Robotic 3D acoustic manipulator --- acoustic vortex tweezers

What is it about?

Robotic manipulation of small objects has shown great potential for engineering, biology, and chemistry research. However, existing robotic platforms have difficulty in achieving contactless, high-resolution, 4-degrees-of-freedom (4-DOF) manipulation of small objects, and noninvasive maneuvering of objects in regions shielded by tissue and bone barriers. Here, we present chirality-tunable acoustic vortex tweezers that can tune acoustic vortex chirality, transmit through biological barriers, trap single micro- to millimeter-sized objects, and control object rotation. Assisted by programmable robots, our acoustic systems further enable contactless, high-resolution translation of single objects. Our systems were demonstrated by tuning acoustic vortex chirality, controlling object rotation, and translating objects along arbitrary-shaped paths. Moreover, we used our systems to trap single objects in regions with tissue and skull barriers and translate an object inside a Y-shaped channel of a thick biomimetic phantom. In addition, we showed the function of ultrasound imaging–assisted acoustic manipulation by monitoring acoustic object manipulation via live ultrasound imaging.

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Photo by Ketan Yeluri on Unsplash

Photo by Ketan Yeluri on Unsplash

Why is it important?

This paper presents robot-assisted chirality-tunable acoustic vortex tweezers (illustrated in Fig. 1), which leverage a unique chirality-tunable acoustic vortex tweezing device integrated with a programmable robot, for enabling contactless, multifunctional, high-resolution, 4-DOF manipulation of micro- to millimeter-sized single objects in a large 3D space. Moreover, our acoustic device can generate through-biological-barrier acoustic vortex tweezers to trap and manipulate objects in the 3D space shielded by biological barriers (e.g., tissue and skull) and can be integrated with ultrasound phased array imaging for monitoring the acoustic object manipulation process. To enable these abilities, we developed a chirality-tunable acoustic vortex tweezing device that uses a coaxial holographic chiral acoustic lens to transform coaxial incident acoustic waves into counter-chirality–focused acoustic vortex beams (see Fig. 2B). Compared to previous hologram-based acoustic devices, our device is able to switch acoustic vortex chirality and tune the acoustic orbital angular momentum by modulating a dual-frequency excitation signal. Hence, our device can generate acoustic tweezers to not only trap an object at the center of the vortex beam’s ring-shaped potential field but also control the rotation (Ωz) of the trapped object. With the assistance of programmable robotic modules, our acoustic platform further enables high-resolution 3D translation (ux, uy, and uz) of the acoustically trapped micro- to millimeter-sized single objects in a large 3D space. To demonstrate the capabilities of the robot-assisted chirality-tunable acoustic vortex tweezers, a series of experiments were performed showing the trapping of micro- to millimeter-sized single objects, the control of an object’s rotation, as well as the translation of single objects along 2D letter-like and 3D helical paths. We also demonstrated through-biological-barrier acoustic vortex tweezers by transmitting acoustic vortex beams through a ~6-mm-thick tissue with the skin and a ~1.6-mm-thick skull to trap and rotate single objects and translating an object inside a Y-shaped channel in a 36-mm-thick synthetic gelatin phantom, mimicking a tissue with a branched blood vessel. Last, the acoustic tweezing system was combined with ultrasound imaging to monitor the translation of an acoustically trapped object along a complex letter-like path. The functionalities demonstrated by our developed platform prove its huge potential in a wide range of applications ranging from advanced manufacturing to clinical medicine.

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