Theoretical And Numerical Study On Microfluidic Flowing Behavior Under The Synergistic Driving Loads Of The Pressure Gradient And Electric Field In Cell Culture Chamber

Microfluidic chip has a wide application because of its low dosage,much integrations,and high volume production in many fields.Cell culture in microfluidic chip does not only have bionic hermetic micro-chamber in human body,but also produce fluid shear stress(FSS)by controlling external physical field(pressure gradient or electric field),which stimulates seed cells to regulate the expression of genes,thus controlling differentiation and growth of cells.It is difficult to experimental quantifications the fluid flowing behavior in the cell culture chamber.The theoretical modeling is thought to be an effective way.In this paper,a theoretical model and finite element model for microfluidic flow in the rectangle cell culture chamber is developed to link the applied external physical fields(pressure gradient and electrical field)to intraluminal fluid velocity(FV),FSS and fluid flow rate(FFR).The theoretical and finite element models of liquid flow under three driving modes: pressure gradient driven(PGD),electric field driven(EFD)and pressure-electric synergic driven(P-ESD)were obtained respectively.The establishment of the model in this paper establishes a quantitative relationship between the external physical field and the physics field that the cell senses.The combined pressure-electricity synergic driven model can be used as the theoretical basis to design the experimental cell microfluidic bioreactor system,meanwhile,provides the references to research the mechanism of cell growth and differentiation under the stimulus of(shear)stress and electricity.The detailed work and main conclusions of this paper are as follows:(?)Neglecting the size of cells,the model of a newtonian microfluidic culture chamber without cells(pressure-driven results are basically consistent with existing experimental results)and a Maxwell microfluidic culture chamber without cells were established,The influence of pressure,electric field,chamber height,frequency,and temperature on the flow field is discussed and the following results are obtained:(1)The solutions under pressure-electricity synergic driven are the superposition of the driven solutions of each pressure gradient and the electric field.(2)FSS,FV and FFR amplitudes of newtonian fluid in chamber are proportional to the amplitudes of applied external physical fields,but decrease and change little as the frequencies of pressure gradient and electric field grows,The Maxwell fluid FSS,FV and FFR amplitude increase nonlinearly with the amplitude of the external physical field,but it is not obvious as the frequency increases.(3)The higher chamber height is,the larger FSS and FFR amplitudes generalized in the pressure gradient driven model,while not obvious change in the electric field driven model.(4)The results of newtonian fluid are not influenced when the culture medium temperature varies at the physiological level.At the generalized cell response level,electric field driven model can provides the larger FSS amplitude,while the pressure driven flow model is good at inducing the larger FFR amplitude under two fluid properties.(?)The results of a newtonian microfluidic culture chamber finite element model without cells are identical with a theoretical and analytical solution from(1).Regularity of distribution of FSS,pressure,the distribution rules of cell deformation and stress are analyzed by a newtonian microfluidic culture chamber finite element model with cells.The conclusions are as follows:(1)The maximum of shear stress is zero in the vertex place by the pressure driven flow.However,the maximum of shear stress is smaller in the vertex place by an electric field.P-ESD can make the surface of cells appear uniform distribution of shear stress.(2)When pressure driven,pressure value affected by cell reduce to zero from import to exit of lumen,besides,deformation of cells embody vertical direction.When electric field driven,pressure value of cells maintain certain stability and deformation of cells focus on horizontal direction.Cells under different physical field can produce stress concentration.(?)FSS,pressure,the distribution rules of cell deformation and stress are discussed by established a power-law microfluidic culture chamber finite element model with cells.The model contrasts with flow field and cell shear deformation under power-law fluid and a Newtonian fluid.The discussions are as follows:(1)Driven by the same imposed load,variation trend of shear stress felt by cells,pressure change and cell response(deformation,stress)are identical with cells under newtonian fluid environment from(2),but the value is different.(2)Most of the time,FSS under power-law fluid is less than FSS under newtonian fluid environment driven by pressure but conversely when driven by electric field.(3)Anytime the pressure under power-law fluid is identical with pressure under newtonian fluid environment driven by pressure but is less than pressure under Newtonian fluid environment driven by electric field.(4)Anytime deformation and stress of cells under power-law fluid environment are identical with those under newtonian fluid environment driven by pressure but are greater than deformation and stress of cells under newtonian fluid environment driven by electric field.