Design and optimization of an octuple-electrode array for micro-particle chain rotation via electrorotation integrated with machine vision technology.

Microparticle rotation is an important process in biomedical engineering, such as biosensors, cell injection or cell morphology. Single particle rotation has been widely investigated, while rotation of particle chains has gained rare attention. In this paper, we utilize a noncontact manipulation method to rotate microparticle chains via electrorotation by designing an octuple-electrode array (OEA). Finite element simulations were conducted for analyzing the desired electrode field and optimizing the structure of microelectrode pairs. The direction of the electric field in the workspace is investigated with different voltage signal inputs through specially designed circuits. In the experiment, microparticles are driven to form several chains in the proposed electrode fields. With the rotation of the electric field, particle chains could be rotated synchronously. Automated rotation and detection of polystyrene microspheres and yeast cell chains are achieved using machine vision technology. Results show that the proposed method could be utilized to rotate ordered microparticles with an appropriate input signal.

A Hand-Held Platform for Boar Sperm Viability Diagnosis Based on Smartphone.

The swine fever virus seriously affects pork production, and to improve pork production, pig breeding efficiency needs to be improved, and the detection of boar sperm activity is an important part of the pig breeding process. Traditional laboratory testing methods rely on bulky testing equipment, such as phase-contrast microscopes, high-speed cameras, and computers, which limit the testing scenarios. To solve the above problems, in this paper, a microfluidic chip was designed to simulate sperm in the oviduct with a channel thickness of 20 um, which can only accommodate sperm for two-dimensional movement. A miniature microscope system which can be used in combination with a smartphone is designed that is only the size of the palm of the hand and has a magnification of about 38 times. An intelligent diagnostic app was developed using Java language, which can automatically identify and track boar sperm with a recognition rate of 96.08% and an average tracking rate of 86%. The results show that the proposed smartphone-based hand-held platform can effectively replace the traditional microscope compound computer to diagnose sperm activity. In contrast, the platform is smaller, easier to use and is not limited by the usage scenarios.

Contactless acoustic tweezer for droplet manipulation on superhydrophobic surfaces.

Droplet manipulation on superhydrophobic surfaces (DMSS) without conventional pipetting is an emerging liquid handling technology, which can be potentially used for diagnostic, analysis, and synthetic processes. Despite notable progress, controlling droplet motion on superhydrophobic surfaces by contactless acoustic waves is rarely reported. Herein, we report a contactless acoustic tweezer (CAT) for DMSS based on establishing ultrasonic standing wave between an ultrasound transducer (UST) and a superhydrophobic substrate to manipulate droplets without physical contact. The CAT utilizes acoustic radiation forces to trap and move droplets on superhydrophobic surfaces, which allows for precise and controllable movement of droplets by controlling the movement of the UST. Small droplets with volume less than 20 µL can be levitated in mid-air for out-plane manipulation, and large droplets with volume up to 500 µL can be trapped for in-plane manipulation. Experimental results demonstrate the versatility of the CAT for manipulating droplets with various compositions and volumes on various superhydrophobic substrates, offering a versatile and cross-contamination-free liquid handling approach for applications, including but not limited to high-throughput surface-enhanced Raman scattering.

Navigation and closed-loop control of magnetic microrobot in plant vein mimic environment.

In recent years, research on the manipulation and control of microrobot has gradually matured. In order to improve the intelligence of microrobots, navigation study also becomes an important research topic. In practice, microrobots could be disturbed by the flowing liquid when it moves in a microfluidic environment. As a result, the actual trajectory of microrobots will deviate from the intended one. In this paper, firstly, different algorithms for the navigation of microrobots in a simulated plant leaf vein environment are investigated. According to the simulation results, RRT*-Connect is then selected as the path planning algorithm with a relatively better performance. Based on the pre-planned trajectory, a fuzzy PID controller is further designed for precise trajectory tracking, which can effectively eliminate the random disturbance caused by micro-fluid flow during the motion and make it quickly recover to a stable movement state.

Path planning and optimization for micro-robot in a vessel-mimic environment.

Manipulating micro-robots in blood vessels is an essential technology for medical researchers in applications such as drug delivery and thrombus removal. The usage of micro-robots in medicine can help overcome the limitations of many conventional clinical methods. In this study, we aimed to make the micro-robot more intelligent while moving through blood vessels. First, the skeleton of an image of the blood vessels is extracted, which is further used for path planning. Then, the skeleton-extraction-based A* algorithm was used for determining a best route for the movement of the microrobot at a safe distance from the vascular wall. Finally, the gradient descent algorithm was utilized to smooth the planned path. Simulations were conducted to verify the effectiveness of the proposed algorithms. The proposed methods would improve the efficiency for the further manipulation of the micro-robot in the blood vessel environment.

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.

Engineered bone scaffolds with Dielectrophoresis-based patterning using 3D printing.

Patterning of cells into a specific pattern is an important procedure in tissue engineering to facilitate tissue culture and ingrowth. In this paper, a new type of 3D-printed scaffold utilizing dielectrophoresis (DEP) for active cell seeding and patterning was proposed. This scaffold adopted a concentric-ring design that is similar to native bone tissues. The scaffold was fabricated with a commercial three-dimensional (3D) printer. Polylactic Acid (PLA) was selected as the material for the printer and the fabricated scaffold was coated with gold to enhance the conductivity for DEP manipulation. Simulation from COMSOL confirmed that non-uniform electric fields were successfully generated under a voltage input. The properties of the scaffold were first characterized through a series of experiments. Then, preosteoblast MC3T3-E1 cells were seeded onto the coated scaffold and multiple cellular rings were observed under the microscope. The biocompatibility of the material was also examined and mineralized bone nodules were detected using Alizarin Red S Staining after 28 days of culture. The proposed scaffold design can enable formation of multiple ring patterns via DEP and the properties of the scaffold are suitable for bone tissue culture. This new type of 3D-printed scaffold with cell seeding mechanism offers a new and rapid approach for fabricating engineered scaffolds that can arrange cells into different patterns for various tissue engineering applications.

Characterization of a Honeycomb-Like Scaffold With Dielectrophoresis-Based Patterning for Tissue Engineering.

OBJECTIVE: Seeding and patterning of cells with an engineered scaffold is a critical process in artificial tissue construction and regeneration. To date, many engineered scaffolds exhibit simple intrinsic designs, which fail to mimic the geometrical complexity of native tissues. In this study, a novel scaffold that can automatically seed cells into multilayer honeycomb patterns for bone tissue engineering application was designed and examined. METHODS: The scaffold incorporated dielectrophoresis for noncontact manipulation of cells and intrinsic honeycomb architectures were integrated in each scaffold layer. When a voltage was supplied to the stacked scaffold layers, three-dimensional electric fields were generated, thereby manipulating cells to form into honeycomb-like cellular patterns for subsequent culture. RESULTS: The biocompatibility of the scaffold material was confirmed through the cell viability test. Experiments were conducted to evaluate the cell viability during DEP patterning at different voltage amplitudes, frequencies, and manipulating time. Three different mammalian cells were examined and the effects of the cell size and the cell concentration on the resultant cellular patterns were evaluated. CONCLUSION: Results showed that the proposed scaffold structure was able to construct multilayer honeycomb cellular patterns in a manner similar to the natural tissue. SIGNIFICANCE: This honeycomb-like scaffold and the dielectrophoresis-based patterning technique examined in this study could provide the field with a promising tool to enhance seeding and patterning of a wide range of cells for the development of high-quality artificial tissues.