 Dr. Panos Datskos is both architect and builder of a tiny universe; one that can generate switches, sensors, and nanoelectronics with the potential to improve everything from the way we communicate to the safety of our cars. To do this, he sketches out the plans, gathers the materials, and builds miniature systems called MEMS (micro-electro-mechanical systems) and NEMS (nano-electro-mechanical systems), testing them to see how they respond to different variables. "We're looking at some basic processes at the microscale and nanoscale," said Dr. Datskos, a research associate professor in the physics department and a member of the Engineering Science and Technology Division at Oak Ridge National Laboratory. TINY DEVICES: BIG SENSITIVITYThe centerpiece for much of his research is a tiny device called a cantilever, which he said is "as simple as a diving board." These miniscule marvels are usually made out of silicon or silicon nitrate. They range in length from 50 to 200 micrometers and in width from one-tenth to two micrometers. (To put this in perspective, consider that a penny is roughly 20,000 micrometers wide.) But their size belies the power of these tiny objects, which are sensitive enough to pick up the body heat of a person doing no more than sitting in an office. Dr. Datskos explained that when a cantilever interacts with photons, chemicals, or magnetic fields, surface stresses cause it to bend. "As it bends," he said, "that translates into how much energy was used in the transaction." Isolating the forces that make a cantilever bend and measuring the deflections can explain a great deal about the material's sensitivity and selectivity, the basis for developing sensors and detectors. Using silicon chips, for example, it's possible to measure chemicals, flow, or fluid movements, as well as a deflection of no more than one angstrom (a penny is two million angstroms wide). Dressing cantilevers up or stripping them down provides a wide range of possibilities. By applying a chemical coating to a cantilever, Dr. Datskos can change the way it responds to outside stresses. For example, if silicon is coated with gold and exposed to photon-induced stress, the silicon will shrink but the gold will not, therefore causing the cantilever to bend. Using a method called MAPLE (matrix-assisted pulsed laser evaporation), he can transfer molecules, particles - even bugs for bacterial studies - to a cantilever. He also uses a focused ion beam milling machine, which can focus a beam of one micron or less, to remove unwanted elements from the surface, independent of material. Using a cantilever with a tip allows Dr. Datskos to make nanoscratches - gaps of a few nanometers - to alter surfaces for study. While the concepts of these studies are not new, he said, the tools are. The fabrication capabilities and scale necessary for this research are a relatively recent phenomenon. "People could not make these 50 years ago," he said. Bimaterials and other advances have dramatically altered the field. It's now possible to make cantilevers with materials that have a longer wavelength (e.g., Mercury MCT) to see how photons interact with the structure. "We can use any semiconductor, any metal or any insulator" to make these tiny systems for study, Dr. Datskos explained, a benefit of both technological advances and ORNL resources. Beyond building the small systems that act as highly sensitive sensors, Dr. Datskos also builds nanomechanical devices from different materials to see how electric fields and mechanical stress will affect their electronic behavior. These devices can act as transistors on the scale of a nanosecond. While ordinary transistors use millions of electrons in motion to generate heat, single electron transistors in the nanoworld use electron tunneling to amplify current and are sensitive enough to detect a single molecule. Dr. Datskos said the nanostructures he uses (a 3x3 micrometer space) "can serve both as chemical sensors and nanomechanical electronics." Even more exciting is the prospect of using photons rather than electrons to create optical transistors for super-fast switches. There are a number of practical applications for the research Dr. Datskos is pursuing. Cantilevers detecting proteins can provide the basis for biological sensors capable of picking up chemical warfare agents. Thermal seekers serve as the basis for night vision tools and can aid soldiers and law enforcement officials. Microscale motion sensors in cars can deploy airbags. Faster transistors can speed up e-commerce and other information processes.  A JOINT EFFORTThe close relationship between UT and ORNL is an added advantage in building MEMS and NEMS. Dr. Datskos works with Chemistry Professor Mike Sepaniak on chemical sensors. Physics graduate students Kelly Davisson and Stephanie Steffens are working on their master's degrees in Dr. Datskos's group, which also includes Ph.D. graduate Larry Senesac and two doctoral candidates from Tennessee Tech, James Corbeil and Shawn Goedeke. His research projects are also popular with the students who come to campus each year through the Science Alliance Summer Research Fellowship program. "A lot of students want to work with him," said Dr. Jim Parks, associate head of the physics department. "We have more student requests in the Science Alliance program than he can accommodate." The interest nanotechnology inspires, as well as its many applications, means Panos Datskos will be busy for a long time, building and analyzing those tiny systems with unlimited potential.Cross Sections, Fall/Winter 2001 Issue, Contents Page UT Physics News & Notes Page UT Physics Home Page This page was last updated on December 21, 2001. Please send comments to cal@utk.edu. |