Gel Electrodes Research Articles

Preparation of activated carbon paper by a novel method and application as high-performance supercapacitors

In this paper, the commercial carbon papers were firstly treated by potassium dichromate lotion. Their surfaces became rougher and specific surface areas were enlarged. Accordingly, their surface hydrophilicity were enhanced due to the intake of hydrophilic groups such as hydroxyl (–OH), carbonyl (>C=O), and carboxyl (–COOH), and they act as strong polar sites to absorb water molecules. Supercapacitors were then constructed with the treated carbon paper as electrode and PVA-H3PO4 gel as electrolyte, and they provided high areal capacitances, high-rate capability, long-life cycle, and low resistance due to the synergistic effect of enlarged specific surface area and enhanced surface hydrophilicity.

Transcutaneous Supraorbital Nerve Stimulation (t-SNS) with the Cefaly® Device for Migraine Prevention: A Review of the Available Data.

So far, among the different non-invasive neurostimulation methods, only transcutaneous supraorbital nerve stimulation (t-SNS) with the Cefaly® (Cefaly Technology sprl, Herstal, Belgium) device has randomized controlled trial-based evidence for safety and efficacy and obtained American Food and Drug Administration approval for the prevention of episodic migraine. In a double-blinded, randomized, sham-controlled trial on 67 episodic migraine patients (mean pre-treatment migraine days/month: 6.9), the 50% responder rate after 3 months was significantly higher in the active group (38.2%) than in the sham group (12.1%); attack frequency and total headache days were also significantly reduced, but not headache severity. Acute anti-migraine drug intake was reduced by 36.7% in the active group. Statistical sub-analysis suggested that t-SNS was more effective in patients with a higher attack frequency. In a large survey on 2313 Cefaly users about safety and satisfaction only 4.3% of subjects reported side effects, all of which were minor and fully reversible, the most frequent being intolerance to the paresthesia feeling and the most severe an allergic skin reaction to the electrode gel. The efficacy/safety ratio of the Cefaly device was therefore most favorable, especially when compared to preventive anti-migraine drugs. The therapeutic efficacy of t-SNS with Cefaly with low-frequency migraine (≤5 attacks/month) was recently confirmed in an open randomized trial. No published data are available in chronic migraine. According to preliminary results of a fluorodeoxyglucose-positron emission tomography study, Cefaly might exert its effect in migraine by increasing activity in crucial areas of the limbic system and salience matrix such as orbitofrontal and anterior cingulate cortices.Electronic supplementary materialThe online version of this article (doi:10.1007/s40122-015-0039-5) contains supplementary material, which is available to authorized users.

Patterned Vertical Carbon Nanotube Dry Electrodes for Impedimetric Sensing and Stimulation

Traditional wet or gel impedimetric electrodes for neuro-physiological signal (e.g., electroencephalography and electrocardiography) monitoring are usable for a short duration, as the performance of electrodes deteriorates rapidly when exposed to the environment. Dry impedimetric electrode is a promising alternative tool for long duration monitoring, however suffers from high interfacing impedance. This paper describes a novel dry interfacing electrode utilizing patterned vertical carbon nanotube (pvCNT) for impedimetric sensing. The electrodes were fabricated on circular stainless steel foil substrates (thickness = 2 mil) that are laser cut to circular discs (O = 10 mm). Pattern on the substrate was developed with a custom shadow mask while sputter coating the substrate with Al2O3 and iron. Electrically conductive multiwalled CNTs were then grown vertically in pillar formation ( $100~\mu \text{m}^{}$ each side of square footprint) with various interpillar spacing (50, 100, and $200~\mu \text{m}$ for various masks). The heights of the CNT pillars were between 1 and 1.5 mm. The impedances of the electrodes were 1.92, 3.11, and $8.15~\Omega $ for 50-, 100-, and 200- $\mu \text{m}$ spacing, respectively. A comparative in vitro study with commercial wet and gel electrodes showed pvCNT electrode has lower interfacial impedance, comparable signal capture quality, and ability to be used for stimulation. Long duration study showed minimal impedance degradation for pvCNT electrodes over a week. The results demonstrate pvCNT is a promising dry electrode for impedimetric sensing and stimulation of neurophysiological signals over a prolonged duration.

PVC gel based artificial muscles: Characterizations and actuation modular constructions

Polymer materials based artificial muscles have the properties of being soft, lightweight, and flexible which are similar to the nature muscular actuators. In our previous study, we have developed a contraction type artificial muscle based on plasticized poly vinyl chloride (PVC) gel and meshed electrodes. And we have improved the characteristics to make it close to the level of natural muscle. It has many positive characteristics, such as stable actuation in the air, high output, notable response rate, and low power consumption. So a wide application is expected. However, for practical applications, it is necessary to consider some specific criteria, such as performance criteria and structural criteria. In this study, we introduced the most updated properties of PVC gel artificial muscles and proposed three types of mechanical actuation modular constructions for making the PVC gel artificial muscle as a robust actuation device for robotics and mechatronics. And we tested a prototype to examine the effectiveness of the proposed modules. Finally, an analytical model for the static characteristics of PVC gel artificial muscles at different applied voltages was derived and showed good agreement with experimental results measured by a prototype of modules.

Electrocardiographic Pad for Efficient Cardiac MR Gating.

To assess feasibility and reliability of electrocardiographic (ECG)-gated cardiac magnetic resonance (MR) imaging with a simplified reusable electrode design that does not touch the skin. In this institutional review board-approved, HIPAA-compliant study, a silicon positioner held four ECG leads and detected ECG signals without requiring shaving, adhesive, or removal of the gown. The patient lies down on the device and the patient's weight ensures good lead contact against patient's gown; electrode gel that soaks through the gown provides electrical contact with the skin. It was tested at 1.5 T on 12 volunteers and 52 patients by using double inversion recovery, steady-state, fast gradient-echo time course perfusion, and delayed inversion recovery sequences. Paired Student t test was used to assess the significance of differences in durations to apply and remove ECG pad and standard leads. Image quality was assessed and rated on a four-point scale by two readers. The ECG signal quality obtained from pad and leads was rated on a five-point scale. Ventricular septal sharpness and signal-to-noise ratio were measured on images generated by ECG gating from pads and standard leads. Application and removal duration was 444 seconds with standard leads compared with 296 seconds with the ECG pad, and mean difference in setup time was 148 seconds (P = .005). Ventricular septal sharpness (1/slope) was 165 for ECG pad and 152 for standard leads (P = .3). Septal signal-to-noise ratio on images generated by cardiac gating with ECG pad was 38 ± 12 (standard deviation) compared with 39 ± 14 for standard leads (P = .7). The qualitative image quality score for ECG pad (3.9 ± 0.19) was comparable to ECG leads (3.8 ± 0.45; P = .47). The mean ECG signal qualitative scores were also comparable (pad vs leads, 4.9 ± 0.43 vs 4.9 ± 0.14, respectively; P = .9). Volunteers preferred the ECG pad and reported that it was comfortable and convenient. ECG pad was successful in 50 of 52 (96%) patients. Two patients, including one with large pleural effusions and another with ventricular tachycardia, were not successfully gated. This simplified approach to ECG gating is faster to set up and more convenient and comfortable for patients.

Influence of Charge Transportation in Nitroxyl-Radical Polymer Gel on Charging Characteristics for Organic Radical Batteries

Introduction Organic-Radical battery (ORB) is a rechargeable battery based on a radical polymer cathode. Nitroxyl-radical polymers such as poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA) are used as a cathode material of the ORB.1,2 PTMA exists in gel state in the battery because it can absorb and swell in organic electrolyte. The polymer gel electrode is considered to be suitable as a component for flexible and bendable battery. Our previous studies showed that the ORB with PTMA cathode can charge /discharge at large current with high capacity retention2. Furthermore, it was also found that the high charge/discharge rate capability is attributed to the fast charge transportation of PTMA gel brought by high mobility of the electrolyte anion3. In this study the dependence of electrolyte salts on charge transportation in PTMA gel and the influence of the transportation on charging characteristics were investigated. Experiments 1.0 M of Lithium hexafluorophosphate(LiPF6) and 1.0 M Lithium bis(fluorosulfonyl)imide(LiFSI) in ethylene carbonate (EC)/dimethyl carbonate (DMC) are used as the electrolyte with the ionic conductivity of 11.0 mS/cm and 11.7 mS/cm, respectively, to investigate the performance of organic radical battery. Electrolyte swelled PTMA gels were prepared by dispersing PTMA powder into electrolyte. Diffusion coefficient of PTMA gels were measured from potential step chronoamperometry. The PTMA cathode containing 70-wt.% PTMA and 21-wt.% carbon as a conductive additive was used for ORB. The capacity of the ORBs cell was controlled as 2.5 mAh and measured under a charging current range from 2.5 mA(1C) to 300 mA(120C) at 20°C. Results and discussion The ORB showed an excellent rate capability that the 20C-charge capacity retained 90% and 95% capacity, respectively, in 1.0 M LiPF6- and LiFSI-based electrolyte compare with 1C-charge capacity. However, the capability of much higher rate was drastically deteriorated such as less than 40% capacity retention for a 120C-charge in both LiPF6- and LiFSI-based electrolyte. On the other hand, the use of higher concentration LiFSI (1.5 M) can improve the retention from 40% to 60% in 120C. It is considered the use of electrolyte with high concentration could solve the problem of lack of anion at the cathode surface. In contrast with LiFSI, the 120C-charge capacity of the ORB decreased to below 20% capacity in 1.5 M LiPF6 electrolyte. It is concluded that the rate performance in 120C depends on the anion species in high concentration (1.5M) electrolyte. This is because the diffusion coefficient of PTMA gel in 1.5 M LiFSI was 4.8 x 10-9 cm2/s from the measurement of potential step chronoamperometry is almost two times higher than that of PTMA gel even in 1.0 M LiPF6. It is suggested high charge transportation of the PTMA gel with LiFSI can be used for ultra-high rate organic radical batteries. References (1) K. Nakahara,; S. Iwasa,; M. Satoh,; Y. Morioka,; J. Iriyama,; M. Suguro,; E. Hasegawa Chem. Phys. Lett., 2002, 359, 351-354. (2) K. Nakahara,; J. Iriyama,; S. Iwasa,; M. Suguro,; M. Satoh,; E. J. Cairns J. Power Sources., 2007, 165, 870-873. (3) K. Nakahara,; K. Oyaizu,; H. Nishide,; J. Mater. Chem., 2012, 22, 13669.

On the importance of electrode parameters for shaping electric field patterns generated by tDCS

Transcranial direct current stimulation (tDCS) uses electrode pads placed on the head to deliver weak direct current to the brain and modulate neuronal excitability. The effects depend on the intensity and spatial distribution of the electric field. This in turn depends on the geometry and electric properties of the head tissues and electrode pads. Previous numerical studies focused on providing a reasonable level of detail of the head anatomy, often using simplified electrode models. Here, we explore via finite element method (FEM) simulations based on a high-resolution head model how detailed electrode modeling influences the calculated electric field in the brain. We take into account electrode shape, size, connector position and conductivities of different electrode materials (including saline solutions and electrode gels). These factors are systematically characterized to demonstrate their impact on the field distribution in the brain. The goals are to assess the effect of simplified electrode models; and to develop practical rules-of-thumb to achieve a stronger stimulation of the targeted brain regions underneath the electrode pads. We show that for standard rectangular electrode pads, lower saline and gel conductivities result in more homogeneous fields in the region of interest (ROI). Placing the connector at the center of the electrode pad or farthest from the second electrode substantially increases the field strength in the ROI. Our results highlight the importance of detailed electrode modeling and of having an adequate selection of electrode pads/gels in experiments. We also advise for a more detailed reporting of the electrode montages when conducting tDCS experiments, as different configurations significantly affect the results.

Effects of conducting media and gender on an electric pulp test

(1) To determine the pulpal sensory thresholds in human teeth obtained from using various EPT conducting media and (2) to determine whether there are gender differences. One intact maxillary central incisor was randomly selected from each of 40 participants (20 male, 20 female) aged 19-24 year. A constant-current electrical stimulator (University of Bristol, UK) was used to apply electrical stimuli with different conducting media at intervals of 1 min on the middle of the crown to evaluate the sensory threshold of the tooth. The tip of the electrode was coated with a thin layer of test media. The sensory thresholds and the pain scores were measured simultaneously after applying stimuli twice a second and gradually increasing the intensity until felt by the participants. Test media included water-based gels (K-Y UltraGel; Xylocaine 2% Jelly, electrode gel, fluoride gel) and toothpastes (Colgate Total; Sensodyne Repair & Protect; Dentiste' Plus White; Sparkle White). The sensory threshold data were evaluated using two-way anova followed by the Tukey test. Xylocaine 2% Jelly and fluoride gel evoked significantly lower threshold values when compared with Sensodyne Repair & Protect (P < 0.001). With all test media, the mean sensory threshold from the female group was significantly lower than that of the male group (P < 0.001). The sensory thresholds to electrical stimuli in human teeth was influenced by the type of conducting media and gender.

Simultaneous comparison of 1 gel with 4 dry electrode types for electrocardiography

We designed a spandex tank top with dry electrodes for continuous electrocardiogram (ECG) recording. This pilot study determined the best fabric, the best electrode types, sizes, and locations. Optimal electrodes provide high signal to artifact ratio (SAR) and reliability by meeting the following criteria: 1) low baseline shift, 2) high adhesion, 3) good physical stability, 4) large effective area, 5) thin with high flexibility (Luo et al ). We compared electrodes from three main groups: Ag/AgCl gel electrode, commercial conductive rubber and foam-metal based electrodes. Ag/AgCl gel electrodes are easy to apply, make good body contact and do not slip during the course of an experiment. We found that higher SARs are obtained when electrode area is increased (40 mm diameter) and the two dry measurement electrodes are located on convex areas (over chest muscle) rather than concave areas (over sternum), so the spandex will apply light pressure to the dry electrode to yield good electrode to skin contact. We experimentally validated findings with 24 subjects: 12 men and 12 women wearing the tank top with gel and dry electrodes, by monitoring movements imitating daily life while continuously recording their ECGs.

Embroidered electrode with silver/titanium coating for long-term ECG monitoring.

For the long-time monitoring of electrocardiograms, electrodes must be skin-friendly and non-irritating, but in addition they must deliver leads without artifacts even if the skin is dry and the body is moving. Today's adhesive conducting gel electrodes are not suitable for such applications. We have developed an embroidered textile electrode from polyethylene terephthalate yarn which is plasma-coated with silver for electrical conductivity and with an ultra-thin titanium layer on top for passivation. Two of these electrodes are embedded into a breast belt. They are moisturized with a very low amount of water vapor from an integrated reservoir. The combination of silver, titanium and water vapor results in an excellent electrode chemistry. With this belt the long-time monitoring of electrocardiography (ECG) is possible at rest as well as when the patient is moving.

Method of Photoplethysmography Diagnostics of Domesticated Animals Cardiovascular Diseases

At present time the standard procedure to diagnose cardiovascular diseases (CVD) of domesticated animals (dogs) is electrocardiography (ECG) monitoring at animal clinic. Sadly, results, obtained that way, are often mistaken because of stressful state of the animal, caused by medical manipulations [1]. The usage of photoplethysmography (PPG) method can become a good substitute for CVD monitoring. Main advantages of PPG, in compare with ECG, are single probe placement (on the ear or tailset), no need of gel electrodes and capability of measuring actual CVS parameters without need of special medical training or laboratory conditions. It is one of non-invasive methods for measuring the amount of the blood volume changes inside the blood vessels, applicable for cardio activity estimation by calculating heart rate variability. In most cases, PPG monitoring devises are small, easy to place and can monitor different physiological parameters of the animal, such as heart rate, pulse wave characteristics, blood oxygen saturation, etc.

Chemo-ionic-conformational memory from reactive dense gels: a way to explore new multivalent memories and brain memory

ABSTRACTSo far we ignore how brain stores memory. Neurons communicate by pulses where the charges are carried between them by ions flowing through channels. Those pulses present a characteristic maximum related to the conformational movements of the channel protein opening and closing. Electrochemical responses from dense gel electrodes of conducting polymers mimic those pulses. Here we proved that the biomimetic pulse includes simultaneously electrical, chemical and conformational information related to the energy stored by the initial conformational packed state of the polymer. This energetic memory increases linearly with the potential used to reduce and pack (write) the initial state: hundreds of different values can be written (stored) in a full reproducible way (multivalent memory). Every state constitutes a chemo-ionic-conformational (CHEMICONF) memory. Each multivalent memory is read and erased by the reverse electrochemical reaction. Crosslinking states produce permanent memories not erased while reading. Developing CHEMICONF memories can provide new hypothesis to reveal brain memory mechanisms.

Soft, comfortable polymer dry electrodes for high quality ECG and EEG recording.

Conventional gel electrodes are widely used for biopotential measurements, despite important drawbacks such as skin irritation, long set-up time and uncomfortable removal. Recently introduced dry electrodes with rigid metal pins overcome most of these problems; however, their rigidity causes discomfort and pain. This paper presents dry electrodes offering high user comfort, since they are fabricated from EPDM rubber containing various additives for optimum conductivity, flexibility and ease of fabrication. The electrode impedance is measured on phantoms and human skin. After optimization of the polymer composition, the skin-electrode impedance is only ∼10 times larger than that of gel electrodes. Therefore, these electrodes are directly capable of recording strong biopotential signals such as ECG while for low-amplitude signals such as EEG, the electrodes need to be coupled with an active circuit. EEG recordings using active polymer electrodes connected to a clinical EEG system show very promising results: alpha waves can be clearly observed when subjects close their eyes, and correlation and coherence analyses reveal high similarity between dry and gel electrode signals. Moreover, all subjects reported that our polymer electrodes did not cause discomfort. Hence, the polymer-based dry electrodes are promising alternatives to either rigid dry electrodes or conventional gel electrodes.

A new method to assess skin treatments for lowering the impedance and noise of individual gelled Ag–AgCl electrodes

A model-based new procedure for measuring the single electrode–gel–skin impedance (ZEGS) is presented. The method is suitable for monitoring the contact impedance of the electrodes of a large array with limited modifications of the hardware and without removing or disconnecting the array from the amplifier. The procedure is based on multiple measurements between electrode pairs and is particularly suitable for electrode arrays. It has been applied to study the effectiveness of three skin treatments, with respect to no treatment, for reducing the electrode–gel–skin impedance (ZEGS) and noise: (i) rubbing with alcohol; (ii) rubbing with abrasive conductive paste; (iii) stripping with adhesive tape. The complex impedances ZEGS of the individual electrodes were measured by applying this procedure to disposable commercial Ag–AgCl gelled electrode arrays (4 × 1) with a 5 mm2 contact area. The impedance unbalance ΔZ = ZEGS1 − ZEGS2 and the RMS noise (VRMS) were measured between pairs of electrodes. The tissue impedance ZT was also obtained, as a collateral result. Measurements were repeated at t0 = 0 min and at t30 = 30 min from the electrode application. Mixed linear models and linear regression analysis applied to ZEGS, ΔZ and noise VRMS for the skin treatment factor demonstrated (a) that skin rubbing with abrasive conductive paste is more effective in lowering ZEGS, ΔZ and VRMS (p < 0.01) than the other treatments or no treatment, and (b) a statistically significant decrement (p < 0.01), between t0 and t30, of magnitude and phase of ZEGS.Rubbing with abrasive conductive paste significantly decreased the noise VRMS with respect to other treatments or no treatment.

The influence of the synthesis method of Ti/RuO2 electrodes on their stability and catalytic activity for electrochemical oxidation of the pesticide carbaryl

In this study, we developed dimensionally stable anodes of titanium covered with ruthenium oxides (Ti/RuO2) using sol–gel, Pechini and ionic liquid (IL) methodologies. The electrochemical efficiency of these electrodes was then evaluated regarding electrochemical degradation of the pesticide carbaryl. The UV–visible spectroscopy measurements showed that the electrodes obtained by the IL and Pechini methods were more effective at pesticide degradation compared with the sol–gel electrode, especially at high current density values. Carbaryl degradation after 2 h of electrolysis at 30 mA cm−2 was 96.4% and 95.5% for the electrodes obtained by the IL and Pechini methods, respectively, while the degradation was 65.0% for the electrodes obtained by the sol–gel method. Additionally, the electrodes prepared by the IL and Pechini methods showed greater physical and electrochemical stability when compared to electrodes obtained by the sol–gel method. Electrodes prepared by the IL method with a few covering layers (three) achieved an elevated and constant area in a more efficient way than electrodes prepared by the Pechini and sol–gel methods. This fact can be attributed to the higher viscosity of the ionic liquid-based precursor solution, which transfers a higher amount of Ru in one single layer, compared to the other methods studied, thus reducing the time for synthesis, the number of calcination steps and the production costs of electrodes.

Interaction between dye and zinc in the dye-dispersing ZnO films prepared by a wet process

Dye-dispersing ZnO precursor gel films were prepared on indium tin oxide electrodes from a zinc acetate solution containing eosin Y by dip-coating, steam treatment, and then heating at a low temperature. The electronic interaction between the dye and zinc in the dye-dispersing gel films were investigated by spectroscopic and electrochemical measurements. A photocurrent was observed in the dye-dispersing gel electrodes before the steam treatment. The photocurrent value increased by the steam treatment and heating due to crystallization of the gel and removal of organic impurities. The dye molecules existed between the interlayers of the layered zinc hydroxide coexisting with the ZnO. The photoexcited electron in the dye should be injected into the ZnO conduction band via the layered zinc hydroxide. The value increased with an increase in the dye content even though the ZnO crystallinity decreased. The dye–zinc interaction, i.e., the complex formation and photoinduced electron injection, played an important role in the electron transport and photoelectric conversion.

High-performance polymer actuators based on poly(ethylene oxide) and single-walled carbon nanotube–ionic liquid-based gels

The electrochemical and electromechanical properties of actuators based on the polymer electrolyte poly(ethylene oxide) (PEO), fabricated using a single-walled carbon nanotube (SWCNT)-ionic liquid (IL)-based gel electrode, were compared with those of actuators based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF(HFP)).The ionic conductivity of the PEO/IL gel electrolyte layer was much smaller than that of the PVdF(HFP)/IL layer. This is likely because the interaction between the oxygen atoms of PEO and the cations of the IL was larger than that between the fluorine atom of PVdF(HFP) and the IL cations. The maximum strain of the PEO electrolyte layer was smaller than that of the PVdF(HFP) electrolyte layer. Further, the maximum strain of an EMI[TFSI]/PEO electrode-based actuator was approximately 1.3 times larger than that of an EMI[TFSI]/PVdF(HFP) electrode-based actuator, where EMI[TFSI] is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide. These results indicated that the PEO electrode-based actuators exhibited better performances than those based on a PVdF(HFP) electrode.In the case of the PEO electrode-based actuators, it was also found that the ion size, and the self-diffusion coefficient, as well as the rate of ion transport in the electrodes and electrolyte, were of critical importance for realizing low-voltage actuators. Finally, a simple model for the actuation mechanism was also proposed. The model, which was based on the product of the ionic transport number and the ionic volume, was shown to successfully explain the actuator behavior.

Epidermal Electronics: Capacitive Epidermal Electronics for Electrically Safe, Long‐Term Electrophysiological Measurements (Adv. Healthcare Mater. 5/2014)

On page 642, integration of capacitive sensing capabilities to ultra-thin, soft, and elastic electronics enable robust electrophysiological signal measurements through electrical coupling between tissues and electrodes, mediated by an intervening dielectric layer. The capacitive skin electronics shown by John A. Rogers and co-workers are reusable, electrically safe, and minimally sensitive to motion artifacts. The presented device provides levels of fidelity in ECG, EMG, and EOG recordings comparable to those of standard gel electrodes.

Microfluidic dielectrophoretic sorter using gel vertical electrodes.

We report the development and results of a two-step method for sorting cells and small particles in a microfluidic device. This approach uses a single microfluidic channel that has (1) a microfabricated sieve which efficiently focuses particles into a thin stream, followed by (2) a dielectrophoresis (DEP) section consisting of electrodes along the channel walls for efficient continuous sorting based on dielectric properties of the particles. For our demonstration, the device was constructed of polydimethylsiloxane, bonded to a glass surface, and conductive agarose gel electrodes. Gold traces were used to make electrical connections to the conductive gel. The device had several novel features that aided performance of the sorting. These included a sieving structure that performed continuous displacement of particles into a single stream within the microfluidic channel (improving the performance of downstream DEP, and avoiding the need for additional focusing flow inlets), and DEP electrodes that were the full height of the microfluidic walls ("vertical electrodes"), allowing for improved formation and control of electric field gradients in the microfluidic device. The device was used to sort polymer particles and HeLa cells, demonstrating that this unique combination provides improved capability for continuous DEP sorting of particles in a microfluidic device.

Electrochemical and electromechanical properties of carbon black/carbon fiber composite polymer actuator with higher performance than single-walled carbon nanotube polymer actuator

The electrochemical and electromechanical properties of poly(vinylidene fluoride-co-hexafluoropropylene) based actuators using carbon black (CB)/vapor grown carbon fiber (VGCF)/ionic liquid (IL) composite gel electrodes formed without ultrasonication were compared with those of actuators using only CB or VGCF. The double-layer capacitance of the CB/VGCF/IL electrodes was larger than that of the CB/IL electrodes and increased with VGCF content. The amount of strain exhibited by the CB/VGCF/IL actuators was also larger than that for the CB/IL actuators, with the highest strain being produced for an actuator with a CB:VGCF ratio of 1:1. This was slightly larger than that for a polymer actuator using single-walled carbon nanotubes (SWCNTs), indicating that the proposed actuators exhibit sufficiently high performance for real-world applications without the need for expensive SWCNTs. Furthermore, the frequency dependence of the displacement response of the CB/VGCF/IL polymer actuators was successfully simulated using an electrochemical kinetic model similar to that for SWCNT-based actuators. The results yielded the strain in the low-frequency limit and the time constant of the response.