Ab initio modeling and experimental analysis of electronic conductivity in PEDOT:PSS-PEO films for extrusion-based manufacturing.

In this study, a combination of ab initio modeling and experimental analysis is presented to investigate and elucidate the electronic conductivity of films composed of conducting polymer blend PEDOT:PSS-PEO. Detailed density functional theory (DFT) calculations, aligned with experimental data, aided at profound understanding of the chemical composition, band structure, and the mechanical behavior of these composite materials. Systematic evaluation across diverse ratios of PEDOT, PSS, and PEO revealed a pronounced transformation in electronic properties. Specifically, the addition of PEO into the polymer matrix remarkably changes the band gap, with a marked alteration observed near a PEO concentration of 52 wt-%. This adjustment led to a substantial enhancement in the electrical conductivity, exhibiting an increase by a factor of approximately 20, compared to the original PEDOT:PSS polymer. The present investigation determined the crucial role of the PEDOT to PSS ratio in band gap determination, emphasizing its significant impact on the material's electrical conductivity. Concurrently, the mechanical property analysis unveiled a consistent increase in Young's modulus, reaching up to 765.93 MPa with increased PEO content, signifying a notable mechanical stiffening of the blend. The obtained combined theoretical and experimental insights illustrate a detailed perspective on the conductivity anomalies observed in PEDOT:PSS-PEO systems, establishing a robust framework for designing highly conducting and mechanically stable polymer blends. This comprehensive approach elucidates the interplay between chemical composition and electronic behavior, offering a strategic pathway for extrusion-based manufacturing techniques such as Direct Ink Writing (DIW).

Electro-Thermopneumatically Actuated, Adhesion-Force Controllable Octopus-Like Suction Cup Actuator.

A light-weight actuator developed in this work belongs to a class of soft robots, and in a sense, resembles an octopus. Its main function is in the attachment or detachment to a solid surface driven by an electro-thermopneumatic mechanism. In this study, a suction cup similar to that of an octopus is manufactured from an elastomer, which is actuated by an electro-thermopneumatic system, mimicking the movement of the octopus' acetabular muscle. Accordingly, the adhesion force generated by such an actuator is regulated by releasing the inner air or adjusting the cup's elasticity. This actuator is designed to be an assistive device that facilitates the individual's physical strength in case of conditions related to aging or cerebellar disease, or a person who lost limbs. In this study, the actuator capabilities are demonstrated in the form of a grip-assisting glove and prosthetic attacher. Moreover, the adhesion mechanism is quantified by numerical simulations and verified experimentally.

Multimetallic glycerolate as a precursor template of spherical porous high-entropy oxide microparticles.

High-entropy materials have received notable attention concern on account of their unique structure, tunable properties, and unprecedented potential applications in many fields. In this work, for the first time a NiCoMnZnMg-containing high-entropy glycerolate (HE-Gly) particles has been synthesized using a scalable solvothermal method. The HE-Gly particles were used as a precursor in design of porous high-entropy oxide (HEO) microparticles. The morphological and structural characterizations demonstrate that the temperature of the annealing process, and the composition of the metal ions in the HE-Gly precursors play important roles in determining porosity, crystallinity, and phase separation in HEOs. In fact, HE-Gly exhibited a porous structure of spinel HEOs with secreted MgO phase after annealing process at 800 °C, while the annealing process at 400 °C led to a low-crystallinity spinel phase without phase segregation. Overall, this work describes HE-Gly as a new precursor for altering the composition, crystallinity, and porosity of HEOs. This strategy is scalable for potential high mass productions, paving a new path toward industrial application of high-entropy materials.

Nanotextured Soft Electrothermo-Pneumatic Actuator for Constructing Lightweight, Integrated, and Untethered Soft Robotics.

In this study, we fabricated a nanofiber-based electrothermo-pneumatic soft actuator (ETPSA) using electrospinning technique. The actuator uses liquid-vapor phase transition. The ETPSA developed in the present study goes beyond the limitations of the existing pneumatic soft actuators. The present ETPSA has a built-in source of heat (Joule heating from an embedded metal wire) and allows the smooth anthropomorphic movement of the actuator and, in particular, eliminates the use of external pumping systems that are indispensable in the existing pneumatic soft actuators and robots. In addition, since the present ETPSA can be operated effectively even using a portable miniature battery, it holds great promise as an adaptable soft actuator for various robotic applications with high energy efficiency and programmable motions.

Evolution and Shape of Two-Dimensional Stokesian Drops under the Action of Surface Tension and Electric Field: Linear and Nonlinear Theory and Experiment.

The creeping-flow theory describing evolution and steady-state shape of two-dimensional ionic-conductor drops under the action of surface tension and the subcritical (in terms of the electric Bond number) electric field imposed in the substrate plane is developed. On the other hand, the experimental data are acquired for drops impacted or softly deposited on dielectric surfaces of different wettability and subjected to an in-plane subcritical electric field. Even though the experimental situation involves viscous friction of drops with the substrates and wettability-driven motion of the contact line, the comparison to the theory reveals that it can accurately describe the steady-state drop shape on a non-wettable substrate. In the latter case, the drop is sufficiently raised above the substrate, which diminishes the three-dimensional effects, making the two-dimensional description (lacking the no-slip condition at the substrate and wettability-driven motion of the contact line) relevant. Accordingly, it is demonstrated how the subcritical electric field deforms the initially circular drops until an elongated steady-state configuration is reached. In particular, the surface tension tends to round off the non-circular drops stretched by the electric Maxwell stresses imposed by the electrodes. A more pronounced substrate wettability leads to more elongated steady-state configurations observed experimentally than those predicted by the two-dimensional theory. The latter cases reveal significant three-dimensional effects in the electrically driven drop stretching. In the supercritical electric fields (corresponding to the supercritical electric Bond numbers), the electrical stretching of drops predicted by the present linearized two-dimensional theory results in splitting into two separate droplets. This scenario is corroborated by the predictions of the fully nonlinear results for similar electrically stretched bubbles in the creeping-flow regime available in the literature as well as by the present experimental results on a substrate with slip.

Solution-Blown Poly(hydroxybutyrate) and ε-Poly-l-lysine Submicro- and Microfiber-Based Sustainable Nonwovens with Antimicrobial Activity for Single-Use Applications.

Antimicrobial nonwovens for single use applications (e.g., diapers, sanitary napkins, medical gauze, etc.) are of utmost importance as the first line of defense against bacterial infections. However, the utilization of petrochemical nondegradable polymers in such nonwovens creates sustainability-related issues. Here, sustainable poly(hydroxybutyrate) (PHB) and ε-poly-l-lysine (ε-PLL) submicro- and microfiber-based antimicrobial nonwovens produced by a novel industrially scalable process, solution blowing, have been proposed. In such nonwovens, ε-PLL acts as an active material. In particular, it was found that most of ε-PLL is released within the first hour of deployment, as is desirable for the applications of interest. The submicro- and microfiber mat was tested against C. albicans and E. coli, and it was found that ε-PLL-releasing microfibers result in a significant reduction of bacterial colonies. It was also found that ε-PLL-releasing antimicrobial submicro- and microfiber nonwovens are safe for human cells in fibroblast culture. Mechanical characterization of these nonwovens revealed that, even though they are felt as soft and malleable, they possess sufficient strength, which is desirable in the end-user applications.

Computer simulation of the SARS-CoV-2 contamination risk in a large dental clinic.

COVID-19, caused by the SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) virus, has been rapidly spreading worldwide since December 2019, causing a public health crisis. Recent studies showed SARS-CoV-2's ability to infect humans via airborne routes. These motivated the study of aerosol and airborne droplet transmission in a variety of settings. This study performs a large-scale numerical simulation of a real-world dentistry clinic that contains aerosol-generating procedures. The simulation tracks the dispersion of evaporating droplets emitted during ultrasonic dental scaling procedures. The simulation considers 25 patient treatment cubicles in an open plan dentistry clinic. The droplets are modeled as having a volatile (evaporating) and nonvolatile fraction composed of virions, saliva, and impurities from the irrigant water supply. The simulated clinic's boundary and flow conditions are validated against experimental measurements of the real clinic. The results evaluate the behavior of large droplets and aerosols. We investigate droplet residence time and travel distance for different droplet diameters, surface contamination due to droplet settling and deposition, airborne aerosol mass concentration, and the quantity of droplets that escape through ventilation. The simulation results raise concerns due to the aerosols' long residence times (averaging up to 7.31 min) and travel distances (averaging up to 24.45 m) that exceed social distancing guidelines. Finally, the results show that contamination extends beyond the immediate patient treatment areas, requiring additional surface disinfection in the clinic. The results presented in this research may be used to establish safer dental clinic operating procedures, especially if paired with future supplementary material concerning the aerosol viral load generated by ultrasonic scaling and the viral load thresholds required to infect humans.

Supersonically Sprayed Washable, Wearable, Stretchable, Hydrophobic, and Antibacterial rGO/AgNW Fabric for Multifunctional Sensors and Supercapacitors.

Wearable electronic textiles are used in sensors, energy-harvesting devices, healthcare monitoring, human-machine interfaces, and soft robotics to acquire real-time big data for machine learning and artificial intelligence. Wearability is essential while collecting data from a human, who should be able to wear the device with sufficient comfort. In this study, reduced graphene oxide (rGO) and silver nanowires (AgNWs) were supersonically sprayed onto a fabric to ensure good adhesiveness, resulting in a washable, stretchable, and wearable fabric without affecting the performance of the designed features. This rGO/AgNW-decorated fabric can be used to monitor external stimuli such as strain and temperature. In addition, it is used as a heater and as a supercapacitor and features an antibacterial hydrophobic surface that minimizes potential infection from external airborne viruses or virus-containing droplets. Herein, the wearability, stretchability, washability, mechanical durability, temperature-sensing capability, heating ability, wettability, and antibacterial features of this metallized fabric are explored. This multifunctionality is achieved in a single fabric coated with rGO/AgNWs via supersonic spraying.

Reusable Filters Augmented with Heating Microfibers for Antibacterial and Antiviral Sterilization.

Numerous threats to human health and ecosystems on earth exist due to air pollution and the spread of fatal diseases. Airborne pollutants and particulate matter (PM) pose serious public health risks. In addition, the emergence and spread of bacterial and viral diseases constantly threaten public health and safety. Although various approaches have been implemented thus far to protect humans from air pollution and exposure to diseases, several challenges remain to be addressed. In this study, we developed a hybrid air filter consisting of filtration, heating, and thermal insulation layers. The air filtration layer can effectively capture airborne PM1 particles (less than 1.0 µm in diameter). Furthermore, the heating layer enables the hybrid air filter to generate temperatures above 100 °C, and the insulation layer prevents the heat from being transferred to the other side (e.g., the human skin, if the hybrid air filter is used in a facemask). Since several bacteria and viruses are incapacitated under high temperatures, this hybrid air filter holds great promise for antibacterial and antiviral protection.

Performance Enhancement of Soft Nanotextured Thermopneumatic Actuator by Incorporating Silver Nanowires into Elastomer Body.

To improve performance of thermopneumatic soft actuators, which have recently been developed for various industrial applications, we embedded different nanoscale materials into their elastomer bodies. This yields a significant enhancement in the actuator performance via improving the mechanical and thermal properties of the elastomer bodies. In addition, the use of nanoinclusions diminished losses of the working fluid from the actuators by decreasing vapor leaks through the elastomer body and thus improving longevity. Notably, when using different working fluids with low boiling temperatures, the operating temperature range of the actuators can be lowered and widened. The hybrid approach proposed in this study is expected to advance the industrial feasibility of thermopneumatic actuators.

Multifunctional Platform Based on Electrospun Nanofibers and Plasmonic Hydrogel: A Smart Nanostructured Pillow for Near-Infrared Light-Driven Biomedical Applications.

Multifunctional nanomaterials with the ability to respond to near-infrared (NIR) light stimulation are vital for the development of highly efficient biomedical nanoplatforms with a polytherapeutic approach. Inspired by the mesoglea structure of jellyfish bells, a biomimetic multifunctional nanostructured pillow with fast photothermal responsiveness for NIR light-controlled on-demand drug delivery is developed. We fabricate a nanoplatform with several hierarchical levels designed to generate a series of controlled, rapid, and reversible cascade-like structural changes upon NIR light irradiation. The mechanical contraction of the nanostructured platform, resulting from the increase of temperature to 42 °C due to plasmonic hydrogel-light interaction, causes a rapid expulsion of water from the inner structure, passing through an electrospun membrane anchored onto the hydrogel core. The mutual effects of the rise in temperature and water flow stimulate the release of molecules from the nanofibers. To expand the potential applications of the biomimetic platform, the photothermal responsiveness to reach the typical temperature level for performing photothermal therapy (PTT) is designed. The on-demand drug model penetration into pig tissue demonstrates the efficiency of the nanostructured platform in the rapid and controlled release of molecules, while the high biocompatibility confirms the pillow potential for biomedical applications based on the NIR light-driven multitherapy strategy.

Reopening dentistry after COVID-19: Complete suppression of aerosolization in dental procedures by viscoelastic Medusa Gorgo.

The aerosol transmissibility of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has impacted the delivery of health care and essentially stopped the provision of medical and dental therapies. Dentistry uses rotary, ultrasonic, and laser-based instruments that produce water-based aerosols in the daily, routine treatment of patients. Abundant aerosols are generated, which reach health care workers and other patients. Viruses, including SARS-CoV-2 virus and related coronavirus disease (COVID-19) pandemic, continued expansion throughout the USA and the world. The virus is spread by both droplet (visible drops) and aerosol (practically invisible drops) transmission. The generation of aerosols in dentistry-an unavoidable part of most dental treatments-creates a high-risk situation. The US Centers for Disease Control and The Occupational Safety and Health Administration consider dental procedures to be of "highest risk" in the potential spreading of SARS-CoV-2 and other respiratory viruses. There are several ways to reduce or eliminate the virus: (i) cease or postpone dentistry (public and personal health risk), (ii) screen patients immediately prior to dental treatment (by appropriate testing, if any), (iii) block/remove the virus containing aerosol by engineering controls together with stringent personal protective equipment use. The present work takes a novel, fourth approach. By altering the physical response of water to the rotary or ultrasonic forces that are used in dentistry, the generation of aerosol particles and the distance any aerosol may spread beyond the point of generation can be markedly suppressed or completely eliminated in comparison to water for both the ultrasonic scaler and dental handpiece.

Transparent Metallized Microfibers as Recyclable Electrostatic Air Filters with Ionization.

Air-quality control remains a major environmental concern as polluted air is a threat to public safety and health in major industrialized cities. To filter pollutants, fibrous filters employing electrostatic attraction have been widely used. However, such air filters suffer from some major disadvantages, including low recyclability and a significant pressure drop owing to clogging and a high packing density. Herein, we developed ionization-assisted electrostatic air filters consisting of nonwoven nanofibers. Ionization of particulate matter (PM) using air ionization enhanced the electrostatic attraction, thereby promoting efficient filtration. Metallization of the fibers facilitated strong electrical attraction and the consequent capture of PM of various sizes. The low packing density of the metallized fibers also facilitated efficient filtration of the PM, even at low driving pressures, which in turn reduced the energy consumption of the air-filtration device.

Mutual Sliding Motion of Wrapped Filaments for Biomedical and Engineering Applications.

Here we aim at understanding and modeling of macroscopic interactions and sliding motion of curved filaments during muscles' isometric action in which tension is developed without overall contraction. A generic dynamic model of a curved elastic filament undergoing sliding, twisting, and unraveling around a cylindrical filament affected by the interfilament friction force is developed in full detail. In particular, the dynamic equations describing the general sliding motion of a curved filament wrapped around a cylindrical filament and pulled by a constant force applied to a free end are derived and solved numerically; the other end of the curved filament is considered to be fixed at the cylindrical one. The model predicts propagation of an elastic wave over the wrapped filament determined by the filament stiffness and the interfilament friction. The wrapped filament deformation and its ultimate arrest are predicted, and the final configurations of such filaments are revealed. Accordingly, the wrapped filament strain is predicted as a function of time for different values of the friction coefficient. The potential applications and possible biomechanical links of the proposed generic model are also discussed.

Transparent Body-Attachable Multifunctional Pressure, Thermal, and Proximity Sensor and Heater.

A multifunctional sensor capable of simultaneous sensing of temperature, pressure, and proximity has been developed. This transparent and body-attachable device is also capable of providing heat under low voltage. The multi-sensor consists of metal fibers fabricated by electrospinning and electroplating. The device comprises randomly deposited metal fibers, which not only provide heating but also perform as thermal and proximity sensors, and orderly aligned metal fibers that act as a pressure sensor. The sensor is fabricated by weaving straight rectangular electrodes on a transparent substrate (a matrix). The sensitivity is readily enhanced by installing numerous matrices that facilitate higher sensing resolution. The convective heat transfer coefficient of the heater is h = 0.014 W·cm-2·°C-1. The temperature coefficient of resistivity (TCR) and pressure sensitivity (ηP) are 0.038 °C-1 and 5.3 × 10-3 kPa-1, respectively. The superior sensitivity of the device is confirmed via quantitative comparison with similar devices. This multifunctional device also has a superior convective heat transfer coefficient than do other heaters reported in the literature.

Solution Blowing Synthesis of Li-Conductive Ceramic Nanofibers.

Solid state electrolytes (SSEs) offer great potential to enable high-performance and safe lithium (Li) batteries. However, the scale-up synthesis and processing of SSEs is a major challenge. In this work, three-dimensional networks of lithium lanthanum titanite (LLTO) nanofibers are produced through a scale-up technique based on solution blowing. Compared with the conventional electrospinning method, the solution blowing technique enables high-speed fabrication of SSEs (e.g., 15 times faster) with superior productivity and quality. Additionally, the room-temperature ionic conductivity of composite polymer electrolytes (CPEs) formed from solution-blown LLTO fibers is 70% higher than the ones formed from electrospun fibers (1.9 × 10 -4 vs 1.1 × 10-4 S cm-1 for 10 wt % LLTO fibers). Furthermore, the cyclability of the CPEs made from solution-blown fibers in the symmetric Li cell is more than 2.5 times that of the CPEs made from electrospun fibers. These comparisons show that solution-blown ion-conductive fibers hold great promise for applications in Li metal batteries.

In vitro evaluation of Pt-coated electrospun nanofibers for endovascular coil embolization.

Recently, endovascular coil embolization has been introduced to treat intracranial aneurysms because it has lower morbidity and mortality than surgical clipping. The endovascular coils prevent the extravasation of blood by decreasing the permeability of an aneurysm flow governed by Darcy's law. Here, we developed and explored Pt-coated micro-ropes for potential use as endovascular coils. Electrospinning with subsequent electroplating were employed to fabricate Pt-coated nanofibers, which were tightly twisted to form micro-ropes. The compatibility of Pt micro-ropes with commercial delivery catheters was verified and their performance was experimentally explored in an in vitro experimental model. The developed Pt-coated micro-ropes demonstrated feasibility as efficient and low-cost endovascular coils. STATEMENT OF SIGNIFICANCE: The use of Platinum (Pt)-coated polymer nanofibers to prevent blood extravasation has been demonstrated. These Pt nanofibers were installed within a microfluidic channel, and the resulting reduced permeability was evaluated using a fluid similar to blood. Based on the obtained results, these newly developed nanofibers are expected to decrease the operation cost for aneurysmal subarachnoid hemorrhage (SAH), owing their reduced size and low material cost. Overall, the use of this new material should reduce the operational risk associated with the multiple steps required to place the Pt coils at the SAH site. The compatibility of Pt micro-ropes with commercial delivery catheters was verified and their performance was experimentally explored in an in vitro experimental model. The developed Pt-coated micro-ropes demonstrated feasibility as efficient and low-cost endovascular coils.

Supersonic Cold Spraying for Energy and Environmental Applications: One-Step Scalable Coating Technology for Advanced Micro- and Nanotextured Materials.

Supersonic cold spraying is an emerging technique for rapid deposition of films of materials including micrometer-size and sub-micrometer metal particles, nanoscale ceramic particles, clays, polymers, hybrid materials composed of polymers and particulates, reduced graphene oxide (rGO), and metal-organic frameworks. In this method, particles are accelerated to a high velocity and then impact a substrate at near ambient temperature, where dissipation of their kinetic energy produces strong adhesion. Here, recent progress in fundamentals and applications of cold spraying is reviewed. High-velocity impact with the substrate results in significant deformation, which not only produces adhesion, but can change the particles' internal structure. Cold-sprayed coatings can also exhibit micro- and nanotextured morphologies not achievable by other means. Suspending micro- or nanoparticles in a liquid and cold-spraying the suspension produces fine atomization and even deposition of materials that could not otherwise be processed. The scalability and low cost of this method and its compatibility with roll-to-roll processing make it promising for many applications, including ultrathin flexible materials, solar cells, touch-screen panels, nanotextured surfaces for enhanced heat transfer, thermal and electrical insulation films, transparent conductive films, materials for energy storage (e.g., Li-ion battery electrodes), heaters, sensors, photoelectrodes for water splitting, water purification membranes, and self-cleaning films.

Slow Discharge Theory and Calculation of the Potential Drop across the Compact Layer at High Electrode Voltages.

A novel approach presented in this work allows one to calculate the potential drop across the compact layer in electrostatic atomization with high voltages applied at the electrode. Ionic conductor liquids employed in electrostatic atomization have a low dielectric constant, which causes almost all of the potential drop across the double layer to occur inside the compact layer. In the previous article of this group (Sankarn, A., et al. Langmuir 2017, 33, 1375-1384), it was shown that faradaic reactions in the kinetics-limited regime are responsible for liquid electrification in electrostatic atomization. Here, we apply the Frumkin slow discharge theory to calculate the electric potential at the interface of the compact and diffuse layers. The electric potential value at the interface of the compact and diffuse layers is required in computational models accounting for the discharge of counterions due to faradaic reactions when solving the ionic transport equations. The activation energy of the electron transfer reaction is calculated through the Marcus theory. Knowing the counterion flux value at the electrode surface from the concurrent experimental measurements, the ionic concentration and net charge distribution across the polarized diffuse layer are also found from the numerical simulations. Considering canola oil to be the ionic conductor liquid, two different examples are used to demonstrate the application of this approach to calculate the electric potential at the interface of compact and diffuse layers.

Wearable, Stretchable, Transparent All-in-One Soft Sensor Formed from Supersonically Sprayed Silver Nanowires.

The demand for wearable, stretchable soft electronics for human-machine interface applications continues to grow given the potential of these devices in humanoid robotics, prosthetics, and health-monitoring devices. We demonstrate fabrication of multifunctional sensors with simultaneous temperature-, pressure-, proximity-, and strain (or bending)-sensing capabilities, combined with heating and UV-protection features. These multifunctional sensors are flexible, light, and transparent and are thus body-attachable. Silver nanowires are supersonically sprayed on a large-scale transparent and flexible roll-to-roll substrate. The junctions between nanowires are physically fused by a strong impact resulting from supersonic spraying, which promotes adhesion and efficient deposition of the nanowire network. Accordingly, nanowires are strongly interconnected, facilitating efficient propagation of electric signals through the fused nanowire network, which allows simultaneous operation of such sensors while maintaining significant transparency. These multifunctional sensors are mechanically durable and retain long-term stability. A theoretical discussion is provided to explain the respective mechanisms of heating and proximity, pressure, and strain sensing.