Conditions for a microfluidic creep experiment for microparticles using a cross-slot extensional flow device.

Area of Science:

• * Biophysics
• * Microfluidics
• * Rheology

Background:

• * Micromechanical measurements face challenges in repeatability due to complex stress modeling.
• * Previous numerical studies suggested viscoelastic capsules achieve quasi-steady strain in cross-slot flow.
• * Experimental validation of quasi-steady strain in microfluidic cross-slots for particles is lacking.

Purpose of the Study:

• * To experimentally demonstrate conditions for a microfluidic cross-slot device to perform microscale uniaxial creep tests.
• * To enable high-throughput measurement of viscoelastic properties of microscale biological objects.
• * To develop an analytical model for extracting linear viscoelastic properties from particle strain data.

Main Methods:

• * Utilizing large-dimension cross-slots relative to microparticle diameter to create an adequate extensional flow region.
• * Employing agarose hydrogel microparticles to observe strain plateau near the stagnation point.
• * Applying particle image velocimetry to map the unperturbed velocity field and identify extensional flow regions.

Main Results:

• * Demonstrated experimental conditions for a microfluidic cross-slot to replicate uniaxial creep tests at the microscale.
• * Observed agarose hydrogel microparticles achieving a strain plateau in the cross-slot extensional flow region.
• * Developed an analytical model to extract linear viscoelastic properties from particle strain histories.

Conclusions:

• * The developed microfluidic cross-slot method enables accurate and precise measurement of viscoelastic properties of microscale biological objects.
• * The strain plateau achieved in the cross-slot is crucial for reliable viscoelastic property extraction.
• * Provided recommendations for applying the method to other biomaterials and criteria for identifying quasi-steady strain states.