Piezoelectric-based flexible transducers

Fig. 3 Spotting tools for non-contact printing a Bubble ink-jet A heating coil locally heats the loaded sample, resulting in a changed viscosity and expansion of fluids. The generated droplet can be easily expelled from delivery nozzles, b Microsolenoid A microsolenoid valve, fitted with the ink-jet nozzle is actuated by an electric pulse transiently opening the channel and dispenses a defined volume of the pressurized sample, c Piezo ink-jet A piezoelectric transducer that is fitted around a flexible capillary confers the piezoelectric effect based on deformation of a ceramic crystal by an electric pulse. An electric pulse to the transducer generates a transient pressure wave inside the capillary, resulting in expulsion of a small volume of sample...

The two major types of electromechanical transducers are based on the piezoelectric and magnetostrictive effects the former is most commonly used to power bath- and probe-type sonicators. Although more expensive than mechanical transducers, electromechanical transducers are by far the most flexible and widely used. Laser-induced ultrasound is a more recent type of transducer. 

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