Optofluidic system for laser tweezers has no pesky cover slip

A new version of a type of optofluidic system designed to be used with laser "tweezers" for 3D manipulation of biological cells under a microscope has been created by researchers at Technische Universitvät Ilmenau (Ilmenau, Germany). While the old version requires a 0.17 mm thick glass cover slip between the optofluidic system and the microscope, the new version does not. The new geometry has an important advantage: direct access to the optofluidic system, which allows other analytical tools such as electrodes to be added at any time.

Pre-existing systems of this sort consist of a replicated polydimethylsiloxane (PDMS) fluid-channel system mounted to a standard cover slip; the slip is necessary, as the PDMS channel surfaces, which are created with a silicon or photoresist mold, are not of optical quality. In contrast, the new version is replicated using a polymethylmethacrylate (PMMA) master mold of optical quality, allowing the cover (through which the specimen cells are viewed) to be part of the PDMS channel structure. The PMMA mold is created through micromilling, a precision process that uses a diamond tool with a diameter of 1 mm that rotates at a speed of 55,000 rpm. Optical trapping and viewing of 3 µm polystyrene particles was successfully performed. Contact Stefan Sinzinger at[email protected].

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