One of the unresolved issues in physiology is how exactly myosin moves in a filament as the smallest responsible organ for contracting of a natural muscle. In this research, inspired by nature, a model is presented consisting of DPD (dissipative particle dynamics) particles driven by electro-osmotic flow (EOF) in micro channel that a thin movable impermeable polymer membrane has been attached across channel width, thus momentum of fluid can directly transfer to myosin stem. At the first, by validation of electro-osmotic flow in micro channel in different conditions with accuracy of less than 10 percentage error compared to analytical results, the DPD results have been developed to displacement of an impermeable polymer membrane in EOF. It has been shown that by the presence of electric field of 250 V/m and Zeta potential − 25 mV and the dimensionless ratio of the channel width to the thickness of the electric double layer or kH = 8, about 15% displacement in 8 s time will be obtained compared to channel width. The influential parameters on the displacement of the polymer membrane from DPD particles in EOF such as changes in electric field, ion concentration, zeta potential effect, polymer material and the amount of membrane elasticity have been investigated which in each cases, the radius of gyration and auto correlation velocity of different polymer membrane cases have been compared together. This simulation method in addition of probably helping understand natural myosin displacement mechanism, can be extended to design the contraction of an artificial muscle tissue close to nature.
In this paper, we simulate the inflation of fixed two ends polymer chain curvature as nano sensor in EOF which it provides a porous media for DPD (dissipative particles dynamics) solvent particles and inflation is resulted. Particles are driven by electroosmotic flow in nanochannel which is as an external force in DPD algorithm and part of particles should move through a non-charged polymer chain which they affect on curvature of polymer chain. Our results for simple nanochannel in EOF are validated with analytical results and we have developed our results when a fixed two ends polymer chain subject in nanochannel as nano sensor in both cases including simple and stenosis nanochannel. Amount of inflation (displacement) of fixed two ends polymer chain is related to electroosmotic forces and interaction between particles. Our aim is that a relation between effective parameters in electroosmotic flow such as electric field, zeta potential, kh parameters and amount of inflation in polymer chain curvature (interaction between particles) is provided for each test case. Based on our results, there is a linear relation between some parameters such as external electrical field, zeta potential and kh parameters (effect of Debye length and channel height) in low electrosmotic forces but non-linear behavior is observed for high electroosmotic forces especially for stenosis channel case. This study opens some new way toward designing proper nano EOF sensors to measure flow characteristics in EOF applications.
In this paper, the effect of Magneto Hydro-Dynamics (MHD) on a polymer chain in the micro channel is studied by employing the Dissipative Particle Dynamics simulation (DPD) method. First, in a simple symmetric micro-channel, the results are evaluated and validated for different values of Hartmann (Ha) Number. The difference between the simulation and analytical solution is below 10%. Then, two types of polymer chain including short and long polymer chain are examined in the channel and the effective parameters such as Ha number, the harmony bond coefficient or spring constant (K), and the length of the polymer chain (N) are studied in the MHD flow. It is shown that by increasing harmony bond constant to 10 times with Ha = 20, the reduction of about 80% in radius of gyration squared, and half in polymer length compared to Ha = 1 would occur for both test cases. For short and long length of polymer, proper transfer of a polymer chain through MHD particles flow is observed with less perturbations (80%) and faster polymer transfer in the symmetric micro-channel.
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