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Abstract Leveraging robot-assisted technology to manipulate tiny objects has shown significant potential in the fields of engineering, chemistry, and biology. However, achieving high-resolution, non-invasive manipulation of objects shielded by biological barriers remains a major challenge. In this work, we present a robot-assisted acoustic vortex end effector system capable of generating acoustic vortex beams for contactless manipulation of small objects. First, instead of generating a fixed acoustic vortex beam, our acoustic end effector can tune the chirality of the vortex beam by adjusting the topological charge number encoded in the holographic lens, allowing for customization of the size of the corresponding potential well to accommodate various sizes of trapped particle. Second, by leveraging acoustic vortex beams as a non-invasive manipulator, we successfully achieved acoustic manipulation through biomimetic barriers. In a proof-of-concept experiment, we demonstrated the high-resolution contactless acoustic manipulation of a plastic ball (3 mm diameter) within a straight phantom mimic-vessel. Third, by combining the acoustic vortex end effector with a real time ultrasound imaging system, our approach enables continuous, real-time monitoring of the entire acoustic manipulation process. This integration paves the way for acoustic trapping and manipulation in non-transparent environments. Overall, our research demonstrates the advantages of acoustic manipulation technologies in biomedical and clinical applications, offering a biocompatible solution for medical interventions in the future. 

Abstract Ultrasonics structural health monitoring (SHM) is widely recognized as an effective technique that enables early damage detection in large-scale structures and helps prevent potential catastrophic failures. Ultrasonic phased array technology has gained prominence in SHM due to its ability to inspect a large area with high spatial resolution. However, conventional systems often rely on physical wired sensor networks, limiting their deployment for hard-to-access regions. In this study, we present a wireless ultrasonic phased array system capable of dual-mode operation for both wall thickness measurement and structural damage detection. The system integrates wireless power transfer (WPT) modules and customized matching circuits, enabling efficient and flexible deployment. Proof-of-concept experiments demonstrate successful wall thickness evaluation and accurate defect localization in metallic structures using both delay-and-sum (DAS) and minimum variance (MV) imaging methods, with the MV algorithm offering improved imaging resolution. Future work will focus on advancing real-time monitoring through machine learning, enabling 3D imaging, and extending system applicability to anisotropic composite materials. 

Abstract The development of smart materials capable of dynamic shape morphing and rapid responsiveness has garnered significant interest for applications in soft robotics, tissue engineering, programmable materials, and adaptive structures. Hydrogels, owing to their intrinsic biocompatibility and flexibility, are promising candidates for such systems. Embedding micro-scale materials within hydrogel networks can further enhance their mechanical and functional properties. In this study, we present a hybrid fabrication platform that integrates surface acoustic wave (SAW)-based acoustofluidics with digital light processing (DLP) photopolymerization to fabricate smart hydrogel composites with programmable shape-memorable behavior. Using the SAW-induced acoustic potential field, silicon carbide (SiC) micro-whiskers are aligned within a custom UV-curable hydrogel ink and subsequently fixed via high-resolution DLP photopolymerization. This dual-control approach enables independent manipulation of micro-whisker orientation and structural geometry. Numerical simulations and Laser Doppler vibrometry-based validation were employed to characterize the acoustic field. To evaluate shape-memory behavior, the fabricated hydrogels were subjected to dehydration and rehydration cycles. The resulting shape transformations, driven by internal stress gradients within the aligned microparticle framework, enabled humidity-responsive actuation. This work establishes a novel strategy for constructing 4D-printed smart hydrogels, offering a versatile platform for the development of next-generation programmable materials and adaptive structures. 

Abstract Precise manipulation of nanomaterials has shown great potential in facilitating the fabrication of functional hydrogel nanocomposites in applications such as soft robotics, biomedicine, structural health monitoring, and wearable sensing. Surface acoustic wave (SAW)-based acoustofluidics offers a contactless approach for nanoparticle manipulation. Meanwhile, digital light processing (DLP) has been extensively utilized in the hydrogel printing process due to its high-resolution fabrication capabilities. This study presents an innovative SAW acoustofluidics-assisted DLP system, enabling the patterning of nanoparticles embedded in matrix materials while facilitating programmed light exposure for the controllable photopolymerization of customized hydrogel nanocomposites. Instead of utilizing the acoustic potential field generated by SAWs, we leverage the accompanying electric field due to the piezoelectric effect of the lithium niobate (LiNbO3) substrate to generate electric field, enabling the electric field-driven patterning of multi-walled carbon nanotubes (MWCNTs) Laser Doppler vibrometry confirms the SAW-generated acoustic intensity fields. The analytical simulation together with the scanned data predicted the co-current electric field predicted the distribution of MWCNTs. By applying a programmed light pattern, we successfully fabricated hydrogel nanocomposites in the shape of a VT logo and produced hydrogel nanocomposite sensors. The capabilities of printed hydrogel nanocomposite sensors were demonstrated through beam vibration sensing, proving its potential application in structural health monitoring. The fabricated sensors demonstrated the capability to track finger movements, indicating their potential for wearable sensing applications. In summary, this study offers a unique approach for nanocomposites fabricating multi-material integration and material anisotropy control, thereby facilitating advanced smart material development. Future work will focus on exploring the fabrication of hydrogels containing other types of nanomaterials to enhance material conductivity and achieve other functions, aiming with the goal of developing nanocomposite sensors for applications in soft robotics, biomedicine, structural health monitoring, and wearable sensing. 

The graphic illustrates how an external acoustic field stabilizes the SEI layer by enhancing lithium-ion mass transfer at slip lines and kinks, reducing pit formation and promoting a more uniform SEI, ultimately improving battery performance. 

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. 

Anisotropic collagen-based biomaterials have gained significant attention in the fields of tissue engineering and regenerative medicine. They have shown great potential for wound dressing, corneal grafting, and exploring the mechanism of cancer cell invasion. Various external physical field-based methods for the fabrication of anisotropic collagen-based biomaterials have been developed, including electrospinning, microfluidic shearing, mechanical loading, and so on. In this study, we put forward an acoustic streaming-based method that uses acoustic wave-induced fluid streaming to control collagen self-assembly and fiber arrangement. Our acoustic device leverages a piezoelectric transducer to generate traveling acoustic waves in fluids, and the wave-fluid interaction further induces fluid streaming, known as acoustic streaming. If the fluid contains collagen macromolecules, the acoustic streaming is able to affect the collagen self-assembly process to create biomaterials containing directionally arranged collagen fibers along the streaming velocity direction. Therefore, this acoustic streaming-based method allows for manufacturing collagen hydrogel layers that contain acoustically arranged collagen fibers and have controlled anisotropic material properties. We performed a series of proof-of-concept experiments by using a fabricated acoustic device to control the self-assembly process of collagens loaded in a Petri dish. Our results show the effectiveness of arranging collagen fibers that follow the flow direction of acoustic streaming. To better understand the collagen manipulation mechanism, we used particle image velocimetry to characterize the acoustic wave-induced fluid streaming. We expect this study can contribute to the fabrication of collagen-based anisotropic biomaterials for biomedical applications. 

aser Doppler vibrometry and wavefield analysis have recently shown great potential for nondestructive evaluation, structural health monitoring, and studying wave physics. However, there are limited studies on these approaches for viscoelastic soft materials, especially, very few studies on the laser Doppler vibrometer (LDV)-based acquisition of time–space wavefields of dispersive shear waves in viscoelastic materials and the analysis of these wavefields for characterizing shear wave dispersion and evaluating local viscoelastic property distributions. Therefore, this research focuses on developing a piezo stack-LDV system and shear wave time–space wavefield analysis methods for enabling the functions of characterizing the shear wave dispersion and the distributions of local viscoelastic material properties. Our system leverages a piezo stack to generate shear waves in viscoelastic materials and an LDV to acquire time–space wavefields. We introduced space-frequency-wavenumber analysis and least square regression-based dispersion comparison to analyze shear wave time–space wavefields and offer functions including extracting shear wave dispersion relations from wavefields and characterizing the spatial distributions of local wavenumbers and viscoelastic properties (e.g., shear elasticity and viscosity). Proof-of-concept experiments were performed using a synthetic gelatin phantom. The results show that our system can successfully generate shear waves and acquire time–space wavefields. They also prove that our wavefield analysis methods can reveal the shear wave dispersion relation and show the spatial distributions of local wavenumbers and viscoelastic properties. We expect this research to benefit engineering and biomedical research communities and inspire researchers interested in developing shear wave-based technologies for characterizing viscoelastic materials.