologies.

"The accurate temperature regime is critical for medical applications. All of the biological systems are temperature sensitive," said Nicholas Kotov, associate professor of chemical engineering at the University of Michigan.

"We are designed to operate at 37 degrees---if the temperature gets higher or lower that makes a tremendous change in our feeling of health. Similarly large differences occur with biomedical measurements based on protein reactions," Kotov said. "For example a microfluidics diagnostic device that is becoming more common now may show you that you have cancer when you don't, when temerature of the process is slightly off."

But there's no convenient way to measure temperature in micro- and nano-scale volumes of water because the spaces are in some cases thousands of times smaller than the commas on a page.

The particular nanothermometer was made by attaching a core gold particle and a semiconductor particle to opposite ends of flexible polymer, which acts as the so-called spring. The particles interact optically, and when many polymers connect to the gold core they fan out and form a corona shape.

The polymer spring acts like a coiled garden hose that contracts and tightens in the cold and relaxes in the heat. As the polymer responds to heat or cold, the particles attached to the ends move closer or father apart. With the molecular spring, scientists can detect temperature changes down to one or two degrees.

But the responses aren't limited to temperature, Kotov said. "In terms of applications, this stimulus-response system is actually just the beginning of many other, similar structures of sensing devices," he said. Researchers can design the particle to respond to any number of stimuli, such as a biological pathogen or an explosive. "The fact that they are different materials but interact make them a member of a class of metamaterials. These hold great promise because you can combine the properties of two types of solids."

A paper on the topic, "Nanoparticle Assemblies with Molecular Springs: A Nanoscale Thermometer," is available online at the Journal Angewandte Chemie International Edition. The paper was written by Kotov and collaborators Dr. J. Lee, a post-doctoral associate in Chemical Engineering Department and professor A.O. Govorov in the Department of Physics and Astronomy at Ohio University. Kotov also has appointments in biomedical engineering and materials science and engineering. The research is funded mainly by NSF and DARPA.

For more information on Kotov, see: http://www.engin.umich.edu/dept/cheme/people/kotov. html

To see the abstract: http://www3.interscience.wiley.com/cgi-bin/abstract/112125760/ABSTRACT

The University of Michigan College of Engineering is ranked among the top engineering schools in the country. Michigan Engineering boasts one of the largest engineering research budgets of any public university, at $135 million for 2004. Michigan Engineering has 11 departments and two NSF Engineering Research Centers. Within those departments and centers, there is a special emphasis on research in three emerging areas: nanotechnology and integrated microsystems; cellular and molecular biotechnology; and information technology. Michigan Engineering is seeking to raise $110 million for capital building projects and program support in these areas to further research discovery. Michigan Engineering's goal is to advance academic scholarship and market cutting edge research to improve public health and well-being. For more information, see the Michigan Engineering home page: http://www.engin.umich. edu

Contact, Laura Bailey, (734) 647-7087 or (734) 647-1848 baileylm@umich.edu