An acoustic rectifier

Abstract

The detection of acoustic signals is of relevance for a range of practical applications, for example in medical diagnostics. However, whereas rectification of electric current and other energy forms such as thermal flux has been demonstrated, acoustic rectification has not yet been achieved. Here, on the basis of the earlier theoretical proposal of an 'acoustic diode', we present the first experimental demonstration of a rectified energy flux of acoustic waves. A one-dimensional acoustic rectifier is fabricated by coupling a superlattice with a layer of ultrasound contrast agent microbubble suspension. A significant rectifying effect is observed within two frequency bands at locations that agree well with theoretical predictions. Following optimization of the concentration of the microbubble suspension, rectifying ratios can be as high as ~10(4). This realization of an acoustic rectifier should have substantial practical significance, for example in the focusing of ultrasound in medical applications.

PT-Symmetric Acoustics

“…Previously, asymmetric acoustic transport has also been explored using nonlinear material [22]. Other structures of one-way acoustic devices, such as asymmetric nonlinear bead chains, have been demonstrated thereafter [23].…”

“…Recent advancements in man-made materials ("metamaterials") have resulted in intriguing achievements in acoustic and phononic transport manipulation [1]. These discoveries include dynamic negative density and a bulk modulus [2][3][4][5][6][7][8], subwavelength imaging [9][10][11], acoustic and surface wave cloaking [12][13][14][15], a phononic band gap [16,17], extraordinary acoustic transmission [18,19], Anderson localization [20], and asymmetric transmission [21][22][23][24][25]. These works, so far, are based on the modulation of the real part of the acoustic parameters.…”

Non-reciprocal and highly nonlinear active acoustic metamaterials

“…Thus, the extended range of material parameters provided by metamaterials has lead to the implementation of devices such as acoustic lenses [1][2][3][4][5][6] , or even exotic structures designed using coordinate transformation methods 7,8 . Recently, significant attention has been given to unidirectional devices that pass acoustic energy in only one direction [9][10][11][12][13][14][15] and therefore mimic the general behaviour of diodes in the microwave regime, and Faraday rotator media in the optical domain.…”

Granular acoustic switches and logic elements

“…In analogy with electrical and optical counterparts [1][2][3] , a growing number of papers have proposed and tested acoustic diodes [4][5][6][7][8][9] . For example, directional acoustic propagation was shown using a superlattice coupled with a nonlinear material 4 . Other research exploited nonlinear bifurcation phenomena to realize a tunable acoustic diode 5 .…”