The development of optical tweezers dates back to the 1970s when a Bell Laboratory scientist, Arthur Ashkin, first discovered the effect of gradient forces and optical light scattering on a particle. Shortly thereafter, Drs. Ashkin and JM Dziedzic were successfully able to lift a particle in air by creating a single-beam trap. However, it was not until 1986 that the concept of the modern optical tweezer was born. In 1987, Dr. Ashkin and his colleagues first applied the technology to the biological sciences. Throughout the 1990s, the technology was primarily experimental, but in the early 2000s, companies began to commercialize it.

In simple terms, optical tweezers use focused laser beams to manipulate particles in the nano to micro size range. Optical tweezers oftentimes utilize the technology found in commercial optical microscopes, primarily the objective and condenser, to tightly focus the laser beam on the sample plane which create a strong electrical field gradient and an optical trap. When the particles come in contact with the optical trap, scientists can manipulate them.

Optical tweezers can be used to manipulate a variety of particles, including those in biological samples, such as DNA, proteins, carbohydrates and living cells. As a result, they can be used to alter cellular structures, sort cells and test the breakage points of DNA strands and cellular structures. Furthermore, they can be used to test the elasticity of cells and for microbiology applications.

The advantage of optical tweezers is that they can manipulate particles without physical contact. Using lasers with wavelengths of 600–1064 nm, scientists can greatly minimize, and in most cases eliminate, the damage caused to biological particles by using optical tweezers. Nevertheless, current optical tweezers tend to be low throughput and expensive.

There are only a handful of companies making optical tweezers. Carl Zeiss MicroImaging GmbH manufactures the PALM MicroTweezers, which are capable of manipulating particles in 3D (in the XYZ coordinates). Elliot Scientific offers several different models ranging from those capable of 3D manipulation, to other configurations with a variety of laser options and force-measurement capabilities. MMI Molecular Machines & Industries AG manufactures the mmi CellManipulator, which can manipulate cellular and sub-cellular particles sized 0.1–200 mm. JPK Instruments offers a nano-scale system called the nanoTracker. The company entered the market by acquiring Nambition in 2006 (see IBO 8/31/06).

The current market for optical tweezers is estimated to be less than $10 million. While the technology is currently used for research, it shows great promise in the therapeutic and medical fields. Although the hefty initial system price tag has been a limiting factor, increased governmental funding for stem cell applications is expected to be a driving force for the market.

Optical Tweezers at a Glance:

Leading Suppliers

• Carl Zeiss MicroImaging

• Molecular Machines and

Industries

• JPK Instruments

Largest Markets

• Academia

• Government

• Biotechnology

Instrument Cost

• $100,000–$500,000