System and method for determination of viscoelastic properties from given time-dependent penetration of a test liquid creeping inside a channel
Disclosed is a system and method for determination of the viscoelastic properties of a viscoelastic substance based on the type of non-mechanical forces which drive the viscoelastic substance inside a channel. These forces may comprise capillary, gravitational, electric, magnetic, or any other type where neither a pump nor any relative velocity between solid surfaces is needed to induce the transport of fluid medium. As a result, the design of the system remains simple, and the system is capable of yielding results devoid of noise produced by mechanical forcing. The present disclosure a general analysis describing extraction of viscoelastic properties by observing flow-systems driven by any non-mechanical means, including capillary force and electro-osmotic force. Such time-dependent penetration depth may be recorded by optical, electrical or mechanical means and may further include the use of a computing device.
1. A system for determining viscoelastic properties of a viscoelastic substance comprising:
(a) a free surface for introduction of said viscoelastic substance in a form of a drop;
(b) an inlet in a capillary channel brought in contact with said free surface for receiving said viscoelastic substance;
(c) the capillary channel in fluid communication with said inlet and, wherein
(i) the capillary channel has an area A and a perimeter s,
(ii) the capillary channel is arranged horizontally to the free surface so that gravity does not affect flow dynamics,
(iii) the capillary channel has a longitudinal direction, and
(iv) the viscoelastic properties are based upon measurement of time-dependent penetration of a creeping viscoelastic substance under an action of a capillary force; and
(d) an electric potential applied to the longitudinal direction of the capillary channel, wherein the electrical potential is positioned to induce additional transiency in the flow dynamics of the viscoelastic substance by an electro-osmotic force, wherein the measurement of time-dependent penetration of a creeping viscoelastic substance having fluctuating electric potential on an inside surface of the capillary channel is configured to determine a frequency-dependent viscosity of the viscoelastic substance.
2. The system of claim 1 , wherein the capillary channel is an axisymmetric rheometer.
3. The system of claim 1 , wherein the capillary channel is comprised of an open channel flow having at least one surface which is a free surface.
4. The system of claim 1 , wherein the measurement comprises forces selected from a group consisting of: capillary, gravitational, electric, magnetic, and combinations thereof.
5. The system of claim 1 , wherein the measurement comprises one or more forces not requiring relative velocity between solid surfaces in order to induce transport of a viscoelastic substance.
6. The system of claim 1 , comprising determining rheological coefficients G′ and G″ to further determine an amplitude and a phase difference of a sinusoidal strain-rate in the viscoelastic substance under the action of a sinusoidal stress.
7. The system of claim 1 , further comprising determining frequency-dependent coefficients of a viscoelastic substance by correlating one or more unsteady dynamics of the viscoelastic substance flow by relating a complex viscosity of the viscoelastic substance to its time-dependent penetration length within the channel.
8. A device for measuring viscoelastic properties of a viscoelastic substance comprising:
(a) a drop of viscoelastic substance with free surface capable of being a source of fluid transport to a capillary channel;
(b) an inlet for introduction of the said viscoelastic substance from the said drop to a fluid communication due to the sole or combined actions of non-mechanical forces;
(c) a capillary channel in fluid communication with a first opening, wherein
(i) the capillary channel has an area A and a perimeter s, and
(ii) the capillary channel is arranged horizontally to the free surface; and
(d) at least one rheometric measurement instrument for time versus penetration data, wherein the viscoelastic substance in fluid communication with the capillary channel is capable of creeping into the capillary channel and capable of measurement with at least one measurement instrument; and
(e) an electric potential applied to a longitudinal direction of the capillary channel, wherein the electrical potential is positioned to induce additional transiency in flow of the viscoelastic substance by an electro-osmotic force, wherein a measurement of time-dependent penetration of a creeping viscoelastic substance having fluctuating electric potential on an inside surface of the capillary channel is configured to determine a frequency-dependent viscosity of the viscoelastic substance.
9. The device of claim 8 , wherein the capillary channel is a narrow one-dimensional channel having a determined cross-section.
10. The device of claim 8 , wherein the capillary channel is a closed channel wherein non-mechanical force is capable of driving the viscoelastic substance.
11. The device of claim 10 , wherein the capillary channel is rectangular.
12. The device of claim 10 , wherein the capillary channel is an axisymmetric rheometer.
13. The device of claim 8 , wherein the at least one measurement instrument is capable of determining rheological coefficients G′ and G″ to further determine an amplitude and a phase difference of a sinusoidal strain-rate in the viscoelastic substance under the action of a sinusoidal stress.
14. The device of claim 8 , wherein the at least one measurement instrument is capable of rapid determination of frequency-dependent viscoelastic coefficients by relating a complex viscosity of a medium to its time dependent penetration length within a channel.
15. A method for determining viscoelastic properties of a viscoelastic substance comprising:
(a) introducing a viscoelastic substance in a form of a drop onto a free surface having an inlet to a capillary channel through said inlet of the capillary channel via non-mechanical forces, wherein the step of introducing the viscoelastic substance into the channel comprises placing the viscoelastic substance on the free surface having contact with the inlet;
(b) measuring a time-dependent penetration of a creeping viscoelastic substance inside the capillary channel; and
(c) determining, by combined action of capillary force and electro-osmotic force in a presence of fluctuating electric potential on an encroaching capillary channel, a frequency-dependent viscosity of the viscoelastic substance driven by the capillary force of the viscoelastic substance in the capillary channel.
16. The method of claim 15 , further comprising determining rheological coefficients G′ and G″ to further determine an amplitude and a phase difference of a sinusoidal strain-rate in the viscoelastic substance under the action of a sinusoidal stress.
17. The method of claim 15 , further comprising determining frequency-dependent coefficients of a viscoelastic substance by correlating one or more unsteady dynamics of the viscoelastic substance flow by relating a complex viscosity of the viscoelastic substance to its time-dependent penetration length within the capillary channel.
18. The method of claim 15 , further comprising recording time-dependent penetration depth by optical, electrical or mechanical means.
19. The method of claim 15 , further comprising measuring the non-mechanical forces selected from a group consisting of: capillary, gravitational, electric, magnetic, and combinations thereof.
20. The method of claim 15 , further comprising measuring one or more non-mechanical forces not requiring relative velocity between solid surfaces in order to induce transport of a viscoelastic substance.
21. The method of claim 15 , further comprising determining frequency-dependent coefficients of a viscoelastic substance by relating its complex viscosity to its time-dependent penetration length within the capillary channel.