Faraday wave:
Faraday ripples, named after Michael Faraday, are non-linear standing waves that appear on liquids enclosed by a vibrating receptacle. When the vibration frequency exceeds a critical value, the flat hydrostatic surface becomes unstable. This is known as the Faraday instability. Faraday first described them in an appendix to an article in the Philosophical Transactions of the Royal Society of London in 1831.
If a layer of liquid is placed on top of a vertically oscillating piston, a pattern of standing waves appears which oscillates at half the driving frequency, given certain criteria of instability. This relates to the problem of parametric resonance. The waves can take the form of stripes, close-packed hexagons, or even squares or quasiperiodic patterns. Faraday waves are commonly observed as fine stripes on the surface of wine in a wineglass that is ringing like a bell. Faraday waves also explain the 'fountain' phenomenon on a singing bowl. The Faraday wave and its wavelength is analogous to the de Broglie wave with the de Broglie wavelength in quantum mechanics. Application Faraday waves are used as a liquid-based template for directed assembly of micro scale materials including soft matter, rigid bodies, biological entities (e.g.,individual cells, cell spheroids and cell-seeded micro carrier beads). Unlike solid-based template, this liquid-based template can be dynamically changed by tuning vibrational frequency and acceleration and generate diverse sets of symmetrical and periodic patterns. |
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