Cornstarch In Water Research Articles

Shear thickening in dense suspensions: an experimental study

<h2>Abstract</h2> Shear thickening is an intriguing rheological behaviour which consists in a brutal increase in the viscosity above a critical shear rate. It is famously encountered in suspensions of corn starch in water. Despite having been discovered in the early 1930's, its underlying mechanisms remained a mystery for a long time. In 2013–14, numerical and theoretical works [1–3] put forward a frictional transition scenario to explain this phenomenon. In this talk, I will present experimental work investigating this frictional transition scenario. In order to test the ideas of this model, one has to go further than standard rheological techniques, since they do not provide access to the frictional state of the measured suspension. I will thus focus on the techniques that we developed in order to evidence the frictional transition and link it to the presence of a shear-thickening behaviour.

Aqueous mixtures of cornstarch and Pluronic® F127 studied by experimental and computational techniques

The possibility of interaction between cornstarch (CS) and amphiphilic molecules, such as the micelle-forming triblock copolymer Pluronic® F127 (F127), also known by Poloxamer 407, indicates that CS-F127 aqueous mixtures can regulate either the starch solubility or the copolymer micellization. Herein experimental and computational techniques were used to investigate CS-F127 aqueous mixtures aiming to highlight the role of these compounds on the molecular complexation. Dynamic light scattering results show that CS in water is highly polydisperse, while the F127 concentration and temperature influence the micellization process and the interaction with CS. Circular dichroism data of CS supernatants indicate the existence of small helical-like granules (Dh ≈ 800 nm) in the CS-F127 mixed aqueous solutions at 25 °C. UV–Vis spectrophotometry shows a small absorption band around 267 or 275 nm characteristic of micelles, granules, or molecular complexes, while FTIR and X-ray diffractometry indicate negligible structural changes. Lugol iodine tests at 25 °C show that both the precipitate and supernatant in the mixtures undergo some structural changes also indicating molecular complexation. Molecular dynamic simulations show the formation of stabilized inclusion complexes (V-amylose), where the propylene oxide segment of the copolymer inside the amylose helix and the ethylene oxide branches facing the aqueous media. These results together reveal weak CS-F127 interactions, evidencing a small solubility of CS both in the absence and presence of F127 as a solubilizing agent. Furthermore, moderate CS amounts do not change the F127 micelle structure.

Primary breakup of shear‐thickening suspension jet by an annular air jet

AbstractAn experimental investigation is conducted to study the influence of shear‐thickening behavior on the primary breakup process of suspension jets. The primary breakup morphologies of cornstarch–water suspension are observed via a high‐speed camera. The unique hardened breakup mode only occurs when the suspension exhibits discontinuous shear thickening (DST). During hardened breakup mode, the oscillating portion of the suspension jet becomes perpendicular to the air direction and keeps cylindrical instead of deforming into a thin sheet or membrane structure. The suspension jets break off into large pieces rather than tiny droplets. The dimensionless number N is established to describe the relative magnitude of the increment of the viscous force and aerodynamic force during the primary breakup process. The primary breakup regime map of Newtonian fluids and shear‐thickening suspensions is also promoted based on the dimensionless number N and the Weber number We.

Rheological analysis of rice husk-starch suspended in water for sustainable agriculture application

Agriculture usage is one of the major consumers of freshwater resources, however the increasing over dependency on water resources needs effective water management techniques. Water scarcity is one of the main problems in agriculture sector of India where farmers need solution for effective water management with minimum initial cost and which can be implemented with traditional methods. In this study, rheological analysis of rice husk and starch suspended in water are experimentally evaluated. Rice husk was powdered for maximum particle size of 180 µm. Study has measured the viscosity for different shear rate in the range of 0.09–1500 s−1. To understand the effect of temperature study was conducted at 30 °C and 80 °C. The study is performed using the rheometer (RheolabQC), which gives the relationship between the different fluid properties at different temperatures and shear rate. Experimental study was conducted on samples containing various proportions of rice husk and corn starch in water. All the samples at 30 °C shows shear thinning behavior except starch sample, whereas at 80 °C starch also shown shear thinning behavior. Viscosity of some samples increases with increase in temperature. At 30 °C sample containing 7gm rice husk powder and 3 gm starch, shows reduction in viscosity with increase in shear rate. The results are useful to control flow rate of water along with nutrition enrichment of the soil.

Secondary breakup of shear thickening suspension drop

To explore the effect of shear thickening behavior on the secondary deformation and breakup of cornstarch–water suspension droplets, an experimental investigation is conducted by using a high-speed camera. The experimental results demonstrate suspension droplets that exhibit discontinuous shear thickening (DST) exhibit a hardened deformation mode when they fall into the airflow field. When the droplets are in a hardened deformation mode, the windward side of the droplet deforms into a sheet, while the leeward side remains hemispherical until the droplet leaves the airflow field. The dimensionless number N is established to describe the relative magnitude of the increment of the viscous force and aerodynamic force during the secondary breakup process. Based on the suggested dimensionless number N and the Weber number We, the secondary deformation and breakup regime map of Newtonian fluids and DST suspensions is also proposed.

Effect of sugar type and concentration on pasting and textural properties of corn starch in water and skim milk

AbstractBackground and objectivesPasting and textural characteristics of corn starch in water and skim milk were prepared with different types of sugars (glucose, fructose, sucrose, and maltose) and different concentrations (0, 2, 4, 6, and 8%) were examined using Rapid Visco and Texture Analyzer.FindingsPasting parameters such as pasting temperature, peak time, peak, breakdown, trough, final and setback viscosities of corn starch–water and milk were influenced with the addition of sugar type and concentrations. Also, addition of sugar significantly influenced textural properties such as hardness, springiness, gumminess, adhesiveness, chewiness, cohesiveness, and resilience values of samples.ConclusionsThe results showed that addition of sugar to corn starch should be done carefully in terms of textural and pasting properties.Significance and NoveltySugar type and concentration directly influenced the product of corn starch samples.

Studying the Oobleck with video-analysis

We propose a semiquantitative experiment that associates video-analysis and ordinary procedures of experimental physics whose objective is to investigate the dual character of Oobleck, a mixture of cornstarch in water, which appears thicker or thinner depending on how it is physically manipulated. The results are presented and interpreted taking into account a macroscopic model present in the literature. The experiment is easily replicable in the most diverse school realities and it may be useful do discuss many fundamental physics concepts.

Effect of Initial Conformation on the Starch Biopolymer Film Formation Studied by NMR.

The formation of a rigid porous biopolymer scaffold from aqueous samples of 1% w/v (suspension) and 5% w/v (gel) corn starch was studied using optical and nuclear magnetic resonance (NMR) techniques. The drying process of these systems was observed using a single-sided NMR scanner by application of the Carr–Purcell–Meiboom–Gill pulse sequence at different layer positions. The echo decays were analyzed and spin–spin relaxation times (T2) were obtained for each layer. From the depth dependent T2 relaxation time study, it was found that the molecular mobility of water within the forming porous matrix of these two samples varied notably at different stages of film formation. At an intermediate stage, a gradual decrease in mobility of the emulsion sample towards the air–sample interface was observed, while the gel sample remained homogeneous all along the sample height. At a later stage of drying, heterogeneity in the molecular dynamics was observed in both samples showing low mobility at the bottom part of the sample. A wide-angle X-ray diffraction study confirmed that the structural heterogeneity persisted in the final film obtained from the 5% corn starch aqueous sample, whereas the film obtained from the 1% corn starch in water was structurally homogeneous.

Discontinuous rate-stiffening in a granular composite modeled after cornstarch and water

Cornstarch in water exhibits impact-activated solidification (IAS) and strong discontinuous shear thickening, with “shear jamming”. However, these phenomena are absent in cornstarch in ethanol. Here we show that cornstarch granules swell under ambient conditions. We postulate that this granule swelling is linked to an interparticle force scale that introduces a discontinuous rate-dependence to the generation of stable contacts between granules. We studied this force scale by coating sand with ~ 2 μm-thick polydimethysiloxane, creating a material that exhibits a similar IAS and discontinuous deformation rate-stiffening despite being a granular composite, not a suspension. This result suggests rate-dependence can be tuned by coating granular materials, introducing an interparticle force scale from rate-dependent properties present in the coating material. Our work provides insights into the unique behavior of cornstarch in water, bridges our understanding of suspensions and dry granular materials, and introduces a method to make discontinuous rate-dependent materials without suspending particles.

Giant deviation of a relaxation time from generalized Newtonian theory in discontinuous shear thickening suspensions

We investigated the transient relaxation of a Discontinuous Shear Thickening suspension of cornstarch in water. We performed 2 types of relaxation experiments starting from a steady shear in a parallel plate rheometer, followed by either stopping the top plate rotation and measuring the transient torque relaxation, or removing the torque on the plate and measuring the transient tool rotation. We found that at low weight fraction $\phi_{eff}<58.8\pm0.4\%$, the suspensions exhibited a relaxation behavior consistent with a generalized Newtonian fluid. However, for larger weight fraction $58.8\% < \phi_{eff} < 61.0\%$, near the liquid-solid transition $\phi_c=61.0\pm0.7\%$, we found relaxation behaviors different from the generalized Newtonian model. The relaxation time in this range scales with the inverse of the critical shear rate at the onset of shear thickening. In this range the relaxation time was the same in both stress and rate controlled experiments, rather than the viscosity calculated from the relaxation time which is expected to be intrinsic material parameter in the generalized Newtonian model. The discrepancy between the measured relaxation times and the generalized Newtonian prediction was found to be up to $10^4$, and extrapolations diverge in the limit of $\phi_c$ as the generalized Newtonian prediction approaches 0. At the highest weight fractions, the relaxation time scales were measured to be on the order of $\sim 1$ s. The fact that this timescale is resolvable by the naked eye may be important to understanding some of the dynamic phenomenon commonly observed in these systems. We also showed that using the critical shear rate $\dot\gamma_c$ at the onset of shear thickening to characterize the effective weight fraction can more precisely characterize material properties near the critical point $\phi_c$, allowing us to resolve this transition so close to $\phi_c$.

The effect of Ca2+ ions on the pasting, morphological, structural, vibrational, and mechanical properties of corn starch–water system

This work focuses on the effects of different concentrations of Ca2+ ions 0, 0.10, 0.15, 0.25, and 0.35% w/w and the steeping time in corn starch-water system with and without heating, as well as the influence of the Ca2+ concentrations on the pasting profile, regarding the physicochemical changes that take place along the thermal process. The first and second derivatives of the pasting profiles were calculated to identify the main changes originated in the heating and cooling regions. The inclusion of Ca2+ ions has a strong effect at the end of the pasting profile; below the gelatinization temperature starch grains exhibit a semi-crystalline structure and were still integer, at the peak viscosity, the samples were amorphous as a result of the gelatinization, at the final viscosity the structure was complete amorphous observed in the X-ray patterns. Micrographs of the starch-water system with Ca2+ show that the morphology changed rapidly and depends on the Ca2+ concentrations. IR spectroscopy shows that Ca2+ions did not form any new chemical bonds, yet only the van der Waals interaction occurred. We demonstrate for the first time the effect of calcium ions on the elastic and plastic regions of the custard and hydrogels.

Investigation of glycerol concentration on corn starch morphologies and gelatinization behaviours during heat treatment

The effects of various glycerol concentrations (0%, 5%, 10%, 20%, and 50%, w/w) on the morphologies and gelatinization behaviours of corn starch were evaluated by confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and rapid visco-analyzer (RVA). When corn starch granules with no added glycerol were treated at 65°C, the granules of corn starch were almost completely broken and tightly connected, and the characteristic birefringence of the starch granules disappeared. Various microscopic techniques revealed that starch gelatinization was delayed to higher temperatures as the glycerol concentration increased. In the presence of glycerol-water systems (5%, 10%, 20%, and 50%, w/w), the peak temperatures of corn starch increased by 1.6°C, 7.4°C, 10.7°C, and 19.7°C, respectively, compared to corn starch in water. The RVA pasting profiles showed that the gelatinization temperature increased as the glycerol concentration increased, which was consistent with polarized light microscope observations and DSC tests.

Role of hydrogen bond interactions in water–polyol medium in the thickening behavior of cornstarch suspensions

Rheological properties of suspensions are influenced by changes in the particle’s or suspending medium’s traits. Due to the ability of water and cornstarch to develop strong hydrogen bonds with each other and with hydroxyl groups of other liquids, it is promising to modify the suspending media with polyols to analyze the change in the Newtonian behavior of the suspensions. Cornstarch–water suspensions were prepared by adding different polyols viz.., glycerine, ethylene glycol (EG), and polyethylene glycol (PEG) to the suspending liquid (water) at various concentrations. The presence of possible chemical interaction due to the hydroxyl groups within the water–polyol systems was confirmed by Fourier transfer infrared spectroscopy (FTIR). The rheological parameters of pure cornstarch–water suspension were compared with that of water–polyol-based shear thickening fluids (STFs). The thickening behavior enhanced by three orders of magnitude with increasing glycerine and EG content for a constant particle concentration. However, the presence of PEG in the suspension resulted in a shear thinning phenomenon with a high yield stress unlike the other polyols. Thus, the presence of O–H interactions in the suspending liquid was presumed to control the flow phenomenon of these suspensions. A possible mechanism based on interactions has been proposed for the non-Newtonian flow in each suspension. The current work is one of a kind in demonstrating the role of hydrogen interactions within suspending medium on the thickening behavior of the cornstarch–water suspensions.

Dramatic effect of fluid chemistry on cornstarch suspensions: Linking particle interactions to macroscopic rheology.

Suspensions of cornstarch in water exhibit strong dynamic shear thickening. We show that partly replacing water with ethanol strongly alters the suspension rheology. We perform steady and nonsteady rheology measurements combined with atomic force microscopy to investigate the role of fluid chemistry on the macroscopic rheology of the suspensions and its link with the interactions between cornstarch grains. Upon increasing the ethanol content, the suspension goes through a yield-stress fluid state and ultimately becomes a shear-thinning fluid. On the cornstarch grain scale, atomic force microscopy measurements reveal the presence of polymers on the cornstarch surface, which exhibit a cosolvency effect. At intermediate ethanol content, a maximum of polymer solubility induces high microscopic adhesion which we relate to the macroscopic yield stress.

Dynamic shear jamming in dense granular suspensions under extension.

Unlike dry granular materials, a dense granular suspension like cornstarch in water can strongly resist extensional flows. At low extension rates, such a suspension behaves like a viscous fluid, but rapid extension results in a response where stresses far exceed the predictions of lubrication hydrodynamics and capillarity. To understand this remarkable mechanical response, we experimentally measure the normal force imparted by a large bulk of the suspension on a plate moving vertically upward at a controlled velocity. We observe that, above a velocity threshold, the peak force increases by orders of magnitude. Using fast ultrasound imaging we map out the local velocity profiles inside the suspension, which reveal the formation of a growing jammed region under rapid extension. This region interacts with the rigid boundaries of the container through strong velocity gradients, suggesting a direct connection to the recently proposed shear-jamming mechanism.

Paradoxical ratcheting in cornstarch

In this paper, we demonstrate that vertically vibrating a plate in a cornstarch suspension causes the suspension to vigorously ratchet up the plate. We show that this is a necessary consequence of the fact that cornstarch in water is shear thickening: when the plate moves up it opposes gravity and so the fluid stiffens; when it moves down it works with gravity and so the fluid flows. This produces asymmetric ratcheting that opposes gravity. We find several unusual states that result in this simple experimental system, and we reproduce the essential effect in two different numerical simulations.

Large amplitude oscillatory shear rheology of three different shear-thickening particle dispersions

We present a large amplitude oscillatory shear rheology (LAOS) investigation of three different shear-thickening particle dispersions - fumed silica in polyethylene oxide (FLOC), fumed silica in polypropylene glycol (HydroC), and cornstarch in water (JAM). These systems shear-thicken by three different mechanisms - shear-induced formation of particle clusters flocculated by polymer bridging, hydrocluster formation, and jamming. The viscoelastic non-linearities of the three fluids were studied as a function of strain and strain-rate space through the use of Lissajous-Bowditch curves and local nonlinear viscoelastic moduli of an oscillatory shear cycle. The nonlinear behaviors of the three fluids were compared and contrasted to understand the nonlinear shear-thickening mechanism of each. Both HydroC and JAM dispersions were found to exhibit strong strain stiffening of the elastic moduli and strain thickening of the loss moduli behavior associated with possible hydrocluster formation and particle jamming. However, the FLOC dispersion, in contrast, showed strong strain softening and strain thinning behavior at large strain amplitudes associated with yielding of the microstructure. The expected thickening of the loss modulus of FLOC in LAOS with increasing strain was not observed even though viscosity of FLOC was found to shear-thicken in steady-shear measurements. This disagreement is likely due to very large strain amplitudes required for shear-thickening to occur by shear-induced polymer bridging mechanism. The hypothesis was confirmed through stress growth experiments. Conversely, the HydroC and JAM dispersions required relatively small applied strains for shear-thickening to occur by hydrocluster and jamming mechanism. The comparison of local intra-cycle nonlinearity through Lissajous-Bowditch plots and nonlinear viscoelastic parameters indicated that the elastic nonlinearities of all three systems are primarily driven by a strong dependence on the magnitude of the applied strain-rates within an oscillatory cycle rather than the amplitude of the applied strain. A close inspection of the LAOS data reveals strong differences in the viscoelastic nonlinearities of these three different shear-thickening dispersions which can be used to create a nonlinear rheological fingerprint for each and offers valuable new insights into the nonlinear dynamics associated with each of the shear-thickening mechanisms.

The role of shear in the transition from continuous shear thickening to discontinuous shear thickening

Dense non-Brownian suspension has rich rheology and is hard to understand, especially for distinguishing continuous shear thickening (CST) from discontinuous shear thickening (DST). By studying the shear stress dependent rheology of a well-known DST suspension of cornstarch in water, we find that the transition from CST to DST could occur not only by increasing the volume fraction ϕ but also by increasing the shear stress σ. For the recovery process of jammed suspension, we observe that the shear activates the time-dependent nature of particle rearrangement. DST can then be interpreted as the consequence of shear-induced jamming. Based on the test data, we plot the schematic phase diagram in the ϕ-σ plane and find out that ϕ and σ perform almost the same effect on flow-state transition.

Ultrasonic frequency effect on corn starch and its cavitation

With the same ultrasonic power, time and temperature, different ultrasonic frequency (20 kHz, 25 kHz and 20 kHz + 25 kHz) effects on the structure and properties of corn starch in water were studied, as well as its cavitation. Brabender viscometer and Scanning Electron Microscope (SEM) were used to determine the viscosity and microstructure of starch respectively. The experimental results indicated that the peak viscosity of starch without ultrasound was 1076.0BU, however it decreased by 18.87% and 17.66% with 25 kHz and 20 kHz, respectively. Ultrasound could significantly change the thermal stability, retrogradation, gel properties of starch, and caused depression on the surface of starch granules. Iodine release yield was used to present the cavitational yield at different frequencies of ultrasound. Compared to these with each single frequency ultrasound, the change of the above properties of corn starch granules microstructure with dual-frequency (20 kHz + 25 kHz) ultrasound were smaller, but had much more depression on their surfaces. Dual-frequency ultrasound produced more cavitation yields and caused faster collapse of bubbles than each single frequency. In conclusion, (20 kHz + 25 kHz) proved an more evident effect on corn starch structure and properties, and as a possible mechanism, it has more ultrasonic cavitations.

Pregnancy in Women With Glycogen Storage Disease Ia and Ib

Over the past 9 decades since glycogen storage disease (GSD) was described, an almost universally fatal disease has become one where women are living well into adulthood and choosing to bear children. This inborn error of metabolism associated with the creation and utilization of glycogen, when untreated, manifests with unrelenting hypoglycemia. The initiation of continuous feeds has improved outcomes, and later in 1982, the administration of intermittent doses of cornstarch in water provided a continuous supply of exogenous glucose. As metabolic control has improved, morbidity has decreased. Glycogen storage disease Ib has the same severity of hypoglycemia as GSD Ia, with associated immune disturbance. Prior to the introduction of granulocyte colony-stimulating factor (G-CSF), infections caused significant mortality in GSD Ib. Pregnancy in patients with GSD Ia and Ib poses unique challenges during gestation and delivery. Good metabolic control before conception and throughout pregnancy is directly related to successful outcomes. There is no nursing literature to date addressing perinatal and neonatal care in this population.