Water Vapor Transmission Properties Research Articles

Low cytotoxicity, antibacterial property, and curcumin delivery performance of toughness-enhanced electrospun composite membranes based on poly(lactic acid) and MAX phase (Ti3AlC2)

MXenes, synthesized from their precursor MAX phases, have been extensively researched as additives to enhance the drug delivery performance of polymer matrices, whereas there is a limited number of previous reports on the use of MAX phases themselves for such applications. The use of MAX phases can exclude the complicated synthesis procedure and lessen resultant production and environmental costs required to convert MAX phases to MXenes. Herein, electrospun membranes of poly(lactic acid) (PLA) and a MAX phase (Ti3AlC2) have been fabricated for curcumin delivery. The composite membrane exhibits significantly higher toughness (8.82 MJ m−3) than the plasticized PLA membrane (0.63 MJ m−3) with low cytotoxicity, supporting proliferation of mouse fibroblast L929 cells. The curcumin-loaded composite membrane exhibits high water vapor transmission (∼7350 g m−2 day−1), porosity (∼85 %), water wettability, and antibacterial properties against E. coli and S. aureus. Seven-day curcumin release is enhanced from 45 % (PLA) to 67 % (composite) due to curcumin diffusion from the polymer fibers and MAX phase surface that contributes to overall increased curcumin adsorption and release sites. This work demonstrates the potential of the MAX phase to enhance both properties and curcumin delivery, promising for other eco-friendly systems for sustainable drug delivery applications.

Hygrothermal Performance of Lime-Based Thermal Insulation Mortars: Water Absorption, Hygroscopic Sorption, and Water Vapour Permeability

Lightweight mortars, which are able to capture carbon, offer moisture buffering and increase the thermal resistance of building elements could be useful for both new and renovated buildings. The hygrothermal properties of lime-based renovation and insulation mortars were studied and the possibilities of reducing water absorption was the main focus of the study. Water absorption coefficient, hygroscopic sorption, and water vapour transmission properties were studied according to EN 1015-18, ISO 12571 and ISO 12572. Hydrated lime was used as the main binder and volcanic sand as an aggregate, white cement and silane in two different concentrations acted as additives. Half of the specimens were kept in forced carbonation conditions (CO2 was added regularly). Drying and carbonation processes were monitored by weighing the specimens regularly. Silane had the ability to reduce water absorption and sorption. Forcing carbonation reduced water absorption and sorption and slightly increased water vapour permeability.

Measurement of water vapor transmission properties using the cup method – error caused by air buoyancy

The determination of water vapor transmission properties is commonly performed using the cup method. The method is based on periodic weighing of the cup assembly over time. If the air density surrounding the balance differs between weighings, measured change of mass is affected by the difference of ambient air buoyant force. For the correction of this effect can be used a mathematical formula presented in the literature and standards. The ASTM E96 states that this correction is important if observing changes of water vapor mass 0–100 mg. This paper therefore analyses possible errors of measured water vapor transmission properties based on a single 100 mg mass change without applying the buoyancy correction. It was found that for most common samples of building materials (sd < 3 m) and regular sizes of cup assemblies the error of a single mass change measurement can be up to ca. ±13 %, while assemblies with higher volume, higher mass, or more vapor tight samples can experience an error up to ±26 %. However, the vapor transmission properties are usually determined based on five consecutive weight changes. In that case the error can be up to five times lower (±2.5–5 %). Regarding the formula of the buoyancy correction the most important parameter was found to be the chosen volume of the cup assembly which, however, depends on particular setup and sample air-permeance. Only two extreme scenarios regarding this topic were analyzed while the full understanding of the accurate correction is still unsolved in its complexity.

Determination of Water Vapor Transmission Properties of Sandstones in the Yungang Grottoes

ABSTRACT The Yungang Grottoes, one of China’s most notable cultural heritage sites, are located in sandstone strata. The main causes of deterioration observed in the field are associated with moisture action, which greatly affects the long-term performance of the material. In particular, for immovable cultural heritage that is exposed to natural climatic fluctuations throughout the year, interaction with water vapor cannot be avoided. To obtain an insight into the water vapor transmission properties of local sandstone, a series of laboratory tests were conducted using the wet-cup method. The correlation of water vapor transmission with environmental relative humidity and pore structure was examined. The results indicate that as the relative humidity increased, the diffusion coefficient increased considerably due to the contribution of capillary condensate flow. In addition, a positive relationship was found between the diffusion coefficient and open porosity. The water vapor diffusion in sandstone occurred in transitory mode and the diffusion coefficient was estimated from the average pore radius. The calculated values were two orders of magnitude larger than those measured in the tests, reflecting the complex microstructural features concerning diffusion paths and area. The weathering processes constantly alter the sandstone’s diffusion parameters, causing various damages in the Yungang Grottoes.

Moisture Characteristics of Glycerol Treated Bacterial Cellulose Nonwoven

ABSTRACT Bacterial cellulose is one of the high potential sustainable materials with numerous applications. This research work analyses the moisture handling ability of the alkali-treated (purified), bleached and dyed bacterial cellulose after glycerol treatment focusing on fashion application. The developed samples are dried at room temperature and evaluated for water absorbency, wicking, water vapor transmission properties, and moisture management indices. Glycerol treated bacterial cellulose nonwovens showed a better absorbency than the dried non-woven. A faster absorbency of 1.48 minutes was noted for the glycerol treated bleached sample. In the case of wicking, bleached and dyed dry samples showed minimum wicking of 5 and 8 mm. No other samples showed wicking ability including the glycerol treated samples. The water vapor permeability results also increased notably after glycerol treatment. An increment of 55% water vapor permeability was noted with purified sample and a 36.9% increment with bleached sample after glycerol treatment. Though the glycerol treated dyed sample showed a similar vapor transmission to the glycerol treated bleached sample, the untreated dyed sample had a maximum vapor permeability of 621.10 g/m2/day. The moisture management analysis results indicated that the glycerol treatment improved the waterproof nature of bacterial cellulose nonwoven to fast-absorbing slow drying fabric. The subjective analysis on the nonwoven fabric handle showed that the glycerol treatment statistically increased the smoothness, softness, flexibility, and draping nature of the sample than the dried sample. However, the subjective analysis also reported that the glycerol treatment significantly increased the stickiness of the nonwoven.

Water vapour transmission properties of uncoated and coated wood-based panels

ABSTRACT Knowing the properties of wood-based building materials is essential for their proper use. Moisture transfer properties of building materials are crucial to proper building design and the prevention of moisture-related problems. In selecting materials for the building, it is important to know their water vapour transmission properties. In this research the water vapour transmission properties of uncoated and coated particleboard, oriented strand board (OSB) and birch plywood were studied using wet cup method and a moisture gradient in the samples was additionally measured. The water vapour transmission rate of free films of three commercial transparent coatings was also studied. Results showed that particleboard had the highest water vapour permeability and that the coatings reduced the water vapour permeability of all tested wood-based panels. Moreover, sanding increased the water vapour permeability of uncoated particleboard and OSB. The moisture gradient in all tested wood-based panels was linear. The highest water vapour transmission rate was recorded for acrylic water-borne coating, followed by polyurethane water-borne coating and the lowest for polyurethane solvent-based coating.

Polyvinyl alcohol/xanthan gum composite film with excellent food packaging, storage and biodegradation capability as potential environmentally-friendly alternative to commercial plastic bag

Polyvinyl alcohol (PVA)-xanthan gum (XG) composite films with good degradation properties were prepared by casting method. The effects of XG amount on thickness, moisture content, water solubility, water vapor transmission (WVP), transmittance and mechanical properties of the composite film were investigated. All composite films produced uniform and transparent films and Fourier transform infrared (FT-IR) spectroscopy, as well as X-ray diffraction (XRD) had proven the formation of hydrogen bonds and subsequently compatibility of the two polymers. In general, addition of XG in PVA was able to decrease moisture content, water solubility and WVP more than the pure PVA films, with sample PX30 demonstrated the best performance. This sample also had the best mechanical properties. It also demonstrated food packaging and capability better than that of commercial plastic bag. More importantly, our sample can be fully decomposed in soil and water within 12 h, which was not only significantly shorter than commercial plastic bag, but also other biodegradable materials. Therefore, PVA/XG-based food packaging material has demonstrated huge potential to be commercialized and replaces commercial plastic bag as an alternative packing material which is renewable, sustainable and environmentally friendly.

Physical and functional properties of fish gelatin-based film incorporated with mangrove extracts.

BackgroundThe fishery processing industry produces a remarkable number of by-products daily. Fish skin accounts for one of the significant wastes produced. Fish skin, however, can be subjected to extraction to yield gelatine and used as the primary raw material for edible film production. To increase the functionality of edible films, bioactive compounds can be incorporated into packaging. Mangroves produce potential bioactive compounds that are suitable as additional agents for active packaging. This study aimed to create a fish gelatine-based edible film enriched with mangrove extracts and to observe its mechanical and biological properties.MethodsTwo mangrove species (Bruguiera gymnorhiza and Sonneratia alba) with four extract concentrations (control, 0.05%, 0.15%, 0.25%, and 0.35%) were used to enrich edible films. The elongation, water vapour transmission, thickness, tensile strength, moisture content, antioxidant and antibacterial properties of the resulting packaging were analysed.ResultsThe results showed that the mangrove species and extract concentration significantly affected (p < 0.05) the physical properties of the treated films such as elongation (16.89–19.38%), water vapour transmission (13.31–13.59 g/m2), and active packaging-antioxidant activities (12.36%–60.98%). The thickness, tensile strength, and water content were not significantly affected. Potent antioxidant activity and relatively weak antimicrobial activity of this active gelatine packaging were observed.

Synergistic Effect of Screen-Printed Single-Walled Carbon Nanotubes and Phosphorylated Cellulose Nanofibrils on Thermophysiological Comfort, Thermal/UV Resistance, Mechanical and Electroconductive Properties of Flame-Retardant Fabric.

Single-walled carbon nanotubes (SWCNTs) and phosphorylated nanocellulose fibrils (PCNFs) were used as functional screen-print coatings on flame-retardant (FR) fabric, to improve its thermal resistance and thermophysiological comfort (wetting, water vapour and heat transmission) properties, while inducing it with electrical conductivity and UV protection. The effect of PCNF printing, followed by applying a hydrophobic polyacrylate (AP), on the same (back/B, turned outwards) or other (front/F, turned towards skin) side of the fabric, with and without the addition of 0.1–0.4 wt% SWCNTs, was studied by determining the amount of applied coating and its distribution (microscopic imaging), and measuring the fabric’s colour, air permeability, thickness, mechanical, flame and abrasion resistance properties. Due to the synergistic effect of PCNF and SWCNTs, both-sided printed fabric (front-side printed with PCNF and back-side with SWCNTs within AP) resulted in an increased heat transfer (25%) and an improved thermal resistance (shift of degradation temperature by up to 18 °C towards a higher value) and UV protection (UPF of 109) without changing the colour of the fabric. Such treatment also affected the moisture management properties with an increased water-vapour transfer (17%), reduced water uptake (39%) and asymmetric wettability due to the hydrophilic front (Contact Angle 46°) and hydrophobic back (129°) side. The increased tensile (16%) and tear (39%) strengths were also assessed in the warp direction, without worsening the abrasion resistance of the front-side. A pressure-sensing electrical conductivity (up to 4.9∙10−4 S/cm with an increase to 12.0∙10−4 S/cm at 2 bars) of the SWCNT-printed side ranks the fabric among the antistatic, electrostatic discharge (ESD) or electromagnetic interference (EMI) shielding protectives.

Developments of biodegradable polymer based on polylactic acid (PLA) with natural color extracts for packaging film applications

This research was interested in the use of natural colorants to replace hazardous synthetic pigments in the plastic polymer industry. The natural colors were selected from local plants indigenous to southeast Asia, which were Hibiscus sabdariffa roselle calyx (RS) and Caesapinia sappan Linn heartwood (SP). Natural colorant extracts were used as additives in poly(lactic acid ) (PLA). These were manufactured using a twin screws extruder and blow film extruder to obtain biodegradable thin films for use as packaging materials. Biodegradable films were characterized by color index, light barrier properties, water vapor transmission (WVTR), morphology, mechanical and chemical properties. The results showed high compatibility between PLA and natural color extracts confirmed via SEM morphology. Moreover, the films have the colors associated with the added RS and SP extracts, with a pink tone for the RS film and a yellow-orange tone for the SP film. Films incorporated with the extracts also possessed improved light barrier properties, which were reduced from 98.66% to 78.00% in the UV-A region and 99.33% to 90.00% in the visible region. Water vapor transmission rate was also decreased with incorporation of SP from 4.02 g⋅m-2*day to 2.98 g⋅m-2*day at 7 days and RS 1.66 g⋅m-2*day to 1.59 g⋅m-2*day at 14 days. Moreover, films containing the natural color extracts had higher tensile strength and tensile modulus than pure PLA films. These properties improvement confirm that these extracts are suitable for producing biodegradable packaging thin films.

Lightweight Vapor-Permeable Plasters for Building Repair Detailed Experimental Analysis of the Functional Properties.

Three types of lightweight plasters for building repair were prepared and tested. The composition of plasters was designed in respect to their compatibility with materials used in the past in historical masonry. For the hardened plasters, detailed testing of microstructural and macrostructural parameters was realized together with the broad experimental campaign focused on the assessment of mechanical, hygric, and thermal properties. As the researched plasters should find use in salt-laden masonry, specific attention was paid to the testing of their durability against salt crystallization. The mechanical resistance, porosity, water vapor transmission properties, and water transport parameters of all the researched plasters safely met criteria of WTA directive 2-9-04/D and standard EN 998-1 imposed on repair mortars. Moreover, the tested materials were ranked as lightweight plasters and due to their low thermal conductivity they can be used for the improvement of thermal performance of repaired masonry. The salt crystallization test caused little or no damage of the plasters, which was due to their high porosity that provided free space for salt crystallization. The developed plasters can be recommended for application in repair of damp and salt masonry and due to their compatible composition also in historical, culture heritage buildings. The added value of plasters is also their good thermal insulation performance.

Characterization of minocycline loaded chitosan/polyethylene glycol/glycerol blend films as antibacterial wound dressings

AbstractWound care has been a challenging subject for medical teams and researchers. Bacterial infections are one of the most serious complications in injured skins that often affect healing process. Antibacterial wound dressings can be used to facilitate wound healing process. The purpose of this study is to fabricate chitosan (Chito)/polyethylene glycol (PEG) antibacterial wound dressing doped with minocycline, and to evaluate the influence of composition ratio on the blending properties of the films. To improve the mechanical properties of these films, we examined various amounts of glycerol as a plasticizer. Moreover, we investigated morphological and mechanical aspects, water uptake, degradation, water vapor transmission and wettability properties of the films prepared with various ratios of Chito/PEG/Gly. Assessment of mechanical properties revealed that film containing 80:20 ratio Chito/PEG with 40 PHR Gly content exhibits the highest ultimate tensile strength and elongation at break (9.74 MPa and 45.73% respectively). Furthermore, results demonstrated that upon increasing PEG and Gly contents, degradability and hydrophilicity of the films increased whereas water uptake decreased. Water vapor transmission rate of the films was close to the range of 530–1200 g/m2d, indicating that the as formed films are possible candidates for dressing low exudate wounds or burns. Minocycline loaded films exhibited a biphasic drug release profile and it was more effective on gram‐positive bacteria than on gram‐negative bacteria. The polymeric film with the highest amount of loaded drug (2%) exhibited insignificant cytotoxicity (88%) against normal fibroblast cell line.

Investigation of some atmospheric effects in the laboratory tests on deterioration of andesite (Iscehisar-Turkey) used as the building stone of cultural heritages

Natural stones are exposed to long-term atmospheric effects in accordance with the area that they are used in. They are affected not only by salt crystallization, freezing-thawing, and heat effect, but also by the emissions into the atmosphere (air pollution, several gases, and vapour). These effects may cause negative changes on both physico-mechanical properties and exterior appearances of natural stones. The present paper has aimed to point out some atmospheric effects and their consequences on the durability of the andesite (Iscehisar, Turkey) used as the building stones for cultural heritages. For this purpose, the characterization of the tested andesite was determined by various analytical techniques such as petrographic, mineralogical (polarizing microscope, SEM-EDX and XRD), chemical (XRF), physical, and mechanical tests. Subsequently, the changes on andesite caused from atmospheric pollution such as SO2, salt, and water vapour were investigated through several laboratory experiments. These ageing tests consisted of the determination of resistance to ageing by SO2 action in the presence of humidity, determination of resistance to ageing by salt mist, and determination of water vapour transmission properties. These experiments were performed with untreated and treated andesite samples with siloxane-based water repellent applied. The total porosity ratio of the andesite was 19.73%, and it shows pore size ranges between 0.01 and 100 μm. The change in the weight of resistance to ageing by salt mist experiment was 0.488% for the untreated andesite samples, and for the treated andesites, it was 0.285%. The treatments with water repellents could generally be considered successful concerning their influence on SO2, salt, and water vapour effect on the andesite samples. After the experiment of resistance to ageing by salt mist, the ultrasonic P-wave velocity decrease was determined for the untreated andesite samples as 1.34% and for the treated samples as 0.67%. Water repellent material on the tested andesite was decreased water vapour transmission by 57.07% on average.

Water vapor transmission properties of acrylic organic coatings

In this work, we evaluate the water vapor transmission rate (WVTR), the permeability (P), solubility (S), and diffusion (D) coefficients of Paraloid B44, Paraloid B72, and Incralac coatings in the temperature range of 5–35°C. The Arrhenius function—diffusion activation energy and preexponential factor—has also been determined from the data: D_{B44} = 35.2;{text{cm}}^{2} ;{text{s}}^{ - 1} exp left( { - 25;{text{kJ mol}}^{ - 1} /{text{RT}}} right); D_{B72} = 9.5;{text{cm}}^{2} ;{text{s}}^{ - 1} exp left( { - 23;{text{kJ mol}}^{ - 1} /{text{RT}}} right); D_{text{Incralac}} = 622.8;{text{cm}}^{2} ;{text{s}}^{ - 1} { exp }left( { - 28;{text{kJ mol}}^{ - 1} /{text{RT}}} right). These resins are important coating materials, for example, for conservators to protect metallic artifacts, such as statues, against corrosion. Despite Paraloid B44 and B72 resins being considered as reference materials in conservation practice, that is, new coating materials (either water vapor retarders or transmitters) are often compared to them, there are no comprehensive data for the quantities describing the vapor permeability (P, S, D) of these materials. The measurements are based on the ISO cup-method using substrate/coating composite samples. The strength of this technique is that it can also be used when the coating is non-self-supporting; nevertheless, P, S, and D can be deduced for the coating layer itself, and it seems to be a standardizable procedure for comparative performance testing of coating materials. Paraloid B72 layers exhibited higher WVTRs—from 39 to 315 g m−2 day−1 as the temperature increased from 5 to 35°C—compared to Paraloid B44 and Incralac coatings—from 17 to 190 g m−2 day−1, respectively. The transmission rate parameters were also compared to the results of corrosion tests. Incralac was the most effective corrosion inhibitor, and the performance of the B44 was better than the B72, which is in good agreement with the transmission rate tests.

Development Of Polyethylene Oxide Film Hydrogels With The Addition Of Banana Sap For Wound Dressing Applications

Hydrogels having been developed so far are those with polymer bases without any additives. For the acceleration of wound healing, it can be developed hydrogels with the addition of banana sap (Musa Paradisiaca) as a drug that is expected to accelerate the wound healing process. The preparation of Banana PEO-PEGDMA-Hydrogel Banana was made using a new method of dissolving banana juice with PEO-PEGDMA before crosslinking. The formulations of banana sap concentration used ranged from 0% to 15% (volume) and they were irradiated with gamma rays. The characteristics measured include gel fraction, swelling ratio, velocity of water vapor transmission and mechanical properties. The chemical and morphological structures were analyzed using the Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM). The acceleration of wound healing speed was analyzed by invivo test. The results showed that the value of gel fraction, swelling ratio and velocity of water transmission of PEO-PEGDMA-Banana Gum hydrogel increased at a concentration of 0-15%. Hydrogel tensile strength decreased with the addition of banana sap and conversely the percentage of elongation of hydrogel increased with it. PEO-PEGDMA hydrogel film with the addition of banana sap has been proven to accelerate the wound healing through the Invivo Test. This shows that hydrogels can be developed from PEO-PEGDMA- Banana Sap which can be used as wound dressing.

Water Vapor Transmission Properties of Men’s Quick-Dry Sportswear

This study evaluated the quick dry properties of summer men’s sportswear T-shirts of different brands (Nike, Adidas, Laishilong and Columbia) by studying the water vapor transmission behavior. The results indicate that Laishilong was the best sample in terms of water vapor transmission rate, whereas Columbia was the poorest. Moreover, samples of Nike, Adidas, Laishilong and Columbia, had similar water vapor transmission rate. This implies that they had comparatively similar performance in water vapor permeability.

Polyurethane-modified graphene oxide composite bilayer wound dressing with long-lasting antibacterial effect

In order to obtain a novel multifunctional wound dressing with good water vapor permeability and long-lasting antibacterial properties, a skin-like thermoplastic polyurethane (TPU) bilayer membrane containing self-made polyhexamethylene guanidine hydrochloride (PHMG) grafted graphene oxide (MGO) was prepared by non-solvent phase separation and particle filtration. The antibacterial properties and wound-healing ability of TPU, GO-TPU, MGO-TPU composite porous membrane are systematically compared. The results show that with the incorporation of MGO, the porous MGO-TPU membrane exhibits good biocompatibility, excellent water vapor transmission properties, and long-lasting broad-spectrum antibacterial properties (the antibacterial property remains unchanged for 30days under continuously shaking and washing). The wound healing results for mouse model show that MGO-TPU could significantly accelerate the healing rate of wounds as it provides a sterile environment and also promotes the formation of re-epithelialization during wound healing.

Improvement of water vapor barrier and mechanical properties of sago starch‐kaolinite nanocomposites

AbstractThe composite films of sago starch were prepared by incorporation of various amount of kaolinite (K) and kaolinite intercalated by dimethyl sulfoxide (DMSO) (KD) via solution blending method in order to reduce the water vapor transmission and enhance mechanical properties of starch based films. The kaolinite intercalation by DMSO and the composite films were characterized by using X‐ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscope techniques. The result showed that well‐dispersed kaolinite layers were delaminated in the starch matrix attesting to intercalate and exfoliate composite films. The effect of kaolinite content on the water vapor transmission and tensile properties of the composite films was investigated. The water vapor transmission of the starch film (neat starch film ca. 0.132 g.cm3/h) decreased with the addition of K and KD to the starch. It was also observed that the maximum tensile strength (5.18 MPa) was attained for the composite film with 4% by weight of clay content. The improvement in the tensile strength and modulus of starch‐based composites was due to the strong interfacial interaction between matrix and kaolinite clay, correlating to the change of morphology of the starch composite films as revealed by scanning electron microscopy.

Tofu-Based Hybrid Hydrogels with Antioxidant and Low Immunogenicity Activity for Enhanced Wound Healing.

Free radicals and inflammation in the skin suffering from trauma cause oxidative damage and delayed healing, leading to adverse wound conditions. To adequately investigate the effects of free radicals and controlled immunogenicity for wound healing, we propose a tofu-based hybrid hydrogel with antioxidant and low immunogenicity properties that can be used for wound healing. Tofu, a food source material, was introduced for the first time into gelatin methacryloyl (GelMA) hydrogels by the photo-crosslinking method. The results demonstrated that the incorporation of tofu influenced the pores, swelling, water vapor transmission and compressive properties of hydrogels greatly. The antioxidant activities of hydrogels had been enhanced with increasing rations of tofu, and the fibroblast culture showed good proliferation on the hybrid hydrogels, as well as slight immunogenicity, thereby inducing the M2 differentiation of macrophages. Further, a full-thickness skin wound model was created to study the healing effect of hybrid hydrogels. In vivo results confirmed that the antioxidant activity and slight immunological stimulation properties of tofu hydrogels could accelerate the wound healing rate and improve the skin tissue regeneration effect. The present study validates that the tofu-based hybrid hydrogels have multiple bioactivities and could be potential antioxidant and immunoregulation hydrogels in wound healing applications.

A green and simple process to develop conductive polyurethane foams for biomedical applications

In this work, conductive polyurethane (PU) foam is developed to be used as skin electrode for long term use medical devices. Water based polyurethane and other eco-friendly substances are selected to implement a green process, where the composite is produced in the shape of film and foam, by a transfer coating process. Different formulation and process materials are considered to evaluate the effect on surface resistivity and percolation threshold. The time stability, water vapor transmission, elongation and stress-strain properties, are studied. Results show that the realized material is suitable to be used as electrode for biomedical applications.