The world's smallest abacus

Zurich, Switzerland, 13 Nov 1996—Scientists at the IBM Research Division's Zurich laboratory have built an abacus with individual molecules as beads with a diameter of less than one nanometer, one millionth of a millimeter. The world's smallest abacus will hardly be found at a trade fair in the Far East, where calculators of this simple kind are still used by dealers, because the "finger" required to move beads as tiny as individual molecules is the ultrafine tip of a scanning tunneling microscope (STM)—a needle of conical shape terminating in a single atom at the very tip. The STM also makes the result of a "calculation" visible when operated in imaging mode.

IBM scientists succeeded in forming stable rows of ten molecules along steps just one atom high on a copper surface. These steps act as "rails", similar to the earliest form of the abacus, which had grooves instead of rods to keep the beads in line. Individual molecules were then approached by the STM tip and pushed back and forth in a precisely controlled way to count from 0 to 10 (see image above).

"We have made significant progress in handling objects and creating functional units on the nanometer scale at room temperature", says James K. Gimzewski, leader of the nanoscience project at the Zurich Research Laboratory. "Our work demonstrates a further step in the new and fascinating field of 'nano-engineering', where solid-state physics and chemistry merge. We may be able to assemble more complex structures from the bottom up, as nature does, molecule by molecule, and thus break ground for entirely new fabrication technologies with a broad range of applications."

The beads used in the abacus experiment are the amazing soccer-ball-like molecules formed by 60 carbon atoms (C₆₀), the discoverers of which were recently announced as the recipients of the 1996 Nobel Prize in chemistry. These molecules are also known as buckminsterfullerenes or "buckyballs" , named after the American architect Buckminster Fuller, who invented the geodesic dome using the same pattern of hexagons and pentagons.

The researchers who have long been studying the properties and behavior of individual atoms and molecules and who have now realized the nano-abacus are Maria Teresa Cuberes, James K. Gimzewski, and Reto R. Schlittler at IBM Research - Zurich. The effort is part of the "PRONANO" (processing on the nanometer scale) project sponsored by the Swiss Federal Office of Education and Science within the European Strategic Program for Research in Information Technology (ESPRIT) of the European Union. 

The scientific report on the subject has been published in Applied Physics Letters, Volume 69, Number 20 (p. 3016), November 11, 1996.