Artificial Ions Research Articles

PH-Regulated Ionic Diode Based on an Asymmetric Shaped Multiple-Layer Polymer Membrane

Smart artificial ion channels with tunable properties have wide applications in many fields to achieve ion transport manipulation. Most reported artificial ions are constructed with vertical structures, limiting the further integration of ionic diodes into complex iontronic systems. Inspired by the asymmetric concentration polarization induced by the asymmetric geometry of nanochannels, a novel method is developed to construct horizontally arranged and pH-regulated ionic diodes in nanofluidic chips by self-assembling pH-responsive polymers. The effects of the fabrication and operation parameters on the performance of the ionic diode are systematically investigated. The current rectification ratio of the ionic diode can be modulated flexibly by regulating the pH conditions of the working fluid. An ionic diode bridge circuit for rectifying alternating current signals is built in a single nanofluidic chip and demonstrated, highlighting the feasibility of the ionic diode for complex iontronic system integration. The method presented in this paper provides a promising platform for the development of smart nanofluidic iontronic devices with widespread applicability in biological analysis, sensing, and logic computing.

Removal of artificial iron ions using activated carbon from sago pith waste

In the present day, the industry is growing rapidly. Every process in the industries brings out pollution. Heavy metals, especially iron ions have contaminated water resources due to industrial activity. The high concentration of iron ions is dangerous for human life. To solve this issue an activated carbon from sago pith waste was developed to remove iron ions from industrial wastewater represented by artificial iron solution. The objective of this research is to measure the adsorption capacity of sago pith waste activated carbon (SPWAC) for treating artificial iron solution. The adsorbent was carbonized at 300 °C and 80 min. Further, it was activated by citric acid 0.1 M. The treated iron solution was analyzed by condutometer to examine the iron content. Subsequently, the functional groups of SPWAC were tested via Fourier Transform Infra-Red (FTIR). The result indicates that the SPWAC can reject iron ions of more than 80 % with an iron ions concentration of 1.81 mg/L at 60 min and 300 rpm. While, FTIR analysis show alkenes, carbonyl, and hydroxyl groups are present in SPWAC. The iron ions concentration in treated water is below the allowable threshold (0.3 mg/L) based on World Health Organization (WHO) guidelines for drinking water. Therefore, the SPWAC is promising technology to be applied for treating industrial wastewater.

Interactions between Artificial Channel Protein, Water Molecules, and Ions Based on Theoretical Approaches

Contemporary techniques of molecular modeling allow for rational design of several specific classes of artificial proteins. Transmembrane channels are among these classes. A recent successful synthesis of self-assembling, highly symmetrical 12- or 16-helix channels by David Baker’s group prompted us to study interactions between one of these proteins, TMHC6, and low-molecular-weight components of the environment: water molecules and ions. To examine protein stability in a polar environment, molecular dynamics (MD) with classical force fields of the AMBER family was employed. Further characteristics of the chosen interactions were obtained using interaction energy calculations with usage of partially polarizable GFN-FF force field of Spicher and Grimme, symmetry-adapted perturbation theory (SAPT) and atoms in molecules (AIM) approaches for models of residues from the channel entry, crucial for interactions with water molecules and ions. The comparison of the interaction energy values between the gas phase and solvent reaction field gives the quantitative estimation of the strength of the interactions. The energy decomposition via the SAPT method showed that the electrostatics forces play a dominant role in the substructure stabilization. An application of the AIM theory enabled a description of the intermolecular hydrogen bonds and other noncovalent interactions.

(Invited) visco-Poroelastic & Iontronic Pump: New Strategy for Ultrasensitive Artificial Skin Sensors

Creating artificial sensor skins that shows the tactile- and chemical-sensing capability of human skin has been a big challenge in wearable sensor research. In particular, biomimetics has emerged as a burgeoning area in the field of deformable tactile sensor skins that has led innovations in material designing and device structure manipulation with the aim of imitating multimodal sensing features of human skin intelligently. Herein, inspired by the sophisticated physiological sensing mechanism of living cells, we describe a uniquely designed visco-poroelastic, iontronic pump consisting of artificial ions confined into polymeric network matrix or well-designed hybrid interface. Novel bottom-up strategy employed here resulted into supramolecular polymer networks through non-covalent interactions between poroelastic artificial ions and viscoelastic polymer chains, which endows effective iontronic pumping under mechanical stimuli and electronic field, simultaneously. This design for visco-poroelastic, iontronic, and ion confined artificial mechanoreceptors allows for ultrasensitive mechanosensing over a wide spectrum of pressure (Pa~150kPa) beyond capabilities of human skin. Moreover, our devices could visualize the local variation in the applied pressure or electronic field without using spatially distributed device arrays.

Pillar[n]arenes for Construction of Artificial Transmembrane Channels

AbstractPillar[n]arenes have been intensively used during the last decade in supramolecular chemistry as host systems for guest recognition and self‐assembly, toward functional materials and devices. They present electron‐rich and tuneable size cavities, as well as reactive rims for further functionalization. Their unique pillar shape promotes pillar[n]arenes as molecular analogues of carbon nanotubes. For this reasons pillar[n]arenes have been embedded into membranes and used to construct artificial water, proton, ions and molecular channels. This review discusses the incipient developments of the first artificial channels based on pillar[n]arenes. We include also systems that integrate pillar[n]arenes as synthetic elements for the construction of selective pores of nanodevices for ion rectification.

An Ultrastable Ionic Chemiresistor Skin with an Intrinsically Stretchable Polymer Electrolyte.

Ultrastable sensing characteristics of the ionic chemiresistor skin (ICS) that is designed by using an intrinsically stretchable thermoplastic polyurethane electrolyte as a volatile organic compound (VOC) sensing channel are described. The hierarchically assembled polymer electrolyte film is observed to be very uniform, transparent, and intrinsically stretchable. Systematic experimental and theoretical studies also reveal that artificial ions are evenly distributed in polyurethane matrix without microscale phase separation, which is essential for implementing high reliability of the ICS devices. The ICS displays highly sensitive and stable sensing of representative VOCs (including toluene, hexane, propanal, ethanol, and acetone) that are found in the exhaled breath of lung cancer patients. In particular, the sensor is found to be fully operational even after being subjected to long-term storage or harsh environmental conditions (relative humidity of 85% or temperature of 100 °C) or severe mechanical deformation (bending to a radius of curvature of 1 mm, or stretching strain of 100%), which can be an effective method to realize a human-adaptive and skin-attachable biosensor platform for daily use and early diagnosis.

The effects of spacecraft charging and outgassing on the LADEE ion measurements

AbstractAbnormal ion signals can be usually seen in the Lunar Atmosphere and Dust Environment Explorer (LADEE) mission, including a suddenly enhanced current observed by the Lunar Dust Experiment (LDEX) near the sunlight‐shadow boundary and an unexpected water ion measured by the neutral mass spectrometer (NMS), with their magnitudes insensitive to the convection electric field of solar wind but dependent on the SW density and the elapsed time of LADEE mission. By analyzing both the LDEX measurements and the NMS measurements, we find that the current enhancement can be caused by a negatively charged spacecraft in the shadow region while the significant water ions should be some artificial ions from spacecraft outgassing. The artificial water ions show a peak near 8:00 LT that may be related to a sunlight‐controlled surface outgassing. In addition, the H2O flux can be enhanced near the end of the mission when the spacecraft has a lower altitude. It is found that the H2O enhancement is actually caused by an exosphere‐contributed return flux, rather than a real water exosphere.

Feasibility study of artificial rainfall system using ion seeding with high voltage source

Abstract A non-linear computational modelling of ions from the ground station for electrifying the atmosphere to make feasibility study of artificial rainfall system is proposed and analyzed. The model considers generation of intermediate ions and ionized airflow velocity. The governing electro hydrodynamic (EHD) equations of the model shows that the space charge density, electric field intensity and velocity of the ionized airflow are function of high input voltage applied to generate the ions. The number of ions generated and their velocity is proportional to the applied ion generator voltage. These artificial ions will be introduced in the atmosphere which will act in a similar manner as cosmic rays. These ions will ionize the aerosols and catalyze nucleation processes and thus electrify the atmosphere which will form cloud droplets to get artificial rain. The mathematical model to study the feasibility of artificial rainfall is also validated under favourable conditions.

Optimizing the Accuracy and Efficiency of Fast Hierarchical Multipole Expansions for MD Simulations.

Based on p'th order Cartesian Taylor expansions of Coulomb interactions and on hierarchical decompositions of macromolecular simulation systems into hierarchies of nested, structure-adapted, and adaptively formed clusters of increasing size, fast multipole methods are constructed for rapid and accurate calculations of electrostatic interactions. These so-called SAMMp algorithms are formulated through totally symmetric and traceless tensors describing the multipole moments and the coefficients of local Taylor expansions. Simple recursions for the efficient evaluation and shifting of multipole moments are given. The required tensors are explicitly given up to order p = 4. The SAMMp algorithms are shown to guarantee the reaction principle. For systems with periodic boundaries, a reaction field (RF) correction is applied, which introduces at distances beyond the "minimum image convention" boundary a dielectric continuum surrounding each cluster at the top level of coarse graining. The correctness of the present SAMMp implementation is demonstrated by analyzing the scaling of the residuals and by checking the numerical accuracy of the reaction principle for a pair of distant molecular ions in vacuum. Molecular dynamics simulations of pure water and aqueous solutions containing artificial ions, which are enclosed by periodic boundaries, demonstrate the stability and low-noise behavior of SAMMp/RF.

Cooperative effects of artificial chaperone and Mg 2+ ions on alkaline phosphatase refolding

The refolding of GuHCl-denatured alkaline phosphatase (ALP) has been investigated by a new elegant strategy using the artificial-chaperone assisted two-step mechanism. However, using detergent and cyclodextrin, which are both poorly soluble in aqueous solutions, necessitates large sample dilutions to earn adequate refolding yield. In the present work, to overcome this obstacle, we studied the concomitant effects of the artificial chaperone and metal ions on ALP refolding at 0.2 mg/ml concentration. The method presented is a high-yielding process with few operational steps which may result in a low process cost. Based on this approach, refolding of GuHCl-denatured ALP raised from 20%, in the absence of anti-aggregators, to about 50% in the presence of artificial chaperone and/or MgSO 4 and to 82% in the concomitant presence of the artificial chaperone and MgSO 4 while the extent of aggregation was totally quenched. Using different salts of Mg 2+ resulted in different recovered yields probably due to their variable interactions with cyclodextrin. Under the same experimental conditions except for the metal ions, Zn 2+ and Ca 2+, worked neither alone nor in combination with the artificial chaperone showing that Mg 2+ can work as an auxiliary agent because of its structural role.

Hemolymph osmolality and cation concentrations in Litopenaeus vannamei during exposure to artificial sea salt or a mixed-ion solution: Relationship to potassium flux

Interest in culturing the Pacific white shrimp Litopenaeus vannamei in low-salinity and brackish-well waters has led to questions about the ability of this species to osmo- and ionoregulate in environments containing low concentrations of ions and in environments with ionic ratios that differ from those found in sea water. After seven days, hemolymph osmolality and potassium, sodium and calcium values were all significantly affected by salinity (as artificial sea salt) with values decreasing with decreasing salinity. These decreases were small, however, relative to decreases in salinity, indicating iono- and osmoregulation with adjustment for gradients. The hemolymph osmolality and sodium and calcium concentrations in shrimp exposed to either 2 g/L artificial sea salt or 2 g/L mixed-ion solution (a mixture of sodium, potassium, calcium, and magnesium chlorides that approximate the concentrations and ratios of these cations found in 2 g/L dilute seawater) did not differ significantly. However, hemolymph potassium levels were significantly lower in shrimp held in the mixed-ion environment. Potassium influx rates were similar in shrimp held in either artificial sea salt or mixed ions. The results of this study indicate that salinity affects hemolymph-cation concentrations and osmolality. Further, differential potassium-influx rates do not appear to be the basis for low hemolymph potassium levels observed in shrimp held in mixed-ion environments.

Telemetry radio wave interactions with the atmospheric plasma

Model calculations of telemetry radio wave induced perturbations of the atmospheric plasma are presented. The computed results show that P-band radio waves (255–390 MHz) and to a much lesser extent S-band radio waves (1.5–5.2 GHz) both commonly used onboard atmospheric probes for online data transmission may cause perturbations of the electrical and optical properties of the atmosphere in the vicinity of the probes. It is shown that S- and P-band radio waves interact most efficiently with the atmospheric plasma at middle stratospheric and lower mesospheric altitudes, respectively. The calculations presented here may also explain well the first unambigous detection of artificial telemetry radio wave ions produced around the stratopause by Pfeilsticker and Arnold (1987, J. atmos. terr. Phys. 49, 11). Moreover, they reveal that several in situ measurements of various atmospheric electrical properties may have been affected by telemetry radio wave emissions of the payloads.

Membrane potential generation by submitochondrial particles associated with a lipid-impregnated filter

Transmembrane electrochemical H’ potential difference (AjIH+) was postulated by Mitchell to be an obligatory intermediate in oxidative and photosynthetic phospho~lation [l]. Progress in the membr~e bioenergetics not only verified this postulate but also resulted in elucidation of the fact that AjiH+, like ATP, may serve as a convertible form of energy in the living cell [2]. AiiH+ comprises electric (A$) and chemical (ApH) constituents [I]. Since the electric capacitance of a biomembrane is usually much lower than the pH buffe~ng capacity of the membraneseparated aqueous phases [3,4], it is A$ rather than ApH which should be the initial form of ApH+ produced by a A,&,+ generator. Therefore, direct A+ measurements are advantageous in studies on membrane-linked energy transduction. Since the method of artificial penetrating ions was introduced some ten years ago [5,6], which enabled us to verify the existence of A$ in a variety of energytransducing membranes [6-91, we have developed a number of novel facilities in collaboration with Professor E. A. Liberman’s group [lo-161. Of these, the association of membranous vesicles with lipidimpregnated ftlters proved a convenient and potent method of Aj, monito~g, ~cIuding the measurement of rapid kinetics. This method was used in our studies of bacteriorhodopsin [12,13,15], and the results were confirmed by [ 19,201. Chromatophores of Rhodo-

CHAPTER II:Earlier attempts to employ artificial atmospheric ions or electric charges as therapeutic agents.

CHAPTER II:Earlier attempts to employ artificial atmospheric ions or electric charges as therapeutic agents.