Breakthrough research paves way for nanomanufacturing in healthcare applications

The new tip is said to be 100,000 times smaller than the tip of a pencil, and paves the way for nanomanufacturing for applications, including bio sensors for healthcare and the environment. Scientists from the University of Pennsylvania, the University of Wisconsin, Madison and IBM Research Zurich sought to develop a nano sized tip that is both ultrasharp and physically robust, particularly under extreme temperatures and harsh chemical environments. "The dream tip material for thermomechanical nanofabrication should have a high hardness, temperature stability, chemical inertness, and high thermal conductivity," said Dr Mark Lantz, manager in storage research at IBM Research - Zurich. "With this novel tip we continue to deliver on IBM's vision of a smarter, instrumented world with microscopic sensors monitoring everything from water pollution to patient care." According to the researchers, they have developed a new, resistant nano sized tip that wears away at the rate of less than one atom per millimetre of sliding on a substrate of silicon dioxide. This, they claim, is much lower than the wear rate of conventional silicon tips and its hardness is 100 times greater than that of the previously state of the art silicon oxide doped diamond like carbon tips they developed last year. "Compared to our previous work in silicon, the new carbide tip can slide on a silicon dioxide surface about 10,000 times farther before the same wear volume is reached and 300 times farther than our previous diamond like carbon tip," said Prof Robert Carpick, University of Pennsylvania. "This is a significant achievement that will make nanomanufacturing both practical and affordable." To create the new tip, the researchers developed a process whereby the surfaces of nanoscale silicon tips are exposed to carbon ions and then subjected to annealing - a process of heating and slow cooling in order to toughen and reduce brittleness. A strong silicon carbide layer is formed, but the nanoscale sharpness of the original silicon tip is maintained. Although silicon carbide has long been known as an ideal candidate material for such tips, the unique carbon implantation and annealing process made it possible to harden the surface while maintaining the original shape and ensuring strong adhesion between the hardened surface of the tip and the underlying material - similar to how steel is tempered to make it harder. The tip consists mainly of carbon and silicon and is sharpened to a nano sized apex and integrated on the end of a silicon microcantilever for use in atomic force microscopy. According to the researchers, the importance of the development lies not only in its ability to maintain the sharpness of the tip and its resistance to wear, but also in its endurance when sliding against a hard substrate such as silicon dioxide. Because silicon - used in almost all integrated circuit devices - oxidises in the atmosphere, forming a thin layer of its oxide, this system is among the most relevant for emerging applications in nanolithography and nanomanufacturing applications. The scientists hope that the new tip can be used to fabricate bio sensors, for example for managing glucose levels in diabetic patients or monitoring pollution levels in water. Probe based technologies are expected to play a predominant role in many such technologies. However, poor wear performance of the tip materials used so far, especially when slid against silicon oxide, have previously limited their usefulness for experimental applications. The next step for scientists is to begin testing the new tip for use in applications, starting with nanomanufacturing. The study is published today in Advanced Functional Materials journal.