6 research outputs found
Optimal motion of triangular magnetocapillary swimmers
A system of ferromagnetic particles trapped at a liquid-liquid interface and
subjected to a set of magnetic fields (magnetocapillary swimmers) is studied
numerically using a hybrid method combining the pseudopotential lattice
Boltzmann method and the discrete element method. After investigating the
equilibrium properties of a single, two and three particles at the interface,
we demonstrate a controlled motion of the swimmer formed by three particles. It
shows a sharp dependence of the average center-of-mass speed on the frequency
of the time-dependent external magnetic field. Inspired by experiments on
magnetocapillary microswimmers, we interpret the obtained maxima of the swimmer
speed by the optimal frequency centered around the characteristic relaxation
time of a spherical particle. It is also shown that the frequency corresponding
to the maximum speed grows and the maximum average speed decreases with
increasing inter-particle distances at moderate swimmer sizes. The findings of
our lattice Boltzmann simulations are supported by bead-spring model
calculations.Comment: 10 pages, 11 figure
Simulation of a Hard-Spherocylinder Liquid Crystal with the pe
The pe physics engine is validated through the simulation of a liquid crystal
model system consisting of hard spherocylinders. For this purpose we evaluate
several characteristic parameters of this system, namely the nematic order
parameter, the pressure, and the Frank elastic constants. We compare these to
the values reported in literature and find a very good agreement, which
demonstrates that the pe physics engine can accurately treat such densely
packed particle systems. Simultaneously we are able to examine the influence of
finite size effects, especially on the evaluation of the Frank elastic
constants, as we are far less restricted in system size than earlier
simulations
Magnetocapillary self-assemblies: locomotion and micromanipulation along a liquid interface
This paper presents an overview and discussion of magnetocapillary
self-assemblies. New results are presented, in particular concerning the
possible development of future applications. These self-organizing structures
possess the notable ability to move along an interface when powered by an
oscillatory, uniform magnetic field. The system is constructed as follows. Soft
magnetic particles are placed on a liquid interface, and submitted to a
magnetic induction field. An attractive force due to the curvature of the
interface around the particles competes with an interaction between magnetic
dipoles. Ordered structures can spontaneously emerge from these conditions.
Furthermore, time-dependent magnetic fields can produce a wide range of dynamic
behaviours, including non-time-reversible deformation sequences that produce
translational motion at low Reynolds number. In other words, due to a
spontaneous breaking of time-reversal symmetry, the assembly can turn into a
surface microswimmer. Trajectories have been shown to be precisely
controllable. As a consequence, this system offers a way to produce microrobots
able to perform different tasks. This is illustrated in this paper by the
capture, transport and release of a floating cargo, and the controlled mixing
of fluids at low Reynolds number.Comment: 10 pages, 8 figures review pape
A Novel Propeller Design for Micro-Swimming robot
The applications of a micro-swimming robot such as minimally invasive surgery, liquid pipeline robot etc. are widespread in recent years. The potential application fields are so inspiring, and it is becoming more and more achievable with the development of microbiology and Micro-Electro-Mechanical Systems (MEMS). The aim of this study is to improve the performance of micro-swimming robot through redesign the structure.
To achieve the aim, this study reviewed all of the modelling methods of low Reynolds number flow including Resistive-force Theory (RFT), Slender Body Theory (SBT), and Immersed Boundary Method (IBM) etc. The swimming model with these methods has been analysed. Various aspects e.g. hydrodynamic interaction, design, development, optimisation and numerical methods from the previous researches have been studied.
Based on the previous design of helix propeller for micro-swimmer, this study has proposed a novel propeller design for a micro-swimming robot which can improve the velocity with simplified propulsion structure. This design has adapted the coaxial symmetric double helix to improve the performance of propulsion and to increase stability. The central lines of two helical tails overlap completely to form a double helix structure, and its tail radial force is balanced with the same direction and can produce a stable axial motion.
The verification of this design is conducted using two case studies. The first one is a pipe inspection robot which is in mm scale and swims in high viscosity flow that satisfies the low Reynolds number flow condition. Both simulation and experiment analysis are conducted for this case study. A cross-development method is adopted for the simulation analysis and prototype development. The experiment conditions are set up based on the simulation conditions. The conclusion from the analysis of simulation results gives suggestions to improve design and fabrication for the prototype. Some five revisions of simulation and four revisions of the prototype have been completed. The second case study is the human blood vessel robot. For the limitations of fabrication technology, only simulation is conducted, and the result is compared with previous researches. The results show that the proposed propeller design can improve velocity performance significantly.
The main outcomes of this study are the design of a micro-swimming robot with higher velocity performance and the validation from both simulation and experiment