Re-dispersion ability of multi wall carbon nanotubes within low viscous mineral oil

The main purpose of this study is to focus the light for the first time on the recognized re-dispersion ability of the sonicated MWCNTs within low viscous mineral oil. For that, pure MWCNTs, without any special treatment, were dispersed in mineral oil by sonication without using any stabilization method. After full agglomeration, it was realized that agitating, shaking or even blowing compressed air on the agglomerated nanolubricant is able to break down the aggregation of the MWCNTs. Microscopic video is presented to clarify the behavior of the tubes during the re-dispersion process. Quantitatively, particle size distribution (PSD) was employed to evaluate the re-dispersion quality. The viscosity and thermal conductivity of both recently sonicated and re-dispersed samples were also investigated with accurate measurement setups at four different weight concentrations (0.05, 0.1, 0.2 and 0.3 wt.%). It was observed that the sonicated MWCNTs are separated, saturated, lubricated, and surrounded by oil layers, which not only ease its motion within the lubrication oil, but also give them the ability of detaching by applying any slight force. Moreover, the PSD results with the equal values of the viscosity and thermal conductivity, obtained within the uncertainty of the measurements, confirm that the MWCNTs were re-dispersed to the same quality of the recently sonicated ones by just shaking

Effect of the coil shape on magnetic field of an electromagnet for contactless power transmission to microrobots

© Springer International Publishing AG 2018.This paper proposes a comparative study in order to investigate the effect of the coil geometry on the intensity and homogeneity of the magnetic field. For this purpose, a solenoid with rectangular prism core and two different coil shapes, cylindrical and cuboid, was modeled. Several finite element numerical studies at different structural design parameters combinations for two different distances between the coils were carried out. The obtained results were evaluated according to the flux intensity and the homogeneity at the center region between the coils. Consequently, it was found that cylindrical coils generate higher flux intensity with more homogeneous magnetic field

Evaluating the thermal conductivity and viscosity of Cuo-nanolubricants

© 2017 Trans Tech Publications, Switzerland.In the presented work, thermal conductivity of CuO and its viscosity at three different weight concentrations were investigated. A two-steps method was deployed in order to sonicate successfully CuO nanolubricants samples at three different weight concentrations (0.2, 0.5, & 1 wt%). The measurements of thermal conductivity were carried out with a lab-made measurement set, which is based on a 3method. The obtained enhancements were 1%, 1.7% and 2.8% for 0.2, 0.5, and 1 wt.%, respectively. Viscosity was also investigated under different temperatures and it was obtained that adding CuO to the mineral oil had a slight effect on its viscosity at lower concentrations. However, the maximum increment at lower temperature for the higher concentration was 13.1%. Based on the enhancement in thermal conductivity and the low increment in viscosity, CuO nanolubricant can be recommended for enhancing the heat transfer characteristic of the refrigeration compressor

High-throughput imaging measurements of thermoelectric figure of merit

We demonstrate a method for the simultaneous determination of the thermoelectric figure of merit of multiple martials by means of the lock-in thermography (LIT) technique. This method is based on the thermal analyses of the transient temperature distribution induced by the Peltier effect and Joule heating, which enables high-throughput estimation of the thermal diffusivity, thermal conductivity, volumetric heat capacity, Seebeck or Peltier coefficient of the materials. The LIT-based approach has high reproducibility and reliability because it offers sensitive noncontact temperature measurements and does not require the installation of an external heater. By performing the same measurements and analyses with applying an external magnetic field, the magnetic field and/or magnetization dependences of the Seebeck or Peltier coefficient and thermal conductivity can be determined simultaneously. We demonstrate the validity of this method by using several ferromagnetic metals (Ni, Ni95Pt5, and Fe) and a nonmagnetic metal (Ti). The proposed method will be useful for materials research in thermoelectrics and spin caloritronics and for investigation of magneto-thermal and magneto-thermoelectric transport properties

Electromagnet design for untethered actuation system mounted on robotic manipulator

Electromagnetic actuation systems have remarkably proved themselves in the field of contactless power transmission systems. Nevertheless, the stationary position of the operated electromagnets or their rotation around a fixed axis resulted in a restrictive and limited versatile workspace. In this paper, a new design of a steel cored solenoidal coil is proposed for a novel microrobot electromagnetic actuator. The new system combines a 6 DOF industrial robotic manipulator with co-axially movable electromagnets. Considering the maximum weight and workspace limitations of the robotic manipulator, seven essential dimensions of the electromagnet were investigated with the aid of a simulation software. A set of parametric studies were carried out in order to optimize the homogeneity of the induced magnetic field at the highest achievable intensity based on Ad hoc method. The results showed that an electromagnet with a square prism core and a large front, induces a more homogeneous and intense magnetic field. Moreover, by shortening the length of the coil and increasing the length of the core, the intensity of the magnetic field significantly increases without much affecting its homogeneity. The electromagnet was fabricated according to the final result of the numerical studies and evaluated by performing experimental measurements on the induced magnetic field. Furthermore, with several programed motions, the performance of the proposed untethered electromagnetic actuation system was demonstrated experimentally. (C) 2018 Elsevier B.V. All rights reserved

Dynamical electromagnetic actuation system for microscale manipulation

Electromagnetic actuation systems (EMA) have excelled themselves in microscale manipulation. Yet, the fastened structure of the current systems tethers the controlled workspace. In this paper, a new electromagnetic actuation principle is investigated. The actuator structure consists of a pair of coaxially movable electromagnets integrated to a robotic manipulator. The pair induces a coaxial homogeneous magnetic field or gradient to control the magnitude of the magnetic torque or force by changing the distance between the electromagnets asymmetrically. The robotic manipulator, on the other hand, transports the pair at five degrees of freedom to manipulate a microrobot in 3D space by closed-loop control with integrated vision feedback system. Numerical analyses are performed to investigate the induced electromagnetic field at the symmetrical/asymmetrical configuration of the coaxial pair. Accordingly, a correlation between the magnitude of the magnetic force and the asymmetric distance is obtained for flexible force control. A proof of concept prototype is constructed to validate the proposed actuation principle and evaluate its performance experimentally. The experimental results verify the numerical analysis and show the system applicability of inducing controlled forces on a micro-object in 2D and 3D workspaces at a velocity range of 65 to 157 mu m/s. Moreover, micromanipulation on a helical route is also demonstrated with an absolute error mean from the reference path of 191 mu m