Hielscher - Ultrasound Technology

The sonotrodes are the tools that transmit the ultrasound into the liquid. The selection of the sonotrodes depends on the sample volume and on the required ultrasound intensity. Thin-bodied sonotrodes achieve very high amplitudes up to 250µm, that result in very high ultrasound power densities under the oscillating end surface. A small but very intensive cavitation zone is generated. The bigger the diameter, the higher is the ultrasound power, that is transmitted via the consequently bigger end face of the sonotrode. The ultrasound power density i.e. the ratio between power and oscillating surface becomes smaller. The cavitation zone becomes larger but less intensive.

A titanium alloy has proven to be the best sonotrode material as it allows very high amplitudes and as it is resistant to most liquids. Therefore this titanium alloy is the standard material for our sonotrodes and the ultrasonic processors are adjusted to it. For special application cases we manufacture sonotrodes made of stainless steel, glass or ceramics. The max. amplitudes of the sonotrodes made of these materials are significantly below those of the titanium sonotrodes.

The lengths of the sonotrodes are determined by lambda/half. If the ultrasonic processor has the frequency of 24kHz, the titanium sonotrode has approx. the length 100mm but can also be manufactured in manifold lengths. Sonotrodes with O-rings or oscillating-free flanges are used for the input of ultrasound in flow cells or in closed or pressurized systems.

The cavitation, that takes place at the sonotrode surface, results in an abrasional effect. At the max. amplitude, approx. 1mm of the sonotrode abrades within 1000 hours of operation in water.The frequency scanning system of our ultrasonic processors raises then automatically the frequency, so that an abrasion of up to 5mm of the sonotrode does not result in a considerable loss of power.