Comparative study of iontophoresis-assisted transdermal delivery of bupivacaine and lidocaine as anesthetic drugs.

Postoperative pain management is an important aspect of the overall surgical care process. Effective pain management not only provides patient comfort but also promotes faster recovery and reduces the risk of complications. Bupivacaine (BUP) and Lidocaine (LID) transdermal drug deliveries via thermoplastic polyurethane matrix (TPU) and iontophoresis technique are proposed here as alternative routes for postoperative pain instead of the injection route. Under applied electric field, the amounts of BUP and LID released were 95% and 97% from the loaded amounts, which were higher than the passive patch of 40%. The time to equilibrium of BUP turned out to be faster than the time to equilibrium of LID by approximately 1.5 times. This was due to 2 factors namely the drug molecular weight and the drug pKa value; they play an important role in the selection of a suitable drug for fast-acting or long-acting for the postoperative patients. By using this transdermal patch via iontophoresis system, BUP was deemed as the suitable drug for fast-acting due to the shorter time to equilibrium, whereas LID was the suitable drug for long-acting. The in-vitro drug release - permeation study through a porcine skin indicated the efficiency and potential of the system with the amounts of drug permeated up to 76% for BUP and 81% for LID. The TPU transdermal system was demonstrated here as potential to deliver BUP and LID for postoperative patients.

Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) as an insulin carrier in silk fibroin hydrogels for transdermal delivery via iontophoresis.

In this study, silk fibroin (SF) was utilized as the starting material to fabricate physically crosslinked hydrogels. Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) was synthesized and characterized as a drug carrier, with insulin as the model drug. PEDOT:PSS, with a high electrical conductivity of 1666 ± 49 S cm-1, interacted with insulin molecules via electrostatic interaction by replacing the dopant PSS molecules. Insulin-loaded PEDOT:PSS embedded in the SF hydrogel resulted in an increase in the degree of swelling, pore size, and mesh size of the hydrogel. In the in vitro release and release-permeation experiments, the amounts of insulin release and release-permeation were investigated using a modified Franz diffusion cell, under the effects of SF concentrations, electric fields, and pH values. The amounts of insulin release and release-permeation from the pristine SF hydrogel and the PEDOT:PSS/SF hydrogel followed the power laws with the scaling exponents close to 0.5, indicating the Fickian diffusion or the concentration gradient. Under electric fields, with or without PEDOT:PSS used as the drug carrier, the insulin amount and diffusion coefficient were shown to increase with the increasing electric field due to the electro-repulsive forces between the cathode and insulin molecules and SF chains, electroosmosis, and SF matrix swelling. The SF hydrogel and PEDOT:PSS as the drug carrier are demonstrated herein as new components in the transdermal delivery system for the iontophoretically controlled insulin basal release applicable to diabetes patients.

Screen-printed electrode designed with MXene/doped-polyindole and MWCNT/doped-polyindole for chronoamperometric enzymatic glucose sensor.

The enzymatic glucose sensors as modified by MXene-dPIn and MWCNT-dPIn on a screen-printed carbon electrode (SPCE) were investigated. Herein, MXene was molybdenum carbide (Mo3C2) which has never been utilized and reported for glucose sensors. The biopolymer type to support the enzyme immobilization was examined and compared between chitosan (CHI) and κ-carrageenan (κC). MWCNT-dPIn obviously showed a larger electroactive surface area, lower charge transfer resistance and higher redox current than Mo3C2-dPIn, indicating that MWCNT-dPIn is superior to Mo3C2-dPIn. For the chitosan-based sensors, the sensitivity value of CHI-GOD/Mo3C2-dPIn is 3.53 µA mM-1 cm-2 in the linear range of 2.5-10 mM with the calculated LOD of 1.57 mM. The sensitivity value of CHI-GOD/MWCNT-dPIn is 18.85 µA mM-1 cm-2 in the linear range of 0.5-25 mM with the calculated LOD of 0.115 mM. For the κ-carrageenan based sensors, κC-GOD/MWCNT-dPIn exhibits the sensitivity of 15.80 µA mM-1 cm-2 and the widest linear range from 0.1 to 50 mM with the calculated LOD of 0.03 mM. The presently fabricated sensors exhibit excellent reproducibility, good selectivity, high stability, and disposal use. The fabricated glucose sensors are potential as practical glucose sensors as the detectable glucose ranges well cover the glucose levels found in blood, urine, and sweat for both healthy people and diabetic patients.

Iontophoretically controlled insulin delivery via water-soluble conductive polymer PANI:PSS and thermoplastic polyurethane matrix.

Transdermal insulin delivery is an alternative route to deliver insulin through the body skin with the challenges to overcome the low drug skin permeability and high molecular weight. Polyaniline doped with poly(4-styrenesulfonic acid) (PANI:PSS), a conductive polymer with the high electrical conductivity, was synthesized and utilized as a drug carrier to improve the drug delivery capability from a porous thermoplastic polyurethane (TPU) matrix. The insulin was electrostatically attached to PANI:PSS based on the ion exchange between insulin and PSS. For the in vitro drug release of insulin loaded PANI:PSS relative to the pristine insulin alone, the amount of insulin released was improved to 84.70% with the time to equilibrium of 2 h under the electrical field of 6 V. For the ex vivo release-skin permeation, the amount insulin released and permeated became lower at 57.02% with time to equilibrium of 2 h, due to the pig skin acting as a barrier for insulin permeation. The modified insulin transdermal delivery, with PANI:PSS as the drug carrier and drug enhancer relative to without, is shown here to influence the insulin release rate, amount, and duration, suitable to treat diabetes patients.

A label-free electrochemical immunosensor based on 11-mercaptoundecanoic acid grafted chitosan and poly(N-methylaniline) for the detection of carcinoembryonic antigen.

Carcinoembryonic antigen (CEA) is a cancer marker used for monitoring cancer treatment. Herein, a label-free electrochemical immunosensor for determining CEA concentration composed of the thiolated chitosan (tCHI) and the doped poly(N-methylaniline) (dPNMA) is proposed. The tCHI served as a support matrix for the immobilization of CEA antibodies (anti-CEA) and was prepared by using 11-mercaptoundecanoic acid (MUA) as a grafting agent on chitosan (CHI). The excellent electrical conductivity of the dPNMA was utilized as an electron transfer layer for the proposed immunosensor. The successful preparation of the tCHI was confirmed by the attenuated-total reflection Fourier transform spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) were used to illustrate the performance of the proposed immunosensor. The determination of CEA concentration was relied on the decrease in the DPV current response with increasing CEA concentration from the creation of the antigen-antibody immunocomplex. The proposed immunosensor demonstrated a broad concentration range of 0.01 to 30 ng mL-1 with a low limit of detection (LOD) of 0.01 ng mL-1. In addition, the present sensor exhibited excellent selectivity, reproducibility, and long-term stability, suggesting its potential use to determine CEA in clinical immunoassay.

Dual electro- and magneto-induced bending actuators of magnetite-loaded agarose ionogels.

Magnetic ionogels are a new kind of gel composites which combine the elastic properties from the swollen gel matrix and the magnetic properties from a magnetic filler. The dual electro-magneto-responsive agarose ionogels (AG IGels) were fabricated by a solution casting method using 1-butyl-3-methylimidazolium chloride [Bmim][Cl] as the ionic liquid solvent, and embedded with magnetite nanoparticles (Fe3O4 NPs). The addition of Fe3O4 NPs induced the high bending responses under applied electric and magnetic fields via the electronic polarization and magnetic interaction. The 3.0 wt.% Fe3O4/AG MagIGel showed the largest deflection distances relative to other magnetic gel composites; 14.92, 8.96, and 21.63 mm under the applied electric fields of 600 V/mm in silicone oil, 60 V/mm in air, and under the applied magnetic field of 600 G in air, respectively. The bending distances were of comparable in magnitudes to other electro-magneto-responsive materials. Thus, the fabricated Fe3O4/AG MagIGels are demonstrated here as potential for soft electric-magnetic actuator applications.

Chronoampermetric detection of enzymatic glucose sensor based on doped polyindole/MWCNT composites modified onto screen-printed carbon electrode as portable sensing device for diabetes.

Doped-polyindole (dPIn) mixed with multi-walled carbon nanotubes (MWCNTs) were coated on a screen-printed electrode to improve the electroactive surface area and current response of the chronoamperometric enzymatic glucose sensor. Glucose oxidase mixed with chitosan (CHI-GOx) was immobilized on the electrode. (3-Aminopropyl) triethoxysilane (APTES) was used as a linker between the CHI-GOx and the dPIn. The current response of the glucose sensor increased with increasing glucose concentration according to a power law relation. The sensitivity of the CHI-GOx/APTES/dPIn was 55.7 µA mM-1 cm-2 with an LOD (limit of detection) of 0.01 mM, where the detectable glucose concentration range was 0.01-50 mM. The sensitivity of the CHI-GOx/APTES/1.5%MWCNT-dPIn was 182.9 µA mM-1 cm-2 with an LOD of 0.01 mM, where the detectable glucose concentration range was 0.01-100 mM. The detectable concentration ranges of glucose well cover the glucose concentrations in urine and blood. The fabricated enzymatic glucose sensors showed high stability during a storage period of four weeks and high selectivity relative to other interferences. Moreover, the sensor was successfully demonstrated as a continuous or step-wise glucose monitoring device. The preparation method employed here was facile and suitable for large quantity production. The glucose sensor fabricated here, consisting of the three-electrode cell of SPCE, were simple to use for glucose detection. Thus, it is promising to use as a prototype for real glucose monitoring for diabetic patients in the future.

Metformin delivery via iontophoresis based on κ-carrageenan cryogels.

Transdermal drug delivery system (TDDS) is the system for transmitting a drug through the skin into the blood circulation. In this work, κ-Carrageenan (κC) was used as the drug matrix material. The porous κC matrices were fabricated by dissolving the κC in deionized water to obtain hydrogels and then using the freeze-dryer to obtain cryogels. The porous (κC) matrices showed interconnected pore sizes varying between 6.05 to 25.8 nm. In the drug release experiments, the drug diffusion coefficient increased and the drug release duration was reduced with decreasing κC concentration due to the larger κC pore sizes. The diffusion coefficient increased with a shorter release time under the applied electric strength of +1.0 V due to the electro-repulsive force between the Metformin and the anode. For the drug release-permeation of the κC 0.8 % v/v cryogel through the pig skin under applied positive electrical potentials, the amounts of drug release-permeation and diffusion coefficients were enhanced with shorter durations relative to without electrical potential. The κC 0.8 % v/v matrix at the applied electric strength of +6.0 V has been shown here to be potential to be used as the Metformin transdermal controlled delivery patch for abdominal obesity and diabetes.

Synthesis of Highly Conductive Poly(3-hexylthiophene) by Chemical Oxidative Polymerization Using Surfactant Templates.

Poly(3-hexylthiophene) (P3HT) was systematically synthesized by chemical oxidative polymerization in chloroform with ferric chloride (FeCl3) as the oxidizing agent and various surfactants of the shape templates. The effects of 3HT: FeCl3 mole ratios, polymerization times, and surfactant types and concentrations on the electrical conductivity, particle shape and size were systematically investigated. Furthermore, dodecylbenzenesulfonic acid (DBSA), p-toluenesulfonic acid (PTSA), sodium dodecyl sulfate (SDS), and sodium dioctyl sulfosuccinate (AOT) were utilized as the surfactant templates. The P3HT synthesized with DBSA at 6 CMC, where CMC stands for the Critical Micelle Concentration of surfactant, provided a higher electrical conductivity than those with PTSA, SDS and AOT. The highest electrical conductivity of P3HT using DBSA was 16.21 ± 1.55 S cm-1 in which the P3HT particle shape was spherical with an average size of 1530 ± 227 nm. The thermal analysis indicated that the P3HT synthesized with the surfactants yielded higher stability and char yields than that of P3HT without. The P3HT_DBSA electrical conductivity was further enhanced by de-doping and doping with HClO4. At the 10:1 doping mole ratio, the electrical conductivity of dP3HT_DBSA increased by one order of magnitude relative to P3HT_DBSA prior to the de-doping. The highest electrical conductivity of dP3HT_DBSA obtained was 172 ± 5.21 S cm-1 which is the highest value relative to previously reported.

Enhanced transdermal insulin basal release from silk fibroin (SF) hydrogels via iontophoresis.

Insulin is the peptide hormone used to treat the diabetes patient. The hormone is normally taken by injection. The transdermal drug delivery system (TDDS) is an alternative route. The silk fibroin (SF) hydrogels were fabricated via solution casting as the insulin matrix. The release and release-permeation experiments of the insulin loaded SF hydrogels were carried out using a modified Franz-diffusion cell at 37 °C for 36 h, under the effects of SF concentrations, pH, and electric field. The release-permeation mechanism through the pig skin was from the Case-II transport with the constant release rate. The diffusion coefficient (D) increased with decreasing SF concentration due to a larger mesh size, and with increasing electric field due to the electroreplusive forces between the insulin and the SF hydrogels against the negatively-charged electrode, and the induced SF hydrogel expansion. The rate and amount of insulin release-permeation became relatively lower as it required a longer time to generate aqueous pathways through the pig skin. The present SF hydrogels are demonstrated here deliver insulin with the required constant release rate, and the suitable amount within a prescribed duration.

Synthesis and characterization of CoxFe1-xFe2O4 nanoparticles by anionic, cationic, and non-ionic surfactant templates via co-precipitation.

The cobalt ferrite nanoparticles (CoxFe1-xFe2O4) were synthesized by the surfactant templated co-precipitation method using various surfactants namely sodium dodecyl sulfate (SDS), hexadecyltrimethylammonium bromide (CTAB), and Tween20. Under the substitution, the CoxFe1-xFe2O4 particles were synthesized at various Co2+ and Fe2+ mole ratios (x = 1, 0.6, 0.2, and 0) with the SDS. The cobalt ferrite nanoparticles were characterized for their morphology, structure, magnetic, and electrical properties. All CoxFe1-xFe2O4 nanoparticles showed the nanoparticle sizes varying from 16 to 43 nm. In the synthesis of CoFe2O4, the SDS template provided the smallest particle size, whereas the saturated magnetization (Ms) of CoFe2O4 was reduced by using CTAB, SDS, and Tween20. For the CoxFe1-xFe2O4 as synthesized by the SDS template at 1.2 CMC, the Ms increased with increasing Fe2+ mole ratio. The highest Ms of 100.4 emu/g was obtained from the Fe3O4 using the SDS template. The Fe3O4 nanoparticle is potential to be used in various actuator and biomedical devices.

A highly selective and sensitive electrochemical sensor for dopamine based on a functionalized multi-walled carbon nanotube and poly(N-methylaniline) composite.

Dopamine (DA) is an important neurotransmitter used for diagnosing various diseases from its abnormal concentrations in human fluids. Herein, an electrochemical sensor based on a composite of re-doped poly(N-methylaniline) (rePNMA) and modified multi-walled carbon nanotubes (fMWCNTs), termed fMWCNT-rePNMA, was developed to measure DA concentration. The successful modification of the fMWCNT surface was confirmed by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Cyclic voltammetry (CV) displayed an excellent electrocatalytic activity of the fMWCNTs-rePNMA composite towards the oxidation of DA. The developed fMWCNTs-rePNMA composite demonstrated a broad linear range from 5 to 90 µmol L-1 with a low limit of detection (LOD) value of 2.23 µmol L-1, and a fast response with a high sensitivity of 251.5 nA µmol-1 L as determined from the calibration curve of the DA determination. In addition, the fMWCNTs-rePNMA composite selectively identified and quantified DA in the presence of ascorbic acid (AA) and uric acid (UA). Therefore, the fMWCNTs-rePNMA composite sensor shows potential to determine the level of DA in human urine.

Electrically controlled transdermal delivery of naproxen and indomethacin from porous cis-1,4-polyisoprene matrix.

This study is focused on the inquiry of using a porous polymeric structure to absorb and release transdermally two drugs through a skin from deproteinized natural rubber latex (DPNR). The porous DPNR films were fabricated from the internal formation of surfactant micelles and their subsequent leaching out to generate porous structures. The pore size of DPNR films increased with increasing surfactant amount. The model drugs were naproxen and indomethacin; their releases and release-permeations were investigated under the effects of surfactant amount, electrical potential, and drug size. Without electric field, the drug release mechanism was mainly driven by concentration gradient. The higher amount of drug released was obtained from the matrix with a larger pore size. Under electric field, the higher amounts of drug release were obtained in the shorter drug release durations, via the electrorepulsive force between the negatively charged drugs and the cathode electrode. The molecular drug size was a factor for the drug absorption, release rate and amount. For the drug release-permeation experiment through the pig skin, there were two release-permeation periods as governed by the combination of concentration gradient and swelling in the first period, and the matrix erosion in the second period. The fabricated porous DPNR films have been shown here to be potential to be used as a transdermal patch with electrically controllable drug release rate, amount and duration along with the facile drug-matrix loading and absorption.

Hyaluronic Acid and Graphene Oxide-incorporated Hyaluronic Acid Hydrogels for Electrically Stimulated Release of Anticancer Tamoxifen Citrate.

Transdermal drug delivery is the transport of drug across the skin and into the systemic circulation. Patch is a one of transdermal device that is used to attach on skin and contains drug. The drug matrices from hyaluronic acid (HA) and graphene oxide (GO) incorporated HA hydrogel were fabricated for the release of tamoxifen citrate (TMX) as the anticancer drug under applied electrical field. The pristine HA hydrogels as the matrix and GO as the drug encapsulation host were fabricated for transdermal patch by the solution casting using citric acid as the chemical crosslinker. In vitro drug release experiment was investigated by utilizing the modified Franz-diffusion cell under the effects of crosslinking ratio, electric potential, and GO. The TMX release behaviors from the hydrogels were found to be from the three mechanisms: the pure Fickian diffusion; the anomalous or non-Fickian diffusion; and Super case II transport depending on the crosslinking conditions. The TMX diffusion and release amount from the pristine HA hydrogels were increased with smaller crosslinking ratios. With applied electrical potential, the enhanced TMX diffusion and release amount were observed when compared to that without due to the electro-repulsive force. Furthermore, the TMX diffusion from the HA hydrogel with GO as the drug encapsulation host was higher by two orders of magnitude than without GO.

Synthesis and Characterization of Fe0.8Mn0.2Fe2O4 Ferrite Nanoparticle with High Saturation Magnetization via the Surfactant Assisted Co-Precipitation.

Manganese ferrite nanoparticles (MnFe2O4) were synthesized via surfactant-assisted co-precipitation, where sodium dodecyl sulfate (SDS) was used as the template to control particle size at various SDS concentrations. The substitutions of iron (II) (Fe2+) into the MnFe2O4 ferrite nanoparticles were carried out to obtain Fe(1-x)MnxFe2O4, with various Mn2+: Fe2+ molar ratios. The synthesized ferrite nanoparticles were characterized by the Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analyzer (TGA), X-ray diffractometer (XRD), energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscope (TEM), two-point probe, and vibrating sample magnetometer (VSM) techniques. The experimental Mn:Fe mole ratios of the Fe(1-x)MnxFe2O4 ferrite nanoparticles were verified to be in agreement with the theoretical values. The synthesized MnFe2O4 and Fe(1-x)MnxFe2O4 ferrite nanoparticles were of mixed spinel structures, with average spherical particle sizes between 17-22 nm, whereas the magnetite ferrite nanoparticles (Fe3O4) were of the inverse spinel structure. They showed soft ferromagnetic behavior. The synthesized Fe0.8Mn0.2Fe2O4 ferrite nanoparticle possessed the highest saturation magnetization of 88 emu/g relative to previously reported work to date.

Conductive poly(2-ethylaniline) dextran-based hydrogels for electrically controlled diclofenac release.

Transdermal drug delivery systems (TDDS) are used as an alternative route to deliver drugs into the blood system for therapy. The matrix materials that have been widely used in TDDS are hydrogels. The dextran hydrogels were prepared by the solution casting using trisodium trimetaphosphate (STMP) as the crosslinking agent, and diclofenac sodium salt (Dcf) as the anionic model drug. Poly(2-ethylaniline) (PEAn) was successfully synthesized and embedded into the dextran hydrogel as the drug encapsulation host. The in-vitro release of Dcf from the hydrogels was investigated using a modified Franz-Diffusion cell in a phosphate-buffered saline (PBS) solution at the pH of 7.4 and at 37 °C for a period of 24 h, under the effects of crosslinking ratios, dextran molecular weights, electric potentials, and the conductive polymer PEAn. The release mechanism of Dcf from the dextran hydrogels and the composite without electrical potential was the diffusion controlled mechanism or the Fickian diffusion. Under applied electrical potentials, the release mechanism was a combination between the Fickian diffusion and the matrix swelling. The Dcf diffusion coefficients from the dextran hydrogels without electrical potential increased with decreasing crosslinking ratio and molecular weight. Under electrical potentials, the corresponding diffusion coefficients were much higher due mainly to the electro-repulsive force between the negatively charged electrode and the negatively charged dextran and the induced dextran expansion. For the Dcf-loaded PEAn/dextran composite, the diffusion coefficient was enhanced by two orders of magnitude when the electric potential was applied, specifically illustrating the unique features of PEAn as an efficient drug encapsulation host without electric field, and as a drug release enhancer under electric field through the reduction reaction.

Electrically controlled release of anticancer drug 5-fluorouracil from carboxymethyl cellulose hydrogels.

Transdermal drug delivery is a technique used to introduce a drug through the skin and into the blood system. The drug-matrix hydrogels based on carboxymethyl cellulose (CMC) were prepared by solution casting method using citric acid as the crosslinking agent at various amounts. The 5-fluorouracil, an anticancer non-ionic drug, was released from the CMC hydrogels under applied electrical field. The diffusion coefficient and the release mechanism of the drug of the CMC hydrogels were investigated by the modified Franz-diffusion cell with the PBS buffer solution at the pH value of 7.4 and at 37 °C for the duration of 24 h. The effects of mesh size, electric potential, and electrode polarity were systematically investigated. The swelling test illustrated an increase in the mesh size with decreasing crosslinking agent. In addition, the drug diffusion coefficient increased with decreasing crosslinker: repeated group mole ratio. The diffusion coefficient depended critically on the applied electric potential and the electrode polarity. The non-ionic drug release mechanisms were identified as the matrix deswelling and electroosmosis, in addition to the pure diffusion without electric field. Thus, CMC has been shown a potential bio-based matrix for electrically controlled non-ionic drug delivery.

High sensitivity room temperature sulfur dioxide sensor based on conductive poly(p-phenylene)/ZSM-5 nanocomposite.

Recently, there has been growing interests in the development of composite materials as the new alternative gas sensing materials for replacing metal oxide based sensors which require the elevated operating temperature. Herein, we reported the fabrication and testing of new sensing composite materials based on the conductive poly(p-phenylene) (PPP) nanoparticle and zeolites for sulfur dioxide (SO2) detection at room temperature under the effects of doping, zeolite type, zeolite content, SO2 concentration as well as interferences and humidity. The relative electrical conductivity response depended critically on the doping agent type, doping ratio, and doping temperature. The addition of porous zeolites into the doped-PPP (dPPP) matrix induced the improvement in selectivity and sensing performances towards SO2 as it promoted more surface area for SO2 adsorption and its new synergistic effect with the conductive dPPP, related to the additional conductive polymer doping from the dissolution of the SO2 in intrazeolitic water as identified and reported here. Among all materials, the dPPP/ZSM-5 composite with perchloric acid (HClO4) as the doping agent, the doping ratio of 50:1, the doping temperature of 70 °C, and the zeolite content of 30% exhibited the highest relative response of 25.42 towards 500 mg L-1 SO2 with good repeatability. This composite provided the SO2 sensitivity of 0.0483 L mg-1 with R2 of 0.9927 and the limit of detection (LOD) of 5 mg L-1 as determined from the electrical conductivity signal to noise ratio. The present sensing material is a potential candidate in the practical detection of SO2 at room temperature.

Facile formation of agarose hydrogel and electromechanical responses as electro-responsive hydrogel materials in actuator applications.

The agarose hydrogels (AG HyGels) were fabricated by a solvent casting method at various agarose concentrations, resulting in the 3D hydrogel networks via the physical crosslinking from the hydrogen bonding. The actuator performances were investigated at various agarose contents and electric field strengths. For the electromechanical properties, the AG HyGel_12.0 %v/v possessed the highest storage modulus (G') and storage modulus relative response (ΔG'/G'0) of 4.48 × 106 Pa and 1.07, respectively under applied electric field strength of 800 V/mm due to the electrostriction effect. In the electro-induced bending measurement, the highest deflection distance was obtained from the AG HyGel_2.0 %v/v due to its initial lower rigidity. Relative to other bio-based hydrogels, the present AG HyGels are first demonstrated here as electroactive materials showing comparable magnitudes in the electroactive responses, but with the simple fabrication method without toxic ingredients required. Thus, the present AG HyGels are potential material candidates for soft actuator applications.

Synthesis and Characterization of Hollow-Sphered Poly(N-methyaniline) for Enhanced Electrical Conductivity Based on the Anionic Surfactant Templates and Doping.

Poly(N-methylaniline) (PNMA) is a polyaniline derivative with a methyl substituent on the nitrogen atom. PNMA is of interest owing to its higher solubility in organic solvents when compared to the unsubstituted polyaniline. However, the electrical conductivity of polyaniline derivatives suffers from chemical substitution. PNMA was synthesized via emulsion polymerization using three different anionic surfactants, namely sodium dodecylsulfate (SDS), sodium dodecylbenzenesulfonate (SDBS), and dioctyl sodium sulfosuccinate (AOT). The effects of surfactant structures and concentrations on electrical conductivity, doping level, crystallinity, morphology, and thermal stability were investigated. The re-doping step using perchloric acid (HClO4) as a dopant was sequentially proceeded to enhance electrical conductivity. PNMA synthesized in SDBS at five times its critical micelle concentration (CMC) demonstrated the highest electrical conductivity, doping level, and thermal stability among all surfactants at identical concentrations. Scanning electron microscopy (SEM) images revealed that the PNMA particle shapes and sizes critically depended on the surfactant types and concentrations, and the doping mole ratios in the re-doping step. The highest electrical conductivity of 109.84 ± 20.44 S cm-1 and a doping level of 52.45% were attained at the doping mole ratio of 50:1.