Holographic laser tweezers in microscopy

We intend to develop new applications in the fast growing field of microscopic manipulations with optical forces in the micro- and nanoregime. This is done by steering laser tweezers with an advanced holographic method providing hithero unequaled flexibility. The method employs a recently available, very high resolution liquid crystal screen, which is used to display computer generated holograms in real-time. The holograms diffract a laser beam in a predesigned way to create specialized optical traps in a microscope object plane. This provides the flexibility of trapping a large number of microscopic particles, like cells, cell components, bacteria or nanotubes at the same time in individually steerable traps, and to move them interactively to any desired three-dimensionally controllable position in the microscope field of view. Using sophisticated holographic methods for wavefront control of the laser beam it will be also possible to shape the trapping light field such that only objects with a desired size and shape are trapped. This morphology-dependence has a high practical potential in medical diagnostics, as e.g. for automatically fishing for degenerate cells in cell suspensions. Additionally, the high resolution holographic beam steering provides the possibility to create special laser modes which transfer orbital angular momentum to microscopic particles. These laser modes can be transformed into pumps and "conveyer belts" which create a precisely controlled dynamic micro-flow in a liquid volume or at an air-liquid surface, even with static laser fields. Applications involve the automatic sorting of cells in an optically induced flow, the creation of microfluidic devices enabling the mixing of minute amounts of liquids under microscopic supervision, or they can be even a first step to the realization of an optical workshop in the nanoregime, e.g. used for the controlled automatic assembling of selected particles (like nanotubes) into predesigned micro-conglomerates.

The project`s most important results (scientific advances) from the project leader`s point of view should be presented on a single page (DIN A4, 11 pt type, line spacing 1.5) in a way that is accessible to the general public. It is important to use as few technical terms as possible, so that the text is interesting and understandable to people not familiar with the field. The main point should be placed at the start of the summary. Please keep descriptions of the issues addressed and results obtained short and succinct. Possible applications to or implications for social, cultural, ecological, medical, economic or technological areas should be briefly mentioned. The summary should be submitted as hardcopy and also electronically both in German and in English (in Word for Windows format, without special symbols). The summaries will be made available via the FWF`s project database. The FWF will not edit the summaries, so the authors bear full responsibility for the contents. We intend to develop new applications in the fast growing field of microscopic manipulations with optical forces in the micro- and nanoregime. This is done by steering laser tweezers with an advanced holographic method providing hithero unequaled flexibility. The method employs a recently available, very high resolution liquid crystal screen, which is used to display computer generated holograms in real-time. The holograms diffract a laser beam in a predesigned way to create specialized optical traps in a microscope object plane. This provides the flexibility of trapping a large number of microscopic particles, like cells, cell components, bacteria or nanotubes at the same time in individually steerable traps, and to move them interactively to any desired three-dimensionally controllable position in the microscope field of view. Using sophisticated holographic methods for wavefront control of the laser beam it will be also possible to shape the trapping light field such that only objects with a desired size and shape are trapped. This morphology-dependence has a high practical potential in medical diagnostics, as e.g. for automatically fishing for degenerate cells in cell suspensions. Additionally, the high resolution holographic beam steering provides the possibility to create special laser modes which transfer orbital angular momentum to microscopic particles. These laser modes can be transformed into pumps and "conveyer belts" which create a precisely controlled dynamic micro-flow in a liquid volume or at an air-liquid surface, even with static laser fields. Applications involve the automatic sorting of cells in an optically induced flow, the creation of microfluidic devices enabling the mixing of minute amounts of liquids under microscopic supervision, or they can be even a first step to the realization of an optical workshop in the nanoregime, e.g. used for the controlled automatic assembling of selected particles (like nanotubes) into predesigned micro-conglomerates.