In order to observe the individual particles in a solution, Prof. Madhavi Krishnan and her co-workers entice each particle into an electrostatic trap. It works like this: between two glass plates the size of a chip, the researchers create thousands of round energy holes. The trick is that these holes have just a weak electrostatic charge. The scientists than add a drop of the solution to the plates, whereupon each particle falls into an energy hole and remains trapped there. But the particles do not remain motionless in their trap. Instead, molecules in the solution collide with them continuously, causing the particles to move in a circular motion. We measure these movements, and are then able to determine the charge of each individual particle, explains Prof. Madhavi Krishnan.
Put simply, particles with just a small charge make large circular movements in their traps, while those with a high charge move in small circles. This phenomenon can be compared to that of a light-weight ball which, when thrown, travels further than a heavy one. The US physicist Robert A. Millikan used a similar method 100 years ago in his oil drop experiment to determine the velocity of electrically charged oil drops. In 1923, he received the Nobel Prize in physics in recognition of his achievements. But he examined the drops in a vacuum, Prof. Krishnan explains. We on the other hand are examining nano particles in a solution which itself influences the properties of the particles.
Electrostatic charge of nano drugs packages
For all solutions manufactured industrially, the electrical charge of the nano particles contained therein is also of primary interest, because it is the electrical charge that allows a fluid solution to remain stable and not to develop a lumpy consistency. With our new method, we get a picture of the entire suspension along with all of the particles contained in it, emphasizes Prof. Madhavi Krishnan. A suspension is a fluid in whi
|Contact: Prof. Dr. Madhavi Krishnan|
University of Zurich