Patent ID: 8104329

Claim:
A method of determining at least one rheological characteristic of an unknown fluid, the method comprising the following steps: causing both a reference fluid having known rheological characteristics and said unknown fluid of at least one rheological characteristic that is to be determined to flow in parallel in a flow microchannel; identifying the position of an interface between said two fluids in said parallel flow by measuring the width of the unknown fluid in the flow microchannel; determining the viscosity of said unknown fluid numerically from said measured width, by applying the following equations: ∂ u ∂ x ⁢ ( x , y , z ) = 0 ( 1 ) ∂ P i ⁡ ( x , y , z ) ∂ x = η i ⁡ ( ∂ 2 ⁢ u ⁡ ( y , z ) ∂ 2 ⁢ y + ∂ 2 ⁢ u ⁡ ( y , z ) ∂ 2 ⁢ z ) ( 2 1 ) ∂ P i ⁡ ( x , y , z ) ∂ y = 0 ( 2 2 ) ∂ P i ⁡ ( x , y , z ) ∂ z = 0 ( 2 3 ) P i ⁡ ( x , y , z ) = ( P i - out * x = P i - in * ( L - x ) ) / L ( 3 ) Q i = ∮ u i ⁡ ( y , z ) ⁢ ⅆ y ⁢ ⅆ z ( 4 ) u 1 = u 2 ( 5 ) η 1 ⁢ ⁢ γ 1 = η 2 ⁢ ⁢ γ 2 ( 6 ) wherein η 1 and γ 1 represent the viscosity and the shear rate of the unknown fluid and where η 2 and γ 2 represent the viscosity and the shear rate of the reference fluid; and determining a curve for the flow of the unknown fluid from the viscosity, by varying the shear rate.