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.

N-Hydroxy-Phe-Phe, a new dipeptide, and cytotoxic macrocyclic trichothecenes from the lethal toxic mushroom Podostroma cornu-damae.

Podostroma cornu-damae, commonly referred to as the red deer's horn mushroom due to its distinct resemblance to the antlers of a deer, is a lethal toxic mushroom that causes vomiting, dehydration, diarrhea, disturbance of consciousness, and even death. In continuation of our research aiming to investigate the novel structural and/or biological principles present in Korean wild mushrooms, a new N-hydroxyphenylalanine-phenylalanine dipeptide, N-hydroxy-Phe-Phe (1), and three known macrocyclic trichothecenes, satratoxin H (2), 12'-episatratoxin H (3), and roridin F (4), were isolated from the MeOH extract of a plate culture of the poisonous mushroom P. cornu-damae. The chemical structure of the new dipeptide (1) was determined by analyzing 1D and 2D NMR spectra and high-resolution (HR)-electrospray ionization mass spectroscopy (ESIMS), along with a computational method combined with a statistical procedure (DP4+), and its absolute configuration was unambiguously assigned by quantum chemical ECD calculations. To the best of our knowledge, compound 1 is the first dipeptide found in P. cornu-damae. Upon evaluating the cytotoxicity of compounds 1-4 against four human-derived cancer cell lines namely SK-OV-3, SK-MEL-2, A549, and HCT15, 12'-episatratoxin H (3) displayed potent cytotoxic effects toward all four cell lines tested, with IC50 values ranging from 0.7 to 2.8 nM, which was found to be stronger than that of doxorubicin. Satratoxin H (2) also demonstrated moderate cytotoxic potency against all four cell lines, with IC50 values ranging from 1.93 to 4.22 µM. Our findings provide experimental data supporting the potential of the poisonous mushroom P. cornu-damae as a source of anticancer agents.

Recent advances in pain management based on nanoparticle technologies.

BACKGROUND: Pain is a vital sense that indicates the risk of injury at a particular body part. Successful control of pain is the principal aspect in medical treatment. In recent years, the advances of nanotechnology in pain management have been remarkable. In this review, we focus on literature and published data that reveal various applications of nanotechnology in acute and chronic pain management. METHODS: The presented content is based on information collected through pain management publications (227 articles up to April 2021) provided by Web of Science, PubMed, Scopus and Google Scholar services. RESULTS: A comprehensive study of the articles revealed that nanotechnology-based drug delivery has provided acceptable results in pain control, limiting the side effects and increasing the efficacy of analgesic drugs. Besides the ability of nanotechnology to deliver drugs, sophisticated nanosystems have been designed to enhance imaging and diagnostics, which help in rapid diagnosis of diseases and have a significant impact on controlling pain. Furthermore, with the development of various tools, nanotechnology can accurately measure pain and use these measurements to display the efficiency of different interventions. CONCLUSIONS: Nanotechnology has started a new era in the pain management and many promising results have been achieved in this regard. Nevertheless, there is still no substantial and adequate act of nanotechnology in this field. Therefore, efforts should be directed to broad investigations.

Characterization of Biological Properties of Dental Pulp Stem Cells Grown on an Electrospun Poly(l-lactide-co-caprolactone) Scaffold.

Poly(l-lactide-co-caprolactone) (PLCL) electrospun scaffolds with seeded stem cells have drawn great interest in tissue engineering. This study investigated the biological behavior of human dental pulp stem cells (hDPSCs) grown on a hydrolytically-modified PLCL nanofiber scaffold. The hDPSCs were seeded on PLCL, and their biological features such as viability, proliferation, adhesion, population doubling time, the immunophenotype of hDPSCs and osteogenic differentiation capacity were evaluated on scaffolds. The results showed that the PLCL scaffold significantly supported hDPSC viability/proliferation. The hDPSCs adhesion rate and spreading onto PLCL increased with time of culture. hDPSCs were able to migrate inside the PLCL electrospun scaffold after 7 days of seeding. No differences in morphology and immunophenotype of hDPSCs grown on PLCL and in flasks were observed. The mRNA levels of bone-related genes and their proteins were significantly higher in hDPSCs after osteogenic differentiation on PLCL compared with undifferentiated hDPSCs on PLCL. These results showed that the mechanical properties of a modified PLCL mat provide an appropriate environment that supports hDPSCs attachment, proliferation, migration and their osteogenic differentiation on the PLCL scaffold. The good PLCL biocompatibility with dental pulp stem cells indicates that this mat may be applied in designing a bioactive hDPSCs/PLCL construct for bone tissue engineering.

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.

Phytochemical Investigation of Marker Compounds from Indigenous Korean Salix Species and Their Antimicrobial Effects.

Salix species, including willow trees, are distributed in the temperate regions of Asian countries, including South Korea. Willow trees are used to treat pain and inflammatory diseases. Due to the medicinal properties of willow trees, pharmacological studies of other Salix spp. have gained attention; however, only a few studies have investigated the phytochemicals of these species. As part of our ongoing natural product research to identify bioactive phytochemicals and elucidate their chemical structures from natural resources, we investigated the marker compounds from indigenous Korean Salix species, namely, Salix triandra, S. chaenomeloides, S. gracilistyla, S. koriyanagi, S. koreensis, S. pseudolasiogyne, S. caprea, and S. rorida. The ethanolic extract of each Salix sp. was investigated using high-performance liquid chromatography combined with thin-layer chromatography and liquid chromatography−mass spectrometry-based analysis, and marker compounds of each Salix sp. were isolated. The chemical structures of the marker compounds (1−8), 3-(4-hydroxyphenyl)propyl ß-D-glucopyranoside (1), 2-O-acetylsalicin (2), 1-O-p-coumaroyl glucoside (3), picein (4), isograndidentatin B (5), 2'-O-acetylsalicortin (6), dihydromyricetin (7), and salicin (8) were elucidated via nuclear magnetic resonance spectroscopy and high-resolution liquid chromatography−mass spectrometry using ultrahigh-performance liquid chromatography coupled with a G6545B Q-TOF MS system with a dual electrospray ionization source. The identified marker compounds 1−8 were examined for their antimicrobial effects against plant pathogenic fungi and bacteria. Dihydromyricetin (7) exhibited antibacterial activity against Staphylococcus aureus, inducing 32.4% inhibition at a final concentration of 125 µg/mL with an MIC50 value of 250 µg/mL. Overall, this study isolated the marker compounds of S. triandra, S. chaenomeloides, S. gracilistyla, S. koriyanagi, S. koreensis, S. pseudolasiogyne, S. caprea, and S. rorida and identified the anti-Staphylococcus aureus bacterial compound dihydromyricetin.

Self-Healing Structural Materials.

Self-healing materials have been developed since the 1990s and are currently used in various applications. Their performance in extreme environments and their mechanical properties have become a topic of research interest. Herein, we discuss cutting-edge self-healing technologies for hard materials and their expected healing processes. The progress that has been made, including advances in and applications of novel self-healing fiber-reinforced plastic composites, concrete, and metal materials is summarized. This perspective focuses on research at the frontier of self-healing structural materials.

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.

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.

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.

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.

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.

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.

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.

Electrostatic Transparent Air Filter Membranes Composed of Metallized Microfibers for Particulate Removal.

Particulate matter (PM) from ever-increasing industrialization poses a great public health risk. Although fiber-based filters are used effectively to block PM, filters with high packing densities suffer from excessive pressure drops. Electret filters bypass intermediate- or large-sized particles and thus capture only small particles, the motion of which can be influenced by weak electrostatic fields. In this study, we demonstrate the fabrication of metallized fibers that produce intense electric fields, thereby enabling capture of PMs of a variety of sizes produced by burning incense. The filter consisting of these metallized fibers effectively removes moving particles from air. An electricity-driven filter is relatively thin and has a low packing density, making it light, portable, transparent, and inexpensive. The sizes of the pores between the metallized fibers are readily controlled by manipulating the electrospinning and electroplating times. Sufficiently large pores permit efficient airflow and thus increase permeability without risking an excessive pressure drop. The metallized fiber filter is washable and thus reusable. In this study, a PM removal rate of >97% was recorded using a filter designed under optimal conditions.

Programmable soft robotics based on nano-textured thermo-responsive actuators.

Soft robotic systems are increasingly emerging as robust alternatives to conventional robotics. Here, we demonstrate the development of programmable soft actuators based on volume expansion/retraction accompanying liquid-vapor phase transition of a phase-change material confined within an elastomer matrix. The combination of a soft matrix (a silicone-based elastomer) and an embedded ethanol-impregnated polyacrylonitrile nanofiber (PAN NF) mat makes it possible to form a sealed compound device that can be operated by changing the actuator temperature above/below the boiling point of ethanol. The thermo-responsive actuators based on this principle demonstrate excellent bending ability at a sufficiently high temperature (>90 °C) - comparable with compressed air-based soft actuators. The actuator using the mechanism presented here is easy to manufacture and automate and is recyclable. Finally, the actuation mechanism can be incorporated into a wide variety of shapes and configurations, making it possible to obtain tunable and programmable soft robots that could have a wide variety of industrial applications.

Natural Biopolymer-Based Triboelectric Nanogenerators via Fast, Facile, Scalable Solution Blowing.

Here, we fabricated nanofiber (NF)-based triboelectric nanogenerators (TENGs) from natural biopolymers using the industrially scalable solution blowing. This technique eliminates severe restrictions on solutions to be used and allows one to achieve biocompatible devices. Here, solutions of soy protein and lignin were blown into continuous monolithic NFs of hundreds of nanometers in diameter. The technique we employed yields large-area NF mats within tens of minutes and has never been employed to form TENGs. Furthermore, in contrast to electrospun and meltblown fiber mats, solution-blown NF mats are much fluffier/porous, which is beneficial for achieving higher voltages by means of triboelectricity. In particular, triboelectricity generated by our biopolymer-based TENGs revealed that they hold great promise as sustainable and environmentally friendly self-powered devices for biomedical applications with the highest efficiency in their class. Moreover, these are the first nanotextured plant-derived biopolymer-made TENGs.

Wearable transparent thermal sensors and heaters based on metal-plated fibers and nanowires.

Electrospun metal-plated nanofibers and supersonically sprayed nanowires were used to fabricate hybrid films exhibiting a superior low sheet resistance of 0.18 Ω sq-1, a transparency of 91.1%, and a figure-of-merit of 2.315 Ω-1. The films are suitable to serve as thermal sensors and heaters. Such hybrid transparent conducting films are highly flexible and thus wearable. They can be used as body-temperature monitors and heaters. The employed hybrid approach improved the sheet resistance diminishing it to a minimum, while maintaining transparency. In addition, the low sheet resistance of the films facilitates their powering with a low-voltage battery and thus, portability. The thermal sensing and heating capabilities were demonstrated for such films with various sheet resistances and degrees of transparency. The temperature sensing was achieved by the resistance change of the film; the resistance value was converted back to temperature. The sensing performance increased with the improvement in the sheet resistance. The temperature coefficient of resistivity was TCR = 0.0783 K-1. The uniform distribution of the metal-plated nanofibers and nanowires resulted in a uniform Joule heating contributing to an efficient convection heat transfer from the heaters to the surrounding, demonstrated by an improved convective heat transfer coefficient.

A blister-like soft nano-textured thermo-pneumatic actuator as an artificial muscle.

Here, model blister-like soft thermo-pneumatic artificial muscles with the embedded nanofibers impregnated with ethanol are developed. The muscles are essentially blister-like thermo-pneumatic soft actuators (BTSAs), which deflect in response to heat supplied to their bottom. The resulting deflections are on the scale of 1 cm, and the BTSAs are operational for several cycles. They are able to raise the artificial rigid scales, spines or fur/thin fibers attached to them emulating animals such as pangolin, hedgehog and porcupine. They are also capable of removing the stickiest adhesive tapes attached to them, and thus hold great promise for biomedical applications where artificially grown skin patches should be removed from an underlying substrate without being damaged. The theory of the BTSA proposed in this work is in reasonable agreement with the acquired experimental data.