Optical tweezers, or the single-beam optical gradient force
trap, is becoming a major tool in biology for noninvasive
micromanipulation on an optical microscope. The principles and
practical aspects that influence construction are presented
in an introductory primer. Quantitative theories are also reviewed
but have yet to supplant user calibration. Various biological
applications are summarized, including recent quantitative force
and displacement measurements. Finally, tantalizing developments
for new, nonimaging microscopy techniques based on optical tweezers
are included.
