Special issue on optical tweezers

Optical micromanipulation had come a long way since the seminal work ofArthur Ashkin in the 1970s and 1980s [1, 2]. The pioneering work in these twodecades demonstrated a rather remarkable result, the ability to exert a force on amicroscopic particle using only light. Whilst the forces involved may be small, ofthe order of a few pico-Newtons, this was shown to be enough to stably trap andmanipulate micro-sized dielectric particles and biological cells.Nowadays, with the increased availability of equipment and the reliability ofhigh-power lasers, optical trapping and optical manipulation techniques havebecome commonplace in scientific institutions worldwide. It is, in fact, commonto see optical traps built as undergraduate projects teaching the physics behind theprinciple.Whilst the fundamental science of optical trapping and micromanipulationremains an active field of research in itself, the true success is in its use in diverseareas of science and medicine where it has enabled quantitative studies of a varietyof very interesting phenomena. For example, biologists use optical trapping toidentify diseased cells, chemists use optical trapping to measure surface propertiesand physicists use optical trapping to investigate the interaction between light andmaterials. Recognising that light can modify materials, probe surface properties,and exert forces on a microscopic scale, allows scientists from many disciplines toinvestigate how microscopic effects impact on the macroscopic world.This special issue represents recent work from the diverse range of fields inwhich optical manipulation has made a successful impact. There is work on thelatest developments in interactive control, precision measurements,nano-fabrication and micro-patterning, microfluidics and biophotonics. Many ofthe papers published in this issue are authored by researchers of the current COST(European Cooperation in Science and Technology) Action on OpticalMicro-Manipulation by Nonlinear Nanophotonics. Many of the research articleshave resulted from collaborations and active discussions resulting from recentmeetings and conferences of the Action.As new techniques, tools and resources for optical trapping are continuouslybeing developed and finding a way into interdisciplinary research, the future ofthe field looks bright.