Non-contact Micromanipulation Research Articles

Pose Control of Millimeter-Scale Objects in a Laser-Powered Thermocapillary Manipulation Platform

The miniaturization of technological components requires tools capable of manipulating them. Noncontact micromanipulation has recently gained popularity since it minimizes component damage and adhesion problems. However, the simultaneous position and orientation (pose) control using noncontact tools remains an open challenge. In this work, we propose the pose control of millimeter-scale structures at the air–water interface using laser-powered thermocapillary flows. We achieve autonomous pose control by steering two laser spots around the structure in a closed-loop manner. The controller consists of a linear pose controller and a model inversion. The pose controller defines the required force and torque to reach the target. The model inversion defines the required laser positions to obtain said force and torque. This inversion is performed with an optimization algorithm, without any prescribed strategy. The pose stabilization was validated experimentally, obtaining a position and orientation precision of 0.15 body lengths and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2^{\circ }$</tex-math></inline-formula> , respectively. Additionally, we show the experimental path-following with independent orientation control, obtaining a similar position precision.

Solving the Non-Linear Motion in a Micromanipulation System Powered by Thermocapillary Flows

Non-contact micromanipulation tools have emerged as a promising solution for manipulating small components. However, they are mainly based on non-linear actuation principles requiring ad-hoc control strategies. This paper proposes non-linear control laws to actuate a non-contact manipulation system based on thermocapillary flows for the manipulation of micro-objects on an air-water interface. The actuation system consists of steering a laser beam to locally heat the liquid surface, thus inducing a thermocapillary flow. The resulting flow propels floating objects away from the laser spot with a significant velocity (up to ten body-length per second) but the behavior is highly non-linear. Notably, small errors in the laser positioning are amplified and give place to non-linear motion. Therefore, we developed a control method consisting of a non-linear position controller including a laser position observer. We achieve stable 2D position control in this non-linear system, with a precision of 0.3 mm on a 0.5 mm object.

Optically induced electrothermal microfluidic tweezers in bio-relevant media

Non-contact micro-manipulation tools have enabled invasion-free studies of fragile synthetic particles and biological cells. Rapid electrokinetic patterning (REP) traps target particles/cells, suspended in an electrolyte, on an electrode surface. This entrapment is electrokinetic in nature and thus depends strongly on the suspension medium’s properties. REP has been well characterized for manipulating synthetic particles suspended in low concentration salt solutions (~ 2 mS/m). However, it is not studied as extensively for manipulating biological cells, which introduces an additional level of complexity due to their limited viability in hypotonic media. In this work, we discuss challenges posed by isotonic electrolytes and suggest solutions to enable REP manipulation in bio-relevant media. Various formulations of isotonic media (salt and sugar-based) are tested for their compatibility with REP. REP manipulation is observed in low concentration salt-based media such as 0.1× phosphate buffered saline (PBS) when the device electrodes are passivated with a dielectric layer. We also show manipulation of murine pancreatic cancer cells suspended in a sugar-based (8.5% w/v sucrose and 0.3% w/v dextrose) isotonic medium. The ability to trap mammalian cells and deposit them in custom patterns enables high-impact applications such as determining their biomechanical properties and 3D bioprinting for tissue scaffolding.

A PZT-Driven 6-DOF High-Speed Micromanipulator for Circular Vibration Simulation and Whirling Flow Generation

Existing micromanipulation methods, whether contact micromanipulation or non-contact micromanipulation, can hardly meet the requirements of low damage and multiple functions in the biomedical field. This study provides a high-speed micromanipulator that can simulate circular vibrations and generate microflow, which could be utilized to actuate non-invasive multiple operations of biological targets at the microscale. We design a PZT-driven 6-DOF micromanipulator with a hybrid structure and flexible hinges. Two 3-PRS parallel modules are serially connected in mirror style to achieve high speed, high accuracy, and a big workspace simultaneously, which enables the highly-controllable circular vibration simulation and strong whirling flow generation. The static, dynamic, and trajectory tracking performances were evaluated. The experimental result showed the 324 × 331 × 40 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> workspace, which was also the range of trajectories that could be generated. Trajectory tracking performance evaluation showed that it could realize ∼200 Hz circular vibration with an error of about 2.4% through open-loop control. Finally, the microflow generation experiment indicated the great potential of the proposed micromanipulator and the method of whirling flow generation in operating the biological targets at the microscale.

Noncontact manipulation of particles in air by switching pulse drive of ultrasonic speakers arrayed on a semicylinder

Noncontact micromanipulation techniques are necessary for micromachine technology, biotechnology, materials processing, and so on. By using a bolted Langevin transducer and a reflector, one can trap small objects in air at nodes of sound pressure in a standing wave field, but such a technique requires high-voltage drive and careful tuning to achieve resonance. In this study, a large number of small ultrasonic speakers were placed on the inner surface of a semicylinder to form a strong sound field in the focus line. We showed that the pressure node can be moved, and thus the small object, along the focus line simply by switching the driving ultrasonic speakers without using complex electronics. We also showed that the object can be trapped and manipulated even at a duty ratio of 50% in tone burst waves. The above results are discussed by showing the experimental and calculated sound pressure distributions.

Manufacturing of 3D Helical Microswimmer by AFM Micromanipulation for Microfluidic Applications

Manufacturing of microsystems based on complex three-dimensional microstructures requires critical steps such as mass calibrations and integration process. However, such steps involve several manipulation steps which are not well controlled thus the fragile 3D microstructures could be damaged or destroyed. In this work, we have demonstrated an AFM based direct mass measurement and manufacturing of 3D helical microswimmer. The proposed method shows to be rapid, repeatable and minimally-destructive thanks to the precise force control and manipulation by AFM. The proposed micromanipulation steps consist of the pick-measure-integrate manipulation steps using van der Waals force-based attachment and the mass measurement by resonant frequency shift. For the testing structures, we fabricated the 6 different types of 3D helical microswimmers vertically fabricated on the conical shape microneedle supports for uniform surface metallization and facile detachment. With the mass measurement sensitivity of 25 Hz/pg and the direct integration to microfluidics, we successfully demonstrated the 3D propulsion and non-contact micromanipulation by 3D helical microswimmer in microfluidics.

Thermocapillary micromanipulation: force characterization and Cheerios interactions

Thermocapillary micromanipulation is an emerging non-contact micromanipulation technique, allowing to displace particles in the liquid bulk or at the free surface. When the particles are at the free surface and the surface is heated from the top, the actuation force is repulsive and not attractive. The handling technique is then intrinsically unstable. Therefore, control schemes have been reported recently to deal with this instability. They are based on an experimental characterization of the physical system (depending on the laser, the liquid and the particle properties). In this paper, we explain how we could make use of these handling schemes to estimate the thermocapillary force developed by the laser on the particle to be about 8 nN. This work is a first step towards the handling of multiple particles at the air/liquid interface.

Multifunctional Noncontact Micromanipulation Using Whirling Flow Generated by Vibrating a Single Piezo Actuator.

A noncontact method that can achieve immobilization, transportation, and rotation in the microscale is desired in biological micromanipulation. A multifunctional noncontact micromanipulation method is proposed here based on a vibration-generated whirling flow. Resonance of a cantilever structure is utilized to extend the straight vibration of a single piezo actuator to the 2D circular vibration of a micropipette. The circular vibration in fluids can generate the whirling flow featured with low pressure in the core area and flow velocity gradient. The low pressure can immobilize the objects nearby and transport them together with the micropipette, and the flow velocity gradient is utilized to form a torque to rotate the immobilized object. Experiments of the microbeads are conducted to evaluate the claimed functions and quantify the key parameters that influence the rotation velocity. The cell spheroid is immobilized and rotated for 3D observation, and by assessing the viability of the cells containing in the spheroid, the proposed method is proved noninvasive to living cells. Finally, another important application in operations of mouse egg cells is shown, which indicates that the proposed method is a potential valuable tool in biological micromanipulation.

Thermocapillary Convective Flows Generated by Laser Points or Patterns: Comparison for the Noncontact Micromanipulation of Particles at the Interface

This letter compares the controlled manipulation of micrometer size particles using thermocapillary convective flows generated by laser points or patterns. Such flows are generated when a surface tension stress is generated at the fluid/gas interface due to a thermal gradient. Laser heating allows to generate fast, localized flows that are used to displace a particle towards a desired position. However, these flows are repulsive and so the system is unstable. Although using the simple laser spot with a closed-loop control enables to control the particle displacement, the control of the particle movement direction is somehow difficult and the particle position stabilization remains challenging. In this letter, it is proposed to use laser patterns to overcome these limitations. Experimental tests are performed using a 500-μm-diameter steel spherical particle that is displaced towards a target position. The preliminary experimental results show that it is possible to overcome the above mentioned limitations while still obtaining maximal particle velocities ranging from 4 to 9 mm/s during the displacement phase.

Double-arm optical tweezer system for precise and dexterous handling of micro-objects in 3D workspace

Double-arm manipulators are unfamiliar as equipment used in microscopic work in biomedical laboratories, whereas they are prevalent in factory automation and humanoids. For non-contact micromanipulation in three-dimensional (3D) workspaces, we propose and design a double-arm optical tweezer system that can easily exchange two types of end-effectors (i.e., optical landscapes for laser trapping) with a focus tunable lens and a microlens array. With a time-shared scanning approach under interactive personal computer (PC) mouse controls, the system can perform the precise and dexterous handling of micro-objects in a 3D workspace. As a proof of concept, we demonstrate the two-dimensional (2D) and 3D dexterous handling of microbeads in the motions of solving puzzle rings. We also demonstrate the precise and periodic patterning of microbeads for massive dynamic arrays. This double-arm system can be applied with versatile tools used for various non-contact micromanipulations in the biomedical field and for dynamic arrays in single cell and 3D biology.

Phase-shift feedback control for dielectrophoretic micromanipulation.

In this paper, we present a novel approach to noncontact micromanipulation by controlled dielectrophoresis (DEP). To steer micro-objects in the desired way, the solutions reported in the literature use either DEP cages or amplitude modulation of the voltages applied to the electrodes. In contrast, we modulate the phases, that is, we control the phase shifts of the voltages applied to the electrodes, which simplifies the hardware implementation and extends the set of feasible forces. Furthermore, we introduce an innovative micro-electrode array layout, composed of four sectors with parallel (colinear) electrodes, which is capable of inducing an arbitrary movement in the manipulation area and is easy to fabricate using just an affordable one-layer technology. We then propose a closed-loop cascade control strategy based on real-time numerical optimization and deploy it to our experimental set-up. Numerical simulations and laboratory experiments demonstrate the manipulation capabilities such as positioning and steering of one or several microscopic objects (microspheres with a diameter of 50 μm) and even bringing two objects together and then separating them again. The results from simulations and experiments are compared and the positioning accuracy is evaluated in the whole manipulation area. The error in position is 8 μm in the worst case, which corresponds to 16% of the microsphere size or 0.7% of the manipulation range.

Analysis of the influence of inertia for non-contact micromanipulation

This article aims at analyzing the effect of the inertia of the objects in remotely actuated systems at the micrometer scale. As the size decreases inertia is commonly neglected and the systems are considered quasi-static. However, this article shows that for high velocities (around 8 mm/s) the dynamic behavior of the manipulated particle must be taken into account. To perform this analysis, a remotely magnetically actuated system dedicated to high speed manipulation is used. 60 μm-size particles placed at the air/liquid interface are actuated in 2D at different velocities. Precise trajectory tracking is obtained for velocities up to 2.8 mm/s (around 50 body lengths per second), for which inertia can be neglected. For faster velocities (more than 140 body lengths per second demonstrated in this paper) phase lag appears in trajectory tracking: inertia needs to be considered for the control. Experimental results are corroborated by numerical analysis of the model of the system. This article paves the way toward the control of future high speed remotely actuated systems at the micrometer scale.

Non-contact acoustic manipulation in microchannel

Noncontact micromanipulation technique is needed in micromachine technology, biotechnology, and other fields. In the present paper, a standing wave field is generated in a microchannel and a geometric space, and it is possible to trap small objects at nodes of the sound pressure distribution in the medium. A microchannel and a geometric space were made at the center of a glass plate of 50 mm x 50 mm x 5 mm. In the experiment, when the liquid water containing alumina particles was injected into the microchannel on glass plate irradiated by ultrasound, the particles flowed along several layers in the microchannel. In the geometric space, the particles were trapped in the sound pressure nodes of the standing wave field. By changing the frequency, the geometric pattern of particles aggregation interestingly changed. When the geometric space is a triangular space, the particle moved toward the top from the base of the triangle. When the microchannel is branched at the half circular geometric space, it was able...

Controlled 3D rotation of biological cells using optical multiple-force clamps.

Controlled three-dimensional (3D) rotation of arbitrarily shaped objects in the observation space of optical microscopes is essential for realizing tomographic microscope imaging and offers great flexibility as a noncontact micromanipulation tool for biomedical applications. Herein, we present 3D rotational control of inhomogeneous biological samples using 3D optical multiple-force clamps based on time-shared scanning with a fast focus-tunable lens. For inhomogeneous samples with shape and optical anisotropy, we choose diatoms and their fragments, and demonstrate interactive and controlled 3D rotation about arbitrary axes in 3D Cartesian coordinates. We also outline the hardware setup and 3D rotation method for our demonstrations.

Manipulation of Particles in a Microchannel with Various Geometric Spaces Using Ultrasound

A noncontact micromanipulation technique is required in micromachine technology, biotechnology, and other fields. In this study, a standing wave field was generated in a microchannel with a geometric space. It was possible to trap small objects at nodes of the sound pressure distribution in the medium. A microchannel of 1×50×1 mm3 was formed at the center of a glass plate of 50×50×5 mm3. In the experiment, when the liquid water containing particles was injected into the microchannel on the glass plate irradiated by ultrasound, the particles flowed along several layers. It was shown that the traveling wave was transmitted into the microchannel and the standing wave field was formed in the microchannel. The micromanipulation technique enabled the control of the direction of the particle flow by changing the ultrasound frequency in branched channels with a geometric region at the junction. Moreover, in a triangular region, the particles moved towards the top from the base of the triangle with a fixed frequency.

Laser-Induced Thermocapillary Convection for Mesoscale Manipulation

Modulation of surface stresses is a recent and promising method to perform mesoscale manipulation of components in liquid medium. We present a promising approach using infra red laser-induced thermocapillary-driven flow for handling multiple or single large and heavy objects. The objects are immersed in thin liquid layers and in contact with the substrate surface. These objects can be handled with high speed thermocapillary convection flow reaching significant forces depending on the object sizes. Velocity measurements showed that 92 µm-sized spherical beads can be dragged with velocities of about 5.5 mm/s. Parallel non-contact micromanipulation can be achieved.

Automated manipulation of non-spherical micro-objects using optical tweezers combined with image processing techniques

Automated optical trapping of non-spherical objects offers great flexibility as a non-contact micromanipulation tool in various research fields. Computer vision control enables fruitful applications of automated manipulation in biology and material science. Here we demonstrate fully-automated, simultaneous, independent trapping and manipulation of multiple non-spherical objects using multiple-force optical clamps. Customized real-time feature recognition and trapping beam control algorithms are also presented.

Pole Piece Effect on Improvement of Magnetic Controllability for Noncontact Micromanipulation

A single electromagnet can be used for one-dimensional (vertical) magnetic levitation, but cannot control the distribution of the magnetic field on a horizontal plane. For three-dimensional (3-D) levitated movement of objects, an arrangement of multiple electromagnets is required. A pole piece can connect the individual poles of the electromagnets in order to eliminate the appearance of multiple poles and produce a focal point of maximum magnetic field in the horizontal plane. This paper presents the results of an investigation of the effect on different pole pieces on the regulation and control of a large gap magnetic field for 3-D micromanipulation. In a large and wide magnetic gap, a levitated object tends to stay at the maximum point of magnetic field, B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> , in order to minimize the system energy. By producing a unique B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> point and controlling its position, 3-D levitated movement of a small permanent magnet (single magnetic dipole moment) can be realized. If the B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> point is converted into an area with a uniform field that is stronger than any nearby point (B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> area), complex objects, such as microrobots affixed with several permanent magnets, can be levitated and moved. By selecting a proper pole piece and tuning the electric currents in the electromagnets, the required field distribution will be obtained. The paper proposes a number of pole pieces and discusses their effect on magnetic field distribution. Through simulation results and experimental measurements, it shows that a number of proposed pole piece profiles can generate a magnetic field for 3-D levitated motion. Finally, it reports a demonstration of 3-D levitated motion of a single magnet (using the B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> point) and a microrobot (using the B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> area) to show the feasibility of the proposed method for micromanipulation

F-1222 複数音源を用いた非接触超音波マイクロマニピュレーション(S46-2 マイクロ・ナノ作業(2))(S46 マイクロ・ナノ作業)

Non-contact micromanipulation is one of the fundamental techniques in micromachine technology. This paper describes an advanced technique to manipulate particles one-, two- and three-dimensionally using two, three and four transducers. The transducers are settled with their sound-beam axes crossing at the same point. All transducers are driven at the same frequency, and a standing wave field is generated in the crossing region. When polystyrene particles are poured with a pipette into the sound field, the particles are trapped at the node of the sound pressure in the sound field. When changing the phase of one of the transducers of the three or four used, the trapped particles are transported along the sound beam axis of the transducer. Combining each movement along the four sound beam axes, three-dimensional non-contact manipulation of a particle is accomplished.

Control of a Standing Wave Field Using a Line-Focused Transducer for Two-Dimensional Manipulation of Particles

Control of the positions of particles using acoustic radiation pressure in water was studied to develop a noncontact micromanipulation technique. In this paper a method to transport the particles two-dimensionally using an ultrasonic standing wave field between a line-focused transducer with multiple electrodes and a reflector placed at the focal line is described. When alumina suspension of mean diameter 16 µm was poured into the standing wave field of 2.1 MHz, the particles were trapped and agglomerated at sound pressure nodes existing at half wavelength on the sound beam axis near the reflector. Changing the frequency alters the wave-length and hence the interval of agglomeration. Therefore the trapped particles were transported along the sound beam axis. When the next electrodes were driven, the standing wave field shifted laterally and the trapped particles moved to the corresponding nodal points. Thus two-dimensional transportation was realized using the line-focused transducer. A sound field generated by the line-focused transducer was discussed based on numerical calculations to design an optimum shape of a transducer for manipulation.