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nanotimes News in Brief

if we are to understand why matter and antimatter did not completely cancel each other out after the Big Bang - in other words, if we are to comprehend how the universe actually came into existence.

S. Ulmer, C.C. Rodegheri, K. Blaum, H. Kracke, A. Mooser, W. Quint, J. Walz: Observation of Spin Flips with a Single Trapped Proton, In: Physical Review Letters, Vol. 106(2011), No. 25, June 20, 2011, DOI:10.1103/ PhysRevLett.106.253001: http://dx.doi.org/10.1103/PhysRevLett.106.253001

11-06/07 :: June/July 2011

inspired by sea cucumbers, a soft marine organism whose skin contains multiple collagen fibres and be- comes stiff upon contact. When the animal is calm, these fibres are independent of each other.

But as soon as it is touched, it secretes peptides that enable the fibres to bond together and form a sort of scaffolding which makes its skin rigid. This mechanism is reversible at will and makes the skin of the sea cucumber a natural smart material.

In the scope of the National Research Programme „Smart Materials“ (NRP 62), researchers from the Adolphe Merkle Institute, Université de Fribourg, Switzerland, are taking cues from sea cucumbers to develop shape memory polymers. An initial application could comprise the development of an artificial bait for fishing. The researchers from Fribourg are also planning further, more high-tech applications in the medical field.

When Johan Foster, a group leader from the Adol- phe Merkle Institute (AMI) puts an artificial worm at the end of a fishing hook, the bait is perfectly inert. But once it is in the water it starts to wiggle, thus wondrously imitating its natural counterpart. The explanation: when it comes into contact with water, this piece of shape memory polymer regains its initial geometry.

This innovation from the AMI researchers led by professor Christoph Weder and Johan Foster was

In the case of the artificial worm, the AMI resear- chers inserted crystalline cellulose nanofibres in a polymer. These nanofibres are of natural origin and can be gained by dissolving cotton or paper. Despite being structurally simple, their mechanical properties resemble those of carbon nanotubes. When integrated in a polymer, they join together by means of what chemists call hydrogen bonds.

Depending on the size and the concentration of fibres, the composite can be as hard as a CD jewel case. By adding water, however, you can weaken the hydrogen bonds and make the polymer as soft as rubber. Here again, the mechanism is reversible at will, making this composite a smart material. Christoph Weder and Johan Foster are considering more sophisticated applications of their new materi- als in the biomedical area. They could, for example, serve as a substrate for microelectrodes implanted in the brain, which can only be positioned precisely if extremely rigid.

However, it is this very rigidity that accelerates their rejection by the organism. As the intracranial fluids are essentially composed of water, the mate- rials devised by AMI can play a dual role: rigid for