Biological Micromanipulation Research Articles

Modeling and Evaluation of Penetration Process Based on 3D Mechanical Simulation.

In biological micromanipulation, cell penetration is a typical procedure that precedes cell injection or oocyte enucleation. During this procedure, cells usually undergo significant deformation, which leads to cell damage. In this paper, we focus on modeling and evaluating the cell penetration process to reduce cell deformation and stress, thereby reducing cell damage. Initially, a finite element model (FEM) is established to simulate the cell penetration process. The effectiveness of the model is then verified through visual detection and comparison of cell deformation with experimental data. Next, various mechanical responses are analyzed, considering the influence of parameters, such as the radius and shape of the injection micropipettes, material properties, and size of the cells. Finally, the relationship between the intracellular stress and the cell penetration depth of biological cells is obtained. The evaluation results will be applied to develop optimized operation plans, enhancing the efficiency and safety of the cell penetration process.

Advanced pneumatic microgripper for versatile biomedical micromanipulation

Microgrippers offer better operational flexibility in biological micromanipulation. However, they face challenges in size miniaturization and environmental adaptability (especially in biological liquid environments). To overcome these challenges, a novel pneumatic microgripper is proposed with a thin-walled multi-airbag structure that directly drives the clamping jaws in motion, with a simple and compact overall construction. The microgripper has a maximum clamping range of 925 μm and can provide a clamping force exceeding 25 mN, capable of lifting loads over 300 times its weight. The microgripper is integrative and can be mass-produced with biocompatible resins in a single-step high-precision 3D printing process. The pneumatic microgripper is utilized to achieve the sorting and assisted injection of mouse oocytes (60–80 μm), assisted cutting of porcine oocytes (100–120 μm), and microscopic threading (10–15 μm) operation with two-finger cooperation. These demonstrations confirm it can operate fine manipulation of microscopic biological structures in air and liquid, and has good biocompatibility and cooperative operational ability. The developed pneumatic microgripper shows broad application prospects in biomedical applications such as microsurgery, micro biopsy, and assisted reproduction.

SonoRotor: An Acoustic Rotational Robotic Platform for Zebrafish Embryos and Larvae

Rotation manipulation is an essential component of biological microscopy and can become integral to multidisciplinary research and applications. On-chip rotation of microobjects with spherical shapes like biological cells and model organisms has been demonstrated based on advanced microfluidic techniques. To date, however, biocompatible, easy-to-fabricate, easy-to-operate, and controlled rotation of small animal models with slender bodies remains a challenge. Here, we present SonoRotor, a miniaturized acoustic rotation platform for animal models using a single elongated acoustically activated air bubble. In the presence of an acoustic field, the trapped elongated air bubble oscillates and induces a polarized vortex in the surrounding liquid. Zebrafish embryos (spherical) and larvae (slender), typically larger than hundreds of micrometers, become trapped near the oscillating bubble and undergo a controllable, high-speed, and stable out-of-plane rotation. By controlling the voltage applied to our device, we can adjust the rotation speed of the zebrafish. The developed acoustic rotation manipulation platform is simple, cost-effective, allows multiview imaging, high-throughput operation, and can be combined with downstream analytical techniques to perform a variety of biological micromanipulation on small animal models.

Magnetic Driven Two-Finger Micro-Hand with Soft Magnetic End-Effector for Force-Controlled Stable Manipulation in Microscale.

In recent years, micromanipulators have provided the ability to interact with micro-objects in industrial and biomedical fields. However, traditional manipulators still encounter challenges in gaining the force feedback at the micro-scale. In this paper, we present a micronewton force-controlled two-finger microhand with a soft magnetic end-effector for stable grasping. In this system, a homemade electromagnet was used as the driving device to execute micro-objects manipulation. There were two soft end-effectors with diameters of 300 μm. One was a fixed end-effector that was only made of hydrogel, and the other one was a magnetic end-effector that contained a uniform mixture of polydimethylsiloxane (PDMS) and paramagnetic particles. The magnetic force on the soft magnetic end-effector was calibrated using an atomic force microscopy (AFM) probe. The performance tests demonstrated that the magnetically driven soft microhand had a grasping range of 0–260 μm, which allowed a clamping force with a resolution of 0.48 μN. The stable grasping capability of the magnetically driven soft microhand was validated by grasping different sized microbeads, transport under different velocities, and assembly of microbeads. The proposed system enables force-controlled manipulation, and we believe it has great potential in biological and industrial micromanipulation.

Parallel trapping, patterning, separating and rotating of micro-objects with various sizes and shapes using acoustic microstreaming

Parallel multifunctional methods for cell micromanipulation are invaluable tools in biomedicine, bioengineering, and biophysics. However, one of the key limitations of the most existing lab-on-chip devices is the challenge to integrate multiple operations into single microchip. A novel noncontact acoustic micromanipulation method based on acoustic microstreaming, capable of trapping, patterning, separating, and rotating micro-objects with various sizes and shapes, is proposed. Herein, two types of highly-localized microvortices, referred to as “inner microvortex” and “outer microvortex”, are generated by an acoustic vibration applied to custom-designed microcavity array bottoms, and utilized to achieve parallel multifunctional micromanipulation. Experiments of microbeads are conducted to verify the proposed functions and quantify the key parameters that influence the acoustofluidic device performance. Subsequently, further multifunctional micromanipulation of living cells, including trapping and isolating circulating tumor cells with the capturing efficiency of more than 90 %, or tunable trapping and rotating of swine oocytes, is demonstrated, to show the manipulated forces can be effectively tuned on demand for different cell studies. Finally, another important application in multifunctional operation of motile micro-organisms (that is, Euglena gracilis) in a noninvasive manner (viability: 100 %) is shown. Our AMM technique is easy, robust, biocompatible, and becomes a potential valuable tool in biological micromanipulation.

Magnetic Milli-Robot Swarm Platform: A Safety Barrier Certificate Enabled, Low-Cost Test Bed

Swarms of micro- and milli-sized robots have the potential to advance biological micro-manipulation, micro- assembly and manufacturing, and provide an ideal platform for studying large swarm behaviors and control. Due to their small size and low cost, tens to hundreds of micro/milli robots can function in parallel to perform a task that otherwise would be too cumbersome or costly for a larger macroscopic robot. Here, we demonstrate a scalable system and modular circuit architecture for controlling and coordinating the motion of $ >$ 10's of magnetic micro/milli robots. By modifying the concepts of safety barrier certificates to our magnetic robot hardware, we achieve minimally invasive, collision-free, 2D position control (x, y) of up to N = 16 robots in a low-cost tabletop ( $\text{288 mm} \times \text{288 mm}$ ) magnetic milli-robot platform with up to 288 degrees of freedom. We show that the introduction of random dithering can achieve a $100\%$ success rate (i.e., no deadlocking), enabling the system to serve as a platform for the study of various swarm-like behaviors or multi-agent robotic coordination.

A Microforce-Sensing Mobile Microrobot for Automated Micromanipulation Tasks

This paper presents a microforce-sensing mobile microrobot ( $\mu $ FSMM) for use in automated micromanipulation tasks. The design consists of a planar vision-based microforce sensor end-effector, while the microrobot body is made of chemically etched nickel that is driven by an exterior magnetic field. With a known stiffness, the manipulation forces can be determined from observing the deformation of the end-effector through a camera attached to an optical microscope. After analyzing and calibrating the stiffness of a micromachined prototype, the mobility and in situ force-sensing capabilities are verified through real-time, closed loop, force controlled manipulation tests with automated path planning and navigation. The calibrated stiffness of the microforce sensor end-effectors fabricated is on the order of 10−3 N/m. The online (real time) force-sensing resolution is approximately $1.5~\mu \text{N}$ . The sensing range is 0–20 $\mu \text{N}$ along the two planar directions. In automated micromanipulation experiments with a microcomponent, the $\mu $ FSMM utilizes real-time force control to apply a prescribed force of $6~\mu \text{N}$ to a desired location on a fixed microobject. Similarly, in another automated micromanipulation experiment, the $\mu $ FSMM demonstrates the use of real-time force control to limit the manipulation forces experienced by the microobject to remain below a threshold of 12 $\mu \text{N}$ . Note to Practitioners —This paper was motivated by recent interest single-cell biological micromanipulation tasks that seek to understand the role of environmental forces on the mechanics of cell development (mechanobiology) and the biological mechanisms that control such behavior (mechanotransduction). In addition, tissue engineering applications require the safe micromanipulation of single cells to desired locations in the workspace for growing tissue scaffolds. The $\mu $ FSMM presented here can be easily inserted into existing biological testbeds to use for these aforementioned applications. The designed magnetic coil system is compatible with standard inverted optical microscopes, while a digital camera for real-time image processing is already standard in these testbeds. The developed software interface can be used to prescribe automated microforce controlled manipulations of single cells and tissues in the workspace to carry out these aforementioned tasks. This paper is also suitable for carrying out general automated micromanipulation and microassembly tasks with advanced manufacturing applications.

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.

Design and Testing of a Flexure-Based Constant-Force Stage for Biological Cell Micromanipulation

This paper presents the design of a novel flexure-based precision positioning stage with constant output force for biological cell micromanipulation. One uniqueness of the proposed design is that it produces a constant force without using a force controller. Only a motion control is needed to produce a constant output force, which significantly simplifies the system design process. The stage is driven by a piezoelectric actuator through a displacement amplifier. Analytical models of the displacement amplifier and the zero-stiffness structure are established and verified by conducting finite-element analysis simulations. The structure parameters are optimally designed to guarantee the requirement on output force, motion range, and physical size. A prototype stage is fabricated by 3-D printing process and a series of experiments is carried out. Experimental results show that the developed positioning stage delivers a near constant output force with slight fluctuation in the reachable constant-force motion range of $138~\mu \text{m}$ . The applications of the developed constant-force stage in biological cell manipulation have been demonstrated through experimental investigations. Note to Practitioners —A constant-force stage can produce a constant output force without using a force control. It is attractive for biological micromanipulation. This paper presents the design and testing of a novel constant-force flexure stage. The constant force indicates a zero stiffness for the mechanism. The stage mechanism is devised using modified leaf flexure (MLF) to achieve positive-stiffness structure. Bistable beams are used to design negative-stiffness structure by making use of their postbuckling characteristics. Two bistable beams and two MLFs are combined together to construct a zero-stiffness structure. A conventional stage is also fabricated for comparison study. The performance of the proposed constant-force stage has been verified by simulation and experimental studies. Results indicate that the developed stage system has great superiority over conventional one in terms of reducing driving force, increasing motion range, and reducing force fluctuation. Experimental demonstration of bio-micromanipulation has been presented to reveal its potential applications.

Optical micromanipulation of active cells with minimal perturbations: direct and indirect pushing

The challenge to wide application of optical tweezers in biological micromanipulation is the photodamage caused by high-intensity laser exposure to the manipulated living systems. While direct exposure to infrared lasers is less likely to kill cells, it can affect cell behavior and signaling. Pushing cells with optically trapped objects has been introduced as a less invasive alternative, but the technique includes some exposure of the biological object to parts of the optical tweezer beam. To keep the cells farther away from the laser, we introduce an indirect pushing-based technique for noninvasive manipulation of sensitive cells. We compare how cells respond to three manipulation approaches: direct manipulation, pushing, and indirect pushing. We find that indirect manipulation techniques lessen the impact of manipulation on cell behavior. Cell survival increases, as does the ability of cells to maintain shape and wiggle. Our experiments also demonstrate that indirect pushing allows cell-cell contacts to be formed in a controllable way, while retaining the ability of cells to change shape and move.