Basic laser tweezers.

The basic information has been provided here for designing and building a laser tweezers system for force measurements. If force measurements are not required, then the considerations about the analysis system, a fine piezo stage, and stability are less important. For the initial alignment and characterization of the system, red blood cells provide an easily trapped sample. For a difficult test sample, the smaller latex beads (0.15-0.3 micron in diameter) are stable and easy to obtain. Anyone setting up laser tweezers is encouraged to see a working tweezers system and to compare samples with that system. Everyone has a different background, and there may be aspects critical for you that have not been discussed here. More sophisticated systems are described later in this book.