Wave-momentum shaping for moving objects in heterogeneous and dynamic media

Light and sound waves can move objects through the transfer of linear or angular momentum, which has led to the development of optical and acoustic tweezers, with applications ranging from biomedical engineering to quantum optics. Although impressive manipulation results have been achieved, the stringent requirement for a highly controlled, low-reverberant and static environment still hinders the applicability of these techniques in many scenarios. Here we overcome this challenge and demonstrate the manipulation of objects in disordered and dynamic media by optimally tailoring the momentum of sound waves iteratively in the far field. The method does not require information about the object’s physical properties or the spatial structure of the surrounding medium but relies only on a real-time scattering matrix measurement and a positional guide-star. Our experiment demonstrates the possibility of optimally moving and rotating objects to extend the reach of wave-based object manipulation to complex and dynamic scattering media. We envision new opportunities for biomedical applications, sensing and manufacturing.

Ever since the emergence of optical tweezers1,2, the non-contact manipulation of objects using electromagnetic3,4 and acoustic waves5,6,7 has become a central paradigm in quite diverse fields ranging from optomechanics to bioacoustics. Sound waves, in particular, offer distinct advantages, as they are biocompatible and harmless and their short wavelengths can penetrate a wide range of heterogeneous, opaque and absorbing media. Another key feature of acoustics is its wide frequency range, spanning from hertz to gigahertz, which facilitates the manipulation of particles varying in size from a few centimetres to a few micrometres. In this way, not only Mie8,9,10 and Rayleigh particles can be addressed, but also complex objects including individual biological cells11,12,13.

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