Image of colloid crystal
The new method was used to gather polystyrene particles, which form a well-packed structure called a colloid crystal, as depicted in this image. (Credit: Sen Lab, Penn State)

A simple, inexpensive method uses ultraviolet light to control particle motion and assembly within liquids. The method encourages particles to gather and organize at a specific location within a liquid and, if desired, to move to new locations.

Many applications related to sensors, drug delivery, and nanotechnology require the precise control of the flow of fluids; for example, a fluid pump that relies on this method could potentially replace the bulky and more expensive pumps that require a power source or rely on magnetics or mechanical movement to function.