Three-Dimensional Manipulation of Micromodules Using Twin Optothermally Actuated Bubble Robots.

A 3D manipulation technique based on two optothermally generated and actuated surface-bubble robots is proposed. A single laser beam can be divided into two parallel beams and used for the generation and motion control of twin bubbles. The movement and spacing control of the lasers and bubbles can be varied directly and rapidly. Both 2D and 3D operations of micromodules were carried out successfully using twin bubble robots. The cooperative manipulation of twin bubble robots is superior to that of a single robot in terms of stability, speed, and efficiency. The operational technique proposed in this study is expected to play an important role in tissue engineering, drug screening, and other fields.

Manipulation and Characterization of Submillimeter Shearing Contacts in Graphite by the Micro-Dome Technique.

Manipulation techniques are the key to measuring fundamental properties of layered materials and their monolayers (2D materials) on the micro- and nanoscale as well as a necessity to the solution of relevant existing challenges. An example is the challenge against upscaling structural superlubricity, a phenomenon of near-zero friction and wear in solid contacts. To date, the largest single structural superlubric contact only has a size of a few tens of micrometers, which is achieved on graphite mesa, a system that has shown microscale superlubricity. The first obstacle against extending the contact size is the lack of suitable manipulation techniques. Here, a micro-dome technique is demonstrated on graphite mesas by shearing contacts 2500 times larger in area than previously possible. With this technique, submillimeter graphite mesas are opened, characterized for the first time, and compared to their microscale counterparts. Interfacial structures, which are possibly related to the failure of superlubricity, are observed: commensurate grains, external steps, and carbon aggregates. Furthermore, a proof-of-concept mechanical model is developed to understand how the micro-dome technique works and to predict its limits. Finally, a dual-axis force measuring device is developed and integrated with the micro-dome technique to measure the normal and lateral forces when shearing submillimeter mesas. These results provide a platform technique for future research on structural superlubricity on different scales and manipulation of structures of layered materials in general.

Particle Size-Dependent Component Separation Using Serially Arrayed Micro-Chambers.

The purpose of this research was to enable component separation based on simple control of the flow rate. We investigated a method that eliminated the need for a centrifuge and enabled easy component separation on the spot without using a battery. Specifically, we adopted an approach that uses microfluidic devices, which are inexpensive and highly portable, and devised the channel within the fluidic device. The proposed design was a simple series of connection chambers of the same shape, connected via interconnecting channels. In this study, polystyrene particles with different sizes were used, and their behavior was evaluated by experimentally observing the flow in the chamber using a high-speed camera. It was found that the objects with larger particle diameters required more time to pass, whereas the objects with smaller particle diameters flowed in a short time; this implied that the particles with a smaller size could be extracted more rapidly from the outlet. By plotting the trajectories of the particles for each unit of time, the passing speed of the objects with large particle diameters was confirmed to be particularly low. It was also possible to trap the particles within the chamber if the flow rate was below a specific threshold. By applying this property to blood, for instance, we expected plasma components and red blood cells to be extracted first.

Performance Analysis of a CSFH-Based Microgripper: Analytical Modeling and Simulation.

Microgrippers are promising tools for micro-manipulation and characterization of cells. In this paper, a biocompatible electro-thermally actuated microgripper with rotary capacitive position sensor is presented. To overcome the limited displacement possibilities usually provided by electrothermal actuators and to achieve the desired tweezers output displacement, conjugate surface flexure hinges (CSFH) are adopted. The microgripper herein reported can in principle manipulate biological samples in the size range between 15 and 120 µm. A kinematics modeling approach based on the pseudo-rigid-body-method (PRBM) is applied to describe the microgripper's working mechanism, and analytical modeling, based on finite elements method (FEM), is used to optimize the electrothermal actuator design and the heat dissipation mechanism. Finally, FEM-based simulations are carried out to verify the microgripper, the electrothermal actuator and heat dissipation mechanism performance, and to assess the validity of the analytical modeling.

A Volume-Tuning Capillary Gripper That Enhances Handling Capabilities and Enables Testing of Micro-Components.

Capillary forces are shown to be extremely effective for micro-assembly and pick-and-place processes, especially for their ability to self-align the handled objects. However, in today's machines, micro-objects are submitted to high loads, such as compressions for the electrical testing of the micro-components, or inertial forces coming from the high accelerations of the machines. There, capillary grippers may show some limits. These issues, as well as the difficulty to perform precise visual inspections (due to the tilt of the handled micro-object that can occur after a perturbation, such as the displacement of the gripper), can all be solved by temporarily removing the liquid meniscus. Therefore, we present a novel volume-tuning capillary gripper that provides a solution to these limitations without adding additional significant complexities or changes to the existing pick-and-place machines. A multi-scale prototype was dimensioned and produced by using fast prototyping methods, such as a femtosecond laser-assisted chemical etching process for fused silica. Models bringing a deeper understanding of the subsystems are presented. The proof of concept was extensively tested. Its picking capabilities and enhancements of the handling capabilities during horizontal motions, as well as the repeatability of the tuning of the volume of liquid, are presented.

Numerical Optimization and Map-Based Manipulation With a Quadrupole Electromagnetic Actuated System.

Electromagnetic actuation is a new technique for non-invasive manipulation, which provides wireless and controllable power source for magnetic micro-/nano-particles. This technique shows great potential in the field of precise mechanics, environment protection, and biomedical engineering. In this paper, a new quadrupole electromagnetic actuated system was constructed, which was composed of four electromagnetic coils, each coil being actuated by an independent DC power supplier. The magnetic field distribution in the workspace was obtained through finite element modeling and numerical simulation via COMSOL software, as well as the effect of the current flow through the coil in the field distribution. Moreover, parameters of the electromagnetic system were optimized through parametric modeling analysis. A magnetic field map was constructed for rapidly solving the desired driving current from the required magnetic flux density. Experiments were conducted to manipulate a micro-particle along the desired circular path. The proposed work provides theoretical references and numerical fundamentals for the control of magnetic particle in future.

Probabilistic genotyping of single cell replicates from complex DNA mixtures recovers higher contributor LRs than standard analysis.

DNA mixtures are a common source of crime scene evidence and are often one of the more difficult sources of biological evidence to interpret. With the implementation of probabilistic genotyping (PG), mixture analysis has been revolutionized allowing previously unresolvable mixed profiles to be analyzed and probative genotype information from contributors to be recovered. However, due to allele overlap, artifacts, or low-level minor contributors, genotype information loss inevitably occurs. In order to reduce the potential loss of significant DNA information from donors in complex mixtures, an alternative approach is to physically separate individual cells from mixtures prior to performing DNA typing thus obtaining single source profiles from contributors. In the present work, a simplified micro-manipulation technique combined with enhanced single-cell DNA typing was used to collect one or few cells, referred to as direct single-cell subsampling (DSCS). Using this approach, single and 2-cell subsamples were collected from 2 to 6 person mixtures. Single-cell subsamples resulted in single source DNA profiles while the 2-cell subsamples returned either single source DNA profiles or new mini-mixtures that are less complex than the original mixture due to the presence of fewer contributors. PG (STRmix™) was implemented, after appropriate validation, to analyze the original bulk mixtures, single source cell subsamples, and the 2-cell mini mixture subsamples from the original 2-6-person mixtures. PG further allowed replicate analysis to be employed which, in many instances, resulted in a significant gain of genotype information such that the returned donor likelihood ratios (LRs) were comparable to that seen in their single source reference profiles (i.e., the reciprocal of their random match probabilities). In every mixture, the DSCS approach gave improved results for each donor compared to standard bulk mixture analysis. With the 5- and 6- person complex mixtures, DSCS recovered highly probative LRs (≥1020) from donors that had returned non-probative LRs (<103) by standard methods.

Advanced medical micro-robotics for early diagnosis and therapeutic interventions.

Recent technological advances in micro-robotics have demonstrated their immense potential for biomedical applications. Emerging micro-robots have versatile sensing systems, flexible locomotion and dexterous manipulation capabilities that can significantly contribute to the healthcare system. Despite the appreciated and tangible benefits of medical micro-robotics, many challenges still remain. Here, we review the major challenges, current trends and significant achievements for developing versatile and intelligent micro-robotics with a focus on applications in early diagnosis and therapeutic interventions. We also consider some recent emerging micro-robotic technologies that employ synthetic biology to support a new generation of living micro-robots. We expect to inspire future development of micro-robots toward clinical translation by identifying the roadblocks that need to be overcome.

Theoretical Thermal-Mechanical Modelling and Experimental Validation of a Three-Dimensional (3D) Electrothermal Microgripper with Three Fingers.

This paper presents the theoretical thermal-mechanical modeling and parameter analyses of a novel three-dimensional (3D) electrothermal microgripper with three fingers. Each finger of the microgripper is composed of a bi-directional Z-shaped electrothermal actuator and a 3D U-shaped electrothermal actuator. The bi-directional Z-shaped electrothermal actuator provides the rectilinear motion in two directions. The novel 3D U-shaped electrothermal actuator offers motion with two degrees of freedom (DOFs) in the plane perpendicular to the movement of the Z-shaped actuator. As a result, each finger possesses 3D mobilities with three DOFs. Each beam of the actuators is heated externally with polyimide films. In this work, the static theoretical thermal-mechanical model of the 3D U-shaped electrothermal actuator is established. Finite-element analyses and experimental tests are conducted to verify and validate the model. With this model, parameter analyses are carried out to provide insight and guidance on further improving the 3D U-shaped actuator. Furthermore, a group of micro-manipulation experiments are conducted to demonstrate the flexibility and versality of the 3D microgripper on manipulate different types of small/micro-objects.

Design and Experimental Investigations of Shape and Attitude Carding System for the Wires of Micro Coreless Motor Winding.

The shape and attitude (S&A) of the electrode wire are important characteristics of micro coreless motor winding. The purpose of this paper is to present the design of a robotic micro-manipulation system for micro wire carding with arbitrary S&A, which can be used as the pretreatment system for wire micro-gripper systems. The system is based on the principle of flexible carding, and uses nylon, bristle, nanometer-silk and wool as materials for the brushing micro-manipulator. The trajectory of the brushing micro-manipulator is designed, and the S&A of the electrode wires are straightened through the combined motion mode of horizontal and vertical brushing micro-manipulators. The experimental results show that the material of the brushing micro-manipulator has a great impact on the carding quality. Nanometer-silk material is more suitable for horizontal brushing micro-manipulators, and wool material is more suitable for vertical brushing micro-manipulators. The geometric dimension of the brushing micro-manipulator also affects the carding quality. When the diameter is in the range of 1 mm, the carding effect of the horizontal brushing micro-manipulator with a length of 4.9-8 mm is better. The system can realize the automatic carding of flexible electrode wires with arbitrary S&A, and it will not damage the structure of wires in the process.

Time-resolved particle image velocimetry analysis and computational modeling of transient optically induced electrothermal micro vortex.

Trapping, sorting, transportation, and manipulation of synthetic microparticles and biological cells enable investigations in their behavior and properties. Microfluidic techniques like rapid electrokinetic patterning (REP) provide a non-invasive means to probe into the nature of these micro and nanoparticles. The opto-electrically induced nature of a REP micro vortex allows tuning of the trap characteristics in real-time. In this work, we studied the effects of transient optical heating on the induced electrothermal vortex using micro-particle image velocimetry (µ-PIV) and computational modeling. A near infra-red (980 nm) laser beam was focused on a colloidal suspension of 1 µm polystyrene beads sandwiched between two parallel-plate electrodes. The electrodes were subjected to an AC current. The laser spot was scanned back-and-forth in a line, at different frequencies, to create the transient vortex. This phenomenon was also studied with a computational model made using COMSOL Multiphysics. We visualize fluid flow in custom-shaped REP traps by superposing multiple axisymmetric (spot) vortices and discuss the limitations of using superposition in dynamically changing traps.

Path Planning for 3-D In-Hand Manipulation of Micro-Objects Using Rotation Decomposition.

Robotic manipulation and assembly of micro and nanocomponents in confined spaces is still a challenge. Indeed, the current proposed solutions that are highly inspired by classical industrial robotics are not currently able to combine precision, compactness, dexterity, and high blocking forces. In a previous work, we proposed 2-D in-hand robotic dexterous manipulation methods of arbitrary shaped objects that considered adhesion forces that exist at the micro and nanoscales. Direct extension of the proposed method to 3-D would involve an exponential increase in complexity. In this paper, we propose an approach that allows to plan for 3-D dexterous in-hand manipulation with a moderate increase in complexity. The main idea is to decompose any 3-D motion into a 3-D translation and three rotations about specific axes related to the object. The obtained simulation results show that 3-D in-hand dexterous micro-manipulation of arbitrary objects in presence of adhesion forces can be planned in just few seconds.

Design, Fabrication, and Testing of a Novel 3D 3-Fingered Electrothermal Microgripper with Multiple Degrees of Freedom.

This paper presents the design, fabrication, and testing of a novel three-dimensional (3D) three-fingered electrothermal microgripper with multiple degrees of freedom (multi DOFs). Each finger of the microgripper is composed of a V-shaped electrothermal actuator providing one DOF, and a 3D U-shaped electrothermal actuator offering two DOFs in the plane perpendicular to the movement of the V-shaped actuator. As a result, each finger possesses 3D mobilities with three DOFs. Each beam of the actuators is heated externally with the polyimide film. The durability of the polyimide film is tested under different voltages. The static and dynamic properties of the finger are also tested. Experiments show that not only can the microgripper pick and place microobjects, such as micro balls and even highly deformable zebrafish embryos, but can also rotate them in 3D space.

Size-Controlled Spalling of LaAlO3/SrTiO3 Micromembranes.

The ability to form freestanding oxide membranes of nanoscale thickness is of great interest for enabling material functionality and for integrating oxides in flexible electronic and photonic technologies. Recently, a route has been demonstrated for forming conducting heterostructure membranes of LaAlO3 and SrTiO3, the canonical system for oxide electronics. In this route, the epitaxial growth of LaAlO3 on SrTiO3 resulted in a strained state that relaxed by producing freestanding membranes with random sizes and locations. Here, we extend the method to enable self-formed LaAlO3/SrTiO3 micromembranes with control over membrane position, their lateral sizes from 2 to 20 µm, and with controlled transfer to other substrates of choice. This method opens up the possibility to study and use the two-dimensional electron gas in LaAlO3/SrTiO3 membranes for advanced device concepts.

Recovery of single source DNA profiles from mixtures by direct single cell subsampling and simplified micromanipulation.

Deconvolution of forensic DNA mixtures into their individual component DNA (geno)types is of great investigative value, though often complex and difficult. Two-person mixtures comprising a major and minor contributor are often easily interpreted although, when the DNA ratio of the two individuals is approximately equal (~1:1), deconvolution and interpretation becomes much more difficult. To address this issue, a physical separation of individual-, two- or three- cell subsamples prior to autosomal STR analysis was performed using a simplified micromanipulation technique paired with a decreased reaction volume and increased cycle number PCR. Using this method, single and multiple buccal epithelial cells were collected from a 1:1 two-person mixture (i.e. from individual 'A' and 'B') and directly amplified, omitting standard DNA extraction and purification steps. Single cell subsamples resulted in partial single-source profiles for both contributors while, in accordance with expectations of a quasi-binomial sampling schema, two- and three-cell subsamples resulted in single source informative partial profiles of individual A and individual B as well as complete consensus profiles, and equally mixed 1:1 (2-cell subsamples) and 2:1 (3-cell subsamples) admixed profiles of individual A and B.This proof-of-concept approach shows promise in permitting the DNA deconvolution of mixed samples where the individual contributors are present in similar amounts that would otherwise be difficult to interpret, resulting in an increase in evidentiary value. The subsampling approach can be readily investigated for DNA casework applications without additional investment in costly, new equipment, requiring only a stereo microscope and a tungsten needle.

Surface Tension-Based Alignment of Microfibers on Hydrophilic-Superhydrophobic Grooved Surfaces.

Alignment and orderly distribution of microfibers have a major effect on the mechanical, electrical, and thermal properties of the fiber reinforced materials, biomimetic materials, and soft microsensors. However, it is still a challenging task to precisely align and distribute microfibers and construct complex patterns. This paper proposes a surface tension-based method to align and orderly distribute microfibers. A model was developed to simulate the surface tension driven alignment of the microfiber. We designed and fabricated hydrophilic-superhydrophobic grooved surfaces. We demonstrated that the microfibers can self-align to the hydrophilic-superhydrophobic grooves with different geometries. We studied the influence of the volume of the droplet and bias on the alignment success rate. The results indicate that the process can tolerate large variations of the bias and the volume, unless the volume is not enough to cover the groove. We further investigated the influence of the width of the groove on the alignment accuracy. The results show that the alignment accuracy is largely depending on the size difference between the groove and the microfiber; the better the size of the groove matches the size of the fiber, the higher the alignment accuracy will be achieved. The proposed method has great potential in construction of complex microstructures using microfibers.

An Investigation on a Novel 3-RCU Flexible Micromanipulator.

A novel type of spatial three revolute-cylindrical-universal (3-RCU) flexible micro manipulator is designed based on flexible hinges, and analyzed by finite element analysis (FEA). The piezoelectric actuators are adopted as driving devices in this platform, a new lever amplification mechanism is designed as its micro-displacement amplification mechanism, the workspace of the platform is enlarged, and the theoretical and simulation amplification ratios of the amplification mechanism are 3.056 and 2.985, respectively. The margin of error is just 2.3%. In space, the 3-RCU platform can realize the micro movement of three degrees of freedom. Also, the platform has a high carrying capacity, less motion loss, and the transmission efficiency is higher when the platform works. The decoupling performance, stress under extreme conditions and natural frequency of the platform are simulated by ANSYS Workbench software. A series of simulation analyses show the feasibility and security of the platform. The platform has good decoupling and working performance. The simulation results show that the platform has high simulation stiffness and high positioning accuracy.

Optical Trapping and Manipulating with a Silica Microring Resonator in a Self-Locked Scheme.

Based on the gradient force of evanescent waves in silica waveguides and add-drop micro-ring resonators, the optical trapping and manipulation of micro size particles is demonstrated in a self-locked scheme that maintains the on-resonance system even if there is a change in the ambient temperature or environment. The proposed configuration allows the trapping of particles in the high Q resonator without the need for a precise wavelength adjustment of the input signal. On the one hand, a silicon dioxide waveguide having a lower refractive index and relatively larger dimensions facilitates the coupling of the laser with a single-mode fiber. Furthermore, the experimental design of the self-locked scheme reduces the sensitivity of the ring to the environment. This combination can trap the micro size particles with a high stability while manipulating them with high accuracy.

Different Regimes of Opto-fluidics for Biological Manipulation.

Metallic structures can be used for the localized heating of fluid and the controlled generation of microfluidic currents. Carefully designed currents can move and trap small particles and cells. Here we demonstrate a new bi-metallic substrate that allows much more powerful micro-scale manipulation. We show that there are multiple regimes of opto-fluidic manipulation that can be controlled by an external laser power. While the lowest power does not affect even small objects, medium power can be used for efficiently capturing and trapping particles and cells. Finally, the high-power regime can be used for 3D levitation that, for the first time, has been demonstrated in this paper. Additionally, we demonstrate opto-fluidic manipulation for an extraordinarily dynamic range of masses extending eight orders of magnitude: from 80 fg nano-wires to 5.4 µg live worms.

Development of a Novel Modular Compliant Gripper for Manipulation of Micro Objects.

This paper proposes a modular gripping mechanism for the manipulation of multiple objects. The proposed micro gripper combines traditional machining techniques with MEMS technologies to produce a modular mechanism consisting of a sturdy, compliant aluminium base and replaceable end-effectors. This creates an easily-customisable solution for micro manipulation with an array of different micro tips for different applications. We have provided the kinematic analysis for the gripper to predict the output and have also optimised design parameters based on FEA (finite element analysis) simulation and the effects of altering flexure beam lengths. The gripper is operated by a piezo actuator capable of 18 µ m displacement at 150 V of applied DC voltage. This is then amplified by a factor of 8.1 to a maximum tip displacement of 154 µ m. This is achieved by incorporating bridge and lever amplifying techniques into the design. An initial experimental analysis of the micro gripper is provided to investigate the performance of the micro gripper and to gauge the accuracy of the theory and simulation through comparison with experimental results.