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

Acoustic tweezers based on travelling surface acoustic waves (TSAWs) have the potential for contactless trajectory manipulation and motion-parameter regulation of microparticles in biological and microfluidic applications. Here, we present a novel design of a tri-directional symmetrical acoustic tweezers device that enables the precise manipulation of linear, clockwise, and anticlockwise trajectories of microparticles. By switching the excitation combinations of interdigital electrodes (IDTs), various shape patterns of acoustic pressure fields can be formed to capture and steer microparticles accurately according to pre-defined trajectories. Numerical simulations and experimental tests were conducted in this study. By adjusting the input electric signals and the fluid's viscosity, the device is able to manipulate microparticles of various forms as well as brine shrimp egg cells with the accurate modulation of motion parameters. The results show that the proposed programmable design possesses low-cost, compact, non-contact, and high biocompatibility benefits, with the capacity to accurately manage microparticles in a range of motion trajectories, independent of their physical and/or chemical characteristics. Thus, our design has strong potential applications in chemical composition analysis, drug delivery, and cell assembly.

4D Printed Cardiac Construct with Aligned Myofibers and Adjustable Curvature for Myocardial Regeneration.

As an innovative additive manufacturing process, 4D printing can be utilized to generate predesigned, self-assembly structures which can actuate time-dependent, and dynamic shape-changes. Compared to other manufacturing techniques used for tissue engineering purposes, 4D printing has the advantage of being able to fabricate reprogrammable dynamic tissue constructs that can promote uniform cellular growth and distribution. For this study, a digital light processing (DLP)-based printing technique was developed to fabricate 4D near-infrared (NIR) light-sensitive cardiac constructs with highly aligned microstructure and adjustable curvature. As the curvature of the heart is varied across its surface, the 4D cardiac constructs can change their shape on-demand to mimic and recreate the curved topology of myocardial tissue for seamless integration. To mimic the aligned structure of the human myocardium and to achieve the 4D shape change, a NIR light-sensitive 4D ink material, consisting of a shape memory polymer and graphene, was created to fabricate microgroove arrays with different widths. The results of our study illustrate that our innovative NIR-responsive 4D constructs exhibit the capacity to actuate a dynamic and remotely controllable spatiotemporal transformation. Furthermore, the optimal microgroove width was discovered via culturing human induced pluripotent stem cell-derived cardiomyocytes and mesenchymal stem cells onto the constructs' surface and analyzing both their cellular morphology and alignment. The cell proliferation profiles and differentiation of tricultured human-induced pluripotent stem cell-derived cardiomyocytes, mesenchymal stem cells, and endothelial cells, on the printed constructs, were also studied using a Cell Counting Kit-8 and immunostaining. Our results demonstrate a uniform distribution of aligned cells and excellent myocardial maturation on our 4D curved cardiac constructs. This study not only provides an efficient method for manufacturing curved tissue architectures with uniform cell distributions, but also extends the potential applications of 4D printing for tissue regeneration.