Università Degli Studi di Padova,
Keywords: consistent couple stress theory, bio-nanofluidics, carbon nanotube
Summary:The paper presents the physical design and mathematical formulation of a bio-nanofluidic device for possible applications in nanoengineering in general and bio-nanoengineering in particular such as in precise drug delivery as sensors and actuators. The drug or any other fluid flows through a carbon nanotube and its stream is controlled by its deflection resulted from the electrostatic actuation technique. Fig. 1 shows the deflection of a nanotube under electrostatic actuation modeled by molecular dynamic method . As seen in this figure, deflection of a nanotube results in local bending buckling at the clamped end of the cantilever nanotube (and in the middle of the doubly clamped one) and this buckling tune the fluid flow. The fluid flow affects the mechanical characteristics of the nanosystem including its stiffness and damping . Hence, its electromechanical properties under the mentioned actuation change. In order to have a model with higher compatibility with the experiment, the consistent couple stress theory  is used to capture the size effects for both solid and fluid parts of the model. (EI+4GAl_1^2 ) (∂^4 w)/(∂x^4 )-(N+EA/2L ∫_0^L▒(∂w/∂x)^2 dx) (∂^2 w)/(∂x^2 )+m_c (∂^2 w)/(∂t^2 )+c∂w/∂t=q(x) (1) where E, I, G, A, l1, w, x, N, m¬c, t, c and q(x) are elastic modulus, moment of inertia, shear modulus, cross sectional area, size-dependent parameter, deflection, longitudinal coordinate, axial force, mass per unit length, time, damping coefficient and externally distributed force, respectively. The latter is due to electrostatic actuation, van der Waals interaction and fluid flow. The results of static deflection for cantilever and doubly clamped boundary conditions respectively shown in Fig. 3 (a) and (b) reveal that the deflection and pull-in behavior of the electrostatically actuated carbon nanotube conveying fluid can successfully tune or block the rate of the fluid flow. Thus, it can be applied in precise processes such as in the highly precise drug delivery applications as an actuator. The effects of the fluid velocity, viscosity, density, temperature and pressure on the results are investigated via the mentioned size-dependent theory to analyze its sensory application. References  M. M. S. Fakhrabadi, P. K. Khorasani, A. Rastgoo, and M. T. Ahmadian, “Molecular dynamics simulation of pull-in phenomena in carbon nanotubes with Stone–Wales defects,” Solid State Communications, vol. 157, pp. 38–44, 2013.  M. M. S. Fakhrabadi, A. Rastgoo, and M. T. Ahmadian, “Carbon nanotube-based nano-fluidic devices,” Journal of Physics D: Applied Physics, vol. 47, no. 8, p. 085301, 2014.  A. R. Hadjesfandiari and G. F. Dargush, “Couple stress theory for solids,” International Journal of Solids and Structures, vol. 48, no. 18, pp. 2496–2510, 2011.