Nature 467, 692–695 (2010)

The random Brownian motion experienced by particles in solution can be defied with techniques such as optical trapping in which focused laser beams are used to hold individual objects in place. However, these methods can require sophisticated equipment and trapping of nanoscale objects remains a significant challenge. Madhavi Krishnan and colleagues at ETH Zurich in Switzerland have now created an electrostatic trap that can hold particles with diameters from 20 to 100 nm in place for several hours.

The trap uses fluidic channels formed between a silicon dioxide surface and a glass surface. Grooves and pocket-shaped nanostructures are etched into the silicon dioxide, creating compartments between the two surfaces that are around 300 nm high. The walls of these compartments become negatively charged when exposed to water, and negatively charged particles that are suspended in the water can then be trapped in the compartments owing to electrostatic repulsion.

Krishnan and colleagues illustrate the capabilities of their technique by trapping gold nanoparticles, polymer beads and lipid vesicles. The particles can be trapped without external intervention and the success of the trap relies primarily on the electric charge of the object, rather than its mass, volume or dielectric function. As a result, the Swiss team suggests that under the right conditions they should be able to trap single proteins.