"Self-assembled organic nanofibres, which we know from experience are totally impossible to remove from any normal surface, can be lifted straight off from a nanotube forest," Peter Bøggild told nanotechweb.org. "It is a bit like lifting a fingerprint without damaging it."

Bøggild and colleagues created arrays of multiwalled carbon nanotubes by plasma-enhanced chemical vapour deposition onto nickel-coated silicon wafers. The resulting tubes were around 1 µm tall and vertically aligned. They tested the properties of the nanotube forest surface by adding and then removing nanofibres of para-hexaphenylene, which had a breaking stress of just 20 MPa.

"The sharp tip we use to lift off the organic nanofibres can go down between the nanotubes, under the nanofibre, and really lift it off," said Bøggild. "The nanotubes are flexible and this makes the surface strangely compliant."

The researchers say that this combination of low stiction and compliance enables even structures that assemble by nothing but weak van der Waals forces to be released without damage.

"[This finding] means that the notorious stickiness of even the most soft and fragile materials, which makes them immobilize on any surface and prevents further handling, is a problem that has a solution," added Bøggild. "The key is the extremely small effective surface area – any object on a nanotube forest is practically suspended. Soft latex beads that were stuck on Teflon could be pushed around on the nanotube forests like a soccer ball on a playing field."

The team is taking part in two European Union projects to realize reproducible, automated nanomanipulation.

"Adhesion to surfaces is a huge problem and we believe this work to be a crucial step towards three-dimensional nanomanufacturing," said Bøggild. "In any case, the range of objects we are able to interface to microcircuits has suddenly increased dramatically."

Now the team plans to investigate whether nanofibres of para-hexaphenylene are electroluminescent in the same way as the bulk material is. "In that case we have a supersmall organic LED, with blue, polarized light," said Bøggild.

"We are working towards functionalizing the manipulation tools themselves with carbon nanotubes, to facilitate not only picking up structures, but also an easy 'place' operation of the nanostructures," he added. "We call these 'hairy-MEMS' devices; there are some really powerful concepts we are going to try out with nanotube-dressed microtools. It is a totally new route for microsystems and we don't yet know what can be done – we will see."

The researchers reported their work in Nanotechnology.