Library · Engineering & mechanics
What Colloidal & Suspension Rheology got wrong, from 33 theses
Summary written by a model from the records below: The records examine experimental and theoretical challenges across colloidal suspensions, hydrogels, and complex fluid systems. Investigators frequently encountered failures in constitutive modeling, rheological characterization, direct extrusion, droplet jetting, and multiphase mixing due to non-Newtonian flow behavior and viscosity mismatches. These records come from graduate theses, 2021 to 2026, each labeled with its degree where the repository states it, and each links to its thesis. They were extracted by language models reading the full text, so treat each as a lead to read, not a verdict.
Plus 10 problems the authors left open, listed at the end.
Failure modes, by theses reporting them
Select a mode to jump to its records.
Standard constitutive rheology models fail to capture non-Newtonian regimes and microstructural changes
Classical models such as Carreau, Casson, and Herschel-Bulkley broke down when applied to aerated microstructures, incomplete polymer hydration, or very low shear rates where unphysical flow index values and infinite viscosities were predicted. Researchers also rejected models relying on excessive empirical parameters or rigid cluster assumptions because they could not generalize across disparate shear rates and changing timescales.
Considered and rejected
Considered and rejected: Rejected arbitrary viscosity partitioning in Burgers transient rheological models (e.g. fixing eta_KM / eta_M = 1/10), because it lacks experimental physical basis and cannot be generalized across differing forcing timescales.
Fire and ice: investigating links between mantle dynamics and ice sheet stability · Imperial · PhD
Tried and failed
Casson rheological model fitting applied to aerated complex fluid shear viscosity. Outcome: did not generalise. Reason: standard suspension constitutive model failed across tested shear rates once micro-aeration altered the fluid microstructure
Oral processing of micro-aerated chocolates: a computational mechanics, rheological and tribological study · Imperial · PhD
Tried and failed
Herschel-Bulkley rheological model applied to low shear rate multiphase flow simulation. Reason: Predicts infinite viscosity at near-zero shear rates, causing unrealistic velocity profiles and transport errors
Rheological characterization of complex drilling fluid and the effects on drilling hydraulics · UT Austin · PhD
Tried and failed
Herschel-Bulkley model fitting at low shear rates applied to colloidal hydrogel rheology data. Outcome: unstable. Reason: low shear rate stress instabilities produced inconsistent and unphysical flow index values (>1)
Synthetic, rheological, and morphological control of one-dimensional CdS and Sb₂S₃ nanomaterials · UT Austin · PhD
Considered and rejected
Considered and rejected: Rejected assuming clusters are strictly rigid under flow in the viscosity model, introducing cluster flexibility/rigidity attenuation scaling with cluster size.
Protein-protein interactions and rheological properties of monoclonal antibodies at high concentration · UT Austin · PhD
Considered and rejected
Considered and rejected: Rejected using Cross, Sisko, or Carreau-Yasuda models due to excessive parameters not broadly applicable across disparate colloidal regimes
Predicting the Flow Rate and Extensional Behavior of Colloidal Dispersions for 3D Printing Applications · Texas Tech · PhD
Direct extrusion and additive manufacturing fail when inks lack suitable yield stress or viscosity
Extrusion processes failed when inks had insufficient viscosity and yield stress, which caused deposited filaments to spread and lose shape fidelity, or when time-dependent viscosity changes continuously degraded flow rates. Formulations were also abandoned when paste viscosities were too high to extrude through nozzles, or when extreme viscosity contrasts caused inks to tunnel through surrounding matrices instead of forming cohesive structures.
Tried and failed
semi-solid extrusion 3D printing applied to low-concentration single-component biopolymer hydrogels. Outcome: unstable. Reason: insufficient viscosity and low yield stress caused spreading and loss of shape fidelity post-deposition
Semi-solid extrusion-based 3D printing of biopolymer hydrogels and their applications in food · Iowa State · Master's
Tried and failed
pneumatic extrusion bioprinting applied to time-dependent viscous hydrogel precursor. Outcome: unstable. Reason: viscosity changed over time, causing bioink deposition rate per unit distance to continuously decrease
Development of physiologically representative multi-channel in vitro human skin tissue platforms for quantitative burn injury assessment · UT Austin · PhD
Tried and failed
direct extrusion of undiluted clay paste applied to additive manufacturing of functional pastes. Reason: excessive paste viscosity prevented extrusion through the print nozzle
Printable, functional components with actuatable function and sensing, for CO2 uptake in reduced gravity environments · Imperial · PhD
Considered and rejected
Considered and rejected: Rejected 70 wt% polymer formulations in ethyl acetate for 3D printing due to excessive viscosity exceeding the 10 Pa·s continuous printing threshold.
Photochemical 3D Printing of Prototype Medical Devices from Poly(Propylene Fumarate)-Based Copolyesters · Duke · PhD
Considered and rejected
Considered and rejected: Rejected pure cyclohexane slip casting suspension for direct ink writing due to excessively low viscosity and dilatant behavior at high solid loadings (>55 vol%)
Near-Net Shaping and Additive Manufacturing of Ultra-High Temperature Ceramics via Colloidal Processing · Virginia Tech · Doctorate
Considered and rejected
Considered and rejected: Viscosity ratios eta_ink >> eta_matrix were rejected because the ink tunneled through the matrix during extrusion rather than forming cohesive spherical nodes
Embedded 3D Printing of Polymeric and Ceramic Lattices · Harvard · PhD
Considered and rejected
Considered and rejected: Rejected using pure EGaIn liquid metal directly as DIW ink due to excessive surface tension (624 mN/m) and low water-like viscosity (1.99 mPa·s).
Printing and Recycling of Liquid Metal Composites for 3D Architected Thermoelectric Wearables · University of Washington · PhD
Considered and rejected
Considered and rejected: Rejected using pure cell inks without microparticles for STEP due to their lower storage modulus, loss modulus, yield stress, and apparent viscosity.
Programmable Assembly of Genetically Engineered Human Tissues · Harvard · PhD
High suspension viscosity and particle aggregation impede mixing, dispersion, and liquid processing
Elevated suspension viscosities and particle aggregation prevented uniform mixing during secondary emulsification, binder distribution, and the incorporation of cellulose nanocrystal gels into polymer solutions. Concentrated suspensions also caused excessive mechanical energy dissipation in continuous flow systems, hindered redispersion after dewatering, and produced irregular coatings.
Considered and rejected
Considered and rejected: Rejected continuous flow mode for the semi-solid Na-S flow battery in favor of intermittent aliquot flow due to high suspension viscosity causing mechanical energy dissipation.
Electrochemical Flow System for Li-Ion Battery Recycling and Energy Storage · Virginia Tech · Doctorate
Lost to a baseline
Filter-pressing and freeze drying failed to match ultrasonic dewatering for redispersion ease; filter-pressed samples retained impurities/residues and freeze-dried samples exhibited severe agglomeration that precluded optical and SEM image analysis even after 5 minutes of mixing.
Dewatering of Cellulose Nanomaterials using Ultrasound · Georgia Tech · PhD
Considered and rejected
Considered and rejected: Rejected liquid sucrose aqueous solutions as binders because high viscosity led to inhomogeneous liquid distribution and excessively delayed disintegration times
Novel drug-loaded paper tablets for improved oral drug delivery Neuartige Papiertabletten mit Wirkstoffbeladung für verbesserte orale Arzneimittelverabreichung · University of Marburg · PhD
Considered and rejected
Considered and rejected: Rejected protein concentrations above 2% w/v for microneedle coating due to excessive viscosity causing irregular coating.
Metal-Organic Frameworks for Long-term Vaccine Storage · Georgia Tech · PhD
Considered and rejected
Considered and rejected: Rejected primary emulsion formulations with 1.5%–4% psyllium husk because high viscosity hindered secondary emulsification mixing.
Ultrasound-Assisted Novel Double Emulsion Containing Grape Pomace Polyphenols as a Delivery System to Encapsulate Vitamin E and Omega-3 for Food and Dietary Supplement Applications · Carleton University · Master's
Considered and rejected
Considered and rejected: Rejected testing polymer concentrations above 11–16 wt% in cloud point and dissolution tests due to rapid solution viscosity increase preventing adequate mixing
Solvent-Enabled Molecular Recycling of Polyolefins · University at Buffalo · PhD
Considered and rejected
Considered and rejected: Direct mixing of concentrated CNC/CNF gels into polymer solutions rejected due to poor dispersion and lower gel modulus than composite reverse dialysis
Rheological Characterization of Cellulose Nanomaterials for Quality Control and Processing · Georgia Tech · PhD
Considered and rejected
Considered and rejected: Rejected PAN/LDH composite suspensions with higher LDH contents (≥12.6 wt.%) due to shear-thickening behavior, particle aggregation, and increased suspension viscosity.
Nanostructured Adsorbents for Selective Lithium Recovery: Mechanisms, Fabrication, Performance Evaluation, and Applications in Desalination · Virginia Tech · Doctorate
Rheometry and stability characterization fail from wall slip, sedimentation, and stress instabilities
Rotational rheometry on concentrated inks produced wall slip and sample ejection when tested on smooth plate geometries, while strain-controlled testing of shear-thickening suspensions suffered from extreme stress fluctuations. Characterization protocols also failed when gravitational sedimentation occurred without density matching, when initial settling rates failed to capture long-term regime shifts, and when improper sample preparation inflated low-shear viscosity.
Tried and failed
suspension characterization without solvent density matching applied to dilute colloidal gel systems. Outcome: unstable. Reason: gravitational sedimentation caused sample failure at low volume fractions without precise solvent density matching
Microscopic characterization of macroscopic colloidal gel rheology · MIT · PhD
Tried and failed
strain-controlled rheometry applied to discontinuous shear thickening colloidal suspensions. Outcome: unstable. Reason: extreme stress fluctuations and critical shear rate variability prevented capturing controlled states across the discontinuity
Microscopic characterization of macroscopic colloidal gel rheology · MIT · PhD
Tried and failed
Environmental and mechanical conditioning of yield-stress fluids applied to concentrated colloidal dispersions. Reason: Treatments failed to reliably recreate cohesive structural failure or control rheological breakdown
Extrusion Printing of Carbon Nanotube Inks, from Rheology to Electronics · MIT · PhD
Tried and failed
rotational rheometry with smooth plate geometry applied to yield-stress capillary suspension inks. Outcome: unstable. Reason: smooth geometries induced severe wall slip and sample ejection at high shear rates, underestimating viscosity
Direct ink writing of aqueous electrochemical energy storage devices · Imperial · PhD
Lost to a baseline
Liquid handler viscosity determination underestimated capillary viscometer measurements by ~7 cSt offset due to measurement shear thinning or pressure conversion models.
Synthesis and application of novel hyperbranched polymers · Nottingham · Doctorate
Inkjet printing and droplet jetting fail outside strict viscosity and stability boundaries
Inkjet dispensing failed or was rejected when ink viscosity exceeded narrow operational thresholds, which suppressed droplet formation in the viscous dissipation regime or clogged dispensing tips. Inks with unstable colloidal rheology led to powder agglomeration and microscale cracking, whereas inks with overly low viscosity dispersed too rapidly into substrate pores.
Considered and rejected
Considered and rejected: Rejected using 3D inkjet printing (CeraPrinter X-Series) for membrane fabrication due to powder agglomeration and unstable colloidal ink rheology
Recovering materials from end-of-life lithium-ion batteries · Imperial · PhD
Considered and rejected
Considered and rejected: Rejected dropper-based droplet drying for traditional binder due to excessive viscosity clogging the dropper.
A Technical Study of Fish Collagen-Based Binder for Architectural Polychrome Painting in Jiangsu Province: History and Application · Penn · Master's
Lost to a baseline
Inkjet-printed PEDOT:PSS on nitrocellulose exhibited ~6x lower ON current in modulus compared to dispense-printed PEDOT:PSS due to low-viscosity ink dispersion in pores.
A printable Organic Electrochemical Transistor on paper for biochemical sensing · Politecnico di Torino · PhD
Considered and rejected
Considered and rejected: Rejected inkjet/jetting processes for polymer solutions because high dynamic viscosity (Z ~ 0.05) prevents droplet formation in the viscous dissipation regime.
Sensor-based Characterization and Control of Additive Biomanufacturing Processes · Virginia Tech · Doctorate
Considered and rejected
Considered and rejected: Commercial inkjet printers without electrostatic field, rejected due to poor handling of high-viscosity inks and microscale cracking.
Real-time monitoring of neuronal cells through electrohydrodynamic patterning of flexible graphene microelectrodes · Iowa State · PhD
Considered and rejected
Considered and rejected: Rejected inkjet printing of P(VDF-TrFE) using Dimatix printer due to strict 10–12 mPas ink viscosity constraints not met by dissolution process.
Life cycle monitoring of composite aircraft components with structural health monitoring technologies · Imperial · PhD
Considered and rejected
Considered and rejected: Rejected standard inkjet printing because it requires pressure and is limited to low-viscosity materials (5 to 20 mPa·s).
The E-jet printing of organic inks on organic substrates · Iowa State · Master's
Left open by the authors
Problems the authors named and did not get to.
Left open
Design ionic liquid cations with enhanced Li+ chelating affinity, reduced viscosity, and high chemical stability for lithium-bromine flow batteries. Blocker: Requires chemical synthesis, wet-lab validation, and electrochemical testing facilities
Left open
Apply colloidal synthesis to fabricate MoSe2-carbon heterostructures and evaluate their cycling stability in batteries. Blocker: Requires wet-lab chemical synthesis and battery testing apparatus
Liquid phase synthesis of atomically thin MoSe2 and their applications in energy conversion and storage · Imperial · PhD
Left open
Extend bulk polymer rheology models to predict in-situ apparent viscosity within porous media. Blocker: Requires porous media coreflood experimental data and rheological laboratory measurements for validation.
Left open
Incorporate additive manufacturing microstructural heterogeneities into dynamic failure models to predict spall strength and shock dispersion. Blocker: None
The Effects of Controlled Porosity on the Dynamic Compression and Tensile Failure Strength of Additively Manufactured 316L Stainless Steel · Georgia Tech · PhD
Left open
Measure physical properties and viscosity changes when incorporating tardigrade disordered proteins into pharmaceutical formulations. Blocker: Requires a wet lab and rheological measurement apparatus to formulate and test protein solutions
Intrinsically Disordered Proteins & Regions in Viruses and Possibly Pharmaceuticals · UT Austin
Left open
Systematically vary polymer cross-linker density at fixed particle volume fraction to test the polymer-reinforced aggregate hypothesis. Blocker: Requires a wet lab, chemical synthesis of cross-linked polymers/silica dispersions, and a strain-controlled rheometer.
Mechanical Hysteresis of Fumed Silica Dispersions · Harvard · PhD
Left open
Perform rheological testing on pAA-lactose-C12 and pAA-lactose-C16 polymers to verify shear thinning and viscosity properties. Blocker: Requires physical synthesized polymer samples and specialized rheology measurement equipment/services (Formulaction).
Surface-Active Synthetic Glycocalyx and Lipid Layer Analogs for the Treatment of Dry Eye Disease · Cornell · PhD
Left open
Evaluate the effects of polymer molar mass on dense paste mixing behavior using viscosity-matched binders across different viscosities in RAM. Blocker: Requires a physical chemistry/materials wet lab, Resonant Acoustic Mixer (RAM), and formulation chemicals.
Formulation and Process Considerations for the Manufacturing of Dense Pastes · Georgia Tech · PhD
Left open
Investigate scalings of normal stress differences, complex modulus, and friction coefficients near the frictional shear jamming critical point. Blocker: Requires a physical rheometer and custom piezoelectric transducer apparatus for dense colloidal suspensions
UNDERSTANDING AND TUNING THE RHEOLOGY OF DENSE SUSPENSIONS VIA ITS MICROSTRUCTURE · Cornell · PhD
Left open
Investigate the breakdown of the quasi-static assumption and measure the effects of fluid viscosity on fractal landscape dynamics. Blocker: Requires experimental laboratory apparatus and physical soft jammed emulsion systems to vary strain rate and fluid viscosity.
A fractal landscape dynamics approach to understanding particle motion in soft jammed materials · Penn · PhD
Who has worked on this
Authors of the public theses cited on this page, most-cited first.
- Jae Hyung Cho · MIT · PhD · 2022
Microscopic characterization of macroscopic colloidal gel rheology - Youngshang Han · University of Washington · PhD · 2026
Printing and Recycling of Liquid Metal Composites for 3D Architected Thermoelectric Wearables - Yanan Pan · Virginia Tech · Doctorate · 2026
Nanostructured Adsorbents for Selective Lithium Recovery: Mechanisms, Fabrication, Performance Evaluation, and Applications in Desalination - MARTINA CICOLINI · Politecnico di Torino · PhD · 2026
A printable Organic Electrochemical Transistor on paper for biochemical sensing - Alexandra A. Dobbs · Georgia Tech · PhD · 2025
Formulation and Process Considerations for the Manufacturing of Dense Pastes - Qingrou Dai · Penn · Master's · 2025
A Technical Study of Fish Collagen-Based Binder for Architectural Polychrome Painting in Jiangsu Province: History and Application - Taylor A. Sloop-Cabral · Georgia Tech · PhD · 2024
The Effects of Controlled Porosity on the Dynamic Compression and Tensile Failure Strength of Additively Manufactured 316L Stainless Steel - James Hazzard · Imperial · PhD · 2024
Fire and ice: investigating links between mantle dynamics and ice sheet stability - Jingcheng Lu · Harvard · PhD · 2024
Programmable Assembly of Genetically Engineered Human Tissues - Mohammed Naimul Hoque · Texas Tech · PhD · 2024
Predicting the Flow Rate and Extensional Behavior of Colloidal Dispersions for 3D Printing Applications - Clary Rodriguez Cruz · Penn · PhD · 2024
A fractal landscape dynamics approach to understanding particle motion in soft jammed materials - Gang Cheng · Imperial · PhD · 2023
Liquid phase synthesis of atomically thin MoSe2 and their applications in energy conversion and storage
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