The Swiss nano-alphabet

A Swiss microsystems laboratory headed by Jürgen Brugger at the École Polytechnique Fédérale de Lausanne developed a new method to place nanoparticles on a surface. No one will be surprised that the Swiss accomplished great precision of 1 nm at this task. Thus far, the greatest measure of positioning accuracy was, with luck, 10-20 nm. This opens new perspectives for nano devices such as miniaturized optical and electro-optical nanodevices including measuring sensors where predetermined and selective placement onto large-area substrates such as 1 cm² is needed to utilize the benefits of nanoparticle assembly.

 

Like most great solutions, this one is simple and elegant: gold nanoparticles suspended in a liquid are first heated so they gather in one spot, and then drawn across the surface. Not unlike a miniature golf course, the surface is lithographed with funneled traps and auxiliary sidewalls, thus patterned with barriers and holes. When the nanoparticles hit a barrier (an auxiliary sidewall), they disengage from the liquid and can be deterministically directed to sink into the hole, attaining simultaneous control of position, orientation and interparticle distance at the nanometer level. In this way, position and orientation of the slightly oblong gold nanorods can be steered very precisely. The Swiss research group demonstrated this by writing the world’s smallest version of the alphabet and also shaped complex patterns. This will open new doors for vastly improved assembly of nanodevices.

 

In light of groundbreaking advances in the field, it comes as no surprise that the 2016 Nobel Memorial Prize in Chemistry was just awarded to Jean-Pierre Sauvage (U. Strasbourg), J. Fraser Stoddart (Northwestern U.) and Bernard L. Feringa  (U. Groningen) for work on nanometer-size “molecular machines” that feature characteristics of “smart materials” – an emerging area not only of materials science that opens extremely bright perspectives to nanotechnology overall, bringing nanomachines and microrobots within reach.