Oscillatory Shear Measurements Research Articles

Sparse regression for discovery of constitutive models from oscillatory shear measurements

We propose sparse regression as an alternative to neural networks for the discovery of parsimonious constitutive models (CMs) from oscillatory shear experiments. Symmetry and frame invariance are strictly imposed by using tensor basis functions to isolate and describe unknown nonlinear terms in the CMs. We generate synthetic experimental data using the Giesekus and Phan-Thien Tanner CMs and consider two different scenarios. In the complete information scenario, we assume that the shear stress, along with the first and second normal stress differences, is measured. This leads to a sparse linear regression problem that can be solved efficiently using l1 regularization. In the partial information scenario, we assume that only shear stress data are available. This leads to a more challenging sparse nonlinear regression problem, for which we propose a greedy two-stage algorithm. In both scenarios, the proposed methods fit and interpolate the training data remarkably well. Predictions of the inferred CMs extrapolate satisfactorily beyond the range of training data for oscillatory shear. They also extrapolate reasonably well to flow conditions like startup of steady and uniaxial extension that are not used in the identification of CMs. We discuss ramifications for experimental design, potential algorithmic improvements, and implications of the non-uniqueness of CMs inferred from partial information.

On the Relation between the Viscoelastic Properties of Granular Hydrogels and Their Performance as Support Materials in Embedded Bioprinting.

Granular hydrogels, formed by jamming microgels suspension, are promising materials for three-dimensional bioprinting applications. Despite their extensive use as support materials for embedded bioprinting, the influence of the particle's physical properties on the macroscale viscoelasticity on one hand and on the printing performance on the other hand remains unclear. Herein, we investigate the linear and nonlinear rheology of κ-carrageenan granular hydrogel through small- and large-amplitude oscillatory shear measurements. We tuned the granular hydrogel's properties by changing the stiffness (soft, medium, stiff) and the packing density of the individual microgels. Characterizations in the linear viscoelasticity regime revealed that the storage modulus of granular hydrogels is not a simple function of microgel stiffness and depends on the microgel packing density. At larger strains, increasing the microgel stiffness reduced the energy dissipation of the granular beds and increased the solid-fluid transition point. To understand how the different rheological properties of granular support materials influence embedded bioprinting, we examined the printing fidelity and cellular filament shrinkage within the granular beds. We found that microgels with low packing density diminished the printing quality, while stiff microgels promoted filament roughness. In addition, we found that highly packed stiff microgels significantly reduced the postprinting contraction of cellular filaments. Overall, this work provides a comprehensive knowledge of the rheology of granular hydrogels that can be used to rationally design support beds for bioprinting applications with specific characteristics.

High internal phase Pickering emulsion solely stabilized by low-content chitosan: Insight into relations between network microstructures and rheological properties

Nano-sized and well-dispersed chitosan particles (CSPs) are prepared by adjusting pH towards pKa of chitosan (CS) aqueous solutions. The prepared CSPs are able to stabilize high internal phase Pickering emulsions (HIPPEs) with low CSP contents, at minimum of 0.2 wt% CSP stabilizing a maximum of 85 % oil phase fraction in a near-neutral environment. It is clarified by microscopy, small amplitude oscillatory shear (SAOS) and large amplitude oscillatory shear (LAOS) measurements that CSPs act as Pickering particle emulsifiers to form a network immobilizing oil droplets in HIPPEs. Using power-law analysis on SAOS results, the solid-like but frequency-dependent rheological response is attributed to the physical connection among CSPs, while the overshoot of the loss modulus in LAOS test is assigned to the featured resistance of networks to the applied large deformation. The oil phase fraction, CSP concentration, temperature and ionic strength are found to be key factors for the rheological behavior and emulsion stability. This work is expected to guide the design and processing of HIPPE stabilized solely by polysaccharides.

Physicochemical Attributes and Dynamic-Mechanical Properties of a Traditional Himalayan Cheese – Kalari

ABSTRACT Kalari is a traditionally made Himalayan cheese. It is popular in the hilly belts of Jammu and Kashmir, India, and is also known as the “Mozzarella of Kashmir.” It is prepared from raw milk by natural acidification followed by heat coagulation. The present work aims to evaluate the physicochemical and rheological characteristics of Kalari and to gain insight into its composition and functional properties. Rheological characterization based on small amplitude oscillatory shear (SAOS) measurements reveals the cheese to be a viscoelastic material, with the elastic nature dominating viscous behavior at all test conditions. Temperature sweep and Arrhenius plot also enabled to identify rheological response of Kalari at elevated temperatures, which can further elucidate its functionality. Lower values of activation energy (39.57 KJ mol−1) and phase angle (28°) reiterate that the cheese does not flow extensively but undergoes softening and slight melting on exposure to high temperatures. Physicochemical characterization revealed the cheese to possess more protein (33.8% − 42.6%) and moisture (42.9% − 48.1%) than fat (7.5% − 11.9%).

UV‐photopolymerized acrylic pressure‐sensitive adhesives with semi‐interpenetration structure: Effect of plasticizer structures on adhesion properties

AbstractAcrylic pressure‐sensitive adhesives (PSAs) were synthesized using a solvent‐free ultraviolet‐induced polymerization method. The monomers n‐(isobutoxymethyl) acrylamide, 2‐ethylhexyl acrylate, 2‐hydroxyethyl acrylate, and methyl methacrylate and an initiator, hydroxy dimethyl acetophenone, were used to prepare acrylic copolymers as prepolymers. A multifunctional monomer, trimethylolpropane triacrylate, was added to form a semi‐interpenetrating network, leading to an increase in the modulus and elasticity of the prepolymer. This decreased the peel strength, which is suitable for temporary protective films. Rheological data from small‐amplitude oscillatory shear measurements also revealed consistent results suitable for removable PSAs. The plasticizers, such as dioctyl phthalate and dioctyl terephthalate, possessing favorable interactions with the main resins were found to exhibit transparency, clear debonding, and ultralow release, which are essential features for temporary protective films.

Preparation and Characterization of H-Shaped Polylactide.

An H-polymer has an architecture that consists of four branches symmetrically attached to the ends of a polymer backbone, similar in shape to the letter "H". Here, a renewable H-polymer efficiently synthesized using only ring-opening transesterification is demonstrated. The strategy relies on a tetrafunctional poly(±-lactide) macroinitiator, from which four poly(±-lactide) branches are grown simultaneously. 1H NMR spectroscopy, size exclusion chromatography (SEC), and matrix-assisted laser desorption/ionization (MALDI) spectrometry were used to verify the macroinitiator purity. Branch growth was probed using 1H NMR spectroscopy and SEC to reveal unique transesterification phenomena that can be controlled to yield architecturally pure or more complex materials. H-shaped PLA was prepared at the multigram scale with a weight-average molar mass Mw > 100 kg/mol and low dispersity Đ < 1.15. Purification involved routine precipitations steps, which yielded products that were architecturally relatively pure (∼93%). Small-amplitude oscillatory shear and extensional rheology measurements demonstrate the unique viscoelastic behavior associated with the H-shaped architecture.

Ileal mucus viscoelastic properties differ in Crohn’s disease

Crohn’s disease (CD) is an inflammatory bowel disease (IBD) that can affect any part of the gastrointestinal tract, frequently involving the terminal ileum. While colonic mucus alterations in CD patients have been described, terminal ileal mucus and its mechanobiological properties have been neglected. Our study is the first of its kind to decipher the viscoelastic and network properties of ileal mucus.With that aim, oscillatory rheological shear measurements based on an airway mucus protocol that was thoroughly validated for ileal mucus were performed. Our pilot study analyzed terminal ileum mucus from controls (n=14) and CD patients (n=14). Mucus network structure was visualized by scanning electron microscopy (SEM).Interestingly, a statistically significant increase in viscoelasticity as well as a decrease in mesh size was observed in ileal mucus from CD patients compared to controls. Furthermore, rheological data were analyzed in relation to study participants’ clinical characteristics, revealing a noteworthy trend between non-smokers and smokers.In conclusion, this study provides the first data on the viscoelastic properties and structure of human ileal mucus in the healthy state and in Crohn’s disease, demonstrating significant alterations between groups and highlighting the need for further research on mucus and its effect on the underlying epithelial barrier.

A Simple and Sensitive Approach for Real‐Time Sensing of Enzymatically Catalyzed Hydrogelation

AbstractDespite the critical role of hydrogels in material science and biotechnology, current methods for analyzing their formation lack real‐time monitoring and require complex sample preparation and instrumentation. In this work, an innovative methodology is introduced for the real‐time analysis of enzymatically catalyzed hydrogelation. Electrochemical impedance spectroscopy (EIS) coupled with interdigitated electrodes (IDEs) to sense and transduce the gelation reaction of model precursor carboxymethyl cellulose‐tyramine (CMC‐TA) conjugates that undergoes enzymatic cross‐linking by horseradish peroxidase (HRP) and hydrogen peroxide (H2O2). Real‐time monitoring involves single‐frequency analyses at 3 × 105 Hz, where the measured impedance consists solely of a resistive component, and the admittance equates to solution conductance. The gelation trajectories for all tested enzymatically cross‐linked hydrogel component combinations are determined by substituting the conductance data in the modified Michaelis–Menten kinetic model. Specifically, for CMC‐TA cross‐linked by HRP, the authors calculate apparent KM and kcat values of 82.1 µM and 95.5 s−1, respectively. These findings are further validated through rheological characterization, including oscillatory shear measurements and microrheology. Overall, this research paves the way for a streamlined, accurate, and cost‐effective approach to controllable enzymatically initiated hydrogel synthesis, enhancing their successful application in various fields ranging from material science to biotechnology.

Rheo-PIV study of slip effects on oscillatory shear measurements of a yield-stress fluid

The influence of apparent slip on oscillatory shear measurements of a viscoplastic microgel [0.6 wt. % of poly(acrylic acid)] is analyzed by Couette and parallel-plate rheometry and particle image velocimetry (Rheo-PIV). We first provide direct evidence of a critical shear stress for the onset of slip of the microgel under oscillatory (σos) and nonoscillatory measurements (σs). Afterward, we describe the effect of slip on oscillatory measurements via waveforms, Bowditch–Lissajous curves, Fourier transform (FT) rheology, PIV, and as a sequence of physical processes (SPP). The effect of slip is mainly observed at low oscillating frequencies. For amplitudes of the oscillating stresses σ0 ≤ σos, the microgel exhibits linear viscoelastic behavior with in-phase strain response. For σos &amp;lt; σ0 ≤ yield stress (σy), slip introduces a phase shift in the strain response with a forward-tilted waveform and “mango” shape Bowditch–Lissajous curves. Meanwhile, FT rheology shows negligible even harmonics. The strain measured by the rheometer does not match the true strain determined by PIV in the presence of slip, resulting in waveforms that depend on how the displacement distribution is interpreted. This result indicates a break in the symmetry of the flow, that is, the microgel response no longer follows the imposed oscillation, which makes any attempt to correct oscillatory data for slip complex. This behavior arises from recoil of the slipping microgel after reaching its maximum displacement in a cycle. Finally, we provide an overall picture of the kinematics of the process of yielding in the presence of slip as an SPP.

Non-Stick Length of Polymer-Polymer Interfaces under Small-Amplitude Oscillatory Shear Measurement.

Interfaces in soft materials often exhibit deviation from non-slip/stick response and play a determining role in the rheological response of the overall system. We discuss detection techniques for the excess interface rheology using small-amplitude oscillatory shear (SAOS) measurements. A stacked bilayer of different polymers is sheared parallel to the interface and the dynamic shear response is measured. Deviation of the bilayer shear modulus from the superposition of the shear moduli of the component layers is analysed. Furthermore, we introduce a frequency-dependent non-stick length based on the bilayer SAOS response to characterize the excess interface rheology. We observe an approximate stick response in the interface in bilayers composed of the chemically same monomer as well as an apparent slip in the interface between immiscible polymers. The results suggest that the proposed non-stick length in SAOS is capable of detecting the apparent interfacial slip. The non-stick length in SAOS is readily applicable to other complex interfaces of different soft materials and offers a convenient tool to characterize the excess interface rheology.

Extrapolation of classical rheometry of plant protein pastes to extrusion conditions

This study explores alternative methods to measure the rheology of pastes based on soy and pea proteins, which are commonly used as starting material in extrusion for the preparation of meat analogs. Currently, it is still a challenge to obtain consistent rheological data on such materials for steady shear at conditions that are relevant for the extrusion of such systems. Hence, possibilities are explored for the extrapolation of results obtained with classical rheometers operating at temperatures below boiling point, to conditions that are relevant for the extrusion of such systems. The above was combined, with findings from off-line and in-line capillary rheometers, which can provide steady shear measurements above boiling point and at hydration levels as used in extrusion.We have analysed the consistency of our new results with previous oscillatory shear measurements, performed at conditions similar to those of meat analog extrusion. For validation of the extrapolation we have analysed whether the new rheology data follow similar scaling rules. As classical rheometers can handle only moderate torques, the measurements are limited to hydration levels higher than those used in extrusion (75–85%). Despite this limitation, strain sweeps with classical rheometers show that in this regime the elastic modulus also scales with Tg/T, the ratio of glass transition, and actual temperature. Yet, its dependency on Tg/T appears differently from measurements performed at extrusion-like conditions. Moreover, our current results indicate a strong thixotropic nature of plant protein pastes at temperatures below boiling point. Consequently, flow curves are only stable if performed from high to low shear rates. Nevertheless, our data can be mapped to a single master curve following the Herschel-Bulkley model, with parameters also following a scaling rule dependent on Tg/T.This Tg/T scaling is used to construct master curves with data from the off-line and in-line capillary rheometers. The obtained shift factors for the flow curves are in agreement with old literature data obtained for SPI, but they deviate significantly from our steady shear measurements with classical rheometers. Based on the results of our current and previous study we have a critical, general discussion on the possibility of extrapolation of classical rheometry of plant protein pastes to process conditions used for production of meat analogs.

Designing a swimming rheometer to measure the linear and non-linear properties of a viscoelastic fluid

At low Reynolds numbers, “swirlers” – swimmers with an axisymmetric “head” and “tail” counterrotating about the axis of symmetry – generate no net propulsion in a Newtonian fluid as a consequence of the “scallop theorem”. Viscoelasticity in the suspending fluid breaks the time-reversibility and allows swirlers to propel themselves, with the swim speed being a function of swimmer geometry, fluid elasticity, and swimming gait. Using analytical theory and numerical simulations, we study the unsteady motion of a freely-suspended self-propelled swirler though viscoelastic fluids described by the Giesekus model, allowing for general axisymmetric geometry and time-dependent tail rotation rate. We show the steady swim speed can be calculated for general arbitrary axisymmetric geometries at low Deborah number via the reciprocal theorem and the solution of two Newtonian flow problems. In this “weak flow” limit, we analytically determine the swim speed and its dependence on the parameters of the Giesekus fluid which in turn are related to the primary and secondary normal stress coefficients Ψ1 and Ψ2. Furthermore, at low De, we derive the unsteady swim speed as a function of a specified unsteady tail rotation rate and the material properties of the suspending fluid. We show that for a particular tail rotation rate, the unsteady swim speed can be analyzed to recover the spectrum of fluid relaxation times, analogous to small-amplitude oscillatory shear measurements on a benchtop rheometer. This study expands upon the design space for a “swimming rheometer” by increasing its functionality to make and interpret rheological measurements.

Oscillatory rheology of chitosan and calcium chloride crosslinked pectin blend filmogenic solutions and atomic force microscopy of film surface topography

This work examines the synergistic interaction between chitosan (CS) and calcium crosslinked pectin (CP) in aqueous solution by small-amplitude oscillatory shear measurements at selected CS/CP blend ratios (1:1, 1:2, 1:3, and 1:4) and compares the surface morphology of cast films of those blends using atomic force microscopy (AFM). A 2% (w/v) pectin solution concentration could not produce a film, which was improved with the addition of 0.18 M calcium chloride solution, and the corresponding dynamic moduli increased by 3 log cycles. The mechanical rigidity of the blends increased with increasing CP contents. The complex viscosity (η*) decreased with increasing temperature due to molecular mobility at higher temperatures and the breaking of the junction between CS and CP. The applicability of the Cole-Cole plot to selected blend ratios demonstrated that only the CS/CP ratio of 1:3 best fitted and established the well-miscibility between the polymers. AFM phase imaging further illustrates the distribution of CS and CP particles in the blended films and provides complementary information to the topography image, revealing the variations in the surface properties of the films. AFM proves to be a powerful tool for investigating microstructural changes in polymer blends and complementing rheological measurements.

Viscoelastic properties of fresh cement paste: measuring procedures and influencing parameters

Fresh cement pastes behave as viscoelastic materials below the flow onset. The measurements of viscoelastic properties of fresh cement paste provide valuable insight into the dispersion of solid particles as well as the hydration kinetics at early age and its influence on the structural evolution and solidification behavior at quasi-static conditions. Monitoring the development of viscoelastic properties of fresh cement paste using dynamic oscillatory shear measurements can also elucidate the working mechanisms of chemical admixtures. These properties are efficient indicators to guide mixture proportion design and are necessary to understand the rheology and stability of concrete. In this paper, the most common techniques, including dynamic oscillatory measurements, used to assess the viscoelastic properties of fresh cement paste are presented and discussed. The measurement challenges and their effects on the accuracy of the obtained properties are highlighted. On the other hand, the effects of high-range water-reducer, viscosity-modifying admixture, and supplementary cementitious materials are discussed. Furthermore, the use of viscoelastic measurements to assess yield stress and structural build-up of cement paste is presented.

Physics of Starch System: Rheological and Mechanical Properties of Hydrothermally Modified Elephant Foot Yam Starch

Heat moisture treatment (HMT) was used to improve the functionalities of elephant foot yam starch (EFYS) by using selected heating techniques such as hot air oven (HAO), autoclave (AL), and microwave (MW). The swelling power and solubility were reduced significantly after HMT modification, whereas an increase in amylose content was detectable after HMT modification, and the maximum changes were identified in HAO-modified EFYS (28.48%) as compared to its native counterpart (18.01%). The study demonstrates that the maximum drop in peak viscosity (1045 cP) was perceived in HAO-modified EFYS, which confirms its thermostability as compared to native (1114 cP) and other treated starches (1059 to 1098 cP). All the starch pastes exhibited shear-thinning behavior, however, isothermal heating of starch paste at 95 °C revealed a rise in apparent viscosity with increasing shear rate in all HMT-modified EFYS. Large amplitude oscillatory shear (LAOS) measurements of modified starch samples showed the predominating solid-like behavior in modified EFYS. The HAO-treated EFYS had the highest elasticity of the others, which represents the enhanced structural rigidity due to the formation of transient network structures. Furthermore, Lissajous-Bowditch plots confirmed the early deviation of the structural integrity from elastic to viscous behavior in HAO-treated EFYS. Overall, the HAO-modified EFYS showed significant improvement in functionalities and structural integrities under high shear and high oscillation strain, which infers its potential industrial applications. Based on our results, we propose specific physical models suggesting the effect of molecular structural arrangements of amylose and amylopectin expressing the essential rheological differences between native and HMT EFYS.

Star-to-Bottlebrush Transition in Extensional and Shear Deformation of Unentangled Polymer Melts

A series of model poly((±)-lactide) (PLA) graft copolymers was synthesized by ring-opening metathesis polymerization and used to probe the star-to-bottlebrush transition in shear and extensional flows. Ten samples with backbone degrees of polymerization 11 ≤ Nbb ≤ 420 were investigated using small-amplitude oscillatory shear (SAOS) and extensional rheometry measurements. Each contained one PLA side chain of length Nsc = 72 per two backbone repeating units on average (graft density of z = 0.5). The star-like to bottlebrush transition was identified at Nbb = 50–69 using SAOS. In extension, melt strain hardening is absent in the star-like melts (Nbb ≤ 50) but is prominent in the bottlebrush limit (Nbb > 69). The onset of melt strain hardening occurs at a time scale equivalent to the Rouse time of the backbone. A molecular interpretation of these results builds upon recent conjectures related to strain-induced increases in interchain friction in bottlebrush polymers. These findings will be useful in designing bottlebrush melts that strain harden, which is critical in various types of processing methods involving extensional flows, including foaming, 3D printing, and film-blowing.

Dynamic rheological properties of sesame protein dispersions

AbstractInterest in utilizing new sustainable protein sources is increasing, and understanding the rheological behavior of sesame protein can be useful in further application. Small amplitude oscillatory shear measurements of sesame protein dispersions at varying concentrations of 5.0%, 7.5%, and 10.0% were examined at both linear and nonlinear regions. Although the sesame protein dispersions showed pseudoplastic behavior, the shear‐thickening effect of sesame proteins at higher concentrations makes it possible to apply in beverages without increasing viscosity. The low values of the yield point of the sesame protein explained its feasibility for utilization in varying products such as high‐protein‐enriched beverages without the adverse effect of the high viscosity. The fracture stress and strain indicated the high strength of the sesame protein to the mechanical changes. The mechanical properties of the sesame proteins also confirmed typical strong gel behavior. The complex viscosity (η*) was decreased linearly with frequency demonstrating the shear thinning phenomenon. The frequency dependency of the protein was shown a low n value that explains a relatively elastic gel structure. These rheological characteristics of the sesame proteins might be more reliable than the previous works on the static rheological behavior, which provides a new horizon in the application of a sustainable protein in food industries.

Evaluating the Mechanical Response of Agarose-Xanthan Mixture Gels Using Tensile Testing, Numerical Simulation, and a Large Amplitude Oscillatory Shear (LAOS) Approach.

Large deformation stress response characteristics of hydrocolloid mixture gel systems were investigated based on texture and rheological measurements. Agarose and xanthan mixtures at different ratios (1:0, 0.75:0.25, and 0.5:0.5) were chosen as the model systems. A decrease in failure stress from 2.65 to 1.82 MPa and an increase in failure strain from 0.08 to 0.13 with higher xanthan ratios were obtained based on the ring tensile test, indicating that xanthan molecules could improve the flexibility of the agarose network. The gels showed severe water loss by compression, particularly for the pure agarose gel (6.74%). Compared to the compression test, the gels presented low water loss after the ring tensile test (<1.3%) indicating that the ring tensile test could calculate the correct stress−strain relationship. Digital image correlation (DIC) and numerical simulation revealed that agarose-xanthan gel systems possess a deformation behavior with homogeneous strain distribution before failure. Elastic and viscous Lissajous−Bowditch curves from the large amplitude oscillatory shear (LAOS) measurement at different strains and frequencies elucidated that the agarose-xanthan gel was dominated by the agarose structure with a similar magnitude of elasticity at a low frequency. The large deformation approach from this study has great potential for elucidating and understanding the structure of food and biopolymer gels.

Effects of Concentration and Heating/Cooling Rate on Rheological Behavior of Sesamum indicum Seed Hydrocolloid

Hydrocolloids are known as natural hydrophilic biopolymers that can contribute viscosity and gelation in solution, as well as nutritional benefits, thus, they are widely used in the food industry. In our work, hydrocolloid was isolated by aqueous extraction of Sesamum indicum seed at 80 °C and pH 8.0. The chemical composition and functional properties of Sesamum indicum seed hydrocolloid (SISH) were characterized, and the effects of concentration including 1%, 2%, and 3% as well as heating/cooling rate (1, 5, and 10 °C/min) on the rheological behavior of SISH dispersions in aqueous solution were investigated. The viscoelastic properties of SISH dispersions were characterized by small-amplitude oscillatory shear measurement. The resultant SISH consisted of 60.95% carbohydrate and 23.32% protein, and was thus endowed with a relatively high water-holding capacity, solubility, appropriate emulsifying and foaming properties. Rheological results revealed that the aqueous dispersion of SISH exhibited a non-Newtonian shear-thinning flow behavior. The viscoelastic moduli changes were found to be dependent on SISH concentration, temperature, and heating/cooling rate. Increasing SISH concentrations from 1% to 3% promoted the development of stronger cross-link network. The mechanical spectra derived from strain and frequency sweep measurements showed that the storage moduli were always higher than the loss moduli, and the loss tangent was calculated to be above 0.1 and below 1.0. Furthermore, both moduli had slight frequency dependency, and the complex viscosity exhibited an almost linear reduction with the increase of frequency. Therefore, SISH dispersion behaved as a weak gel-like system. The hysteresis of viscoelastic moduli during heating and cooling reduced with decreasing the heating-cooling rates from 10 to 1 °C/min, suggesting that SISH molecules had enough time to develop a stable and thermally irreversible network. Overall, SISH can be regarded as an acceptable hydrocolloid for generating natural food components with intriguing functional and rheological qualities in the formulation of microstructured goods.

A detailed and systematic study on rheological and physicochemical properties of rhamnolipid biosurfactant solutions

Biosurfactants are widely used in many industrial settings ranging from cosmetic to petroleum industries. Among various biosurfactants available in the market, rhamnolipid is a well-known bacterial biosurfactant produced by the Pseudomonas aeruginosa bacteria. However, despite its wide applications, no detailed and systematic study is available on the rheological characterization of this biosurfactant solution, which is an essential property to investigate for many practical applications. Therefore, this study aims to present a thorough and complete investigation of this biosurfactant's shear and extensional rheological behaviours. While steady shear and small amplitude oscillatory shear (SAOS) measurements were conducted to investigate the shear rheological behaviour, the dripping-onto-substrate (DoS) extensional rheometry technique was used to understand its extensional rheological behaviour. A chemically derived surfactant (cetyltrimethyl ammonium bromide (CTAB)) was also used in our analysis to show and discuss the qualitative and quantitative differences in their rheological behaviours. Along with the detailed rheological study, some studies on the physicochemical properties, such as surface tension, contact angle, particle size analysis, thermal stability, etc., were also conducted to make an overall comparison between the two surfactants. Both surfactants show strong shear-thinning and extensional hardening behaviors in shear and extensional rheological flows, respectively. However, the zero-shear rate viscosity and extensional viscosity are found to be larger for rhamnolipid surfactant solutions than for CTAB. The corresponding shear and extensional relaxation times also follow the same trend. Furthermore, the surface tension is found to be less, and the contact angle is found to be more for rhamnolipid biosurfactant than that for CTAB. Rhamnolipid shows more excellent thermal stability, particularly at high temperatures than CTAB. Therefore, the results and discussion presented in this study will help to choose the present rhamnolipid biosurfactant for any particular application, particularly where the knowledge of the rheological responses of a surfactant solution is essential.