Nanometer-resolved collective micromeniscus oscillations through optical diffraction
Helmut Rathgen, Kazuyasu Sugiyama, Claus-Dieter Ohl, Detlef Lohse, Frieder Mugele
A paper was published in Physical Review Letters (99, 214501 (2007)) in which optical diffraction was used to show that ultrasound can make a field of liquid-gas menisci oscillate. This publication has drawn attention from several national papers including the newspaper “NRC Handelsblad” (article) and will also appear soon in the Belgian newspaper “de Standaard”.
We study the dynamics of periodic arrays of micrometer-sized liquid-gas menisci formed at superhydrophobic surfaces immersed into water. By measuring the intensity of optical diffraction peaks in real time, we are able to resolve nanometer-scale oscillations of the menisci with submicrosecond time resolution. Upon driving the system with an ultrasound field at variable frequency, we observe a pronounced resonance at a few hundred kilohertz, depending on the exact geometry. By modeling the system using the unsteady Stokes equation, we find that this low resonance frequency is caused by a collective mode of the acoustically coupled oscillating menisci.
The full article can be found here.