Chapter Four · failure evidence
What Microfluidics & Lab-on-a-Chip got wrong, from 71 dissertations
The records document technical failures and performance trade-offs encountered across diverse microfluidic and lab-on-a-chip applications. Many microscale devices were impeded by material compatibility defects, channel clogging, emulsion breakdown, bubble formation, mechanical culture detachment, and reduced analytical sensitivity compared to standard bulk assays. These records come from PhD theses at 19 institutions, 2021 to 2026. 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.
Microscale compartmentalization and miniaturization suffer from lower reaction efficiency and analytical sensitivity than bulk methods
Nanoliter-scale reaction volumes often heightened susceptibility to PCR inhibitors, suffered from incomplete cell lysis, and caused low yields during enzymatic amplification. As a result, microfluidic platforms frequently underperformed compared to conventional methods such as bulk PCR, FACS, manual pipetting, and standard immunoassay controls.
Tried and failed
high-throughput microfluidic qPCR assay applied to complex environmental microbial samples. Outcome: no signal. Reason: target gene abundances were below the detection limit of the nanoliter microfluidic platform
Characterization of antimicrobial resistance in agricultural landscapes · Iowa State
Tried and failed
thermal lysis and sonication applied to crude cell lysate droplet digital PCR. Outcome: worse than baseline. Reason: resulted in poor cell and DNA recovery rates
Tried and failed
nanoliter microfluidic high-throughput quantitative PCR applied to inhibitor-rich environmental manure samples. Outcome: no signal. Reason: Extreme nanoliter reaction volumes heightened susceptibility to sample PCR inhibitors, preventing target amplification.
Characterization of antimicrobial resistance in agricultural landscapes · Iowa State
Tried and failed
one-step direct in-droplet RT-PCR applied to single-cell transcript linkage. Outcome: worse than baseline. Reason: poor reaction efficiency and low yield compared to decoupled reverse transcription and amplification steps
Methods and Materials to Generate Antibody Repertoire Libraries · Harvard
Tried and failed
droplet-based single-cell RNA sequencing applied to sucrose gradient-purified isolated nuclei. Outcome: no signal. Reason: inefficient nuclear lysis during microfluidic reverse transcription workflow preventing cDNA amplification
Lost to a baseline
Droplet microfluidics assay yielded poorer diagnostic accuracy and correlation than standard Giemsa thick blood smear microscopy and HRP-2 RDTs
Technology transfer and assay optimisation of the droplet microfluidic assay for malaria diagnostics in human saliva - A pilot study in Gabon · Publikationssystem UB Tuebingen
Lost to a baseline
Convective microfluidic transfection of large multicistronic CRISPR/Cas9 plasmids into iPSCs performed no better than standard Lipofectamine Stem (<1% efficiency).
Microfluidic Cell Processing for Personalized and Regenerative Medicine · Georgia Tech
Lost to a baseline
Microfluidic cell sorting protocols do not yet reach the purity levels of fluorescence-activated cell sorting (FACS)
Profiling, prototyping, and perturbing human immune responses · MIT
Lost to a baseline
Microfluidic selection produced significantly lower sperm concentration (70.93 x 10^6/mL) than unprocessed control (350.05 x 10^6/mL) and colloidal centrifugation (266.39 x 10^6/mL).
OPTIMIZING SPERM SELECTION: EFFECTS OF MICROFLUIDIC AND COLLOIDAL CENTRIFUGATION PROCESSING ON DNA FRAGMENTATION IN FROZEN-THAWED STALLION SPERM · DSpace at SHSU
Lost to a baseline
Manual pipette preparation slightly exceeded the microfluidic device's qPCR linearity (R² = 0.9976 for manual vs R² = 0.9972 for microfluidic device)
The Study of Vacuum-Driven Microfluidic Networks and Their Pumping Methods · DSpace at SUNY Buffalo
Lost to a baseline
Droplet tagmentation using non-dissolvable hydrogels required 1-2 additional qPCR amplification cycles compared to bulk control tagmentation.
Lost to a baseline
Cell pooling performed worse than conventional screens when matching droplet counts due to signal dilution per droplet.
Investigating human disease mechanisms through population genetics and experimental genetic screens · Harvard
Considered and rejected
Considered and rejected: Simultaneous one-step in-droplet RT-PCR was abandoned due to low reaction yields and inefficiency in droplet linking.
Methods and Materials to Generate Antibody Repertoire Libraries · Harvard
Considered and rejected
Considered and rejected: Performing immunofluorescence staining directly on cells lodged inside microfluidic chips, rejected due to reagent diffusion gradients, cell-debris colocalisation, and insufficient cell numbers for statistics.
Tried and failed
PDMS-on-glass microfluidic constriction electrodes applied to single-cell impedance cytometry and electroporation. Outcome: worse than baseline. Reason: exhibited significantly worse signal-to-noise ratio and electroporation performance compared to PCB through-hole design
Single-Cell Impedance Cytometry for the Control of Single-Cell Electroporation in a Flow-Through Device · Georgia Tech
Tried and failed
convective microfluidic constriction cell transfection applied to large plasmid delivery to iPSCs. Outcome: worse than baseline. Reason: substantial cell size heterogeneity prevented uniform mechanical constriction and membrane permeabilization
Microfluidic Cell Processing for Personalized and Regenerative Medicine · Georgia Tech
Lost to a baseline
Capillary-driven microfluidic assays showed slightly lower sensitivity curve slope than standard ELISA due to spontaneous target dilution and ultra-short incubation times.
Capillary-driven Microfluidic Biosensing Platforms for Digital Biomolecule Detection · Texas Tech
Polydimethylsiloxane devices fail due to solvent swelling, small molecule adsorption, toxic leaching, and bonding delamination
Polydimethylsiloxane absorbed organic solvents and non-specifically sequestered small molecules, fluorescent dyes, and hydrophobic compounds during device operation. In addition, devices suffered from uncrosslinked oligomer toxicity, cure inhibition from 3D-printed resin molds, and structural delamination under elevated operating pressures.
Tried and failed
Casting PDMS in SLA 3D printed molds applied to Microfluidic device fabrication. Reason: Uncured resin components and photoinitiators leach into PDMS and inhibit platinum-catalyzed crosslinking
Design and development of cost-effective and portable 3D printed biomedical equipment · Iowa State
Tried and failed
fluorinated solvent microfluidic hydrodynamic focusing in PDMS applied to nanoparticle self-assembly. Reason: Solvent absorption into PDMS and wetting caused broad, polydisperse size distributions with large aggregates.
Developing artificial cells for delivering drug molecules to micro-engineered heart tissue · Imperial
Tried and failed
multitude interlayer bonding of PDMS microfluidics applied to microfluidic chromatin immunoprecipitation devices. Reason: improper interlayer bonding and sealing caused device fluid leaks
DEVELOPMENT AND EXPLORATION OF TECHNIQUES TO STUDY THE SPATIAL ORGANIZATION OF THE HUMAN GENOME · Cornell
Tried and failed
cell culture in unwashed PDMS microfluidic devices applied to bacterial spore germination. Outcome: no signal. Reason: Leaching of toxic uncrosslinked PDMS oligomers inhibited spore germination entirely without extensive solvent washing.
Microbes-on-a-chip: deciphering the responsiveness of microbes using microfluidic chemostats · Imperial
Tried and failed
Hydrogel membrane bonding without surface silanization applied to PDMS microfluidic devices. Outcome: unstable. Reason: Inconsistent membrane adhesion sensitive to water content and buffer composition.
Tried and failed
3D-printed and milled molds for soft lithography applied to microfluidic channel fabrication. Reason: Molds produced via stereolithography, FDM, and CNC milling failed to yield functional PDMS channels
Tried and failed
all-PDMS microfluidic channels under high operating pressure applied to intracellular delivery in microfluidic devices. Outcome: unstable. Reason: Severe channel deformation above 3 bar and delamination above 4 bar caused irreproducible processing
A biomechanics-based delivery strategy to primary immune cells for generating cell therapy with multiple gene knockout · Georgia Tech
Tried and failed
combinatorial fluorescent dye multiplexing in microfluidics applied to single cell optical barcoding. Outcome: unstable. Reason: Severe spectral shifts, non-specific PDMS adsorption, and intercellular cross-staining prevented reliable multiplexed decoding.
Development of high-throughput imaging-based single cell genotype-phenotype mapping platforms · Harvard
Considered and rejected
Considered and rejected: Rejected PDMS for microfluidic platform fabrication because of small molecule absorption and low throughput, opting for polystyrene injection molding and 3D DLP printed rigid resin.
Engineering Brain Tumor Microenvironment with Controlled Physical Features · Georgia Tech
Considered and rejected
Considered and rejected: Rejected using standard hydrocarbon-based organic solvents (toluene, chloroform, cyclohexane) in PDMS microfluidics due to PDMS swelling affecting channel width and surface treatments.
Considered and rejected
Considered and rejected: Rejected PDMS-based microfluidics for final innervation platform due to small molecule absorption, laborious molding, and lack of open-top compound access.
Modelling Sensory Innervation of Cancer Using Organ-on-Chip Technology · Publikationssystem UB Tuebingen
Considered and rejected
Considered and rejected: Rejected PDMS for scalable/commercial microfluidic devices due to time-intensive processing, difficult sealing, swelling in non-polar organic solvents, and extraction of hydrophobic molecules
From Coulombic Materials to Fluids: Complex Behaviors in Physical Systems · Harvard
Considered and rejected
Considered and rejected: Rejected PDMS-based microfluidic chips in favor of borosilicate glass (Micronit) to prevent matrix swelling in the presence of light organic solvents.
Hydrocarbon gas injection for improving oil recovery in tight and shale oil reservoirs · UT Austin
Considered and rejected
Considered and rejected: Single-use PDMS-on-glass thin-section microfluidic chips rejected due to ~50% failure rate (glass cracking, leaking, Si background from PDMS, 1000x Si variance) in favor of a 304 stainless steel device
Kinetic analysis of leaching reactions in multi-component mineral systems · MIT
Microchannels and fluidic components become clogged by cell aggregation, particle sedimentation, viscous fluids, and biofilms
Particulate samples, dense cell suspensions, and highly viscous biofluids frequently sedimented and formed aggregates that blocked narrow channels, needles, and connecting tubing. Excessive backpressure, biofilm accumulation, and nanovial deformation further contributed to complete operational failure and device clogging.
Tried and failed
microfluidic device interaction assays applied to inter-organism microbial interactions. Outcome: unstable. Reason: unresolvable fluid currents caused severe channel clogging despite degassing and hydration modifications
Investigating the role of chemotaxis in the natural source zone depletion of petroleum hydrocarbons · Imperial
Tried and failed
continuous microfluidic particle delivery using syringe pumps applied to single-cell droplet encapsulation. Outcome: unstable. Reason: cell sedimentation and aggregation over extended runtimes altered the concentration reaching the microfluidic junction
Deep Learning with Computer Vision for Microfluidic Droplet and Cancer Detection · Texas Tech
Tried and failed
nanolitre dispensing with microfluidic dispenser applied to undiluted human serum. Outcome: unstable. Reason: high sample viscosity caused frequent needle and dispenser blockages
Tried and failed
acoustic streaming microfluidic cell trapping applied to microfluidic cell sorting and collection. Reason: narrow channels clogged from vortex trapping, while wider channels severely reduced pumping efficiency
Considered and rejected
Considered and rejected: Rejected dropper-based droplet drying for traditional binder due to excessive viscosity clogging the dropper.
Considered and rejected
Considered and rejected: Rejected microfluidic droplet generation due to severe clogging, non-sterile workflows, low yield (4 h run yielded only 2 scaffolds), and sticky bead loss during pipetting.
Bioengineered scaffolds as a tool to decode the complexity of cancer cell interactions in vivo · Imperial
Considered and rejected
Considered and rejected: Rejected continuous emulsion flow PASST setup for sample collection due to persistent tubing clogging during in-line droplet freezing.
Porous ceramic frameworks for CO2 utilization · DSpace-CRIS at TU Wien
Considered and rejected
Considered and rejected: Rejected microfluidic droplet generation for sub-10 µm microparticles due to severe backpressure and high channel clogging risk.
Platelet-inspired microparticles for targeted drug delivery to the atherosclerotic plaque · Imperial
Considered and rejected
Considered and rejected: Rejected using 60 µm nanovials for droplet single-cell sequencing because they deformed in microfluidic channels and caused clogging; 35 µm nanovials were used instead.
Modeling the longevity and secretory capacity of engineered human plasma cells · ResearchWorks
Considered and rejected
Considered and rejected: Abandoned use of Nanoparticle Tracking Analysis (NTA) microfluidic cell instrumentation for high-volume wastewater particle concentration measurement due to frequent clogging/rework, switching to DLS.
The Detection and EHS Risk Determination of Nanomaterials in the Semiconductor Industry · Research Repository UCD
Considered and rejected
Considered and rejected: Rejected 16-channel microfluidic flow chip with integrated inflow/outflow distributors due to biofilm clogging within distributor structures causing uneven flow.
Uncovering Transcriptional Heterogeneity during Vibrio cholerae Biofilm Development Aufdeckung der transkriptionellen Heterogenität während der Biofilmentwicklung von Vibrio cholerae · open_UMR Marburg DSpace 10.0
Droplet generation and emulsion stability fail due to surfactant disruption, surface wetting, and rapid evaporation
Emulsion droplets coalesced or failed to pinch off properly due to interference from detergent lysis buffers, cell-free transcription components, or incorrect channel dimensions. Droplet stability was also undermined by surface wetting defects, droplet adhesion to bare microelectrodes, and rapid thermal evaporation during heating.
Tried and failed
undiluted isothermal amplification reaction encapsulation in droplet microfluidics applied to recombinase polymerase amplification mixture droplet generation. Outcome: unstable. Reason: droplets were unstable during microfluidic generation without significant aqueous dilution
Tried and failed
electrochemical manipulation of microdroplets over bare microelectrodes applied to droplet-based microfluidics. Outcome: unstable. Reason: droplets adhered directly to electrode surfaces without fluorinated thiol surfactant, permanently clogging the channel
Tried and failed
microfluidic droplet generation without sample dilution applied to low-concentration protein solutions. Outcome: unstable. Reason: microchannel wettability issues caused droplet generation failure at low protein concentrations
Two-phase microfluidic approaches to study food protein functionality · Texas Tech
Tried and failed
direct ddPCR using commercial detergent lysis buffers applied to cell lysates for DNA quantification. Reason: detergents and harsh chemicals in extraction lysis buffers interfered with droplet formation
Tried and failed
fluorosurfactant-stabilized microfluidic droplet pico-injection applied to cell-free protein synthesis reactions. Outcome: unstable. Reason: in vitro transcription-translation reaction components destabilized fluorosurfactant emulsions, causing severe droplet coalescence
Microdroplet assay development for metabolic engineering and synthetic biology applications · UT Austin
Tried and failed
microfluidic geometric constriction for droplet snap-off applied to oil trapping in microchannels. Reason: Pore throat dimensions exceeding critical aspect ratio failed to induce capillary instability required for spontaneous snap-off
Multiscale visualization of chemical enhanced oil recovery · UT Austin
Tried and failed
oscillatory microfluidic droplet transport at elevated temperatures applied to automated chemical reaction screening. Outcome: unstable. Reason: rapid solvent evaporation, droplet smearing, and condensation in unheated tubing outside the heated zone
Lost to a baseline
Open microfluidic droplet volume monodispersity had a relative standard deviation of 5%–7%, whereas conventional closed-channel methods achieve 1%–3%.
Open microfluidic technologies for fundamental and applied studies of human health and the environment · ResearchWorks
Considered and rejected
Considered and rejected: Operating droplets in continuous oil media on the PurpleDrop board, rejected due to contamination, setup complexity, and failure to stop thermal evaporation during PCR.
Physical and Computational Approaches Towards More Scalable Molecular Systems · ResearchWorks
Considered and rejected
Considered and rejected: Abandoned microfluidic water-in-oil droplet generation due to inconsistent droplet sizing, excessive sample waste during equilibration, and manual dispensing constraints.
Parallel synthesis and screening of optical probes for G-quadruplex DNA · Imperial
Spurious bubble formation, gas permeability, and cavitation disrupt microfluidic flow and analytical measurements
Gas permeability through elastomer membranes and Joule heating during electrical actuation induced unwanted bubble nucleation and electrical arcing in microfluidic channels. Entrapped bubbles and cavitation events caused severe measurement artifacts, fragmented biological tissues, and displaced immobilized cell spheroids.
Tried and failed
microfluidic morphogen gradient patterning applied to elongated embryonic stem cell organoids. Reason: air bubble entrapment in the microfluidic chamber caused tissue fragmentation and disrupted morphogen gradient exposure
Materials and morphogen gradients-guided brain organoid anteroposterior polarization study · Imperial
Tried and failed
pneumatic actuation of elastomer membranes applied to microfluidic flow resistance control. Reason: gas permeability of the elastomer membrane under pressure caused bubble formation in the fluid channels
Lab-on-a-chip and numerical tools for a better understanding and prediction of chemokine gradients · Imperial
Tried and failed
passive microcavity arrays for bubble trapping applied to in situ microfluidic optical spectroscopy. Outcome: unstable. Reason: cylindrical indents lacked reproducibility for trapping stable air bubbles without manual injection
Tried and failed
active flow microfluidics over microwell arrays applied to trapped 3D cell spheroids. Outcome: unstable. Reason: fluid flow introduced air bubbles, dislodged aggregates, and caused shear-induced sample dissociation
Label-free plasmonic microarray for multiplexed analysis of cells and tumor organoids · EPFL
Tried and failed
Electrochemical probe oxygen sensing in microfluidic reservoirs applied to dissolved oxygen monitoring in microfluidics. Outcome: unstable. Reason: Bubble nucleation at probe tip caused measurement artifacts in concentration curves
Integrated Microfluidic Culture Media Oxygenator for Organ-on-a-Chip Applications · MIT
Tried and failed
low-flow continuous microfluidic electroporation applied to bacterial cell transformation. Outcome: unstable. Reason: Joule heating caused bubble formation and electrical arcing at low flow rates
Novel High-throughput Technologies for Applications in Microbiology · MIT
Tried and failed
QCM-D characterisation of surface functionalisation applied to conjugated polymer thin films. Outcome: unstable. Reason: Polymer swelling in organic solvent, film delamination from sensor substrates, and microfluidic bubble formation
Functionalised organic field-effect transistors as biosensors for circulating-tumour DNA detection · Imperial
Tried and failed
microscopy to detect interfacial vapor bubble formation applied to periodic dripping in microfluidic evaporative systems. Outcome: no signal. Reason: No gas-vapor pocket formation was observed at the tube tops to explain the periodic instability.
Scalable Synthetic Trees for Transpiration-Powered Hydraulic Systems · Virginia Tech
Cell detachment, matrix delamination, and excessive shear stress undermine on-chip cell and tissue culture
Cultured cells detached from microchannels under fluid exchange shear, while hydrogel constructs delaminated from channel surfaces and underwent excessive cell-mediated contraction. Furthermore, pump-induced pressure oscillations damaged delicate cellular constructs, leading to poor cell differentiation and lower viability than conventional well plates.
Tried and failed
microfluidic cell monolayer culture under shear stress applied to ovarian cancer cell lines. Outcome: unstable. Reason: cells failed to form stable adherent monolayers and detached under minimal shear during media exchange
Tried and failed
parallel array microfluidic hydrodynamic trap design applied to organoid capture and immobilization. Reason: caused non-uniform particle distribution, difficult loading, and low overall trapping efficiency
Tried and failed
automated mechanical tissue dissociation applied to microfluidic organ-on-chip hydrogel constructs. Outcome: data insufficient. Reason: yielded insufficient cell numbers for downstream flow cytometry analysis
An immune-competent microvascularized human lung-on-chip device for studying immunopathologies of the lung · Georgia Tech
Tried and failed
commercial microfluidic devices with open bottom channels applied to 3D cell invasion assays in hydrogels. Reason: Hydrogel detached and cells migrated along the 2D plastic surface rather than invading the 3D matrix
Tried and failed
synthetic poly(ethylene glycol) hydrogel encapsulation in microfluidics applied to bone marrow organ-on-a-chip vascularization. Reason: Rapid gelling caused channel leakage, bubbling, defective vascular network self-assembly, and aberrant stromal marker expression.
Engineered Systems of the Germinal Center and Bone Marrow for Antigen-Specific B Cell Generation and Longevity · Georgia Tech
Tried and failed
peristaltic pump driven microfluidic perfusion applied to endothelial cell culture under shear. Outcome: unstable. Reason: excessive pressure swings and shear oscillations broke chips and killed cells
Tried and failed
hydrogel compartmentalization in microfluidic pillar arrays applied to in vitro vascular tissue models. Outcome: unstable. Reason: excessive cell-mediated collagen matrix contraction exceeding quality control thresholds
Lost to a baseline
TuJ1 neuronal differentiation expression following dopamine treatment was significantly higher in 24-well plate controls than in the microfluidic chip.
Left open by the authors
Problems the authors named and did not get to.
Left open
Design and validate primer pools to generate linked sequencing libraries for heterodimeric molecules such as T-cell receptors using droplet microfluidics. Blocker: Requires wet lab access, microfluidic apparatus, biological samples, and reagent synthesis
Methods and Materials to Generate Antibody Repertoire Libraries · Harvard
Left open
Optimize workflow for digital droplet or digital partitioning PCR systems to assess inhibitor susceptibility compared to RT-qPCR in wastewater surveillance. Blocker: Requires wet lab facilities, wastewater samples, and digital PCR apparatus/reagents.
Wastewater Surveillance for Emerging Infectious Diseases: Optimization and Implementation of Methods · ResearchWorks
Left open
Develop a digital droplet Telomere Shortest Length Assay (ddTeSLA) by incorporating fluorophore-labeled dUTP into PCR droplet compartmentalization. Blocker: Requires wet lab facilities, molecular biology reagents, and droplet digital PCR equipment.
An Imaging Approach to Examine Telomere Dynamics and Regulation of Gene Expression with Aging · DSpace at UTSWMED
Left open
Design and fabricate microfluidic transistor circuits for multi-particle co-encapsulation and droplet pairing in single-cell sequencing. Blocker: Requires a microfluidics wet lab and physical fabrication facilities for testing flexible membrane fluidic circuits
Microfluidic Transistors for the Control of Liquids and Particles · Harvard
Left open
Adopt digital droplet PCR (ddPCR) to quantify low-abundance cell-free RNA transcripts and reduce stochastic variability. Blocker: Requires a wet lab, biological samples (serum/CSF), and digital droplet PCR (ddPCR) instrumentation.
Evaluation of Cell-Free RNA as Minimally Invasive Biomarkers of Target Engagement · Harvard
Left open
Incorporate barcoding schemes into the droplet microfluidic viral recovery workflow to enable multiplexed detection and sequencing of multiple viruses. Blocker: Requires a wet lab, microfluidic droplet generation and sorting apparatus, and biological reagents.
Single-Virus/Single-Cell Sequencing with Droplet Microfluidics · Harvard
Left open
Develop a continuous flow droplet reactor in tubing to scale up nanoparticle synthesis and improve batch reproducibility. Blocker: Requires a physical chemistry/materials wet lab and specialized microfluidic or flow chemistry hardware
HYBRIDIZED NANOSCALE TRANSITION METAL OXIDES AS ANODE MATERIALS FOR LITHIUM-ION BATTERIES · Georgia Tech
Left open
Optimize droplet microfluidic sorting and amplification protocols to prevent proviral DNA fragmentation and improve post-sort retrieval for full-length single-genome amplification. Blocker: Requires wet-lab facilities, microfluidic cell sorters (Sony MA900), and biological reagents to handle and amplify proviral DNA.
The impact of HIV specific broadly neutralising antibodies on mucosal immunity and the HIV reservoir · Imperial
Left open
Incorporate hydrogel particle-templated droplets or on-bead rolling circle amplification chemistries into the droplet digital extracellular vesicle analysis platform. Blocker: Requires a wet lab, microfluidic devices, chemical reagents, and physical extracellular vesicle samples
Left open
Develop microdroplet applications that mimic fed-batch fermentations to improve translation into benchtop bioreactors. Blocker: Requires a wet lab, microfluidic devices, and biological fermentation setups.
Microdroplet assay development for metabolic engineering and synthetic biology applications · UT Austin
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