IBM researchers bring printing to the nanoscale

Zurich, Switzerland, 11 September 2007—IBM (NYSE: IBM) researchers in collaboration with scientists from the ETH Zurich have demonstrated a new, efficient and precise technique to print at the nanoscale. The method could advance the development of nanoscale biosensors, of lenses that can bend light inside future optical chips, and the fabrication of nanowires that might be the basis of tomorrow’s computer chips.

The achievement, published in the September issue of the journal Nature Nanotechnology, offers a promising and powerful new tool for use in a wide range of fields and industries such as biomedicine, electronics and IT that seek ways to exploit the often unique properties of so-called nanoparticles, i.e. particles that are smaller than 100 nanometers.

Until now, standard top-down microfabrication techniques produce such tiny particles by in effect carving them out of a bigger piece of material. Printing, in contrast, adds ready-made nanoparticles onto a surface in a very efficient way and thus facilitates the combination of different materials such as metals, polymers, semiconductors, and oxides.

For the first time, IBM researchers have printed particles as tiny as 60 nanometers—roughly 100 times smaller than a human red blood cell—with single-particle resolution to create nanopatterns ranging from simple lines to complex arrangements. Translating their resolution into “dots per inch” (dpi), a standard measure that defines how many individual spots of ink can be printed on a certain area, the nanoprinting method yields 100,000 dots per inch, whereas common offset printing today operates with 1,500 dpi.

To demonstrate the efficiency and the versatility of their method, IBM researchers chose to print Robert Fludd’s famous 17th-century drawing of the sun, which was alchemists’ symbol for gold. Quite fittingly, it is printed out of roughly 20,000 gold particles, each of them 60 nanometers in diameter. The printing method precisely placed one particle per dot, thus creating the smallest piece of artwork ever printed from single pigment particles.

Nanoprinting applications

“This method opens up new ways to precisely and efficiently position various kinds of nanoparticles on different surfaces, a prerequisite for exploiting the unique properties of such nanoparticles and for making their use economically feasible,” explains Heiko Wolf, researcher in nanopatterning at IBM’s Zurich Research Lab.

In biomedicine this printing process could, for example, be applied to the printing of large arrays of biofunctional beads that can detect and identify certain cells or markers in the body. One example could be rapid screening for cancer cells or heart attack markers. As part of new point-of-care diagnostic devices, regular arrays of functional beads could enable a fast and automated read-out that only needs the tiniest amounts of samples.

Nanoparticles can also interact with light. With the new method, optical materials with new properties could be printed, for example, for use in optoelectronic devices. So-called “metamaterials” could be created in which the printed structures are as small as the wavelength of the light and therefore act as if they were a single lens with unusual properties.

Moreover, the method holds promise for semiconductors. In one experiment, IBM researchers achieved the controlled placement of catalytic seed particles for growing semiconducting nanowires. Such nanowires are promising candidates for future transistors in microchips.

Printing on the nanoscale

“In traditional gravure printing, ink is scraped into the recessed features of a printing plate, in which pigment particles are randomly dispersed,” explains Tobias Kraus of the nanopatterning team in Zurich. “In our high-resolution printing, a directed self-assembly process controls the arrangement of nanoparticles on the printing plate or template. The entire assembly is then printed onto a target surface, whereby the particle positions are precisely retained at a resolution that is three orders of magnitude higher than in conventional printing.”

The printing template geometries explored include lines to produce closely-packed nanoparticle wires, which could be used in molecular electronics; regularly spaced arrays of gold particles as seeds for nanowire growth; and arbitrary arrangements, such as the printed replica of the sun. The long-range accuracy, which measures the deviation from the desired arrangement on a large area, is similar to that of microcontact printing methods. The next steps will be to refine the method to achieve even higher accuracies, as would be required for large-scale integration in microelectronics, as well as to extend the method to print even smaller particles.

IBM’s leadership in nanotechnology

Today’s announcement builds on IBM’s leadership in nanotechnology: twenty-one years after Gerd Binnig and Heinrich Rohrer of the IBM Zurich Research Lab won the Nobel Prize in Physics for their invention of the scanning tunneling microscope (STM), which opened the door to the world of individual atoms. Since then, IBM scientists and engineers continue to break new ground in nanoscience and nanotechnology.

The breakthrough also comes just two weeks after IBM unveiled two major scientific achievements at the atomic scale: one of them a major step in understanding the ability for single atoms to maintain a specific magnetic direction, making them suitable for future data storage applications and the other a novel, very robust and stable single-molecule switch that can be used as a modular building block for molecular computers.

The scientific paper entitled "Nanoprinting printing with single-particle resolution" has been published in Nature Nanotechnology, Vol 2, No 9, pp. 570 - 576. The authors of the report are Tobias Kraus, IBM Zurich Research Laboratory and ETH Zurich, Laurent Malaquin, Heinz Schmid, Walter Riess, and Heiko Wolf of IBM's Zurich Research Laboratory in Switzerland, and Nicholas Spencer of the ETH Zurich, Switzerland.

About the IBM Zurich Research Laboratory

The IBM Zurich Research Laboratory (ZRL) is the European branch of IBM Research. This worldwide network of some 3500 employees in eight laboratories around the globe is the largest industrial IT research organization in the world. ZRL's spectrum of research activities ranges from basic science and fundamental research in physics and mathematics, to the development of computer systems and software, to the design of novel business models and services.