Poly Ionic Liquid Research Articles

Surface-modified magnetite nanoparticles using polyethylene terephthalate waste derivatives for oil spill remediation.

This work aims at synthesizing new cross-linked poly ionic liquids, CPILs, VIMDE-Cl and CPIL, VIMDE-TFA, utilizing polyethylene terephthalate waste as a precursor and applying them to magnetite nanoparticles surface modification, producing surface-modified magnetite nanoparticles, SMNPs, VDCL/MNPs, and VDTA/MNPs, respectively. The structures of VIMDE-Cl and VIMDE-TFA, VDCL/MNPs, and VDTA/MNPs, were verified using different techniques. The particle sizes of SMNPs, VDCL/MNPs, and VDTA/MNPs, were evaluated with a transmission electron microscope and dynamic light scattering. The compatibility of VDCL/MNPs and VDTA/MNPs with crude oil components and their response to an external magnet were also measured using contact angle measurements and a vibrating sample magnetometer. The data confirmed the formation of SMNPs, nanosized structure, compatibility with oil components, and response to an external magnet. For that, VDCL/MNPs and VDTA/MNPs were applied for oil spill recovery using different SMNP : crude oil weight ratios. The impact of contact time on SMNPs' performance was also evaluated. The data indicated increased performance with an increase in SMNPs ratio, reaching maximum values of 99% and 96% for VDCL/MNPs and VDTA/MNPs, respectively, at SMNPs : crude oil ratio of 1 : 1. According to the results, the optimal contact time was 6 min, resulting in 89% and 97% performance for VDCL/MNPs and VDTA/MNPs at 1 : 4 SMNPs : crude oil ratio.

Amine-modified polyionic liquid supports enhance the efficacy of PdNPs for the catalytic hydrogenation of CO2 to formate.

Palladium nanoparticles stabilised by aniline modified polymer immobilised ionic liquid is a remarkably active catalyst for the hydrogenation of CO2 to formate; the initial TOF of 500 h-1 is markedly higher than either unmodified catalyst or its benzylamine and N,N-dimethylaniline modified counterparts and is among the highest to be reported for a PdNP-based catalyst.

POSS-based polyionic liquids for efficient CO2 cycloaddition reactions under solvent- and cocatalyst-free conditions at ambient pressure.

The conversion of CO2 into value-added chemicals has become an imminent research topic and the cycloaddition of CO2 with a C1 resource to produce cyclic carbonates is a promising pathway for CO2 utilization. Herein, a series of POSS-based polyionic liquids (PILs) were synthesized by the copolymerization of octavinyl polyhedral oligomeric silsesquioxane (POSS) with an imidazolium ion linker. The prepared PILs have the characteristics of hydrogen bond donors, halogen atom sites, stable pore structures, and thermal stability, and are used as heterogeneous catalysts for the cycloaddition of epoxides with carbon dioxide. The effect of linkers on the cycloaddition is investigated by tuning the ratio of POSS units to imidazolium ions. Under the optimized conditions, the conversion of epichlorohydrin can reach 99.18% at atmospheric pressure with neither co-catalysts nor solvents. It is concluded that the reaction of the cycloaddition of epoxides with carbon dioxide follows pseudo-first-order kinetics. Moreover, the presence of the catalysis of PILs leads to a significant decrease in the activation energy barrier for cycloaddition. The catalyst can be facilely recovered due to its high stability, and only a slight decrease in conversion was observed after five successive runs. In addition, the mechanism of PILs catalyzing the cycloaddition reaction of epoxides with CO2 is proposed. This work not only provides a sustainable and green process for CO2 cycloaddition, but also highlights the potential of using PILs for CO2 utilization.

In situ molecular permeation of liquid cationic polymers into solid anionic polymer films enabling self-adaptive adhesion of hydrogel biosensors.

Self-adaptive adhesion is essential for hydrogel sensors. However, the traditional protocol involves covering a pre-prepared hydrogel sensor on a tested surface. As a result, the sensor cannot achieve self-adaptive adhesion owing to an air-layer hindrance between the sensor and tested surface, which inevitably leads to the loss of critical biological signals. To address the issue of air-layer hindrance, this work proposes an in situ permeation method that enables the self-adaptive adhesion of hydrogel biosensors on various surfaces. After applying a liquid solution of poly(methacrylamido propyl trimethyl ammonium chloride-co-acrylamide) (poly(MPTAC-co-AM)) on the testing surface, a thin film of poly(acrylic aminoethane sulfonic acid-co-acrylamide) (poly(AASA-co-AM)) is applied, where the electrostatic interaction between -SO3- and -Me3N+ facilitates rapid permeation of the solution into the solid film, leading to the formation of a hydrogel layer in situ. The coating of liquid poly(MPTAC-co-AM) sweeps away the air layer and works as a natural glue, enabling a strong bonding interaction between the hydrogel layer and the tested surface. Such a hydrogel layer is very thin (microscale), and can retain its self-adaptive adhesion even with deformation of the tested surface. When it is applied on the surface of an active frog heart, the weak heartbeats can be transduced to electrical signals. Moreover, this self-adaptive adhesion can work on both soft and hard surfaces including biological tissues, metals, rubbers, ceramics, and glass. Therefore, this in situ permeation method enables the hydrogel layer to detect weak dynamic changes on various soft and hard surfaces, which might offer a new pathway for physiological signal monitoring.

Preparation of cobalt-containing polyvinylimidazole ionic liquid catalyst and coupling with persulfate for room-temperature ultra-deep desulfurization

Poly-ionic liquid catalyst has both the advantages of ionic liquid and polymer, and overcomes the poor fluidity of ionic liquid, so it has become one of the hot spots in catalytic oxidative desulfurization. A polyvinyl-3-butylimidazolium cobalt chloride salt (poly-[BVIM][CoCl3]) ionic liquid catalyst was prepared and characterized. When coupled with potassium monopersulfate (PMS), the catalyst formed a catalytic oxidative desulfurization system. The results showed that the prepared poly-[BVIM][CoCl3] system had a microsphere morphology with a diameter of 28 μm, and the interior structure was a mesoporous structure formed via the self-assembly of two-dimensional thin-layered nanowires with a carbon skeleton width of 20 nm. The specific surface area was 10.54 m2·g−1, the pore volume was 0.029 cc·g−1, and the average pore diameter was 3.5 nm. The optimum experimental conditions were: a catalyst dosage of 20 mg, 0.4 g of PMS (20 %) as oxidant, a reaction temperature of 20 °C, 2 g of acetonitrile as extractant, simulated sulfur-containing oil with dibenzothiophene (DBT) concentration of 500 ppm, and an initial sulfur content of 6 g. After 20 min, the sulfur removal reached more than 99 % and remained over 90 % even after the catalyst was recycled five times. The desulfurization sequence for different organosulfur compounds was DBT greater than 4,6-dimethyl dibenzothiophene (4,6-DMDBT) > benzothiophene (BT). The main desulfurization product was determined to be DBTO2 by GC–MS analysis, and the speculated desulfurization mechanism was that Co(II) catalyzed PMS to form ·SO4−, which then oxidized the target molecules. The extraction-catalytic-oxidative desulfurization kinetic was established and verified that the desulfurization process accorded with zero-order reaction kinetics. The reaction rate constant (kp) for the production of ·SO4− was estimated to be 4.24 × 10−9 ppm−1·min−1.

Adsorption and catalytic removal of methyl orange from water by PIL-GO/TiO2/Fe3O4 composites

In this paper, an organic-inorganic hybrid material was synthesized via a simple but effective method, the novel material PGO-TiO2/Fe3O4 (PGTF) was produced by loading TiO2 and Fe3O4 onto polymeric ionic liquid(PIL) functionalized graphene oxide(GO). The successful synthesis of PGTF and related structural feature were confirmed by a series of characterizations. The results of UV diffuse reflectance (DRS) demonstrated that the incorporation of PGO-Fe3O4 to TiO2 shifted the light absorption of TiO2 from ultraviolet (UV) to visible region. The band gap energy of the PGTF reduced to1.92 eV as compared to TiO2 (3.12 eV). Different materials were used to remove methyl orange (MO) from the aqueous solution. The results showed that PGTF had a superior capacity to remove dye due to the synergistic effects of adsorption and photocatalysis. The excellent adsorption properties may result from the high specific surface area of GO and the –NH2 in the PIL. The polyionic liquid absorbed electrons due to the electrostatic action of the cation head in the polyionic liquid and GO which had high conductivity favored electron transport. The photocatalytic effectiveness increased as a result of the separation of photoexcited electron-hole pairs. The Langmuir model was investigated to evaluate the adsorption equilibrium behavior of MO dyes by PGTF. The maximum adsorption capacity(Qmax) was 67.88 mg/g for MO dyes. The pseudo-second-order kinetic model, with a correlation coefficient of 0.999, provided a good fit for the adsorption kinetic processes. The adsorption rate constant K2 obtained by this model is 0.0072 g/(mg*min). The degradation rate constant of PGTF for MO in the photocatalytic stage was 0.00881 min−1, which exhibited 3.7, 7.5 and 3 times higher than that of TiO2, FT and GTF. The main reactive species in the degradation process were O2−、·OH、h+. PGTF had excellent repeatability because of the presence of Fe3O4. They can be easily separated from the water. These results indicated that the PGTF composites hold great potential for removing MO from wastewater.

In Situ Polymerization of Ionic Liquid with Tunable Phase Separation for Highly Reversible and Ultralong Cycle Life Zn-Ion Battery.

Severe Zn dendrite growth and side reactions greatly limit the application of aqueous zinc-ion batteries. Herein, we design a layer of polyionic liquid (PCAVImBr) film with a tunable pore size and charge density on the Zn anode to endow homogenized distribution of an electronic field, acerated Zn2+ permeation, and inhabitation of water entry. Such an optimal combination is achieved via a polymerization induced phase separation strategy, where the enhanced cross-linking density arrests the phase separation in a shallow depth and vice versa. Furthermore, the Zn@PCAVImBr electrode has good plating/stripping reversibility, which retains a 99.6% CE efficiency after 3000 cycles. The symmetric cells can achieve a cycle life of more than 2400 h at different current densities. It is worth mentioning that the NVO//Zn@PCAVImBr full cell can still reach a 91.2% capacity retention after nearly 4000 cycles at a high current of 10 A g-1, and provides new insights for the future research of zinc-ion battery anodes.

Evaluation ofbisphenol‐Aepoxy cured with diethylenetriamine by using phosphorus containing liquid poly(1,2‐butadiene) as multifunctional additives

AbstractPhosphorus containing liquid epoxidate polybutadiene (P‐LEPB) is synthesized and used as the additive to improve the flame retardancy and toughness of epoxy resin (EP). The structure of P‐LEPB is confirmed by Fourier transform infrared (FTIR),1H and13C nuclear magnetic resonance (NMR). With the addition of P‐LEPB, EP composites show earlier degradation; and P‐LEPB plays flame retardancy functions as reflected by the increase of limiting oxygen index (LOI) and its promotion of carbonization as seen from the char scanning electron microscopy images after LOI tests. The addition of P‐LEPB improves the water proof performance of EP composites, playing positive effect on resisting water spreading on the surface and immersing in the EP composites as supported by the water absorption rates and contact angle measurements. The elongation at break increases with addition of P‐LEPB and reaches nearly three times higher than the neat epoxy at P‐LEPB addition of 10%, the toughening effect of P‐LEPB is attributed to the diverting function by the P‐LEPB microspheres upon stress loading, which is related to the size and distribution of P‐LEPB additions as seen from their cross‐sectional images of the composites.

Supported catalytic packing prepared from ceramic packing for reactive distillation of ethyl acetate

Here, an “etching – modification filling – graft copolymerization” strategy is proposed to prepare the ceramic Raschig ring with low specific surface into a catalytic packing for reactive distillation. In this work, a strategy of “etching-modification filling-graft copolymerization” was proposed to load the acidic ionic polyionic liquid on the smooth ceramic surface. In this way, commercial ceramic Raschig rings were successfully transformed into the supported catalytic packing for the reactive distillation, and were further evaluated with esterification reaction of ethyl acetate by means of the fully mixed reactor, the ultrasonic destruction, the cyclic catalysis reaction and the lab-scale distillation column experiment. This catalyst coating has good adhesion with the substrate. It can withstand 24 h of ultrasound damage and shows good stability in three cycle catalytic experiments. This kind of coated catalyst has better catalytic activity than the commercial Amberlyst 15 dry. In the lab-scale reaction distillation, the supported catalyst Raschig ring can achieve a higher conversion in comparison with the tea bag catalytic packing of Amberlyst 15 dry under some conditions.

Heteroployacid on the composite of boehmite and polyionic liquid as a catalyst for alcohol oxidation and tandem alcohol oxidation Knoevenagel condensation reactions

Using boehmite as an available and low-cost natural compound, a bi-functional catalytic composite is prepared through vinyl-functionalization of boehmite, followed by polymerization with the as-prepared bis-vinylimidazolium bromide ionic liquid and supporting of phosphotungstic acid. The catalyst was characterized via ICP, XRD, TGA, FTIR, SEM/EDS and elemental mapping analysis and applied for promoting alcohol oxidation reaction and one-pot tandem alcohol oxidation/Knoevenagel condensation reaction in aqueous media under mild reaction condition. The results indicated high catalytic activity of the catalyst for both reactions. This protocol showed high generality and aliphatic, aromatic and heterocyclic alcohols could be applied as substrates to furnish the corresponding products in high to excellent yields. Furthermore, hot filtration test confirmed true heterogeneous nature of the catalysis. The catalyst could also be recovered readily and reused for at least five runs of the reaction with low loss of the activity and phosphotungstic acid leaching upon each run.

Base-functionalized polymeric chemisorbents for succinic acid recovery from aqueous solution

New base-functionalized polymers are synthesized and assessed for their ability to chemisorb succinic acid (SA) from dilute aqueous solution. A hydrogel comprised predominantly of poly(2-N,N-dimethylaminoethylacrylamide) absorbs 0.17 g·SA /g·polymer, representing just 21% of the maximum theoretical yield. The lower-than-expected basicity is attributed to confinement of polymer-bound amine functionality by the swollen crosslink network, which inhibits the solvation needed to stabilize ammonium carboxylate ion pairs. These gel effects are avoided by synthesizing a 1-vinyl-3-dodecylimidizolium based polyionic liquid (PIL) bearing a hydroxide counter ion. This linear, water-insoluble PIL absorbs 0.20 g·SA /g·polymer, and functions effectively at the near-neutral pHs required of most biocatalysts. As such, the material is sufficiently basic to extract succinic acid during its bioproduction, while also facilitating feed-back control of aqueous solution pH.

Triazine crosslinked polyionic liquid: An electrolyte-stable, lithiophilic and electrostatic shielding layer for uniform lithium plating/stripping

Rational design of functional layer on Cu current collector with polymer material is an effective strategy to improve electrochemical performance of batteries with Li anode. Here, a multifunctional solvent-stable layer, which contains triazine crosslinked polyionic liquid (cPIL) as the polymer matrix and in-situ formed LiF nanoparticle as filler (cPIL-LiF), is constructed on Cu foil to regulate the plating/stripping behavior of Li. The cPIL with excellent lithiophilicity and electrostatic shielding performance ensures homogeneous Li+ flux and promotes uniform Li deposition. The LiF nanoparticles and TFSI anions in cPIL-LiF contribute to the formation of the stable LiF- and Li3N-rich solid electrolyte interphase (SEI). Due to these superiorities, excellent interfacial stability is achieved and, consequently, dense and dendrite-free Li deposition is well maintained during cycling. The cPIL-LiF coated Cu enables an improved cycling stability with coulombic efficiency of ∼98% for 200 cycles, much better than the bare Cu and the Cu modified with the commonly used polymers. Moreover, the full cells with Li4Ti5O12/LiFePO4 cathodes and cPIL-LiF-Cu@Li (limited amount of deposited Li) demonstrate apparently enhanced electrochemical performance. This work provides new perspectives to construct electrolyte-stable artificial protective layer on Cu current collector for stable Li plating/stripping and enriches the understanding on the development of high-performance Li metal-based batteries.

An efficient initiator system containing AlCl3 and supported ionic-liquid for the synthesis of conventional grade polyisobutylene in mild conditions

Ionic liquid based systems are used to facilitate the cationic polymerization of isobutylene to conventional grade polyisobutylene (PIB) using AlCl3 as an initiator. Specifically, the compound 1-butyl-3-methylimidazolium chloride (IL) is employed as a reference system due to its simplicity, as well as the polyionic liquid (PIL), prepared via radical polymerization of 1-butyl-3-vinylimidazolium chloride, and the halloysite clay (Hal) supported ionic liquid (S-IL). The overall results stated that the designed AlCl3/S-IL initiator system can be used as a safer and greener alternative to the industrially used BF3 system, in the development of isobutylene polymerizations under mild reaction conditions to conventional grade PIB for viscosity improvement applications. The microstructure and final properties of the as-synthesized PIB was unraveled and compared to Indopole 2100, as a commercial PIB. DFT calculations were performed to understand the different performance of IL and PIL with respect to the S-IL system, and also to show why the catalyst loading for the latter system is lower, as well as to understand how each of the three systems sequesters the catalyst AlCl3. Since the interaction is non-covalent or ionic, in addition to NBO charges, NCI plots were also used.

Enhanced crystallization of poly(lactic acid) bioplastics by a green and facile approach using liquid poly(ethylene glycol)

AbstractPolylactic acid (PLA) bioplastics have attracted increasing attention from both academic and industrial researchers due to their biomass‐derived nature and low toxicity for the human body and environment. A major drawback of PLA is slow crystallization during processing, which considerably limits its commercial applications. In this study, a simple and low‐cost approach involving the addition of eco‐friendly low molecular weight poly(ethylene glycol) (PEG; 400 g/mole) as a green solvent was developed to enhance the PLA crystallization process. Differential scanning calorimetry and polarized optical microscopy data revealed that the introduction of PEG into PLA considerably increased the PLA crystallization rate. In particular, the isothermal crystallization rate of a system with a PLA/PEG mass ratio of 70/30 was more than seven times greater than that of neat PLA. In addition, the miscibility, thermal properties, and microstructures of various PLA/PEG blends were determined. A substantial reduction in the equilibrium melting temperature of PLA after PEG addition confirmed that these polymer blends were thermodynamically miscible in the melt, which strongly influenced the PLA crystallization rate. Furthermore, the addition of PEG increased the regularity of PLA crystals and induced the formation of ring‐banded PLA spherulites with periodic twisted lamellae.

Fabrication of effective electromagnetic shielding leather with a chromium-free multi-network structure

Chrome-free tanning and intelligentization are hot topics in leather-related research. In this work, green chrome-free tanned electromagnetic shielding leather is proposed based on the modification of skin collagen fibers using polyionic liquids (PILs), metal-organic framework-layered double hydroxide (MOF-LDH), and polyaniline (PANI). First, a network-interspersed PILs/MOF-LDH-Zr structure was synthesized using MOF-LDH, ionic liquid, methacrylic acid, and zirconium sulfate as raw materials based on a radical polymerization approach. Then, PANI was grown in situ on the surface of the leather to help construct a green chrome-free tanned electromagnetic shielding leather with a leather shrinkage temperature of 94.5 °C and an effective EMI shielding capability of 32.3 dB. The enhanced tanning performance of PILs/MOF-LDH-Zr may be due to the multi-point cross-linking of –COOH, imidazole groups, and metallic zirconium. The conductive properties of PANI and the porous network structure of leather are helpful to realize electromagnetic shielding of the leather. Interestingly, after 1000 bending tests, more than 99% of the shielding effectiveness (SE) could be retained. As such, an effective and powerful strategy is proposed to construct flexible electromagnetic shielding material based on an eco-friendly chrome-free tanning approach.

Colorimetric and electrochemical detection platforms for tetracycline based on surface molecularly imprinted polyionic liquid on Mn3O4 nanozyme

In this work, a smart tetracycline (TC) imprinted material (DSMIP@Mn3O4) is prepared via atom transfer radical polymerization of dual ionic liquid (IL) monomers on the surface of Mn3O4 nanoparticles. The obtained DSMIP@Mn3O4 shows a core-shell structure with a sphere shape and has high oxidase-like activity and recognition ability. It has been used to construct colorimetric and electrochemical detection platforms for TC. The colorimetric detection is based on the recombined TC blocking the molecular channels on the surface of DSMIP@Mn3O4, which hinders the catalytic oxidation of 3,3′,5,5′-tetramethylbenzidine to the blue product. The linear detection range is 0.5 μM–150 μM and the low detection limit is 0.1 μM. This system is further developed for the visual semi-quantitative detection of TC by using a smartphone. Furthermore, the DSMIP@Mn3O4 is combined with IL-modified carbon nanotube-graphene composite for the sensitively electrochemical detection of TC, which shows a wide linear range of 0.01 μM–20 μM and a low detection limit of 5 nM. The proposed methods have high selectivity and reproducibility and suit different detection situations. Their pracibility is evaluated by determining TC in different samples, and the measurement results are consistent with that obtained by high-performance liquid chromatography. Hence, the colorimetric and electrochemical detection platforms have good application potential.

Polyionic liquids supramolecular hydrogel with anti-swelling properties for underwater sensing

The preparation of hydrogel-based wearable sensors for underwater application with high mechanical properties and electrical conductivity is an urgent challenge. Here, a supramolecular hydrogel based on polyionic liquids was designed and prepared for underwater sensing. The introduction of functional ionic liquid structures effectively increased the supramolecular interaction in the hydrogel network, which made the hydrogel successfully resist the interference of external water molecules. Depending on the effect of charge and hydrophobic interactions, this supramolecular hydrogel sensor exhibited high tensile (759 %), high tensile strength (0.23 MPa), high sensitivity (GF = 10.76) and extensive antibacterial properties, even in seawater environment. The obtained hydrogel sensor successfully monitored the swimming posture, which was helpful to digitally reflect the limb movement of athletes during underwater sports. This work made progress in the field of underwater wearable sensors based on hydrogels, and this design of multifunctional hydrogel provided a new idea for the development of functional sensors.

Mesoporous poly(amino acids) ionic liquid with excellent extraction performance for sunset yellow

The poly amino acid ionic liquid {1-ethyl-3-benzyltriethylammonium alanine P[ETA][Ala]} was synthesized and characterized with Fourier Transform Infrared Spectroscopy (FTIR), Carbon Nuclear Magnetic Spectra(13C NMR), Scanning Electron Microscope (SEM), X-ray (XRD), Brumaire-Emmett-Teller (BET). SEM and BET confirmed that P[ETA][Ala] was a porous material. Under optimized conditions, the linear range of sunset Yellow (SY) was 0.02–20.00 μg mL−1, the limit of detection (LOD) was 0.01 μg mL−1 and the enrichment factor was 11.0 (pre-extraction solution volume/elution volume). The isothermal adsorption and kinetic models were investigated to explain the extraction (adsorption) mechanism of SY on P[ETA][Ala]. This proposed method was successfully applied the analysis of beverage samples with recoveries of 92.0–110.0% and relative standard deviations of 1.1–5.0%.

Preparation of Modified Porous Polyionic Liquid Microspheres and Their Application in High Performance Liquid Chromatography

Polymer microspheres have been widely used as a stationary phase in liquid chromatography. We characterized the properties of the novel polyionic liquid microspheres prepared and explored their application as a stationary phase in liquid chromatography. Cytosine, uracil, benzene, benzene homologs and alkaloids were successfully separated by liquid chromatography with the polymer microspheres as packing materials in the chromatographic column.

Electrically Accelerated Self-Healable Polyionic Liquid Copolymers.

Electrically accelerated self-healable poly(ionic liquids) copolymers that exhibit resistor-capacitor (RC) circuit properties are developed. At low alternating current (AC) frequencies these materials behave as a resistor (R), whereas at higher frequencies as a capacitor (C). These properties are attributed to a combination of dipolar and electrostatic interactions in (1-[(2-methacryloyloxy)ethyl]-3-butylimidazolium bis(trifluoromethyl-sulfonyl)imide) copolymerized with methyl methacrylate (MMA) monomers to form p(MEBIm-TSFI/MMA)] copolymers. When the monomer molar ratio (MEBIm-TSFI:MMA) is 40/60, these copolymers are capable of undergoing multiple damage-repair cycles and self-healing is accelerated by the application of alternating 1.0-4.0V electric field (EF). Self-healing in the absence of EFs is facilitated by van der Waals (vdW) interactions, but the application of AC EF induces back and forth movement of charges against the opposing force that result in dithering of electrostatic dipoles giving rise to interchain physical crosslinks. Electrostatic inter- and intrachain interactions facilitated by copolymerization of ionic liquid monomers with typically dielectric acrylic-based monomers result in enhanced cohesive energy densities that accelerate the recovery of vdW forces facilitating self-healing. Incorporating ionic liquids into commodity polymers offers promising uses as green conducting solid polyelectrolytes in self-healable energy storage, energy-harvesting devices, and many other applications.