Easy tweezy

Researchers at the University of Pennsylvania School of Engineering and Applied Science have developed “electric tweezers” which can manipulate particles and cells on a simple microscope slide.

The research was led by graduate student Brian Edwards, with the help of Nader Engheta and Stephane Evoy, both professors at Penn's Electrical and Systems Engineering Department. While devices with similar functionality using lasers exist, they often cost upwards of £100,000. Edwards' device performs some of the same tasks as laser tweezers, yet at a price anticipated to be in the same range as a high-end desktop computer.

'The tweezers create an electric field that you can use to manipulate almost any object on a microscopic scale. It has the potential of being a powerful tool for research,' said Edwards. 'I hope it will find uses in anything from picking an individual cell out of a culture to fabricating circuits.'

All it would take to use electric tweezers is a computer and a microscope. The tweezers' action occurs on a common glass microscope slide embedded with five electrodes. These electrodes create an electric field that can be used to push, pull, move and spin a selected object in any direction without actual physical contact. Using software Edwards developed, an operator can select an individual object from a microscope image on a computer screen.

The electric tweezers take advantage of the phenomenon known as dielectrophoresis, where electric fields impart a force upon a neutral particle. In essence, the object that is selected surfs over the hills and valleys created by subtly changing the electric field. The principle works best on the microscopic scale, which makes it ideal for this application.

According to Edwards, the electrical field can be attuned to almost anything visible through a microscope. He believes the device will be a boon to smaller laboratories that cannot afford similar devices, as well as to high schools and science hobbyists. Its size, utility and potentially low price could put it into the hands of