We report the rapid assembly of carbon nanoparticles (CNPs) into functional electrical elements utilizing optically induced electroosmotic flow (OIEF) in a specialized microfluidics chip. Numerical simulations of various optically induced electrokinetics forces exerted on CNPs were initially performed to ascertain the viable forces that could overcome the Brownian motion and produce sufficient force to manipulate and assemble the CNPs. The results confirmed the theoretical prediction that only the force induced by OIEF could manipulate the CNPs. Subsequently, a series of experiments for assembling CNPs were conducted. This was followed by electrical characterization of the assembled three-dimensional CNP microstructures. The results proved that OIEF could effectively and rapidly assemble CNPs in about 45 s. We used measurements of the current-voltage relationship to validate that the CNP-based microstructures are resistive elements, and their resistance could be controlled by the width and length of the microstructures. We believe that, by using the OIEF technique, different nanoparticles of varying electrical properties could be assembled rapidly in a specialized microfluidics chip to create micro-electrical elements in the future, including integrating different nanoparticle elements into functional electrical devices.
We report a label-free approach toward the object of characterizing the self-rotational motions of red blood cells (RBCs) during storage under the optically-induced electrokinetics-based microfluidics mechanism. A theoretical analysis of the transmembrane potential across RBCs was performed getting a threshold voltage for keeping cellular biological integrity. Then, by investigation of the self-rotational behaviors of the individual RBCs in larger population, the RBCs that were stored more than three weeks statistically showed the distinctive self-rotational speed. Results verified that the self-rotational biomarkers of the RBCs could be used to label-free reckon the qualities of the stored RBCs in this kind of microfluidics chip. This finding may be further developed as a new criterion to real-time and label-free monitoring of the banked blood qualities, thereby diminishing the blood transfusion venture.
Purpose Nuclear waste tanks need to be cut into pieces before they can be safely disposed of, but the cutting process produces a large amount of aerosols with radiation, which is very harmful to the health of the operator. The purpose of this paper is to establish an intelligent strategy for an integrated robot designed for measurement and cutting, which can accurately identify and cut unknown nuclear waste tanks and realize autonomous precise processing. Design/methodology/approach A robot system integrating point cloud measurement and plasma cutting is designed in this paper. First, accurate calibration methods for the robot, tool and hand-eye system are established. Second, for eliminating the extremely scattered point cloud caused by metal surface refraction, an omnidirectional octree data structure with 26 vectors is proposed to extract the point cloud model more accurately. Then, a minimum bounding box is calculated for limiting the local area to be cut, the local three-dimensional shape of the nuclear tank is fitted within the bounding box, in which the cutting trajectories and normal vectors are planned accurately. Findings The cutting precision is verified by changing the tool into a dial indicator in the simulation and the experiment process. The octree data structure with omnidirectional pointing vectors can effectively improve the filtering accuracy of the scattered point cloud. The point cloud filter algorithm combined with the structure calibration methods for the integrated measurement and processing system can ensure the final machining accuracy of the robot. Originality/value Aiming at the problems of large measurement noise interference, complex transformations between coordinate systems and difficult accuracy guarantee, this paper proposes structure calibration, point cloud filtering and point cloud-based planning algorithm, which can greatly improve the reliability and accuracy of the system. Simulation and experiment verify the final cutting accuracy of the whole system.
The polymorphic phase transition (PPT) near room temperature can induce enhanced electrical properties of KNN-based lead-free piezoelectric ceramics, limiting their temperature stability. In this paper, the 0.98(K0.52Na0.48)1-x Li x NbO3–0.02(Bi0.5Na0.5)0.9 Ca0.1TiO3 (KNLN x -BNCT) lead-free piezoelectric ceramics were prepared by the conventional sintering technique, and the electrical properties and phase structure can be tailored by modifying Li content. The polymorphic phase transition (PPT) from orthorhombic and tetragonal phase around room temperature was identified in the composition range 0.01 ≤ x ≤ 0.02, resulting in improved electrical properties (d 33∼262 pC/N, k p ∼ 0.36, ϵ r ∼ 715, and tan δ∼ 0.03). Moreover, KNLN x -BNCT (x0.02) ceramics with tetragonal structure possess a pertinent temperature stability and a broader application range owing to its higher T C (>400°C).
(1−x)(K0.5Na0.5)NbO3-xBi0.5(Na0.9K0.1)0.5TiO3 ((1−x)KNN-xBNKT) lead-free ceramics were prepared by the conventional solid state reaction technique, and the effects of BNKT on the phase structure, microstructure, ferroelectric and piezoelectric properties of (1−x)KNN-xBNKT ceramics were investigated. The addition of BNKT strongly affects the microstructure of these ceramics, and changes the crystalline structure of these ceramics from an orthorhombic phase with x < 0.02 to a tetragonal phase with x ≥ 0.03 at room temperature. A coexistence of orthorhombic and tetragonal phases was identified in the range of 0.02 ≤ x < 0.03. 0.975KNN-0.025BNKT ceramics show the optimum piezoelectric properties of d 33∼170 pC/N and k p∼0.38.
Through using the basic probability theory and establishing the law of finite chains near the prompt criticality, we deduce the formula of relation between the neutrons number and time in the process of persistent chains initiated by a single-pulse neutron source in burst reaction. The formula is validated by the experiments of CFBR-Ⅱ. The formula is the development of Hansen theory model because it can describe not only the developing tendency in the later stages but also the rapid increasing of neutron number in the early stage. Furthermore, according to the relation between the initial time of burst reaction and the intensity of neutron source, we illustrate that the initial time is hardly dependent on the intensity of weak neutron source.
Fabrication of hydrogel microstructures has attracted considerable attention. A large number of applications, such as fabricating tissue engineering scaffolds, delivering drugs to diseased tissue, and constructing extracellular matrix for studying cell behaviors, have been introduced. In this article, an ultraviolet (UV)-curing method based on a digital micromirror device (DMD) for fabricating poly(ethylene glycol) diacrylate (PEGDA) hydrogel microstructures was presented. By controlling UV projection in real-time using a DMD as digital dynamic mask instead of a physical mask, polymerization of the pre-polymer solution could be controlled to create custom-designed hydrogel microstructures. Arbitrary microstructures could also be fabricated within several seconds (<5 s) using a single-exposure, providing a much higher efficiency than existing methods, while also offering a high degree of flexibility and repeatability. Moreover, different cell chains, which can be used for straightforwardly and effectively studying the cell interaction, were formed by fabricated PEGDA microstructures.
In the last seven years, optoelectronic tweezers using optically-induced dielectrophoretic (ODEP) force have been explored experimentally with much success in manipulating micro/nano objects. However, not much has been done in terms of in-depth understanding of the ODEP-based manipulation process or optimizing the input physical parameters to maximize ODEP force. We present our work on analyzing two significant influencing factors in generating ODEP force on a-Si:H based ODEP chips: (1) the waveforms of the AC electric potential across the fluidic medium in an ODEP chip based microfluidic platform; and (2) optical spectrum of the light image projected onto the ODEP chip. Theoretical and simulation results indicate that when square waves are used as the AC electric potential instead of sine waves, ODEP force can double. Moreover, numerical results show that ODEP force increases with increasing optical frequency of the projected light on an ODEP chip following the Fermi-Dirac function, validating that the optically-induced dielectrophoresis force depends strongly on the electron-hole carrier generation phenomena in optoelectronic materials. Qualitative experimental results that validate the numerical results are also presented in this paper.
We examine the contribution of electromagnetic field to the atomic spin, by adopting two different, both gauge invariant definitions of the electromagnetic angular momentum: and . Notably, at the classical level, gives an exactly null result while gives a finite value. This suggests that leads to a simpler and more reasonable picture of the atomic spin, therefore qualifies as a more appropriate definition of the electromagnetic angular momentum. Our observation gives important hint on the delicate issue of gluon contribution to the nucleon spin.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)