Portable Rheology Sensing for Low-Volume Extensional Fluids
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Solution Overview
Problem
Existing laboratory-based rheometers struggle with measuring extensional rheological properties of low viscosity fluids due to limitations in stretching time, inertial effects, and the need for large sample volumes, leading to inaccurate results and challenges in handling perishable samples.
Innovation Solution
A portable, handheld device that measures extensional rheological properties using a capillary break-up technique with an integrated electrical circuit to apply current and monitor resistance, combined with direct visualization, allowing for calibration-free analysis of fluid samples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laboratory-based rheometers are used to measure extensional rheological properties, then measurement capability is provided, but the devices are cumbersome and require large sample volumes which causes degradation of perishable samples
Solution Approach 1:
The patent replaces traditional mechanical rheometer systems with a microfluidic-based capillary break-up extensional rheometer (CaBER) that uses controlled capillary forces and minimal mechanical intervention. This substitution enables precise extensional rheological measurements while requiring only nanoliter-scale sample volumes, thereby resolving the contradiction between measurement capability and sample volume requirement.
Solution Approach 2:
The invention changes the measurement scale from macroscopic to microscopic by reducing the characteristic length scale of the measurement geometry. The capillary radius is reduced to micrometer scale, which dramatically reduces the required sample volume while maintaining measurement accuracy through scaled physical principles.
2Measurement precision
If capillary break-up technique is used with standard devices, then extensional viscosity can be measured, but inertial effects dominate for low viscosity fluids when stretching time is insufficient
Solution Approach 1:
The patent implements dynamic control of the plate separation process with programmable velocity profiles that can be optimized for different fluid viscosities. The system transitions from static to dynamic measurement capabilities, allowing adaptation of stretching time and rate to match the specific rheological properties of each sample, thereby eliminating inertial effects in low viscosity fluids while maintaining measurement precision.
Solution Approach 2:
The invention incorporates real-time monitoring of filament thinning process with feedback control of plate separation velocity. Sensors detect filament diameter changes and feed this information back to the control system, which adjusts the separation rate to maintain optimal measurement conditions throughout the stretching process, preventing inertial dominance.
3Measurement precision
If existing rheometers are used, then rheological characterization is possible, but the devices are complex and not suitable for point-of-use applications
Solution Approach 1:
The patent segments the traditional monolithic rheometer into modular microfluidic components that can be integrated into portable formats. The measurement system is divided into discrete functional modules (sample loading, plate separation, filament monitoring, data processing) that can be miniaturized and reconfigured for point-of-use deployment while maintaining characterization precision.
Solution Approach 2:
The invention replaces complex mechanical measurement systems with optical and electrical sensing methods. Instead of using sophisticated mechanical transducers, the system uses optical microscopy and electrical resistance measurements to monitor filament thinning, dramatically simplifying the device while preserving measurement accuracy.
4Measurement precision
If laser micrometer is used to monitor filament thinning, then measurement precision is achieved, but the setup is expensive and prevents direct visualization
Solution Approach 1:
The patent merges measurement and visualization functions into a single integrated system. The same optical components used for direct visualization of filament thinning also serve as the measurement tool, eliminating the need for separate laser micrometer equipment. This merging achieves both precise diameter measurement and direct visual observation simultaneously.
Solution Approach 2:
The invention introduces simple optical markers or contrast agents as intermediaries that enhance the visibility of the filament without requiring complex laser measurement systems. These markers allow direct visualization while providing sufficient measurement precision through image analysis of the marked filament structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables rapid, on-site measurement of rheological properties without altering the fluid's natural thinning behavior, providing accurate results for low viscosity fluids and perishable samples with minimal sample volume requirements.
Implementation Method 1
an integrated electrical circuit to apply current and monitor resistance
Implementation Method 2
the necking of the liquid filament is resisted by a combination of viscous and elastic stresses in the fluid thread... under the action of capillary pressure
Data Source
AI summary
Apparatuses and methods designed to allow for on-site, on-demand measurement of rheological properties of a sample are disclosed. The apparatuses and methods utilize both a visual component (e.g., a camera) to obtain information about the sample for making such rheological property determinations and an integrated electrical circuit to apply a current to the sample for also making such rheological property determinations. The application of the current is done in a manner such that a thinning behavior of the sample is unaffected. Further, the apparatuses are configured in a manner that allow them to be portable so that samples can be analyzed shortly after they are received, at a point-of-use. Various configurations and methods associated with such apparatuses are also disclosed.