Non-contact Handling Research Articles

Ultrasound-induced reorientation for multi-angle optical coherence tomography

Organoid and spheroid technology provide valuable insights into developmental biology and oncology. Optical coherence tomography (OCT) is a label-free technique that has emerged as an excellent tool for monitoring the structure and function of these samples. However, mature organoids are often too opaque for OCT. Access to multi-angle views is highly desirable to overcome this limitation, preferably with non-contact sample handling. To fulfil these requirements, we present an ultrasound-induced reorientation method for multi-angle-OCT, which employs a 3D-printed acoustic trap inserted into an OCT imaging system, to levitate and reorient zebrafish larvae and tumor spheroids in a controlled and reproducible manner. A model-based algorithm was developed for the physically consistent fusion of multi-angle data from a priori unknown angles. We demonstrate enhanced penetration depth in the joint 3D-recovery of reflectivity, attenuation, refractive index, and position registration for zebrafish larvae, creating an enabling tool for future applications in volumetric imaging.

A novel two-dimensional non-contact platform based on near-field acoustic levitation

Near-field Acoustic Levitation (NFAL) is an advanced non-contact handling method with promising applications in the field of manufacturing semiconductors and Micro-Electro-Mechanical Systems. This study presents a novel two-dimensional non-contact platform based on NFAL, constructed by two independent bumped and holed rails. The bumped rail is cross-placed under the holed rail, and the bumps are passed through the holes to ensure two rails being nested and combined. The effective region of the platform is consisted of bumped and non-holed regions simultaneously. So, the distribution of the bumps and holes can be designed to optimize the performance of two-dimensional transportation. Two rails can be vibrated independently to realize one-dimensional transportation and simultaneously to realize two-dimensional transportation. The governing equation of squeeze film, considering the amplitude distribution of the rails, is established to analyze the performances. An experimental test-bed is constructed to test the levitation and transportation performance to verify the numerical study. Both numerical and experimental results prove that the platform based on NFAL is a feasible and easy method to realize non-contact two-dimensional transportation.

Parametric analysis of acoustically levitated droplet for potential microgravity application

Acoustic levitation is a versatile technique for the non-contact handling of both solid and liquid samples, yet its potential remains underutilized in container-less processing and lab-on-a-drop application. This study demonstrates the efficient use of acoustically levitated droplets as microgravity simulators on earth similar to clinostat. Using a simple and affordable non-resonant single-axis acoustic levitator called TinyLev, we first investigate the impact of applied voltage and droplet volume on the shape and rotational motion of levitated water droplets. Furthermore, we examine the rotational motion of suspended microparticles within the droplets. Our findings reveal the feasibility of using the levitated droplets as a miniaturized microgravity simulators on earth.

Contactless acoustic micro/nano manipulation: a paradigm for next generation applications in life sciences.

Acoustic actuation techniques offer a promising tool for contactless manipulation of both synthetic and biological micro/nano agents that encompass different length scales. The traditional usage of sound waves has steadily progressed from mid-air manipulation of salt grains to sophisticated techniques that employ nanoparticle flow in microfluidic networks. State-of-the-art in microfabrication and instrumentation have further expanded the outreach of these actuation techniques to autonomous propulsion of micro-agents. In this review article, we provide a universal perspective of the known acoustic micromanipulation technologies in terms of their applications and governing physics. Hereby, we survey these technologies and classify them with regards to passive and active manipulation of agents. These manipulation methods account for both intelligent devices adept at dexterous non-contact handling of micro-agents, and acoustically induced mechanisms for self-propulsion of micro-robots. Moreover, owing to the clinical compliance of ultrasound, we provide future considerations of acoustic manipulation techniques to be fruitfully employed in biological applications that range from label-free drug testing to minimally invasive clinical interventions.

Standing surface acoustic waves, and the mechanics of acoustic tweezer manipulation of eukaryotic cells

Manipulation by focused ultrasound is an emerging technology with much promise for non-contact handling of microscale objects. A particularly promising approach for achieving this with living cells involves incorporating standing surface acoustic waves (SSAWs) into a microfluidic device. SSAWs must be tuned to provide the necessary range of acoustic radiation force (ARF), but models enabling this tuning have neglected the mechanics of the cells themselves, treating cells as rigid or homogenous spheres, and have also neglected energy transfer from the substrate to the fluid at the Rayleigh angle. We therefore applied Mie scattering theory to develop a model of the ARF arising from a SSAW impacting an idealized eukaryotic cell in an inviscid fluid. The cell was treated as a three-layered body with a nucleus, cytoplasm, and cortical layer. Results showed strong dependence on cell structures and the Rayleigh angle that can be harnessed to develop novel applications for cell manipulation and sorting. ARF can be tuned using the new model to both push away and pull back a cell towards the sound source. The proposed analytical model provides a foundation for design of microfluidic systems that manipulate and sort cells based upon their mechanical properties.

Saddle-Node Bifurcations and Design Parameters for Single-Axis Acoustic Levitators

Acoustic levitation (Aclev) is an important tool to noncontact handling of containerless objects. In the recent years, many devices have been successfully developed due to the stable behavior of the Aclev devices. As a result, most of the works on Aclev concentrate on numerical simulations or experimental tests to study the geometry and arrangements of the acoustic emitters, or the influence of various types of perturbations, and most of the mathematical models consider only the acoustic potential. In this work, the nonlinear equation of motion for a levitated particle immersed in a single-axis acoustic field is developed considering dissipative forces. The parameter space is searched for the existence of equilibrium points bifurcations, and a design range for the Aclev device gains is determined from the equilibrium point existence condition, providing hints in order to improve the stability gain margin and, consequently, the robustness to perturbations. In addition, the dynamical behavior of the Aclev device concerning the gains is studied considering also the micro-gravity situation. Numerical simulations corroborate the analytical results.

Stiffness improvement of swirl gripper based on gap height and force estimation

The swirl gripper is an electrically activated noncontact handling device that uses swirling airflow to generate a lifting force. This force can be used to pick up a workpiece placed underneath the swirl gripper without any contact. It is applicable, for example, on a semiconductor wafer production line, where contact must be avoided during the handling and moving of a workpiece to minimize damage. When a workpiece levitates underneath a swirl gripper, the gap height between them is critical for safe handling. Therefore, in this study, we develop a theoretical model of the swirl gripper, based on which a method to estimate the levitation gap height by detecting pressure at two points is proposed. Experiments indicate that the estimated gap height can track changes in actual gap height accurately in real time, when the gap height is relatively small and the inertia of airflow in the gap is negligible. In addition, the force between the gripper and workpiece can also be estimated using the detected pressure. As a result, a desired relationship between the force and gap height can be achieved by adjusting the rotating speed of the fan according to the real-time estimated force and gap height using a microcontroller. The control system was experimentally verified using a desired linear relationship. Because the stiffness of the force decreases with increasing gap height for a constant gripper fan rotating speed, the linear relationship between the force and gap height, which means a constant stiffness, is expected to enhance handling stability of workpieces.

Numerical characterisation of the performance of flow rate on a non-contact vortex gripper

On manufacturing industries like semiconductor wafers, Manufacturing of medicine or Food processing industries require repeated handling of clean products such as wafers, Food products, etc. which are needs to be frequently handled and transported. This handling can be further ameliorated by Vortex Grippers. Vortex levitation can achieve Non-Contact handling by blowing air through a tangential nozzle into a vortex cup, thus swirling air flow forms which generates negative pressure. The suction force generated by the vortex is more than enough to keep the workpiece without contact. In the present study, a non-contact handling device called vortex gripper is modified by changing some design parameters. However, when a conical shaped vortex cup is used, a 60% increase in gripper lifting force is achieved with the same air consumption as reported early.

Au80Sn20-based targeted noncontact nanosoldering with low power consumption.

Energy-efficient nanosoldering technology for realizing connections at the nanoscale is a long-sought-after goal for constructing advanced optoelectronic nanodevices. However, the ability to achieve noncontact handling, low power consumption, and targeted nanosoldering remains a challenge. In this work, we demonstrate a method of targeted photothermal-induced nanosoldering of silver nanowires, which uses Au80Sn20 alloy nanowires as the nanosolder and a 532nm continuous wave laser as the heat source. The required power for fusing the Au80Sn20 solder is reduced by a factor of 55 compared to the previously demonstrated Ag self-nanosolder case. Construction of a few typical nanostructures (including "X"-, "Y"-, and "-"-shaped junctions) is achieved with this method. Besides its low power consumption, it also provides advantages including noncontact and targeted soldering, thereby introducing new avenues for fabricating complex nanostructures and advanced functional nanodevices.

Effect of Surface Grooves on the Characteristics of Noncontact Transportation Using Near-Field Acoustic Levitation

ABSTRACTNear-field acoustic levitation is a novel noncontact handling method. However, low load-carrying capacity and low transportation speed limit its application. This study proposes a novel method in which bar-type grooves are machined on the plate surface to increase load-carrying capacity and transportation speed. An experimental rig with a flexural rail vibrated by piezoelectric transducers is developed to transport the rigid plate and measure the levitation height and transportation speed. The flexural vibration mode of the rail and the dynamic position of the rigid plate are coupled with groove characteristics to determine the gas film thickness between the rail and plate. The Reynolds equation is linearized by using Green's formula and then solved by using an eight-node discrete grid finite difference method. The effects of groove direction, depth, number, width, and length on the load-carrying capacity and transportation speed are also discussed. Numerical results are consistent with the experiment results. The load-carrying capacity and transportation capability can be significantly improved with groove length direction vertical to the rail wave transportation direction. Predicted results show that optimum groove depth, number, width, and length can be used to increase load-carrying capacity and transportation capability.

Ejection of small droplet from microplate using focused ultrasound

We discussed an ultrasonic system for single-droplet ejection from a microplate, which is one of the basic and important procedures in the noncontact handling of droplets in air. In this system, a 1.5 MHz concave transducer located below the microplate is used for chasing the liquid surface through a pulse echo method, and also for the ejection of a 1 µL single droplet by the burst of focused ultrasound. We investigated the relationship between the droplet ejection characteristics, the distance from the transducer to the surface of liquid, the material property, and the excitation condition of the focused ultrasonic transducer. It was verified that the optimal position of the transducer was off the focal point of sound pressure by ±1 mm, because the sound intensity had to be controlled to eject a single droplet. Subsequently, we confirmed experimentally that the ejected droplet volume linearly depended on the surface tension of the liquid, and that the droplet volume and ejection velocity were determined by the Webber number, Reynolds number, and Ohnesolge number. In addition, by optimizing the duration of the burst ultrasound, the droplet volume and ejection velocity were controlled.

Modelling and experimental study on the influence of surface grooves on near-field acoustic levitation

Near-field acoustic levitation is a novel non-contact handling technology. Its key challenge is the limited load-carrying capacity. This study introduced a simple method, i.e., adding grooves on the reflector surface, to improve load-carrying capacity. The flexural vibration mode and frequency of radiator plate were calculated through finite element analysis and validated by an experiment to determine air film thickness between two objects. The theoretical analysis and experimental study both indicated that circumferential grooves increased levitation force, whereas radial grooves decreased this force. Load capacity with different groove parameters was also investigated. Result indicated that groove depth and groove number were the optimal parameters and exhibited superior effects on levitation force, whereas the effect of groove width was smaller.

Optical Bessel tractor beam on active dielectric Rayleigh prolate and oblate spheroids

Optical Bessel tractor beams, designed to produce a negative pulling force on a particle, are gaining increased attention for applications in noncontact remote sampling, particle manipulation, and handling, to name some examples. In the long-wavelength (Rayleigh) limit, known also as the electric dipole approximation, earlier investigations demonstrated that a zeroth-order Bessel beam incident upon a passive dielectric sphere (i.e., no radiating sources in its core) always acts as a repulsor beam, which causes the particle to be pushed away from the source in the forward direction of the linear momentum. In contrast to what has already been established, this work shows that the incident wave field can act as a tractor beam (where a small spheroid is pulled backwards towards the source due to a negative attractive force) in the dipole approximation (Rayleigh) limit, provided that the particle is made of an active material, i.e., a dielectric spheroid acting as an oscillating source for which the extinction energy efficiency is negative. Numerical computations for the Cartesian components of the optical radiation force on active prolate and oblate spheroids with arbitrary orientation are performed. Emphasis is placed on the emergence of the tractor beam behavior and its dependence upon the half-cone angle, the polarization type of the incident beam, the spheroid aspect ratio, as well as its orientation in space. The analysis is extended to calculate the Cartesian components of the spin radiation torque, which causes a rotation of the spheroid around its center of mass in either the counterclockwise or the clockwise (negative) direction of spinning. Unlike the case of a sphere, the optical spin torque arises for a nonabsorptive oblate or prolate spheroid with arbitrary orientation in the field of a zeroth-order Bessel beam. Potential applications in optically engineered metamaterials, optical tractor beams, tweezers, particle manipulation, rotation, and handling would benefit from the results of this study.

Suppression of Vortex Precession in a Non-Contact Handling Device by a Circular Column

Vortex levitation attains non-contact handling by injecting air through a tangential nozzle into a cylindrical cup generating the swirling flow. The precessing of the swirling flow causes pressure fluctuation. This phenomenon becomes apparent as the gap between the cup and workpiece increases, which significantly disturbs the stability of conveyance. In this paper, suppression of pressure fluctuation by a cylindrical column that stabilizes the vortex levitation is described and its mechanism is mentioned. According to the experimental set up, the pressure was measured at the center of the workpiece and the wall of the cup; velocity field under the work piece was visualized by PIV. The result suggested that the larger diameter column denoted the effect on suppression of the fluctuation because the precessing of the swirling flow became stable. On the other hand, variation of the column thickness had insignificant effect on suppressing the fluctuation, but sucking force became weakened since the swirling velocity decreased.

1406 旋回流を用いた非接触搬送系に関する研究 : 渦室形状変更による圧力変動抑制(OS12-2 噴流・後流・剥離流の解明とその利用)

1406 旋回流を用いた非接触搬送系に関する研究 : 渦室形状変更による圧力変動抑制(OS12-2 噴流・後流・剥離流の解明とその利用)

旋回流を利用した非接触吸着装置の開発（性能を支配するパラメータ）

The existing vacuum handling device has some problems because the work becomes dirty and broken. Therefore, now a day the noncontact Bernoulli handling device becomes mainly. However, this device too has also some problems. For example, this device adsorption power is weak. Thus requires large power and flow rate. Hence this research will focus on the noncontact handling device with a swirling flow. The aim of this research is to verify the effect of parameter on the performance of the device.

1216 旋回流を利用した非接触吸着装置の特性(流体工学III)

1216 旋回流を利用した非接触吸着装置の特性(流体工学III)

A Noncontact Picolitor Droplet Handling by Photothermal Control of Interfacial Flow.

We present a noncontact handling of droplets in a microfluidic platform by the Marangoni convection, interfacial tension driven flow, generated by a light-induced local temperature gradient in the surrounding liquid of the droplet. Droplets flowing in a microchannel experience a force due to the interfacial tension gradient when approaching the heated area. This method provides noncontact, selective and flexible manipulation for droplets flowing in microchannel network. In this study, an O/W emulsion system with oleic acid for the dispersed phase and a buffer solution for the continuous one was used. Trajectory control and trapping for droplets with 5 - 65 pL in volume was achieved by patterned laser irradiation. Also, we quantitatively evaluated the driving force exerted on droplets by measuring the fluidic temperature distribution around the droplet. From the balance of the drag force and the photo-induced Marangoni force, the driving force was determined using the measured temperature gradient of the droplet. From the results, the applicability of noncontact droplet manipulation using the photothermal Marangoni effect by continuous-phase heating has been demonstrated.

Magnetic self-assembly with unique rotational alignment for thin chips

In this paper, we demonstrate a novel self-assembly method for non-contact and high precision handling of ultra-thin chips. The chips are manipulated by the magnetic interactions between an externally applied magnetic field and nickel contact pads present on the chip. The asymmetric layout of magnetic material on the chip and the gradient in the applied magnetic field allows achieving a unique rotational alignment. The repeatability of the process is 3σ=25μm in translation and 3σ=2° in rotation, with an alignment duration of 0.2s.

Cell dispensing in low-volume range with the immediate drop-on-demand technology (I-DOT).

Handling and dosing of cells comprise the most critical step in the microfabrication of cell-based assay systems for screening and toxicity testing. Therefore, the immediate drop-on-demand technology (I-DOT) was developed to provide a flexible noncontact liquid handling system enabling dispensing of cells and liquid without the risk of cross-contamination down to a precise volume in the nanoliter range. Liquid is dispensed from a source plate within nozzles at the bottom by a short compressed air pulse that is given through a quick release valve into the well, thus exceeding the capillary pressure in the nozzle. Droplets of a defined volume can be spotted directly onto microplates or other cell culture devices. We present a study on the performance and biological impact of this technology by applying the cell line MCF-7, human fibroblasts, and human mesenchymal stem cells (hMSCs). For all cell types tested, viability after dispensing is comparable to the control and exhibits similar proliferation rates in the absence of apoptotic cells, and the differentiation potential of hMSCs is not impaired. The immediate drop-on-demand technology enables accurate cell dosage and offers promising potential for single-cell applications.