Trapping and moving 3D objects on the nanoscale

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between the spin of an electron and an electric field. ‘‘We use the Rashba effect to produce a magnetic anisotropy [in an ultra-thin ferromagnetic layer], which leads to our control of magnetism,’’ says Barnes. ‘‘We produce the electric field, in part, by an appropriate choice of the magnetic and non-magnetic elements in our bi-layer and by generating an electric field with a capacitor.’’ The team – Barnes from the University of Miami Coral Gables Florida and colleagues

Materials Today  Volume 17, Number 4  May 2014

Jun’ichi Ieda and Sadamichi Maekawa all based at the Advanced Science Research Center, of the Japan Atomic Energy Agency, in Tokai, Ibaraki – explains that thin magnetic films with a controllable perpendicular magnetic anisotropy (PMA) have important applications, not only for MRAM and logic units, but also for electromechanical devices, such as actuators. The researchers’ theoretical work on the phenomena for ferromagnetic/metal and ferromagnetic/oxide insulator interfaces will

now be followed up with experiments to verify the basic principles of the current study. ‘‘The Japanese are working on first principle calculations of the materials,’’ Barnes told Materials Today. ‘‘More important is that there is interest to test the ideas experimentally. We have some suggestions for bi-layer combinations which work more efficiently than existing systems.’’ David Bradley

Trapping and moving 3D objects on the nanoscale Researchers from ICFO – The Institute of Photonic Sciences in Spain have developed a new non-invasive approach to the manipulation of individual nano-objects in three dimensions. The team, led by Romain Quidant, showed for the first time the ability to utilize near-field optical tweezers to trap and manipulate single 50 nm dielectric objects in 3D, which could lead to new techniques for controlling such objects, including heat-sensitive biospecimens. Optical tweezers and using light to manipulate small objects, which was invented in Bell Labs as long ago as the 1980s, has had a fundamental effect on both biological systems and quantum optics. However, the technology has been limited by an inability to directly trap objects smaller than a few hundred nanometers. This has led to an increase in research into nano-tweezers based on plasmonics that could trap nanoscale objects, including proteins and nanoparticles, without overheating and damaging the sample. This new study, published in Nature Nanotechnology [Berthelot, et al., Nat. Nanotechnol. (2014), doi:10.1038/nnano.2014.24], demonstrated the trapping and 3D displacement of specimens as small as tens of nanometers with non-invasive laser intensity. The team had previously found that, by

focusing light on a very small gold nanostructure lying on a glass surface that acted as a nano-lens, it was possible to trap a

specimen near the metal where the light is concentrated. Although this proof of concept demonstrated the mechanism, it did not allow any 3D manipulation necessary for practical applications. The new research went further by implementing the concept of plasmonic nano-tweezers at the extremity of a tapered mobile optical fiber, nano-engineered with a bowtie-like gold aperture. Crucial to the approach was that trapping and monitoring the trapped specimen could be achieved through the optical fiber, thereby manipulating nano-objects in a simple and manageable way outside the lab. The nano-tweezers were completely autonomous and free of bulky optical elements, with the trapping allowing the specimen to be moved over tens of micrometers for several minutes. The innovative approach could lead to a wide range of new research directions that rely on non-invasive manipulation of objects at the single molecule/virus level. This could especially be the case in medicine, where it could provide a better understanding of the biological mechanisms underlying how diseases develop, but could also find value in a range of different fields. The next stage for the team is to apply their nano tool to some practical problems. Laurie Donaldson

research published in Acta Biomaterialia this month [Menon, et al., Acta Biomater. (2014), doi:10.1016/j.actbio.2014.01.033]. Kytai Nguyen of The University of Texas at Arlington, Arlington and the Southwestern

Medical Center at Dallas and colleagues point out that there have been no studies investigating the details of such nanoparticles for the delivery of protein or nucleic acids to the lung. They have now studied

Optical nano-tweezers are able to control 3D objects.

Pulmonary protein and DNA delivery Polymeric nanoparticles that are easily modified and can carry therapeutic and diagnostic agents deep into the lung can also be made biocompatible and have localized action with few side effects, according to

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