The researchers at the Göttingen-based Max Planck Institute can control the frequency with which the water droplets flow through the channels of a microfluidic chip. The chip is a transparent plastic block that is traversed by thin conduits and is approximately nine square centimetres in size. The four transparent tubes transport oil and water into the channels. The researchers control the movement of the droplets by applying an electric field on the chip. The yellow lines shown here are electrodes, while the red and black cables transport the electric current. The researchers have converted the frequency of the droplets into musical notes. (Credit: Nature 2014/MPI for Dynamics and Self-Organization)
Water and oil flow through the tiny channels in the microfluidic chip. Since oil and water do not mix, the water forms tiny droplets in the oil. The researchers in Göttingen applied an AC voltage of up to 1000 Volt in order to control the interval between the droplets travelling through the channels: the higher the applied voltage, the quicker the succession of the droplets – and the higher their frequency. (Credit: Nature 2014/MPI for Dynamics and Self-Organization)
The researchers allocated each of the “droplet frequencies” a different pitch in order to create a melody. The first test was to play the Ode to Joy. The beginning of this Beethoven symphony is easy to recognize, albeit not quite perfect: the frequencies deviate from the original note by up to five percent. These inaccuracies are due to the mechanical properties of the microfluidic chip. Even electric voltage needs time to adopt a new value. This phenomenon is audible as a gliding change in the melody’s pitch.
This video shows water droplets flowing through tiny channels in the microfluidic chip. In order to control the interval between the droplets, the researchers applied an AC voltage of up to 1000 Volt on the chip. The higher the applied voltage, the quicker the succession of the droplets.
