September 7, 2001
Purdue faculty at forefront of nanotech research
WEST LAFAYETTE, Ind. Although its origins can be traced to electronics, nanotechnology now bridges many scientific disciplines. Dozens of Purdue University researchers in fields ranging from electrical engineering to chemistry and physics to agriculture are pursuing a number of projects to advance nanotechnology. Here are some examples of this work:
Mark Lundstrom and Supriyo Datta, professors of electrical and computer engineering, are working to better understand how electricity flows through transistors as they are shrunk to only a few atomic layers. Such information will be critical in designing nanometer-scale electronics and to understand the minimum dimensions at which transistors can still operate. Lundstrom and Datta will soon be recognized for their nanotech research with a prestigious Cledo Brunetti Award from the Institute of Electrical and Electronics Engineers Inc. Their work also will be featured Thursday (9/13) during a National Science Foundation nanotechnology presentation in Washington, D.C.
Datta's work also strives to better understand how electricity flows through organic molecules, such as DNA. That research ties in with international efforts to develop molecular electronic devices and systems that "self assemble," similar to the growth of complex organic structures in living things. Theoretically, once set in motion, such self-assembling devices would build themselves. However, this goal is still a distant vision, caution researchers.
Hicham Fenniri, an assistant professor of chemistry, is working on the design of molecules that automatically find each other and link together to form elaborate structures, and on creating synthetic materials that "evolve" and "adapt" to meet changing environmental conditions. His group is using self-assembly approaches to control the behavior of matter at the molecular level. In that work, molecules are "programmed" to automatically come together in groups of six, making rosette-shaped patterns. Numerous rosettes then combine to form tiny, rod-like structures called nanotubes, which may someday be used to manufacture "molecular photonic and electronic wires," artificial channel systems and biosensors. They also have potential medical applications, making it possible to design a new class of therapeutic devices.
Chemical engineers are working on new methods that use nanometer-size particles to deliver drugs and medications, such as insulin, research that would benefit hundreds of thousands of diabetics in the United States alone. Insulin-dependent diabetes and other conditions require medications to be injected; the drugs cannot be administered orally because they are broken down in the acidic environment of the stomach. To get around this complication, the engineers have made microscopic and nanoscopic particles for drug delivery that protect medicines from the harsh environment of the stomach until they can be released in the intestines and absorbed into the blood. The hope is that pills will replace needles for insulin and other drugs. That work is being headed by Nicholas A. Peppas, Purdue's Showalter Distinguished Professor of Chemical and Biomedical Engineering.
Alexander Wei, an assistant professor of chemistry, has developed specially coated "nanoparticles" that may ultimately prove useful in making new materials for applications ranging from medicine to aerospace. Building such materials from scratch, atom-by-atom, has a downside: Nanoparticles can be so fragile and unstable that if their surfaces touch, they will fuse together, losing their special shape and properties. Wei has found a way to stabilize nanoparticles made of metal by wrapping the tiny structures in a "plastic coat" of molecular thickness. The coating prevents the nanoparticles from fusing together upon contact and allows them to be easily manipulated. Wei and his students have assembled arrays of gold particles that may ultimately prove useful as chemical sensors for applications ranging from the detection of dangerous chemical warfare agents to understanding the mechanisms of drug resistance.
Rashid Bashir, an associate professor of electrical and computer engineering and biomedical engineering, is working in the interdisciplinary field of BioMEMS, which focuses on developing tiny machines called microelectromechanical systems, or MEMs. The research aims to combine micro- and nanotechnology with biotechnology in creating new devices that have biomedical applications and are, in some cases, based on designs that were inspired by natural structures found in living things. Bashir is working on developing methods for assembling semiconductor devices using biological molecules, such as DNA and proteins. The research may yield postage-stamp-size "micro-fluidic bio-chips" and advanced sensors to detect microorganisms, including dangerous bacteria that contaminate foods.
Purdue scientists have created the first protein "biochips," mating silicon computer chips with biological proteins. Future chips containing thousands of proteins could be organized into a device about the size of a handheld computer that could quickly and cheaply detect specific microbes, disease cells and harmful or therapeutic chemicals. The researchers heading this work are Rashid Bashir, an associate professor of electrical and computer engineering and biomedical engineering; Arun Bhunia, an associate professor of food science; and Michael Ladisch, a distinguished professor of biomedical engineering and agricultural and biological engineering. The work is part of a food safety engineering program headed by Richard Linton, an associate professor of food safety.
Bruce Applegate, an assistant professor in food science, is developing bacterial-based "smart" biosensors, which can detect chemical contaminants, signature spoilage molecules or pathogens in food. The biosensors would be used on the farm, in food processing, and even by consumers. These smart sensors will contain multiple regulatory elements found in genes that have been modified to act as sensing elements and also to mimic logic gates found in computers. The whole-cell biosensors will have simple biocomputing capabilities, which will allow them to not only detect food contamination biological, chemical, or both but also process and store the related information.
Ronald Andres, a professor of chemical engineering, has developed 4-nanometer gold clusters, or "nanoclusters," for applications in molecular electronics. The 12-sided, soccer-ball-shape nanoclusters have facets, created automatically as the clusters form, which provide flat surfaces that promote a good electrical contact. Along with David Janes, an associate professor of electrical and computer engineering, Andres and other researchers at Purdue are working to dramatically shrink the metal contacts that are needed to connect transistors to other devices in computer chips. Conventional transistors have features as small as one-tenth of a micron, or 1,000th the width of a human hair. However, the overall size of a transistor is much larger because of the metal contacts needed to connect them to other devices in the circuitry of a computer chip. Those contacts are thousands of times larger than the main structure of a transistor, tiny electrodes known as gates. As a result, the contact size defines how many transistors can be packed together and, ultimately, hinders the ability to make smaller, more powerful computers.
Engineers are trying to solve the problem by finding ways to make the contacts as small as the rest of the transistor. A research team at Purdue has created contacts that are 4 nanometers in diameter, compared with conventional contacts that are measured in microns, or thousandths of a meter.
Ronald Reifenberger, a professor of physics, has a long-term interest in studies that reveal the physics of how matter behaves on the scale of nanometers. His research has focused on trying to understand the fundamental issues that will confront future workers who will build things on such a small scale. He currently is working with engineers and chemists to develop advanced sensors that might one day be used to detect minute quantities of chemicals in the air or in water supplies. Although the experimental sensor technology is probably years away from practical applications, it represents a milestone because it is extremely sensitive, capable of detecting single molecules. If perfected, such sensors might have uses in counterterrorism, environmental and other applications.
Gerold Neudeck, a professor of electrical and computer engineering, is developing a method to make smaller, faster computer chips by stacking electronic devices such as transistors 50 times smaller than a human blood cell in a virtually unlimited number of layers, as opposed to conventional single-layer designs. The vertically connected layers may increase the speed and the number of transistors in a computer chip.
Sources:Ronald Andres, (765) 494-4047, firstname.lastname@example.org
Bruce Applegate, (765) 496-7920, email@example.com
Rashid Bashir, (765) 496-6229, firstname.lastname@example.org
Arun Bhunia, (765) 404-5443, email@example.com
Supriyo Datta, (765) 494-3511, firstname.lastname@example.org
Hicham Fenniri, (765) 494-5241, email@example.com
David Janes, (765) 494-9263, firstname.lastname@example.org
Michael Ladisch, (765) 494-7022, email@example.com
Mark Lundstrom, (765) 494-3515, firstname.lastname@example.org
Gerold Neudeck, (765) 494-3513; email@example.com
Nicholas A. Peppas, (765) 494-7944, firstname.lastname@example.org
Ronald Reifenberger, (765) 494-3032, email@example.com
J. Paul Robinson, (765) 494-6449, firstname.lastname@example.org
Alexander Wei, (765) 494-5257, email@example.com
PHOTO CUTLINESRonald Andres, Purdue professor of chemical engineering, uses an apparatus to produce clusters of gold atoms. The clusters are used to fabricate a molecule-size device that conducts electricity. (Purdue News Service photo by David Umberger) A publication-quality photograph is available at the News Service Web site and at the ftp site. Photo ID: andres.nanolab News Service Web site and at the ftp site. Photo ID: fenniri.nanotube News Service Web site and at the ftp site. Photo ID: ladisch.biochips