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Probing shear-induced rearrangements in Fourier space. II. Differential dynamic microscopy
摘要： We discuss in two companion papers how Fourier-space measurements may be coupled to rheological tests in order to elucidate the relationship between mechanical properties and microscopic dynamics in soft matter. In this second companion paper, we focus on Differential Dynamic Microscopy (DDM) under shear. We highlight the analogies and the differences with dynamic light scattering coupled to rheology, providing a theoretical approach and practical guidelines to separate the contributions to DDM arising from the affine and the non-affine part of the microscopic displacement field. We show that in DDM under shear the coherence of the illuminating source plays a key role, determining the effective sample thickness that is probed. Our theoretical analysis is validated by experiments on 2D samples and 3D gels.
关键词： non-affine deformation,shear,soft matter,affine deformation,rheology,Differential Dynamic Microscopy
更新于2025-09-23 15:23:52
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Nano-rheology printing of sub-0.2 <i>μ</i> m channel length oxide thin-film transistors
摘要： Down-scaling of the channel length of a fully solution-processed oxide thin-film transistor (TFT) to the nanometer-scale is the key to accessing next-generation devices for Internet-of-Things technology. In this work, we report on the fabrication of an oxide TFT with a channel length of 160 nm, which is far less than those obtained by the current direct-printing techniques, by a newly developed nano-rheology printing (nRP) method. The device had an on/off current ratio, subthreshold voltage, hysteresis, and field-effect mobility of approximately 107, 1.7 V, 0 V, and 0.16 cm2 V s-1, respectively. The key to achieving the sub-micron channel printed TFT is the introduction of a new amorphous La–Ru–O material, which exhibits relatively good conductivity and excellent nRP properties at the nanoscale, for source/drain electrode patterns. Such a short-channel TFT would never be achieved with conventional printing methods, and hence, this approach is highly important for accessing next-generation low-cost, large-area and environmentally friendly printed electronics.
关键词： nano-rheology printing,thermal-imprinting,printed electronics,solution process,oxide thin-film transistor
更新于2025-09-23 15:23:52
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Optical twisting to monitor the rheology of single cells
摘要： BACKGROUND: Biological cells exhibit complex mechanical properties which determine their responses to applied force. OBJECTIVE: We developed an optical method to probe the temporal evolution of power-law rheology of single cells. METHODS: The method consisted in applying optically a constant mechanical torque to a birefringent microparticle bound to the cell membrane, and observing dynamics of the particle’s in-plane rotation. RESULTS: The deformation dynamics of the membrane followed a power law of time, which directly relates to cytoskeletal prestress as reported in the literature. The temporal evolution of this rheological behaviour, over time scales of several minutes, showed strong variations of the exponent on single adherent cells not subject to any specific treatment. CONCLUSIONS: The consistent observation of variations in the exponent suggests that, in their normal activity, living cells modulate their prestress by up to three orders of magnitude within minutes.
关键词： power-law rheology,Adhering cells,prestress,optically-induced torque
更新于2025-09-23 15:22:29
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Microfluidic shear rheology and wall-slip of viscoelastic fluids using holography-based flow kinematics
摘要： In this study, we report microfluidic shear rheology and wall-slip using the 3D-resolved flow kinematics obtained from digital holography microscopy (DHM). We computationally reconstruct the recorded holograms to visualize the tracer imbued flow volume in linear microchannels, followed by the implementation of particle tracking velocimetry (PTV) to quantitate spatially resolved velocity fields in 3D. In order to select optimal parameters for DHM-PTV characterization of viscoelastic fluids, we studied the effect of the hologram recording distance, seeding density, and particle size. Using the optimal parameters, we show quantitative characterization of the shear rheology from the velocity fields without any a priori assumptions of wall boundary conditions or constitutive equation. The viscosity vs shear rate data for Newtonian and polyethylene oxide (PEO) solutions could be measured in the range of ≈0.05 to 20 000 s?1 with just three input pressures using sample volumes as low as 20 μl. These data from holographic shear rheometry were found to be in good agreement with computational fluid dynamics simulations and macrorheometry. With respect to the wall-slip, we find that highly viscoelastic PEO solutions can show slip lengths in the order of few microns. Finally, we discuss holographic visualization of particle migration in microfluidic flows, which can limit flow field access, whereas at the same time provide a fingerprint of the suspending fluid rheology.
关键词： viscoelastic fluids,particle tracking velocimetry,wall-slip,digital holography microscopy,microfluidic shear rheology
更新于2025-09-23 15:19:57
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A Supramolecular Gel of Oxalic Acid-Monoethanolamine for Potential Schottky Barrier Diode Application
摘要： A functional supramolecular gel of oxalic acid and monoethanolamine (OXMEA) has been achieved through direct instant mixing of N,N-dimethyl formamide (DMF) solution of oxalic acid and pure monoethanolamine at room temperature under ambient condition. The rheological analysis established the viscoelastic semi-solid type nature of mechanically stable OXMEA supramolecular gel. The morphological pattern, imaged through field emission scanning electron microscopic investigation, explores the bean-seed like hierarchical architecture of the gel network. The semiconducting property of the gel was verified from band gap energy and conductivity estimation. The electrical charge transport property was also analyzed in the form of OXMEA gel based metal-semiconductor junction thin film device. The obtained nonlinear current-voltage characteristics of the device signify Schottky barrier diode nature of the synthesized gel. Overall, this work has been proof of development of semiconducting electronic device by OXMEA gel based gel medium.
关键词： Semiconductor,Morphology,Supramolecular Gel,Rheology,Schottky barrier diode
更新于2025-09-19 17:15:36
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Aligning ?±a??alumina platelets via uniaxial pressing of ceramica??filled polymer blends for improved sintered transparency
摘要： Uniaxial warm pressing was used to align alumina platelet-filled polyethylene-based copolymer blends. The solids loading (30-40 vol.%) and platelet diameter (1.2 and 11 μm) were varied to compare effects on viscosity, percent reduction, and final alignment. All ceramic-filled thermoplastic polymer blends exhibited pseudoplastic behavior. Crystallographic alignment of green body samples was quantified by the orientation parameter (r) and grain misalignment angle (full width at half maximum, FWHM) obtained from rocking curve analysis. Blends with 11 μm diameter platelets displayed a higher temperature sensitivity constant, better flow properties, and higher alignment compared to blends with 1.2 μm diameter platelets. Optimal samples produced with blends containing 30 vol.% of 11 μm diameter platelets demonstrated an alignment of r = .251 ± .017; FWHM = 11.16° ± 1.16°. A sample with optimal alignment was hot-pressed to transparency and obtained an in-line transmission of 70.0% at 645 nm. The final alignment of this pre-aligned hot-pressed sample (r = .254 ± .008; FWHM = 11.38° ± 0.54°) improved when compared to a non-pre-aligned sample (r = .283 ± .005; FWHM = 13.40° ± 0.38°).
关键词： hot pressing,rheology/rheometry,alumina,optical materials/properties
更新于2025-09-19 17:13:59
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Organosoluble Starch-Cellulose Binary Polymer Blend as a Quasi-Solid Electrolyte in a Dye-Sensitized Solar Cell
摘要： This work is a pioneer attempt to fabricate quasi-solid dye-sensitized solar cell (QSDDSC) based on organosoluble starch derivative. Rheological characterizations of the PhSt-HEC blend based gels exhibited viscoelastic properties favorable for electrolyte fabrication. From amplitude sweep and tack test analyses, it was evident that the inclusion of LiI improved the rigidity and tack property of the gels. On the other hand, the opposite was true for TPAI based gels, which resulted in less rigid and tacky electrolytes. The crystallinity of the gels was found to decline with increasing amount of salt in both systems. The highest photoconversion e?ciency of 3.94% was recorded upon addition of 12.5 wt % TPAI and this value is one of the highest DSSC performance recorded for starch based electrolytes. From electrochemical impedance spectroscopy (EIS), it is deduced that the steric hindrance imposed by bulky cations aids in hindering recombination between photoanode and electrolyte.
关键词： dye-sensitized solar cell,phthaloyl starch,rheology,hydroxyethyl cellulose,quasi-solid electrolyte
更新于2025-09-16 10:30:52
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Organosoluble starch derivative as quasi-solid electrolytes in DSSC: Unravelling the synergy between electrolyte rheology and photovoltaic properties
摘要： A novel blend of organosoluble phthaloyl starch (PhSt) and hydroxyethyl cellulose (HEC) was used as the polymer host to fabricate polymer gel electrolytes. Rheological analyses, such as amplitude sweep studies and tack tests, indicate that gels with good rigidity, strength and adhesiveness were attained upon inclusion of 20 wt % of HEC onwards. However, beyond 60 wt% of HEC, the mechanical properties and ionic conductivity of the gels were considerably compromised. Gels comprising 20–60 wt% of HEC were then fabricated into quasi-solid dye-sensitised solar cells (QSDSSC) with the addition of tetrapropylammonium iodide/iodine. The highest efficiency of 3.02% was recorded with gels comprising 70 wt% of PhSt and 30 wt% of HEC, which to the best of our knowledge is the highest ever efficiency in literature for starch-based electrolytes. Electrochemical impedance spectroscopy (EIS) of the QSDSSC revealed that the adhesive property of the gels plays a crucial role in charge transfer processes at the electrode/electrolyte interfaces.
关键词： Rheology,Hydroxyethyl cellulose,Dye-sensitised solar cell,Quasi-solid electrolyte,Phthaloyl starch
更新于2025-09-16 10:30:52
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Toughness enhancers for bone scaffold materials based on biocompatible photopolymers
摘要： Providing access to the benefits of additive manufacturing technologies in tissue engineering, vinyl esters recently came into view as appropriate replacements for (meth)acrylates as precursors for photopolymers. Their low cytotoxicity and good biocompatibility as well as favorable degradation behavior are their main assets. Suffering from rather poor mechanical properties, particularly in terms of toughness, several improvements have been made over the last years. Especially, thiol–ene chemistry has been investigated to overcome those shortcomings. In this study, we focused on additional means to further improve the toughness of an already established biocompatible vinyl ester-thiol formulation, eligible for digital light processing-based stereolithography. All molecules were based on poly(ε-caprolactone) as building block and the formulations were tested regarding their reactivity and the resulting mechanical properties. They all performed well as toughness enhancer, ultimately doubling the impact resistance of the reference system.
关键词： rheology,polyesters,photopolymerization,biomaterials,monomers,FT-IR
更新于2025-09-10 09:29:36
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Evidence for non-Newtonian behavior of intracranial blood flow from Doppler ultrasonography measurements
摘要： Computational fluid dynamics (CFD) studies of intracranial hemodynamics often use Newtonian viscosity model to close the shear rate term in the Navier-Stokes equation. This is based on a commonly accepted hypothesis which state that non-Newtonian effects can be neglected in intracranial blood flow. This study aims to examine the validity of such hypothesis to guide future CFD studies of intracranial hemodynamics. Doppler ultrasonography (DUS) measurements of systolic and diastolic vessel diameter and blood velocity were conducted on 16 subjects (mean age 50.6). The measurements were conducted on the internal carotid (ICA), middle cerebral (MCA), and anterior communicating (AComA) arteries. Systolic and diastolic wall shear stress (WSS) values were calculated via the Hagen-Poiseuille exact solution using Newtonian and three different non-Newtonian models: namely Carreau, power-law and Herschel-Bulkley models. The Weissenberg-Rabinowitsch correction for blood shear-thinning viscosity was applied to the non-Newtonian models. The error percentage between the two sets of models was calculated and discussed. The Newtonian hypothesis was tested statistically and discussed using paired t tests. Significant differences (P < 0.0001) were found between the Newtonian and non-Newtonian WSS in ICA. In MCA and AComA, similar differences were found except in the systole and diastole for the Herschel-Bulkley and power-law models (P = 0.0669, P = 0.7298), respectively. The error between the Newtonian and non-Newtonian models ranged from ? 27 to 30% (0.2 to 2.2 Pa). These values could affect the physical interpretation of IA CFD studies. Evidence suggests that the Newtonian assumption may be inappropriate to investigate intracranial hemodynamics.
关键词： Non-Newtonian flow,Blood rheology,Blood viscosity,Doppler ultrasound,Intracranial hemodynamics
更新于2025-09-09 09:28:46