Search Results (306)

Acoustic tweezers, as advanced micro/nano manipulation tools, play a pivotal role in biomedical engineering, microfluidics, and precision manufacturing. However, piezoelectric-based acoustic tweezers face performance limitations due to multi-physical coupling effects during microfabrication. This study proposes a novel approach using injection molding with embedded electronics (IMEs) technology to fabricate piezoelectric micro-ultrasonic transducers with micron-scale precision, addressing the critical issue of acoustic node displacement caused by thermal–mechanical coupling in injection molding—a problem that impairs wave transmission efficiency and operational stability. To optimize the IME process parameters, a hybrid multi-objective optimization framework integrating NSGA-II and MOPSO is developed, aiming to simultaneously minimize acoustic node displacement, volumetric shrinkage, and residual stress distribution. Key process variables—packing pressure (80–120 MPa), melt temperature (230–280 °C), and packing time (15–30 s)—are analyzed via finite element modeling (FEM) and validated through in situ tie bar elongation measurements. The results show a 27.3% reduction in node displacement amplitude and a 19.6% improvement in wave transmission uniformity compared to conventional methods. This methodology enhances acoustic tweezers’ operational stability and provides a generalizable framework for multi-physics optimization in MEMS manufacturing, laying a foundation for next-generation applications in single-cell manipulation, lab-on-a-chip systems, and nanomaterial assembly. Full article

Background: Cell membrane proteins play crucial roles in signal transduction and nutrient transport. Many membrane proteins are reportedly overexpressed in cancer cells, which is closely related to cancer progression. The targeted degradation of these membrane proteins has been demonstrated to be a promising strategy for tumor treatment. Several strategies using aptamers to mediate membrane protein lysis, such as lysosomal-mediated lysis and proteasome-mediated lysis, have been reported, but their efficiency is limited by the binding affinity of the aptamer to a single target. Methods: We constructed DNA tweezers with replaceable clamps, which can lyse different proteins upon clamp replacement. Moreover, the clamp improved the degradation efficiency of the target proteins by enhancing the specificity and improving the binding affinity. Results: Lysis was verified in different tumor cell lines and the antitumor activity was confirmed in zebrafish. Conclusions: Overall, these DNA tweezers improve the efficiency of the targeted delivery of functional nucleic acids, provide an efficient and versatile strategy for the degradation of disease-causing proteins, and expand the approach to antitumor therapy. Full article

Single-cell adhesion assays can be divided into studies on attachment and detachment events, and several methods that enable the characterization of both processes have been established in the past. Due to their low invasiveness, label-free principles, and contactless operation, optical methods are especially beneficial for this purpose. Historically, optical tweezers (OTs) have been used to explore single-cell detachment events, allowing for the precise determination of minute physical forces. However, it has been noted that OTs can also be used to study single-cell attachment dynamics, including the evaluation of minimum cell-to-cell contact times necessary to establish a stable adhesive bond. Here, we provide a step-by-step protocol to effectively evaluate minute changes in the adhesion of single leukemia–lymphoma cells using optical tweezers with low laser intensities. This serves as a valuable in vitro model to determine the effects of physical and chemical factors on the adhesive properties of leukemia–lymphoma (LL) cells. Full article

We propose a two-qubit phase gate based on trapped ions that uses fast electric field pulses and spin-dependent local traps generated by optical tweezers. The phases are engineered by spin-dependent coherent evolution, interspersed with momentum kicks. We derive a set of commensurability conditions and expressions for the spin-dependent accumulated phase that, when satisfied, realize the target two-qubit phase gate within tens of microseconds. We study the scalability of our proposal in larger-ion crystals and demonstrate the existence of solutions with up to four ions. Gates in larger crystals should also be possible but will require more commensurability conditions to be fulfilled. Full article

Micromotors play a crucial role in microsystems technology, with applications in nanoparticle propulsion, targeted drug delivery, and biosensing. Optical field propulsion, particularly optical tweezers (OTs), enables precise, noncontact control but traditionally relies on Gaussian traps, which require preprogramming and offer limited rotational control. Here, we introduce a micromotor driven by optical vortex beams, utilizing phase gradients to generate optical torque. This eliminates preprogramming and enables real-time control over rotation and positioning. Using this method, we design red blood cell (RBC)-based micromotors for targeted cellular debris collection in liquid environments. Our findings provide a versatile strategy for micro-/nano-object manipulation with potential applications in biomedicine and precision transport. Full article

The research on high-order transverse modes in lasers is a subject as old as the laser itself and has been largely abandoned. However, recently several studies have demonstrated an interest in using, instead of the usual Gaussian beam, a radial Laguerre–Gauss LG_p0 beam, as, for instance, one can observe a strong improvement, for a given power, in the longitudinal and radial forces in optical tweezers illuminated by a LG_p0 beam instead of the usual Gaussian beam. Since in most commercial lasers, the delivered laser beam is Gaussian, we therefore think it opportune to consider the problems of forcing a laser to oscillate individually on a higher-order transverse LG_p0 mode. We propose a comprehensive analysis of the effects of an intra-cavity phase or amplitude mask on the fundamental mode of a plano-concave cavity. In particular, we discuss the best choice of parameters favouring the fundamental mode of a pure radial Laguerre–Gauss LG_p0 model. Full article

Background: Acute myeloid leukemia (AML) is a heterogeneous disease highly resistant to chemotherapeutic agents. Leukemia stem cells (LSCs) can enter a dormant state and avoid apoptosis in the protective niche of the bone marrow (BM) microenvironment. Moreover, bone marrow stromal cells protect leukemia cells by promoting pro-survival signaling pathways and drug resistance. Therefore, attenuating interactions between leukemia cells and BM cells may have a positive therapeutic effect. Objectives: In this work, we hypothesized that sondages may inhibit the adhesion of leukemia cells to the bone marrow by inhibiting the Hedgehog (Hh) signaling pathway. The Hedgehog pathway is a key therapeutic target in AML due to its role in leukemic cell growth and survival. Methods: We investigated the effects of sonidegib on the adhesion of individual OCI-AML3 cells to a bone marrow stromal spheroid derived from the HS-5 cell line. For this purpose, we precisely determined the minimum cell-to-cell adhesion time using optical tweezers under normoxic (21% of O₂) and hypoxic (1% of O₂) conditions. Results: Our results demonstrated that sonidegib significantly increased the minimum cell-to-cell adhesion time necessary for leukemic cells to establish adhesive bonds with bone marrow stromal cells, thereby indicating a reduction in their adhesive properties. Additionally, we showed that sonidegib is particularly effective at hypoxic oxygen concentrations. Conclusions: The results obtained in this study suggest that sonidegib, through its modulation of the Hedgehog signaling pathway, holds promise as a potential therapeutic approach to target leukemic cell adhesion within the bone marrow microenvironment. Full article

Deployment of photocatalysis for water disinfection necessitates engineering the process kinetics and achieving the complete recovery of the photocatalyst following the remediation of water. The recovery of the photocatalysts, especially nanostructured photocatalysts, remains a challenge, as indicated by a previous study by our group where only 57% of TiO₂ nanowires were recovered by gravity-assisted settling and sedimentation from water after its photocatalysis-assisted E. coli inactivation. To overcome this challenge, a novel method involving the use of photocatalysts in the form of porous foams is developed and presented. Use of TiO₂ nanowire foams led to a 2–3-log reduction of E. coli in a span of 180 min when ultraviolet-A (UV-A) light was employed for photoactivation, similar to that observed previously by our group. More importantly, the photocatalyst foams were easily recoverable from water via mechanical separation using tweezers, which in this study led to a recovery of 98–99% of the TiO₂ nanowire photocatalysts. This strategy allows for further optimization of both the process kinetics and the total amount of photocatalysts needed for water remediation through optimization of the porosities and the geometries of the foams and ensuring that all the photocatalyst surfaces remain accessible to both the pollutants and light. Full article

Defect-free atom arrays provide new possibilities for exploring exotic quantum phenomena and realizing quantum computing. However, quickly and efficiently preparing defect-free atom arrays poses challenges. This paper proposes an innovative parallel rearrangement method, namely the parallel compression filling algorithm (PCFA), wherein multiple movable optical tweezers operate simultaneously. By limiting the shape of the initial loading, the method reduces movement complexity. The simulation comparisons show that this algorithm is more efficient in preparing defect-free atom arrays and can also be applied to the generation of other periodic structure arrays. The simulation results show that, in most cases, preparing a defect-free array of 400 atoms requires no more than 30 steps. Full article

An automated micro-tweezers system with a flexible workspace would benefit the intelligent sorting of live cells. Such micro-tweezers could employ a forced vortex strong enough to capture a single cell. Furthermore, addressable control of the position to the vortex would constitute a robotic system. In this study, a spherical micro-object composed of super paramagnetic particles tightly packed in a non-magnetic resin is rotated with a combined magnetic field of permanent magnets. The said magnetic field is articulated by an open-kinematic chain controlled with a simple adaptive PI-control scheme. A vortex is formed as the spherical particle, assumed to be submerged under the surface of fluid, and follows the position and orientation of the external magnetic field. This forced vortex induces a radial pressure gradient that captures the live cell orbiting around the spherical object combined with the inertial effects. Here, a comprehensive mathematical model is presented to reflect on the dynamics of such micro-tweezer systems. Numerical results demonstrate that it is theoretically possible to capture and tow a bacterium cell while meeting extreme tracking references for motion control. Magnetic and fluid forces on the spherical particle traverse the vortex and the bacterium cell, with orbiting and sporadic collusion of the bacterium cell around the spherical particle, and the positions of the end-effector, i.e., the magnets, are analyzed. Full article

An ultra-thin spiral diffractive lens (SDL) was fabricated by using focused ion beam milling on a fiber end-facet coated with a 100 nm thick Au film. Focusing vortex beams (FVBs) were successfully excited by the SDLs due to the coherent superposition of diffracted waves and their azimuth dependence of the phase accumulated from the spiral aperture to the beam axis. The polarization and phase characteristics of the FVBs were experimentally investigated. Results show that the input beams with various polarization states were converted to FVBs, whose polarization states were the same as those of the input beams. Furthermore, the focal length of the SDL and the in-tensity and phase distribution at the focus spot of the FVBs were numerically simulated by the FDTD method in the ultra-wide near-infrared waveband from 1300 nm to 1800 nm. The focal length was tuned from 21.8 μm to 14.7 μm, the intensity profiles exhibited a doughnut-like shape, and the vortex phase was converted throughout the broadband range. The devices are expected to be candidates for widespread applications including optical communications, optical imaging, and optical tweezers. Full article

Nanoscale resonant devices based on optical tweezers are widely used in the field of precision sensing. In the process of driving the nanoresonator based on the Coulomb force, the real-time, precise regulation of the charge carried by the charged resonator is essential for continuous manipulation. However, the accuracy of the existing charge measurement methods for levitated particles is low, and these methods cannot meet the needs of precision sensing. In this study, a novel net charge measurement protocol for levitated particles based on spatial speed statistics is proposed. High-precision mass measurement based on Maxwell’s rate distribution law is the basis for improving the accuracy of charge measurement, and accurate measurement of net charge can be achieved by periodic electric field driving. The error of net charge measurement is less than 7.3% when the pressure is above 0.1 mbar, while it can be less than 0.76% at 10 mbar. This proposed method features real-time, high-precision, non-destructive, and in situ measurement of the net charge of particles in the medium vacuum, which provides new solutions for practical problems in the fields of high-precision sensing and nano-metrology based on levitated photodynamics. Full article

The analysis of nucleic acid structures, topologies, nano-mechanics and interactions with ligands and other biomacromolecules (most notably proteins) at the single molecule level has become a fundamental topic in molecular biophysics over the last two decades. Techniques such as molecular tweezers, single-molecule fluorescence resonance energy transfer, and atomic force microscopy have enabled us to disclose an unprecedented insight into the mechanisms governing gene replication, transcription and regulation. In this minireview, we survey the main working principles and discuss technical caveats of the above techniques, using as a fil-rouge the history of their achievements in dissecting G-quadruplexes. The revised literature offers a clear example of the superior ability of single-molecule techniques with respect to ensemble techniques to unveil the structural and functional diversity of the several polymorphs corresponding to a single G-quadruplex folding sequence, thus shedding new light on the extreme complexity of these fascinating non-Watson–Crick structures. Full article

Acoustic holography technology is widely used in the field of ultrasound due to its capability to achieve complex acoustic fields. The traditional acoustic holography method based on single-phase holograms is limited due to its inability to complete acoustic field control with high dynamics and accuracy. Here, we propose a method for constructing an acoustic holographic model, introducing an ultrasonic array to provide dynamic amplitude control degrees of freedom, and combining the dynamically controllable ultrasonic array and high-precision acoustic hologram to achieve the highest acoustic field accuracy and dynamic range. This simulation method has been proven to be applicable to both simple linear patterns and complex surface patterns. Moreover, it is possible to reconstruct the degree of freedom of the target plane amplitude effectively and achieve a breakthrough in high information content. This high-efficiency acoustic field control capability has potential applications in ultrasound imaging, acoustic tweezers, and neuromodulation. Full article