It has long been a dream for nanotechnologists that robots could one day be used to manufacture things out of nanostructures. A nanogripper controlled by a nanorobotic arm has now picked up a carbon nanofibre and fixed it onto the tip of an atomic force microscope probe-an important tool for measuring nanostructures. In a few years the process will be incorporated in an automatic assembly system.

	Nanogripper

A group of researchers from the Technical University of Denmark (DTU) and University of Oldenburg (UO) have now shown "pick-and-place" assembly of a working device using a silicon gripper - a robotic "hand" some 10000 times smaller than a human hand. They managed to break off a sturdy carbon nanofibre, and position it at the pyramidal tip of an atomic force cantilever. After fixing the nanofibre with by electron beam induced deposition of carbon, the long slender tip was used to scan deep trenches, producing much better images than standard atomic force probes. Associate professor Peter Bøggild from DTU considers this an significant step forward:

"Nanomanipulation has been around for a few decades, but so far mostly been used for basic science and for showing what the future might hold. We have now demonstrated the basic construction of a working device using a small silicon gripper. To turn this into an automatic process we must improve everything: the shape and size of the gripper, the speed and precision of the robot...But now we have a tool that does it job."

How does the gripper work? Parts of the silicon gripper are heated up with an electrical current, and the thermal expansion is converted into a powerful gripping action of the jaws. The distance of the jaws can then be reduced from about 3 micron to zero. The gripper, developed by researchers at DTU, is a part of an advanced nanorobotic system with integrated 3D electron microscopy and image recognition, constructed by Research Associate Volkmar Eichhorn in Sergej Fatikows group at University of Oldenburg.

So far carbon nanotubes and nanofibres with diameters down to 100 nm have been manipulated, but in two years smaller tools will manipulate 10-20 nm wide wires and tubes. There are many problems to solve to reach this goal, however. On the nanoscale, 3D manipulation is painstakingly difficult: the robotic arms must work with extreme precision, and real-time imaging of nanostructures is just about possible. Creating the tiny "hands" for the robot is a great challenge: the fingers must be thin and flexible, and yet have sufficient strength to break off nanotubes from their initial position. Another requirement for automation is that the nanotubes are located at well-defined locations on the surface, which was done by researchers from University of Cambridge.

The results were published in "Nanotechnology".