Library · Materials, chemistry & fabrication
What Dielectric Spectroscopy & Impedance got wrong, from 26 theses
Summary written by a model from the records below: Electrochemical and dielectric impedance techniques encounter severe measurement constraints arising from non-ideal sample geometries, environmental interferences, and high contact resistances. Analytical interpretation also frequently breaks down due to equivalent circuit overparameterization, non-physical modeling assumptions, and frequency-dependent parasitic artifacts. 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.
Dielectric permittivity models and radar inversions fail when applied to irregular or bound media
Physical thickness variations and bound water layers cause analytical dielectric mixing models and transfer matrix approximations to produce inaccurate permittivity values. In addition, low dielectric sensitivity in extremely dry media and multipath interference lead to severe overpredictions or truncated phase shift calculations.
Tried and failed
free-space microwave scattering permittivity extraction applied to irregular uncontained dielectric samples. Reason: physical thickness variations caused inaccurate complex permittivity extraction without large containment fixtures or high-gain antennas
Moisture estimation for precision agriculture through RF sensing · Imperial · PhD
Lost to a baseline
Single homogeneous layer transfer matrix approximation without exponential decay profile resulted in up to a 10% relative deviation in the dielectric constant.
Ultrafast Terahertz Spectroscopy of Collective Excitations in Correlated Materials · MIT · PhD
Tried and failed
Gaussian process regression for SAR inversion applied to very dry soil moisture estimation. Outcome: did not generalise. Reason: Dielectric sensitivity drops significantly below dry thresholds, causing extreme overpredictions.
A Framework for Assessing Lower-Bound Bearing Capacity of Sandy Coastal Sediments from Remotely Sensed Imagery · Virginia Tech · Doctorate
Tried and failed
dielectric soil moisture phase shift modeling applied to radar interferometric phase estimation. Reason: model predicted a maximum phase shift of pi/2 while measured shifts reached approximately pi radians
Transient scattering effects in Sentinel 1 ground deformation analyses of the rural UK · Imperial · PhD
Considered and rejected
Considered and rejected: Rejected the de Loor dielectric mixing model because its internal dielectric parameter e* reduces to bulk permittivity only under assumptions incompatible with bound water layers in natural soils.
How to Assess Unfrozen Water Content Using Capacitance Sensors in Frozen Soils: A New Physics Based Conversion Curve · Queen's University · Master's
Considered and rejected
Considered and rejected: Rejected using TDR volumetric water content measurements obtained during subgrade freezing conditions for FEA model calibration because probes only detect unfrozen liquid water and dielectric constants shift.
Influence of Climatic Factors on Water and Heat Transfer Within Subgrades · York University · PhD
Low frequency noise and electrode polarization obscure impedance spectra in low conductivity environments
Testing in low conductivity fluids or after thermal moisture loss eliminates dispersion behavior and generates excessively high charge transfer resistance that obscures Nyquist plots. At lower frequencies, electrode polarization noise, baseline instability, and lack of semicircular responses prevent reliable parameter fitting.
Tried and failed
low-frequency dielectric spectroscopy applied to high-temperature thermally aged porous minerals. Outcome: no signal. Reason: loss of surface water at elevated aging temperatures eliminated anomalous low-frequency dispersion behavior
PROBING THE MICROSTRUCTURE AND SURFACE CHEMISTRY OF POROUS MEDIA USING DIELECTRIC SPECTROSCOPY AND HANSEN AFFINITY PARAMETERS · Cornell · PhD
Tried and failed
low-frequency dielectric impedance spectroscopy planar regression applied to estimating cell concentration and viability. Outcome: no signal. Reason: electrode polarization noise in alpha-dispersion obscured the signal at low frequencies
REAL-TIME MONITORING OF CELL AND BIOINK PROPERTIES USING DIELECTRIC IMPEDANCE SPECTROSCOPY FOR EXTRUSION BIOPRINTING · Cornell · PhD
Tried and failed
electrochemical impedance spectroscopy for corrosion rate measurement applied to steel alloys in amino acid solvents. Outcome: no signal. Reason: low-frequency noise and lack of semicircular response prevented polarization resistance fitting
Capture of CO₂ Using Potassium Salts of Amino Acids and Guanidine-Based Ligands · Georgia Tech · PhD
Considered and rejected
Considered and rejected: Rejected relying on bioimpedance phase or frequencies below 200 kHz due to baseline instability, clothing material sensitivity, and clenching false positives
An Interdisciplinary Approach to Human Pose Estimation: Application to Sign Language · Tübingen · PhD
Equivalent circuit models suffer from parameter overfitting and non-unique solutions
Incorporating extra circuit elements or multiple constant phase elements leads to overparameterization, fitting discrepancies, and loss of physical meaning. Standard circuit configurations also fail to resolve overlapping relaxation timescales or distinct transport mechanisms in complex interfaces.
Tried and failed
electrochemical impedance spectroscopy to extract ionic conductivity applied to nanocrystalline hydrated thin films. Reason: multiple overlapping semicircles with similar RC timescales caused by nanocrystallinity and hydration gradients
Proton dynamics in ultrathin GdO𝑥H𝑦 films for magneto-ionics · MIT · PhD
Tried and failed
adding circuit elements to equivalent circuit model applied to electrochemical impedance spectroscopy fitting. Outcome: overfit. Reason: increased discrepancies and parameter fitting uncertainties due to model overparameterization
Integrated characterization and design of cathode microstructure for high performance solid oxide fuel cells · Imperial · PhD
Tried and failed
two constant phase element equivalent circuit modeling applied to impedance spectroscopy of functionalized semiconductor interfaces. Outcome: overfit. Reason: overparameterization caused overfitting and obscured the physical interpretation of chemical capacitance
Electronic structure and photoelectrochemistry of Si(111) functionalized by acene derivatives · UT Austin · PhD
Considered and rejected
Considered and rejected: Rejected impedance spectroscopy equivalent circuit curve fitting because the circuit models are typically non-unique and parameters are not scientifically meaningful.
Electric Polarization in Electronic Conductors · University at Buffalo · PhD
Considered and rejected
Considered and rejected: Rejected the Randles equivalent circuit (Circuit 1) and active corrosion model (Circuit 2) for EIS fitting of Cu in [C4C1im]Cl, adopting Circuit 4 (porous layer with Warburg impedance) instead
An investigation into Ionic Liquids, their physicochemcial properties, and corrosion of industrially relevant metals · Imperial · Doctorate
Dry and non-standard electrode materials exhibit higher contact impedance and severe polarization
Novel dry electrodes such as MXenes, stainless steel, and indium display higher contact impedance and worse signal-to-noise ratios than conventional gelled silver or tungsten alternatives. During extended monitoring, dry contact interfaces suffer from continuous impedance drift and low-frequency polarization effects.
Lost to a baseline
After 4.5 hours of continuous monitoring on agarose phantoms, the 10 Hz impedance of dry Ti3C2Tx electrodes rose to 0.48 ± 0.07 kΩ, whereas gelled Ag/AgCl disc and cup electrodes remained stable at 0.20 ± 0.03 kΩ and 0.16 ± 0.03 kΩ, respectively.
DEVELOPING TRANSLATIONAL MULTIMODAL NEUROTECHNOLOGY ACROSS MULTIPLE SCALES USING NOVEL MATERIALS AND APPROACHES · Penn · PhD
Lost to a baseline
Bare IrO2 electrodes exhibited higher impedance than PEDOT:PSS-coated TiN electrodes across large microelectrode diameters (D = 10, 50, 100 µm).
Multimodal And Multifunctional CMOS Cellular Sensing And Actuating Array With Enhanced Electronics-Biology Interface · Georgia Tech · PhD
Lost to a baseline
Indium electrodes exhibited higher impedances and lower SNRs compared to tungsten electrodes integrated via convergence drawing.
Customizing Multifunctional Bidirectional Neural Interfaces through Fiber Drawing · MIT · PhD
Tried and failed
stainless steel dry spherical electrodes applied to low-frequency bioimpedance tomography. Outcome: worse than baseline. Reason: higher contact impedance and polarization effects at low AC frequencies compared to standard Ag/AgCl electrodes
From Systemic to Regional: Personal Health and Medical Monitoring Systems that Adapt to Individual Variance · MIT · PhD
Lost to a baseline
Initial 10 Hz impedance of dry Ti3C2Tx electrodes on agarose phantoms (0.29 ± 0.03 kΩ) was higher than gelled Ag/AgCl disc (0.21 ± 0.02 kΩ) and cup electrodes (0.18 ± 0.04 kΩ).
DEVELOPING TRANSLATIONAL MULTIMODAL NEUROTECHNOLOGY ACROSS MULTIPLE SCALES USING NOVEL MATERIALS AND APPROACHES · Penn · PhD
Parasitic inductive effects and channel crosstalk distort high frequency impedance spectra
Cable artifacts, multi-electrode cross-talk, and bioimpedance measurement errors produce anomalous positive phase angles and non-physical negative resistances at high frequencies. Applying multi-sine broadband excitations further degrades the signal-to-noise ratio in upper frequency decades due to reduced component amplitudes.
Tried and failed
multi-electrode dielectric impedance spectroscopy applied to in-line fluid flow monitoring. Reason: inter-electrode cross-talk at specific high frequencies severely distorted impedance measurements
REAL-TIME MONITORING OF CELL AND BIOINK PROPERTIES USING DIELECTRIC IMPEDANCE SPECTROSCOPY FOR EXTRUSION BIOPRINTING · Cornell · PhD
Tried and failed
simple standard RC equivalent circuit model fitting applied to electrochemical impedance spectroscopy data. Reason: high-frequency pseudo-inductive cable artefacts produced non-physical negative resistance values
Organic electrochemical transistors with PVA hydrogels/PEDOT:PSS channel · Imperial · Master's
Tried and failed
Cole impedance model parameter fitting applied to thoracic bioimpedance spectroscopy measurements. Reason: measurement artifacts and confounding factors caused anomalous positive phase errors at high frequencies
Advancing Pulmonary Monitoring Technologies in Acute Care Settings using Wearable Multimodal Sensing, Signal Processing, and Machine Learning · Georgia Tech · PhD
Tried and failed
multi-sine excitation in broadband impedance spectroscopy applied to neural interface electrodes. Outcome: worse than baseline. Reason: reduced frequency component amplitudes decreased the signal-to-noise ratio in the higher decade
Electrode impedance characterisation for implantable neural interfaces · Imperial · PhD
Unfavorable cell setups and fabrication defects generate erratic spectra or obscure resonance peaks
Testing fragile membranes in liquid immersion or running spectroscopy on pouch cells with long diffusion pathways generates severe measurement artifacts and erratic data. Similarly, microfabrication shorting defects at small electrode spacings and excessive material damping cause unrepeatable spectra or mask electrical resonance peaks entirely.
Tried and failed
electrical admittance measurement of resonant frequencies applied to high-loss piezoelectric composite transducers. Outcome: no signal. Reason: high dielectric and mechanical damping obscured electrical resonance peaks
Miniaturized Acousto-Optic Sensor for RF Field Measurement Under MRI · Georgia Tech · PhD
Tried and failed
Electrochemical impedance spectroscopy in liquid aqueous environment applied to ultra-thin freestanding ceramic membranes. Reason: Liquid immersion produced severe measurement artifacts, requiring testing in humidified gas instead
Tried and failed
electrochemical impedance spectroscopy applied to single-layer pouch cells. Outcome: unstable. Reason: extreme electrode overhang and long diffusion pathways caused erratic, non-repeatable spectra
The effect of micro and nano scale phenomena on system level design and engineering of hybrid pemfc systems · Imperial · PhD
Tried and failed
Non-faradaic impedance spectroscopy on microgap interdigitated electrodes applied to bacterial cell detection. Outcome: unstable. Reason: High microfabrication shorting defects and unrepeatable impedance spectra at small interelectrode spacings
The impact of mass transport and surface charging on the performance of field effect transistor biosensors · Georgia Tech · PhD
Left open by the authors
Problems the authors named and did not get to.
Left open
Investigate why the dielectric-dependent range-separated hybrid functional DD-RSH-CAM overestimates band gaps in liquid water and hexagonal ice. Blocker: None
Nonempirical hybrid functionals for advanced electronic-structure calculations · EPFL · PhD
Left open
Perform frequency- and temperature-dependent dielectric spectroscopy on semiconductor:ferroelectric polymer blends to measure dielectric constant changes and relaxation mechanisms. Blocker: Requires a wet lab, chemical synthesis/blending equipment, and a dielectric spectroscopy apparatus.
Influence of Local Polar Environment on the Optoelectronics of Polymeric Semiconductors · Georgia Tech · PhD
Left open
Quantify how surfactants of varying charges and chemical makeup inhibit droplet wetting modulation during dielectric charge injection. Blocker: Requires a wet lab with dielectric charge injection setup, high-voltage corona discharge apparatus, and chemical surfactant testing facilities.
Controlled deposition of cargo-carrying colloids from dispersed fluid to solid surfaces · Penn · PhD
Left open
Correlate porous media dielectric spectroscopy measurements with X-ray computed tomography and nuclear magnetic resonance datasets for 3D liquid structure characterization. Blocker: Requires experimental laboratory access and hardware for dielectric spectroscopy, XCT, and NMR measurements on physical porous media samples.
PROBING THE MICROSTRUCTURE AND SURFACE CHEMISTRY OF POROUS MEDIA USING DIELECTRIC SPECTROSCOPY AND HANSEN AFFINITY PARAMETERS · Cornell · PhD
Left open
Incorporate first-principles sensor noise models into deep learning loss functions and evaluate temporally dependent loss formulations on sensor characterization data. Blocker: Requires dynamic PEMC sensor impedance spectra data from physical hydrogel characterization experiments.
Knowledge-guided Machine Learning for Sensor-based High-Performance Autonomous Material Characterization · Virginia Tech · Doctorate
Left open
Develop dynamic microwave dielectric characterization for liquid and curing thermosets across frequencies and temperatures tolerant of sample geometry. Blocker: Requires microwave dielectric measurement hardware, wet lab chemical handling, and physical thermoset curing apparatus.
TRANSIENT AND MECHANICAL PROPERTIES OF POLY(PHTHALALDEHYDE) AND THE VARIABLE FREQUENCY MICROWAVE CURING OF HIGH-PERFORMANCE THERMOSETS · Georgia Tech · PhD
Left open
Investigate mechanisms behind frequency-dependent permittivity changes and dry versus hydrated impedance responses in functional polymer sensors. Blocker: Requires wet lab polymer synthesis, device fabrication, and electrical impedance spectroscopy measurements
Functional Polymer Materials: From Iptycenes to Ring-Opening Polymerizations · MIT · PhD
Left open
Determine whether dielectric surface instability slit-like features are closed creases or crack-like separations with finite spacing. Blocker: Requires high-resolution physical confocal microscopy apparatus and experimental elastomer samples
Studies of Electric-Field Induced Surface Instabilities using Confocal Microscopy · Harvard · PhD
Left open
Investigate ionization, attachment, excitation, and avalanche mechanisms in supercritical dielectric fluids under high electric fields. Blocker: Requires specialized high-pressure dielectric breakdown and plasma diagnostics experimental equipment
Supercritical dielectric fluids for high power density applications · Georgia Tech · PhD
Left open
Perform liquid cell dielectric spectroscopy across surfactant concentrations, nanoparticle loadings, and oil-to-water ratios, correlated with confocal microscopy, DLS, and analytical centrifugation. Blocker: Requires wet lab equipment including dielectric spectrometer, confocal microscope, dynamic light scattering, and analytical centrifuge
PROBING THE MICROSTRUCTURE AND SURFACE CHEMISTRY OF POROUS MEDIA USING DIELECTRIC SPECTROSCOPY AND HANSEN AFFINITY PARAMETERS · Cornell · PhD
Who has worked on this
Authors of the public theses cited on this page, most-cited first.
- Abdullah Alshuaibi · Cornell · PhD · 2024
PROBING THE MICROSTRUCTURE AND SURFACE CHEMISTRY OF POROUS MEDIA USING DIELECTRIC SPECTROSCOPY AND HANSEN AFFINITY PARAMETERS - Alicia Matavosian · Cornell · PhD · 2025
REAL-TIME MONITORING OF CELL AND BIOINK PROPERTIES USING DIELECTRIC IMPEDANCE SPECTROSCOPY FOR EXTRUSION BIOPRINTING - Sneha Shankar · Penn · PhD · 2024
DEVELOPING TRANSLATIONAL MULTIMODAL NEUROTECHNOLOGY ACROSS MULTIPLE SCALES USING NOVEL MATERIALS AND APPROACHES - Lee Bradley · Georgia Tech · PhD · 2025
Miniaturized Acousto-Optic Sensor for RF Field Measurement Under MRI - Vichaya Manatchinapisit · Imperial · PhD · 2025
Electrode impedance characterisation for implantable neural interfaces - Quentin Quinn Sapin · Queen's University · Master's · 2025
How to Assess Unfrozen Water Content Using Capacitance Sensors in Frozen Soils: A New Physics Based Conversion Curve - Maria-Paola Forte · Tübingen · PhD · 2025
An Interdisciplinary Approach to Human Pose Estimation: Application to Sign Language - Jesus Antonio Sanchez-Perez · Georgia Tech · PhD · 2024
Advancing Pulmonary Monitoring Technologies in Acute Care Settings using Wearable Multimodal Sensing, Signal Processing, and Machine Learning - Oisin Shaw · Imperial · PhD · 2024
The effect of micro and nano scale phenomena on system level design and engineering of hybrid pemfc systems - Junyi Zhu · MIT · PhD · 2024
From Systemic to Regional: Personal Health and Medical Monitoring Systems that Adapt to Individual Variance - Abishek Kasturi · Georgia Tech · PhD · 2024
Capture of CO₂ Using Potassium Salts of Amino Acids and Guanidine-Based Ligands - Zheng Xie · Imperial · PhD · 2024
Integrated characterization and design of cathode microstructure for high performance solid oxide fuel cells
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