Programmable motion control and trajectory manipulation of microparticles through tri-directional symmetrical acoustic tweezers

Acoustofluidic precise manipulation: Recent advances in applications for micro/nano bioparticles

Acoustofluidic technologies that integrate acoustic waves and microfluidic chips have been widely used in bioparticle manipulation. As a representative technology, acoustic tweezers have attracted significant attention due to their simple manufacturing, contact-free operation, and low energy consumption. Recently, acoustic tweezers have enabled the efficient and smart manipulation of biotargets with sizes covering millimeters (such as zebrafish) and nanometers (such as DNA). In addition to acoustic tweezers, other related acoustofluidic chips including acoustic separating, mixing, enriching, and transporting chips, have also emerged to be powerful platforms to manipulate micro/nano bioparticles (cells in blood, extracellular vesicles, liposomes, and so on). Accordingly, some interesting applications were also developed, such as smart sensing. In this review, we firstly introduce the principles of acoustic tweezers and various related technologies. Second, we compare and summarize recent applications of acoustofluidics in bioparticle manipulation and sensing. Finally, we outlook the future development direction from the perspectives such as device design and interdisciplinary.

The effect of high-frequency acoustic wave vibration pattern on HKUST's multi-level pore structure

The physical properties of materials are critical to their functionality, and the ability to control these properties using external forces is a significant challenge. In this study, we investigate the effect of three high frequency acoustic wave vibration patterns on the structure and morphology of MOF particles. Our results indicate that while regular vibration patterns generated by SAW can alter particle morphology, hybrid waves and Lamb waves with irregular vibration patterns can synthesise MOF crystals with multi-level pores. The vibration pattern of acoustic waves is shown to be a critical factor in controlling the particle morphology process. These results provide new insights into the precise control of crystal structure and the theory of crystallisation by particle attachment (CPA).

Analysis of Acousto-Optic Phenomenon in SAW Acoustofluidic Chip and Its Application in Light Refocusing

This paper describes and analyzes a common acousto-optic phenomenon in surface acoustic wave (SAW) microfluidic chips and accomplishes some imaging experiments based on these analyses. This phenomenon in acoustofluidic chips includes the appearance of bright and dark stripes and image distortion. This article analyzes the three-dimensional acoustic pressure field and refractive index field distribution induced by focused acoustic fields and completes an analysis of the light path in an uneven refractive index medium. Based on the analysis of microfluidic devices, a SAW device based on a solid medium is further proposed. This MEMS SAW device can refocus the light beam and adjust the sharpness of the micrograph. The focal length can be controlled by changing the voltage. Moreover, the chip is also proven to be capable of forming a refractive index field in scattering media, such as tissue phantom and pig subcutaneous fat layer. This chip has the potential to be used as a planar microscale optical component that is easy to integrate and further optimize and provides a new concept about tunable imaging devices that can be attached directly to the skin or tissue.

Swirl-like Acoustofluidic Stirring Facilitates Microscale Reactions in Sessile Droplets

Sessile droplets play a crucial role in the microreactors of biochemical samples. Acoustofluidics provide a non-contact and label-free method for manipulating particles, cells, and chemical analytes in droplets. In the present study, we propose a micro-stirring application based on acoustic swirls in sessile droplets. The acoustic swirls are formed inside the droplets by asymmetric coupling of surface acoustic waves (SAWs). With the merits of the slanted design of the interdigital electrode, the excitation position of SAWs is selective by sweeping in wide frequency ranges, allowing for the droplet position to be customized within the aperture region. We verify the reasonable existence of acoustic swirls in sessile droplets by a combination of simulations and experiments. The different periphery of the droplet meeting with SAWs will produce acoustic streaming phenomena with different intensities. The experiments demonstrate that acoustic swirls formed after SAWs encountering droplet boundaries will be more obvious. The acoustic swirls have strong stirring abilities to rapidly dissolve the yeast cell powder granules. Therefore, acoustic swirls are expected to be an effective means for rapid stirring of biomolecules and chemicals, providing a new approach to micro-stirring in biomedicine and chemistry.

Acoustic tweezers using bisymmetric coherent surface acoustic waves for dynamic and reconfigurable manipulation of particle multimers

HYPOTHESIS

The accurate and dynamic manipulation of multiple micro-sized objects has always been a technical challenge in areas of colloid assembly, tissue engineering, and organ regeneration. The hypothesis of this paper is the precise modulation and parallel manipulation of morphology of individual and multiple colloidal multimers can be achieved by customizing acoustic field.

EXPERIMENTS

Herein, we present a colloidal multimer manipulation method by using acoustic tweezers with bisymmetric coherent surface acoustic waves (SAWs), which enables contactless morphology modulation of individual colloidal multimers and patterning arrays by regulating the shape of acoustic field to specific desired distributions with high accuracy. Rapid switching of multimer patterning arrays, morphology modulation of individual multimers, and controllable rotation can be achieved by regulating coherent wave vector configurations and phase relations in real time.

FINDINGS

To demonstrate the capabilities of this technology, we have firstly achieved eleven patterns of deterministic morphology switching for single hexamer and precise switching between three array modes. In addition, the assembly of multimers with three kinds of specific widths and controllable rotation of single multimers and arrays were demonstrated from 0 to 22.4 rpm (tetramers). Therefore, this technique enables reversible assembly and dynamic manipulation of particles and/or cells in colloid synthesis applications.

Bisymmetric coherent acoustic tweezers based on modulation of surface acoustic waves for dynamic and reconfigurable cluster manipulation of particles and cells

Acoustic tweezers based on surface acoustic waves (SAWs) have raised great interest in the fields of tissue engineering, targeted therapy, and drug delivery. Generally, the complex structure and array layout design of interdigital electrodes would restrict the applications of acoustic tweezers. Here, we present a novel approach by using bisymmetric coherent acoustic tweezers to modulate the shape of acoustic pressure fields with high flexibility and accuracy. Experimental tests were conducted to perform the precise, contactless, and biocompatible cluster manipulation of polystyrene microparticles and yeast cells. Stripe, dot, quadratic lattice, hexagonal lattice, interleaved stripe, oblique stripe, and many other complex arrays were achieved by real-time modulation of amplitudes and phase relations of coherent SAWs to demonstrate the capability of the device for the cluster manipulation of particles and cells. Furthermore, rapid switching among various arrays, shape regulation, geometric parameter modulation of array units, and directional translation of microparticles and cells were implemented. This study demonstrated a favorable technique for flexible and versatile manipulation and patterning of cells and biomolecules, and it has the advantages of high manipulation accuracy and adjustability, thus it is expected to be utilized in the fields of targeted cellular assembly, biological 3D printing, and targeted release of drugs.

Programmable Microparticle Array for In Situ Modification and Multiple miRNA Detection

Simultaneous detection of multiple miRNAs of one disease can greatly reduce misdiagnosis and improve the detection rate, which is helpful for early cancer diagnosis. Here, a programmable microparticle-array-based acoustic microchip for in situ simultaneous multiple miRNAs detection is developed. On this microchip, the multiple probes-labeled microparticle array can be procedurally arranged in a microfluidic reaction chamber when four orthogonally piezoelectric transducers are applied. The probes-labeled microparticle array offers a platform for full molecular contact under dynamic ultrasonic streaming, and the array supplies a multipoint data correction to reduce the false positive of the detection results for more precisely visible fluorescence multiple target miRNAs sensing. We employed miRNA-21, miRNA-210, and miRNA-155 as specific biomarkers of pancreatic cancer and successfully finished the multiple miRNAs simultaneous detection in the microchip with a detection limit of 139.1, 179.9, and 111.4 pM, respectively. Such a device is programmable by adjusting the imputing frequency and voltage, and target biomarkers can be easily collected when the ultrasound force is released for further analysis, which shows great potential in multiple miRNAs enrichment and simultaneous detection for cancer clinical diagnosis.

Cavitation-assisted sonothrombolysis by asymmetrical nanostars for accelerated thrombolysis

Sonothrombolysis with recombinant tissue plasminogen activator (rtPA) and microbubbles has been widely studied to enhance thrombolytic potential. Here, we report different sonothrombolysis strategy in nanoparticles using microbubbles cavitation. We found that different particles in shape exhibited different reactivity toward the cavitation, leading to a distinct sonothrombolytic potential. Two different gold nanoparticles in shape were functionalized with the rtPA: rtPA-functionalized gold nanospheres (NPt) and gold nanostars (NSt). NPt could not accelerate the thrombolytic potential with a sole acoustic stimulus. Importantly, NSt enhanced the potential with acoustic stimulus and microbubble-mediated cavitation, while NPt were not reactive to cavitation. Coadministration of NSt and microbubbles resulted in a dramatic reduction of the infarcts in a photothrombotic model and recovery in the cerebral blood flow. Given the synergistic effect and in vivo feasibility of this strategy, cavitation-assisted sonothrombolysis by asymmetrical NSt might be useful for treating acute ischemic stroke.