Suction-based in vivo cutaneous DNA transfection is a newly developed, cost-effective method that produces high transfection efficiency. This method has shown robust immunogenic responses following SARS-CoV-2 DNA vaccination in both pre-clinical studies and clinical trials. The current work investigates suction-based transfection and immune activation on a detailed, cellular level. The spatiotemporal patterns of antigen expression in rat skin following suction-induced delivery of a pEGFP-N1 plasmid and a SARS-CoV-2 DNA vaccine are evaluated via immunofluorescence staining, which demonstrates early and prolonged expression. The epidermis is identified as the primary location of transfection, and the transfected cells are primarily epidermal keratinocytes. Early immune response is assessed by detection of major histocompatibility complex class II-positive (MHC-II + ) cells following suction-induced DNA vaccination.

Semiflexible polymers are ubiquitous in natural and artificial systems, where their intermediate rigidity gives rise to rich structural and dynamical behavior. Confinement plays a central role in these behaviors, as spatial restrictions can promote chain alignment, induce structural rearrangements, and enable complex self-assembly. While the organization of semiflexible polymers under rigid confinement has been extensively investigated, their behavior within deformable and dynamically evolving microenvironments, such as drying droplets or intracellular compartments, remains poorly understood. In this study, we use dissipative particle dynamics simulations to investigate the self-assembly of crowded semiflexible polymers confined within a deformable droplet, whose size may also change over time. By systematically varying the polymer contour length, concentration, and degree of confinement, we identify distinct assembly regimes. Increasing polymer concentration promotes the formation of ordered fibrillar domains, with orientational alignment strongest near the droplet interface. Chain length critically dictates the morphology of assembled structures: short chains remain largely disordered, chains with intermediate lengths form linear fibrillar structures with maximal nematic order, and long chains assemble into circular bundles. Dynamic confinement further modulates the assembly through the competition between the rate of confinement change and the polymer mobility. A slow increase in the degree of confinement allows polymers to reorganize into highly ordered structures, while rapid crowding kinetically traps the system in disordered states. Our findings elucidate how polymer mechanics and time-dependent confinement jointly govern the organization of semiflexible polymers in deformable, dynamic, and crowded environments.

Macropore-infused nanocomposite emulsion thermosets (MINETs) offer a novel approach for multifunctional monoliths and carbon fiber composites (CFCs), leveraging tunable porosity and material compatibility to meet the demands of aerospace and energy applications. Using 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) and a propylene glycol-ionic liquid (IL) triblock copolymer surfactant, we successfully stabilized an epoxy-IL emulsion with compatibility with particles such as silica, super-activated carbon (SAC), and graphene. Optimal surfactant levels (5.11% for SAC and graphene and 3.46% for silica) facilitated continuous IL phases, enhancing porosity and ionic conductivity, as confirmed by mass loss, mercury porosimetry, and ionic conductivity analyses. SEM revealed well-defined nanostructures, while resin content adjustments highlighted a balance between mechanical integrity and conductivity. These advancements provide a strong foundation for integrating IL-MINETs into multifunctional composites for structural power storage and flame-resistant materials, with significant potential in aerospace and renewable energy systems. Ongoing work focuses on fluorinated IL surfactants to enhance conductivity and stability for advanced multifunctional designs.

The self-limiting regime of electrospray deposition (SLED) is a highly adaptable means to coat complex 3D architectures and 2D templated surfaces. There are, however, drawbacks to this approach, including that (1) SLED coatings cannot be applied in multiple layers and (2) the generally-micron-scale thickness of SLED coatings is determined by the material and spray parameters, preventing nanoscale coatings such as those possible by atomic layer deposition or spin coating. This latter limitation can be circumvented by applying a secondary bias to the spray target, which reduces the SLED thickness and increases uniformity. Here, we demonstrate that the stepwise removal of bias can in turn result in the stepwise increase of the SLED thickness. We thereby demonstrate (i) trilayer polystyrene stacks with bias-controlled thickness, (ii) uniform trilayer coatings on a complex geometry, and (iii) mechanically robust nanocomposite using thermal capillary rise infiltration (CaRI) of electrosprayed bilayer films.

Electrospray deposition applies thin films to conductive or hydrated targets, but not insulators, due to charge repulsion. Pretreatment of coating insulating substrates with the use of removable ionogel thin films 100-800 nm produces (self-limiting) electrospray deposition coatings of similar thicknesses to those produced on conductive surfaces, independent of humidity.

The self‐limiting regime of electrospray deposition (SLED) is a highly adaptable means to coat complex 3D architectures and 2D templated surfaces. There are, however, drawbacks to this approach, including that (1) SLED coatings cannot be applied in multiple layers and (2) the generally micron‐scale thickness of SLED coatings is determined by the material and spray parameters, preventing nanoscale coatings such as those possible by atomic layer deposition or spin coating. This latter limitation can be circumvented by applying a secondary bias to the spray target, which reduces the SLED thickness and increases uniformity. Here, we demonstrate that the stepwise removal of bias can, in turn, result in the stepwise increase of the SLED thickness. We thereby demonstrate (i) tri‐layer polystyrene stacks with bias‐controlled thickness, (ii) uniform tri‐layer coatings on a complex geometry, and (iii) a mechanically robust nanocomposite using thermal capillary rise infiltration (CaRI) of electrosprayed bilayer films.

In electrospray deposition (ESD), a high voltage atomizes a flowing solution into charged microdroplets. The self-repulsive droplets evaporate as they approach the target grounded substrate, depositing the solids and carried charge. In the self-limiting electrospray deposition (SLED) regime, manipulation of the electrostatic repulsion, hydrodynamic forces, and evaporation kinetics results in the accumulation of deposited charge and conformal coating complex 2D and 3D architectures. This is a useful property for a wide range of coatings; however, SLED has previously only been achieved for a narrow range of insulating materials. Here, we hypothesize that SLED is only possible when (1) the arriving charged solvent is rendered immobile either through absorption into the free volume of an amorphous solute or the open pores/surface of a dispersant, and (2) the solvent itself is not capable of ionic dissipation (e.g., water). In alternate regimes of ESD, the charge prevents solvent evaporation and there exists a resulting mobile phase capable of dissipating charge, which is either a supercooled liquid blend of solute and solvent or a solvent rich phase ejected from a drying crystal forming molecule or particle dispersion. Using in situ X-ray scattering measurements, optical microscopy, and electrostatic voltammetry, we related the electrospray behavior of a material to its crystallization throughout the course of the spray. We also demonstrate how combining supercooled liquids and particulate dispersions can also result in SLED sprays, which can occur intrinsically for semi-crystalline polymers. Our results provide a template for finding and achieving SLED over a wide range of particles and small molecules to create functional, conformal coatings.

Self-limiting electrospray deposition (SLED) enables conformal coatings by allowing surface charge buildup to reshape local electric fields, redirecting spray toward uncoated regions. This requires droplets to travel noninertially, so they respond to near-field electric changes, which break down at high flow rates when droplet inertia dominates. Here, we demonstrate that high-flow emitters maintain SLED behavior up to similar to 5 mL/h per tip, an order of magnitude increase in throughput, producing uniform similar to 4-5 mu m PMMA films and conformal coatings on 3D objects. Beyond this, anisotropic deposition arises due to high Stokes numbers. Applying a same-polarity secondary bias softens droplet landing, mitigating inertial overdeposition and restoring uniform deposition at rates up to 12 mL/h. Simulations further show that increased air pressure can achieve similar effects. These results frame SLED as a Stokes-number-dependent regime and offer a scalable strategy to extend conformal electrospray coatings to large areas, complex geometries, and industrially relevant throughputs.

Carbon fiber composites (CFC) are distinguished by their remarkable strength-to-weight ratio, rendering them exceptionally suitable for various applications. This study explores replacing the conventional polymer epoxy matrix in CFCs with macropore-infused graphene nanocomposite emulsion thermosets (MINETs) based on easily sourced materials. The explored MINETs are formed from epoxy resin, graphene particles, and different oils as working fluids. This approach allows CFCs to exhibit multifunctional properties, including enhanced thermal conductivity and flame resistance, making them ideal for fire-proof drone enclosures, electronic casings, and thermal-energy-storage equipment applications. The thermal conductivity was further increased by adding carbon nanotubes (CNT) to the MINET matrix. The rheological properties of MINET allowed for CNT loading concurrently alongside graphene, without preventing processing. Rheological evaluations and Vickers hardness assessments were conducted to optimize the maximum CNT loading for efficient molding and robust mechanical properties. Thermal conductivity analysis demonstrated that CNT-reinforced MINET composites have a higher thermal conductivity when compared to standard graphene-MINET formulations. Infrared thermal imaging confirmed that CFC MINET composites have better dynamic heat transfer properties than CFC epoxy samples. Flammability tests indicated an improved flame resistance, particularly for silicone oil CFC MINET CNT formulations. The results indicate that CNT-infused CFC MINET exhibits exceptional thermal management and enhanced fire resistance co-optimized with mechanical properties, thus rendering it ideal for high heat dissipation, thermal stability, and flame retardancy.

Electrospray deposition (ESD) is a spraying process which utilizes a high voltage emitter to create monodisperse, micron scale droplets. These droplets carry a charge and are highly influenced by the force of the electric field which directs them towards a grounded target. As the droplets contact the grounded surface they deposit their charge, generating a nanoamp current in the process. ESD can take place in one of a few distinct spray modes: dripping, micro-dripping, cone-jet, and multijet. Although there are several factors that determine spray mode, we chose to utilize applied voltage as a means of controlling spray mode. Our application leverages ESD, specifically the cone-jet spray mode, as a means of efficient nutrient delivery to plants. As a part of this project, we have automated the spraying process by monitoring the nanoamp ground current. Specifically, we developed a Python program that analyzes the current signal in discrete time intervals and calculates key statistics such as mean, median, and standard deviation as well as the Fast Fourier Transform of the signal. Based on this information, the program autonomously determines which applied voltage will result in a stable cone-jet spray mode.

Microneedle arrays have been shown to be a minimally invasive method of transdermal drug delivery. However, methods to coat these arrays often require a reservoir of the active ingredient, leading to unused and wasted material. Electrospray deposition is a targeted coating method that offers a competitive alternative for coating microneedles. By architecting the charge landscape of the setup, this technology can achieve coating deposition efficiencies nearing 100%, with little to no material wasted during the coating process. A Middle East respiratory syndrome coronavirus DNA vaccine was used as the model material to assess deposition efficiency as well as the efficacy of fragile biological materials subjected to electrospray deposition. Trehalose and polystyrene-block-polyacrylic acid were used as excipients to encourage coating dispersion. These coatings were inserted into Sprague Dawley rats where the antigen was subsequently detected and located using immunohistochemistry. Both coatings, with and without excipients, showed that protein expression is achieved after the vaccine is subjected to electrospray, however, the presence of excipients qualitatively leads to a more disperse diffusion profile. Further, this work demonstrates the capability of electrospray deposition as a highly efficient method to coat microneedles for transdermal drug delivery.

Traditional approaches to bone healing are limited by factors such as donor availability, immune system rejection, and risk of infection. As a result, cheaper and biodegradable synthetic alternatives are required. This study investigates the use of macropore-infused nanocomposite emulsion thermosets (MINETs) to create a novel bone scaffold. MINETs are formulated using hydrogels and hydroxyapatite to mimic the architecture and chemical content of a porous bone, offering structural stability and supporting recovery with the benefit of biodegradability. According to mass loss tests, Fourier transform infrared spectroscopy, dynamic mechanical analysis, and scanning electron microscopy, agarose- and albumin-based gels formed stable porous structures with the potential to act as bone implants.

The vibrational response of epoxy-A is evaluated as a function of a mixture of boron nitride nanotubes and hexagonal boron nitride (BNNT/h-BN) concentration and aging. This study pursues neat resin and resin with BNNT/h-BN of different concentrations 0.1/0.24 and 0.5/1.21 wt.%. Cantilever beam specimens are excited in agreement with ASTM E756-05 from low 100 Hz to 500 Hz frequencies by an automated electromagnetic shaker using a sine frequency input from a waveform generator. From this testing, the second and third resonant modes of the materials are obtained and analyzed using contactless laser position sensors. This analysis obtains the output over input in the form of compliance, and material properties such as the loss factor and Young's modulus are also obtained. The results show that the epoxy-A resin has remarkable properties for strength and dampening. The addition of nanofiller at the 0.1/0.24 concentration presented several reductions of properties due to its propensity to produce voids and a lack of interconnectivity of constrained regions. Despite this, the 0.1/0.24 concentration could still preserve the material during aging and continued testing. The nanofiller concentration of 0.5/1.21 increased Young's modulus in the sample and, after aging, showed an increase in both the loss factor and Young's modulus, which is a remarkable finding. It is theorized that the increase in BNNT allowed a synergistic effect in BNNT/h-BN interactions with the polymer, and the slightly hydrophilic properties of h-BN assisted in enhancing the interconnection between filler and matrix. This is further evidenced by the distinct reduction of bubble content in the 0.5/1.21 mix.

Abstract Electrospray deposition (ESD) is a technique with emerging relevance for applications requiring micro‐/nano‐scaled coatings. Self‐limiting electrospray deposition (SLED) is a regime of ESD where upon satisfying the criteria for self‐limiting behavior, the charge buildup of the material will eventually begin to repel itself until an asymptotic thickness is achieved, based primarily on the properties of the spray solution and deposited material. This work focuses on controlling the coating thickness further to achieve sub‐micron thicknesses. By applying a voltage bias of the same polarity of the spray onto the target substrate while providing a secondary grounded surface, the thickness of a payload can be manipulated for thinner and more precise thicknesses. The magnitude of the voltage bias is varied to show the effect of voltage bias on thickness, and 2‐D and 3‐D structures are used to demonstrate the generality of this technique for complex substrates. The results show how SLED can be included as a potential alternative for conformal coatings deposited at ambient conditions at the sub‐micron scale.

Electrospray deposition (ESD) was utilized for targeted nutrient and water delivery to the roots of lettuce plants. Compatibility of ESD with nutrient solutions was confirmed; however, detrimental effects of ESD electric fields/current on plant growth were observed. To overcome this, a novel approach called “Staticaponics" was introduced by separating current and mass transport of ESD using a grounded metal mesh surrounding the root zone. This combination of ESD along with aeroponic and hydroponic concepts was shown to have higher nutrient solution use efficiency than either hydroponic or aeroponic growth alone, with acceptable plant nutrient content in the resulting plant tissue.

AbstractMultilayer polymer films are extensively used in multiphase separation. Electrospray deposition (ESD) is an important technique for fabricating such films with tunable morphology. Viscoelastic properties of polystyrene (PS) nanoshell coatings produced by ESD on gold and spin‐coated PS surfaces are evaluated using Quartz Crystal Microbalance with Dissipation (QCM‐D). The thickness of PS films on gold increases with flow rate from ∼200 nm at 0.5 to ∼400 nm at 1.5 mL h−1, accompanied by an order‐of‐magnitude increase in dissipation due to larger particle sizes from shorter droplet flight times. This effect is absent on spin–coated PS films, suggesting the onset of the self‐limiting effect of charges. Although the shear moduli for ESD films calculated from Voigt models is only 0.08%–0.20% of the bulk PS modulus, the stiffness ratio of spray‐coated PS to a single shell is (5.00–13.3) × 103 m−1, due to shell–shell and shell–substrate interactions. These are novel results related to the interparticle friction obtained using QCM‐D for the first time. This work demonstrates that mechanical properties of particulate viscoelastic films with potential applications in high surface area sensors, such as size‐selective membranes for protein or electrolyte adsorption, can be evalauted by QCM‐D with nanograms of material.

AbstractBy combining sacrificial nanoimprint lithography (SNIL) and transfer printing, sacrificial nanotransfer (SNT) lithography can create metalized polymer surfaces that enable lightweight conductive surface composites. SNT begins with a metal mold made from a high surface finish metal possessing high resistance to intermetallic alloying. A thin metallic transfer layer is then electroplated onto the mold by selecting a material unlikely to alloy with the surface. The selected nanomaterial, zinc oxide (ZnO), is grown on the top layer of the plated metallic transfer layer via a seedless hydrothermal approach used to synthesize high‐quality ZnO nanowire arrays. A resin material or laminate is cured in contact with the ZnO nanostructures, such that the ZnO nanorods are embedded onto the top layer of the resin. The embedded nanomaterials provide a larger surface area than the weak transfer layer‐mold interface. As a result, when the final component is removed from the mold, the metallic multilayer is transferred with it. The final metalized polymeric surface resembles the same surface finish as the starting mold, with an exposed metal layer and a durable interface. In this study, the importance of nanomaterial morphology and the selection of metal layers are explored to obtain high‐quality final transfers.

Cutaneous suction-based transfection is a recently developed technique that is painless and simple-to-use for the delivery of DNA for nucleic-acid-based vaccines. The technique promises high efficiency for both antigen expression and immunogenicity as demonstrated in both animal studies and human clinical trials. To realize this promise, a parametric study and systematic evaluation on the efficacy of cutaneous suction as a transfection method was performed. Using Green Fluorescent Protein (GFP) plasmid expression as a transfection reporter in a rat model, the expression level as a function of both suction nozzle size and suction pressure was quantified. A numerical model was employed to compute skin deformation in terms of strain, which was used to correlate with GFP expression. Based on these results, two quantities, total integrated strain and tissue tension, are proposed as indicators of expression level that can be used to guide protocol development and optimization. These indicators are also discussed in relation to possible cellular uptake mechanisms.