Optical Tweezers

Recent years have shown great advances in the field of microscopy, especially with laser based approaches. One of these exploits light to control and steer objects at the cellular scale. These laser traps are called optical tweezers (OT) and are used for contact-free control of micro- and nanometer sized structures. The radiation pressure of light as well as light gradients and polarization are used to create optical forces. One of many powerful appplications is the control of living cells and bacteria in both 2D and 3D.

Comparing to alternative methods of control of cell sized objects, OT has the advantage of

  • Sub-micrometer position resolution
  • No direct contact with the sample, sterile
  • Forces in the pico- to femtonewton range

A major drawback of OT is heating due to absorption, which can be reduced by using wavelengths in the infrared effectively reducing medium-heating.