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Sound waves on a microchip for precision thin film manufacturing

article image RMIT researcher Dr Amgad Rezk with the lithium niobate chip.

RMIT University researchers say they can use sound waves and the surface of a microchip to enable precision micro- and nano-manufacturing.

Professor James Friend, Director of the MicroNano Research Facility at RMIT, said the researchers had developed a portable system for precise, fast and unconventional micro- and nano-fabrication.

“By tuning the sound waves, we can create any pattern we want on the surface of a microchip,” Professor Friend said.

The researchers demonstrated the use of high-frequency sound waves to precisely control the spread of thin film fluid along a specially-designed chip, in a paper published on 25 June 2014 in Proceedings of the Royal Society A.

The researchers found that thin film liquid either flows towards or away from high-frequency sound waves, depending on its thickness. The research shows that when the liquid is ultra-thin ­– at nano and sub-micro depths – it flows away from the high-frequency sound waves.

The flow reverses at slightly thicker dimensions, moving towards the sound waves. But at a millimetre or more in depth, the flow reverses again, moving away.

They also unravelled the complex physics behind the process, enabling precise control and direction for the application of thin film liquid at a micro and nano-scale.

This "acoustowetting" process works on a chip made of lithium niobate, because the material is able to convert electrical energy into mechanical pressure.

The surface of the chip is covered with microelectrodes and the chip is connected to a power source, with the power converted to high-frequency sound waves. Thin film liquid is added to the surface of the chip, and the sound waves are then used to control its flow.

Current thin film manufacturing lacks precision: structures have to be physically spun around to disperse the liquid and coat components with thin film.

The research could have applications ranging from thin film coatings for paint and wound care to 3D printing, micro-casting and micro-fluidics.

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