Electrohydrodynamic Research Articles

A Kirigami‐Driven Stretchable Paper‐Based Hydrovoltaic Electricity Generator

AbstractHydrovoltaic electricity generator (HEG), which converts thermal energy from water evaporation into electrical energy, offers a promising solution for sustainable, low‐power applications such as remote sensors and wearable flexible electronics. However, current HEG suffers from poor deformation adaptability due to its reliance on the rigid ion transport interfaces of hydrovoltaic materials for electrokinetic effects, limiting its potential in wearable electronics. Herein, a stretchable paper‐based hydrovoltaic electricity generator (SP‐HEG) is developed by laser‐cutting an optimized kirigami pattern on paper functionalized with carbon black. The SP‐HEG can stretch up to 200% without compromising its electrical output (open‐circuit voltage of 1.2 V and short‐circuit current of 6.0 µA), as mechanical stress is evenly distributed and stable ion transport interfaces are maintained on the kirigami patterns. Moreover, the SP‐HEG can be used as a wearable energy supply device and self‐powered sweat sensor, with the advantages of stable output unaffected by deformation, sustainable power generation, and environmental friendliness. This study opens up a novel strategy to design deformable energy harvesters, broadening the potential applications of hydrovoltaic power generators in the wearable field.

Prediction of electrohydrodynamic printing behavior using machine learning approaches

Electrohydrodynamic (EHD) printing has been used in various applications (e.g., sensors, batteries, photonic crystals). Currently, research on studying the relationships between EHD jetting behaviors, material properties, and processing conditions is still challenging due to a large number of parameters, cost, time, and the complex nature of experiments. In this research, we investigated EHD printing behavior using a machine learning (ML)-guided approach to overcome limitations in the experiments. Specifically, we investigated two jetting modes and the size of printed material with a broader range of material properties and processing parameters. We used samples from both literature and our own experiment results with different type of materials. Different ML models have been developed and applied to the data. Our results have shown that ML can navigate a vast parameter search space to predict printing behavior with an accuracy of higher than 95% during EHD printing. Moreover, the results showed that ML models can be used to predict the printing behavior and feather size for new materials. The ML models can guide the investigation of EHD printing and helped us understand the printing behavior in a systematic manner with reduced time, cost, and required experiments.

The common structure of multiple instability patterns on free liquid surfaces induced by charge injection

A previously disregarded electrohydrodynamic (EHD) instability pattern at the gas–liquid interface caused by charge injection is elaborately described and identified as the classical EHD instability. The characteristics and evolutionary processes of three classic EHD instability patterns were meticulously described experimentally. A Taylor cone-like conical structure is proposed as the common basis for the formation of all these patterns. A direct numerical model based on coupled hydrodynamic and electrodynamic equations is developed, and the evolution of the free liquid surface from static to classical EHD instability patterns is obtained from numerical simulations. The simulation results match the experiments, providing details that cannot be observed experimentally and proving the similarity between the conical structure and the Taylor cone. The comprehensive experimental observations and efficient numerical models can serve as a valuable inspiration and foundation for various applications related to EHD surface instability.

Modulating the Selective Enrichment and Depletion of Ions Using Electrorheological Fluids in Variable-Area Microchannels.

Electrorheological fluids are suspensions that are characterized by a strong functional dependence of their constitutive behavior on the local electric field. While such fluids are known to be promising in different applications of microfluidics including electrokinetic flows, their capabilities of controlling ion transport and preferential solute segregation in confined fluidic systems remain to be explored. In this work, we bring out the unique role of electrorheological fluids in orchestrating the selective enrichment and depletion of charged species in variable area microfluidic channels. Our reported phenomenon is fundamentally distinctive from other types of nonlinear electrokinetic effects previously reported, in a sense that here the dependence of the flow rheology on the electric field turns out to be the central mechanism toward orchestrating the observed nonlinear ion transport. Our results indicate exclusive features of the resulting ion concentration polarization, such as more pronounced ion concentration polarization, controlled largely by the influence of the variations in the channel cross section on the driving electrokinetic forces and the resistive viscous interactions. The underlying physical mechanism is captured aptly by a simple one-dimensional area-averaged model, and validated by full-scale three-dimensional simulations. Our illustrative case study for a converging-diverging microchannel with cross-sectionally uniform solute concentrations reveals that electrorheological effect with greater contrast between the deep and shallow region depths, greater solute concentration, and larger applied axial electric field, all acting in tandem, magnifies the solute enrichment and depletion in the respective segregation zones, bearing significant implications in analytical chemistry, bioanalysis, and beyond.

Electrohydrodynamic effects on the viscoelastic droplet deformation in shear flows

Droplet deformation under shear flows is widely observed in many practical applications, including droplet-based microfluidics and emulsion processing, whereby the droplet usually exhibits viscoelastic characteristics. It has been shown that the performance of these applications is significantly influenced by the size and shape of the resulting droplets. Therefore, the underlying performance is directly tied to the precision and efficiency of viscoelastic droplet control. Previous studies demonstrate that the electric field is a straightforward and efficient way of manipulating fluid flows. However, the effects of an electric field on the viscoelastic droplet deformation remain unexplored. To this aim, this work investigates the electrohydrodynamic (EHD) control of viscoelastic droplets under shear flows using a hybrid numerical framework coupling the lattice Boltzmann method and finite difference method. Extensive simulations are conducted under various electrical properties, such as conductivity ratio R, permittivity ratio S, and electric field strength CaE. Focus is placed on the quantitative analysis of the viscoelastic droplet morphological metrics including deformation D and inclination angle θ. Phase diagrams of D, θ, and combined D and θ in the plane of R–S are developed, where four regions can be identified based on different droplet behaviors under an electric field. The mechanism of this phenomenon is presented by analyzing the distribution of the electric field, electric charge, and electrical force at different regions. It is further observed that the electric field strength CaE amplifies these effects, either suppressing or promoting the droplet deformation and rotation. While viscoelastic effects are considered, they are found to play a subdominant role compared to EHD forces in controlling or modifying droplet morphology. This study provides insights into the electrohydrodynamic (EHD) effects on the dynamics of viscoelastic droplets in shear flow, contributing to the development of active control strategies for viscoelastic droplets in microfluidic applications, including drug delivery and food processing.

Effects of ultrasound-assisted plasma-activated water pretreatment combined with electrohydrodynamics on drying characteristics, active ingredients and volatile components of yam (Dioscorea opposita).

This paper explores the effect of ultrasound (US) assisted plasma-activated water (PAW) or deionized water (DW) pretreatment combined with electrohydrodynamics (EHD) on the drying of yam. The activity characteristics of four pretreatments (plasma activated water combined with ultrasound (PAW+US), plasma activated water (PAW), deionized water combined with ultrasound (DW+US), and deionized water (DW) (control)) and their effects on drying characteristics, rehydration rate, color, reducing sugars, total phenols, infrared spectra, and volatile compositions of yam under EHD drying process were investigated. The results showed that the media pretreaded by ultrasound (US) combined with plasma-activated water (PAW) has lower media of pH (53.84% lower than that of US+DW), higher nitrite ion concentration (311 times over US+DW), higher oxidation reduction potential (50.58% higher than that of US+DW), and higher electrical conductivity (99.29 times over US+DW). And ultrasonic pretreatment (US) combined with plasma-activated water (PAW) drying resulted in faster drying, better rehydration rate, higher brightness L * (18.35% higher than that of US+DW) and whiteness (1.1% higher than that of US+DW), and retention of more reducing sugars (10.96% higher than that of US+DW) and total phenols (14.04% higher than that of US+DW), and a higher variety and content of volatile components. This provides an experimental and theoretical basis for the application of ultrasonic (US) combined with plasma-activated water (PAW) pretreatment to electrohydrodynamic drying.

A numerical study of electrokinetically generated pre-earthquake geoelectric fields in layered porous Media

Summary The investigation into the physical mechanisms and behavior of geoelectric fields as potential precursors of earthquakes is a crucial yet challenging task in seismo-electromagnetics. Assuming the electrokinetic effect as a potential mechanism, we propose a novel numerical modeling algorithm based on the framework of the Luco-Apsel-Chen generalized reflection and transmission method to explore the behavior of geoelectric fields in stratified porous media during earthquake preparation. This algorithm incorporates two innovative aspects: (1) employing the Jordan decomposition to address the degeneracy problem encountered in the quasi-static regime, and (2) utilizing digital linear filters for Hankel transforms to conduct the wavenumber integration. The accuracy of the algorithm in computing static displacements in an extremely low porosity half-space model is verified through comparison with analytical solutions. Numerical results from a half-space model demonstrate a strong consistency between the behavior of the vertical electric field and filtration displacements. Notably, the maximum amplitude of the vertical electric field can reach approximately 3150.5 mV/km, which is detectable by receivers located at considerable distances from the epicenter. In addition, three distinct types of pre-earthquake electric fields are identified: (1) the localized electric field induced by slow P waves, (2) the interface electric responses, and (3) the direct converted electric field from the source. Results from a multi-layer porous model show the significant influence of the water table on the amplitude of the vertical electric field. This can be attributed to the influence of water saturation and permeability on the coefficient that combines the vertical electric field and the vertical filtration displacement. We also analyze the temporal evolution of different fields during earthquake preparation, which demonstrates a robust correlation between the temporal characteristics of pore pressure and that of the vertical electric field. This indicates that the vertical electric field offers an effective means to detect pore pressure evolution. Furthermore, our analysis demonstrates that the broadening of electric anomalies can be used to roughly estimate the rate of stress accumulation. The sensitivity of the electric signal to the strike, rake and dip angles of potential faults indicates its ability to determine fault geometry related to an impending earthquake. These observations underscore the potential of using geoelectric precursors to study earthquake preparation mechanisms.

High-Resolution Electrohydrodynamic Printing with Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate) Conductive Polymers

Conductive polymer materials, particularly PEDOT:PSS conductive polymers, have gained widespread attention due to their excellent conductivity, processability, and biocompatibility, making them highly applicable in fields such as bioelectrodes, flexible sensors, and soft robotics. With the rapid development of flexible electronics, the demand for micron-scale precision in the processing of conductive polymers grows. However, advanced fabrication techniques, such as 3D printing and screen printing, which are currently popular in research, face challenges in achieving a micron-level resolution, limiting the further application of conductive polymers. In this study, we demonstrate three types of PEDOT:PSS inks and systematically explore their suitability for electrohydrodynamic (EHD) jet printing. We investigate the impact of critical parameters, including voltage, printing speed, and printing height, on the accuracy of printed patterns. Among the formulations, the optimized PEDOT:PSS to ethylene glycol ratio of 1:1 achieves line widths of 20 µm. Based on this ink, we successfully print flexible conductive polymer patterns with line widths ranging from 20 µm to 90 µm and fabricate PEDOT:PSS conductive films with dimensions of 1.5 cm × 0.5 cm. This high-precision PEDOT:PSS ink demonstrates a strong potential for applications in high-density electrode arrays, electrochemical transistors, and brain–machine interfaces, paving the way for advanced flexible electronics.

Electrorheological characterization of complex fluids used in electrohydrodynamic processes: Technical issues and challenges

Abstract The electrorheological (ER) characterization of low-viscosity fluids is paramount for producing micro- and nanoscale products through electrohydrodynamic (EHD) techniques, such as EHD-jet printing, electrospray, and electrospinning. Key properties such as viscosity, surface tension, dielectric properties, electrical conductivity, and relaxation time significantly influence both the quality and properties of the final products and the efficiency of the industrial process. ER characterization is essential for studying the macroscopic effects of the interaction between these physicochemical properties under controlled flow kinematics. Researchers may face several technical challenges in performing rigorous ER characterization of moderate conductive fluids typically used in EHD processes. This characterization is crucial for formulating inks compatible with these processes and for understanding fluid dynamics in EHD processes to ensure stable printing conditions and achieve high-resolution, accurate prints. This work highlights the inherent limitations of current ER cells and proposes methodologies to mitigate their impact on measurement accuracy. Furthermore, we propose the use of microfluidic devices as a solution for the ER characterization of moderate conductive fluids.

Controlling the heating wall temperature during melting via electric field

Thermal energy storage technology utilizing phase change materials (PCMs) is extensively applied in thermal management and energy storage. The inclination angle (θ) plays a critical factor in the phase change melting processes in practical implementations. However, the precise experimental velocity fields of liquid PCM and the impact of active regulation technology on the heating wall temperature at various angles remain unclear. Herein, a transparent melting experiment platform was established to measure velocity, and adjust θ and manipulate input electric voltage. Results from Particle Image Velocimetry indicated that the installation angle significantly impacts natural convection in the convection-dominated melting regime. The liquid fraction decreased from 73.5 % (when θ = 90°) to 54.4 % (when θ = 150°) due to reduced thermal energy absorption, as input energy was stored as sensible heat on the copper wall. The electrohydrodynamic (EHD) effect mitigated thermal resistance between the heater and the melt front, increasing melt thickness. EHD flow exhibited limited ability to regulate heating wall temperature under strong natural convection, with a 6.5 % decrease observed under +20 kV conditions. As natural convection rates decreased, the decrease rate of heating wall temperature increased to 10.7 %. The EHD effect demonstrated a heightened capability in enhancing heat transfer melting with increasing θ, leading to an increase in temperature difference from 3.3 °C to 5.3 °C under the +15 kV input voltage. These findings suggest that the electric field is an efficacious method for controlling the heating wall temperature at different inclination angles during the melting process.

Electrokinetic effects on Brinkman micropolar flow through stationary randomly corrugated microchannels

Electrokinetic effects on Brinkman micropolar flow through stationary randomly corrugated microchannels

Study the effect of ultrasonic pretreatment combined with electrohydrodynamics on drying characteristics and volatile components of carrots

In order to comprehensively and systematically explore the effects of ultrasonic pretreatment combined with electrohydrodynamic (EHD) on the drying characteristics and volatile constituents of carrots. In this experiment, ultrasonic pretreatment assisted by EHD drying method with different power values was used to study carrots. Drying characteristics, rehydration capacity, shrinkage capacity, color, infrared spectra, and volatile components of carrots were measured and analyzed. Ten mathematical models were used to fit the drying of carrots. The results showed that ultrasonic pretreatment can significantly enhance the drying rate of carrots in the electrohydrodynamic system, the rehydration rate had a tendency to increase and then decrease with the increase of ultrasonic power, and the rehydration rate of carrots reached the maximum value under the condition of 240 W. The best performance in terms of color and infrared spectrum was achieved at 180 W. A total of 212 volatile compounds were detected in the dried carrot products, of which 6-methyl-5-hepten-2-one, as a carotenoid degradation product, was the least abundant at 180 W, indicating the best retention of carotenoids at this power pretreatment condition. The Midilli et al. mathematical model was best described the drying process of carrots. This work provides an experimental and theoretical basis for ultrasonic pretreatment combined with EHD in the field of carrot processing.

Seismoelectric Imaging of Aquifer Interface: Theoretical Investigation and Laboratory Experiments

AbstractThe seismoelectric (SE) wave at the vadose zone‐aquifer interface, which results from the electrokinetic effect, is a valuable tool for groundwater exploration. We propose a method for imaging aquifer interfaces using SE waves. The common‐receiver SE gather, generated by multiple sources, is analogous to the exploding‐reflector seismic gather, forming the theoretical foundation of this method. To test this method, two 2D aquifer models are designed to simulate the synthetic common‐receiver SE gather, followed by the application of exploding‐reflector migration. The result shows that the aquifer interface is well imaged by the SE waves. Additionally, laboratory experiments successfully recovering the interfaces of the rocks confirm the validity of the SE imaging method, suggesting its feasible use in real groundwater exploration in the future.

Integrating Electrokinetics with AI-Assisted Raman Spectroscopy for Bacterial Detection in Wastewater

Wastewater-based epidemiology can monitor population-level infection, provide early warnings about disease outbreaks, and help control disease spread at the community level [1,2]. However, broad-spectrum bacterial identification in wastewater presents outstanding challenges; notably, current culturing or fluorescence-based methods [3] to identify bacteria are unsuitable for real-time, high-throughput screening of diverse bacterial species, and may not work well in the complex wastewater matrix. Here, we harness electrokinetics and artificial intelligence (AI)-powered Raman spectroscopy as an innovative approach that promises the identification of a wide range of pathogenic bacteria in wastewater.First, we synthesize gold nanorods that can electrostatically bind to bacteria surfaces, allowing for surface-enhanced Raman spectroscopy (SERS) [4] from cell surfaces. We collect SERS from bacteria spiked into filter-sterilized wastewater, including Staphylococcus aureus, Staphylococcus epidermidis, and Escherichia coli, spanning concentrations from 109 cells/mL to 104 cells/mL. Spectral clustering analysis shows that bacterial signals become less distinguishable in wastewater as the concentrations decrease. To overcome this challenge, we incorporate electrokinetic effects into SERS by employing gold microelectrodes to apply electric fields, utilizing dielectrophoresis (DEP) [5] to rapidly displace and concentrate bacteria. The four types of bacteria responded to 5-100 kHz AC fields based on their different dielectric responses and sizes, and were enriched at the microelectrode within minutes. The enrichment of bacteria is directly visualized through optical and electron microscopy, resulting in up to tenfold increases in Raman signal intensities under electrical fields at bacterial concentrations down to 104 cells/mL. Such enhancement may enable the detection sensitivity to reach environmentally relevant concentrations. Importantly, mixtures of bacteria are now distinguishable from SERS under DEP effects. Finally, employing random forest and convolutional neural network models [6], we identify biologically relevant Raman fingerprint peaks characterizing proteins, nucleic acids, and lipids from bacteria surfaces, allowing for rapid identification of bacteria species in wastewater. We also discuss integrating our method with microfluidic devices to monitor complex wastewater samples. Our method can enable generalized pathogen detection and molecular recognition in complex liquid samples, such as wastewater, blood, and seawater.[1] Hellmér, et al. Applied and environmental microbiology. (2014).[2] Keshaviah, et al. The Lancet Global Health. (2023).[3] Jahn, et al. Nature Microbiology. (2022).[4] Tadesse, et al., Nano Lett. (2020).[5] Pethig. John Wiley & Sons (2010).[6] Ho, et al., Nat. Comm. (2019).

An Image Processing Approach to Quality Control of Drop-on-Demand Electrohydrodynamic (EHD) Printing.

Droplet quality in drop-on-demand (DoD) Electrohydrodynamic (EHD) inkjet printing plays a crucial role in influencing the overall performance and manufacturing quality of the operation. The current approach to droplet printing analysis involves manually outlining/labeling the printed dots on the substrate under a microscope and then using microscope software to estimate the dot sizes by assuming the dots have a standard circular shape. Therefore, it is prone to errors. Moreover, the dot spacing information is missing, which is also important for EHD DoD printing processes, such as manufacturing micro-arrays. In order to address these issues, the paper explores the application of feature extraction methods aimed at identifying characteristics of the printed droplets to enhance the detection, evaluation, and delineation of significant structures and edges in printed images. The proposed method involves three main stages: (1) image pre-processing, where edge detection techniques such as Canny filtering are applied for printed dot boundary detection; (2) contour detection, which is used to accurately quantify the dot sizes (such as dot perimeter and area); and (3) centroid detection and distance calculation, where the spacing between neighboring dots is quantified as the Euclidean distance of the dot geometric centers. These stages collectively improve the precision and efficiency of EHD DoD printing analysis in terms of dot size and spacing. Edge and contour detection strategies are implemented to minimize edge discrepancies and accurately delineate droplet perimeters for quality analysis, enhancing measurement precision. The proposed image processing approach was first tested using simulated EHD printed droplet arrays with specified dot sizes and spacing, and the achieved quantification accuracy was over 98% in analyzing dot size and spacing, highlighting the high precision of the proposed approach. This approach was further demonstrated through dot analysis of experimentally EHD-printed droplets, showing its superiority over conventional microscope-based measurements.

High-Resolution Total Internal Reflection-Based Structural Coloration by Electrohydrodynamic Jet Printing of Transparent Polyethylene Glycol Microdomes.

Total internal reflection (TIR)-based structural coloration is a brilliant strategy to overcome the need for periodic nanostructures and complex fabrication processes. Light entering the microdome structure undergoes TIR, and owing to varying reflection paths, it exhibits a color that changes with the microdome size. Although solution-based printing techniques have been proposed to achieve this effect, they fall short of full-color realization owing to resolution limitations. Herein, we achieved 3628 dpi of full-color and high-resolution structural color images by printing transparent microdome structures with 1.2-9.9 μm diameter using electrohydrodynamic (EHD) jet printing. Additionally, high-resolution EHD jet-printed structural color images display complex encoded information, enhancing the anticounterfeiting effectiveness through their fabrication simplicity and precise control over the microdome size. Because of these advantages, this TIR-based structural coloration technique with EHD jet printing is highly suitable for anticounterfeiting applications.

Effect of electrode arrangement on heat transfer enhancement by electrohydrodynamic conduction pumps in a rectangular channel

The present study investigates heat transfer enhancement by electrohydrodynamic (EHD) conduction pumps in a rectangular channel. The effect of electrode arrangement on flow and thermal performance of the rectangular channel by EHD conduction pumps are quantitatively discussed in terms of pressure drop and Nusselt number. The inlet laminar flow with Reynolds number ranging from 100 to 1000. The innovative point of this paper is validating the optimal electrode arrangement over a wider range of Reynolds numbers, the other one is investigating the impact of the number of electrodes on the heat transfer of the EHD conduction pump. The results show that compared to the arrangement of electrode pairs along the same side, electrode pairs arranged on the opposite side have a higher heat transfer capacity due to the stronger vortex strength and lower vortex temperature. For the above two arrangement methods, the heat transfer capacity can be significantly improved when the length of the high-voltage electrode is greater than that of the low-voltage electrode. This result is mainly due to the fact that the electric force enhances the vortex strength, which promotes the perturbation of the thermal boundary layer. The effect of the number of electrode pairs r on the heat transfer capacity is not monotonic. When r < 6, the heat transfer capacity increases with the increase of r due to the generation of more vortices. However, r > 6, as the number of electrode pairs increases, the heat transfer capacity decreases. This result is mainly due to the decrease in the area of the vortex and the increase in the temperature of the vortex.

High-density, high-frequency and large-scale electrohydrodynamic drop-on-demand jetting via a protruding polymer-based printhead design

Electrohydrodynamic (EHD) printing has critical merits in micro/nanoscale additive manufacturing because of its ultrahigh resolution and wide ink compatibility, making it an advantageous choice for electronics manufacturing, high-resolution prototyping, and biological component fabrication. However, EHD printing is currently limited by its rather low throughput due to the lack of high-frequency and high-density multi-nozzle printheads. This paper presents a novel EHD printhead with a protruding polymer-based nozzle design. An insulated, hydrophobic, and protruding polymer nozzle array with an appropriate geometric structure can effectively address key problems in multi-nozzle jetting, such as electrical crosstalk, electrical discharge, liquid flooding, and nonuniform jetting. By investigating the influence of the electrical and geometric characteristics of the nozzle arrays on the electrical crosstalk behavior and fabricating the optimized nozzle array via MEMS technology, we achieve an EHD printhead with a large scale (256), high density (127 dpi), and high jetting frequency (23 kHz), and addressable jetting can be realized by adding independently controllable extractors underneath the nozzle array. Many functional materials, such as quantum dots, perovskite, and nanosilver inks, can be ejected into high-resolution patterns through the optimized nozzle array, demonstrating the great prospects of our designed printhead in electronics manufacturing. This MEMS-compatible printhead design lays the foundation for high-throughput fabrication of micro/nanostructures and promotes practical applications of EHD printing in functional electronics and biomedical/energy devices.

On the electrohydrodynamic jet printing of two-dimensional material-based inks for printed electronics

Electrohydrodynamic (EHD) jet printing is a well-known advanced manufacturing technique that uses electric fields to generate and control fine jets of fluid for high-precision deposition of materials. This method enables the printing of extremely fine features, making it ideal for applications such as printed electronics. However, little is known about the optimal conditions for achieving consistent jet stability and droplet formation, especially when dealing with complex and volatile fluids laden with two-dimensional (2D) nanoparticles. In this work, we study the electrohydrodynamic printing process of 2D material-based inks using toluene as the main carrier fluid. Adding ethyl cellulose to toluene allows us to increase the stability of the suspensions and establish the steady cone-jet mode of electrospray. A small amount of ethanol increases the fluid conductivity, stabilizing the steady cone-jet mode and reducing the jet diameter. The inks behave as leaky-dielectric, weakly viscoelastic liquids. For this reason, the jet diameter and minimum flow rate obey the scaling laws for electrospray of Newtonian liquids. We determine the optimal parameter conditions for the EHD printing of our inks directly onto a non-conductive substrate. The influence of the substrate's velocity on the width of the printed lines is analyzed. These findings enlarge the knowledge about how to increase the throughput in the EHD jet printing process while controlling the resolution of the printed lines when using volatile solvents, 2D nanomaterials, and non-conductive substrates.

Synthetic Protein Nanoparticles via Photoreactive Electrohydrodynamic Jetting.

Protein nanoparticles are an attractive class of materials for nanomedicine applications due to the intrinsic biocompatibility, biodegradability, and intrinsic functionality of their constituent proteins. Despite the clinical success of select protein nanoparticles, this class of nanocarriers remains understudied and underdeveloped compared to lipid and polymer nanoparticles due to challenges related to formulation optimization, large design space, and their structural complexity. In this work, a modular strategy for protein nanoparticle preparation based on the concept of photoreactive jetting is introduced. The process relies on continuous ultravioletirradiation during electrohydrodynamic (EHD) jetting of protein solutions that contain a homobifunctional photocrosslinker. Protein nanoparticles exhibit nanogel-like architectures comprised of proteins that are linked via synthetic moieties. Compared to conventional protein nanoparticles, this method reduces nanoparticle processing times to minutes, rather than hours to days. The inclusion of an emissive structural motif as the molecular scaffold of the photocrosslinker is used to study the supramolecular architecture of the stable nanoparticles via time-resolved fluorescence spectroscopy.