Planate conducting polymer actuator based on polypyrrole and its application

In this study, we propose a planate actuator which can transform only its central part locally. We have developed a planate conducting polymer actuator based on polypyrrole (PPy) and two types of acids, such as p-phenol sulfonic acid and dodecylbenzene sulfonic acid, by electrodeposition. Its structure was patterned bimorph structure with anion-driven, cation-driven and bimorph layers. The planate conducting polymer actuator could deform only its central part locally. Moreover, we introduce a micro-pump that operates by planate conducting polymer actuator as the drive source. The water level in the flow channel of micro-pump shows the reciprocating motion measuring ±2 mm in accordance with the oscillation of the bimorph conducting polymer actuator which was approximately 28 μl/min. The oscillating volume can be controlled by the application of electrochemical potential and its scan rate applied to the actuator.     

Enhancement of actuation ability of ionic-type conducting polymer actuators using metal ion implantation

In this study, we present the results and implications of an experimental study into the effect of gold-ion implantation on the actuation performance of ionic-type conducting polymer actuators, represented here by cantilevered tri-layer polypyrrole (PPy) actuators. We implant gold ions beneath the outer surfaces of PPy-based conducting polymer layers of the actuators in order to increase the conductivity of these layers, and therefore improve the overall conductivity of the actuators. A Filtered Vacuum Cathode Arc (FVCA) ion source was used to implant gold particles into the conducting polymer layers. Electrode resistance and capacitance, surface resistance, current response, mechanical work output of the actuator samples were measured and/or calculated for the actuator samples with and without gold implantation in order to demonstrate the effect of the gold-implantation. The current passing through the conducting polymer electrodes during their ‘electrochemomechanical’ actuation was measured to determine the charging time constant of the actuators. The mechanical displacement output of the actuators was recorded. The results demonstrate that the conductivity of the actuators increases noticeably, which has a flow on effect on the current response (i.e., charge injected into the polymer layers) and the mechanical work output. While the gold implanted actuators had a higher mechanical stiffness therefore a smaller displacement output, their time constant is smaller, indicating a higher response speed. The gold-implanted actuators generated a 15% higher mechanical work output despite the adverse effects on the polymer of the vacuum processing needed for the ion implantation.     

基于掺杂聚吡咯的硝酸根离子选择性电极

研究了一种基于硝酸根掺杂聚吡咯技术的硝酸根离子选择性电极。该电极以玻碳电极为载体,以包含硝酸根离子的聚吡咯薄膜为电极敏感膜。在含有硝酸根离子浓度数量级为10-4.5,10-4.0,10-3.5,10-3.0,10-2.5,10-2.0mol/L的硝酸钠测试溶液中,电极的响应电势呈现出较为理想的线性关系,且电势斜率值接近于理论值,符合能斯特响应规律;电极操作简便,具有较短的响应时间和较好的重复性。该电极的研发成功,为当前环境水质监测中总氮的实时监测提供了一种有效的解决方案。     

Guiding water into carbon nanopipes with the aid of bipolar electrochemistry

The targeted bipolar electrodeposition of polypyrrole was carried out onto the tips of hydrophilic carbon nanopipes. By aligning an external electric field relative to the nanopipes, the deposition of polypyrrole onto selected ends could be achieved without physically contacting the nanopipes. After deposition, carbon nanopipes with both partially open and fully blocked tips were found. Experiments conducted in an environmental scanning electron microscope showed that water enters the nanopipes through the tip with polypyrrole due to the higher hydrophilicity of the polymer compared to the tube walls. As a result, it was possible to guide the entry of water from a specific end of the tube and fill the tube from the selected side. Condensation experiments conducted on nanopipes with polypyrrole on both tips shows the difference in hydrophilicity of the nanopipes compared to the polypyrrole. The ability to selectively control the site of condensation and uptake of fluid by carbon nanotubes or nanopipes is very important for the development of nanotube-based nanofluidic devices.     

聚吡咯掺杂苯磺酸钠葡萄糖生物传感器

采用电化学聚合技术,用掺杂苯磺酸钠的聚吡咯（PPy）导电薄膜修饰铅笔芯电极,在修饰电极表面吸附葡萄糖氧化酶制备了葡萄糖生物传感器.研究了苯磺酸钠掺杂对PPy薄膜形貌、葡萄糖传感器性能的影响.实验结果表明：掺杂苯磺酸钠能够改变PPy形貌、极大提高其导电性.优化条件下该生物传感器抗干扰能力强、稳定性好,响应电流和葡萄糖浓度在0～0.7 mmol/L范围内有良好的线性相关度（R=0.9976）,灵敏度为26.10 μA/mmol/L,平均响应时间约为6.5s,检测下限为47.2 μmol/L.     

Strain response of polypyrrole actuators induced by redox agents in solution

We report on the chemical actuation of a polypyrrole (PPy) artificial muscle by redox agents in solution without external power supply, such as a battery, connected to the actuator. In particular, hexacyanoferrate and L-ascorbic acid are employed to analyse the strain responses of PPy. The redox agents establish a certain potential at the polymer electrode, which results in a corresponding strain change. The results are in accordance with the strain generated by an external voltage via a potentiostat. We use a bending beam of polyimide/gold/PPy to observe the strain of PPy inside a liquid flow cell. By adding different relative concentrations of the hexacyanoferrate couple to the electrolyte, we achieve a repeatable linear transition in strain without significant hysteresis. Strain changes are induced by redox pairs as well as redox moieties in solution.     

Preparation of gas sensors via dip-pen nanolithography

In the present work, a conducting polymer, doped polypyrrole, was used to develop a gas sensor by dip-pen nanolithography (DPN). The response time of the sensor to 18 ppm CO₂ was 9 s. The sensor response increased linearly as the CO₂ concentration increased. A possible mechanism for the CO₂ sensing was discussed.     

A novel polypyrrole–phenylboronic acid based electrochemical saccharide sensor

A novel N-phenylboronic acid substituted polypyrrole based sensor for saccharide detection was investigated. As the first time, 3-(1H-pyrrol-1-yl)phenylboronic acid was synthesized and used for the preparation of sensing surface on platinum (Pt) electrode by using electrochemical cyclic voltammetry technique (CV). Characterization of the monomer and the polymer were performed using NMR, FTIR, TOF-MS, SEM and AFM. The applicability of this sensor was examined for potentiometric detection of saccharides (d-glucose, d-fructose, d-galactose, d-lactose and d-sucrose). The binding interaction between polypyrrole–phenylboronic acid and saccharides was followed in the order of d-fructose > d-glucose > d-galactose > d-lactose > d-sucrose. The effect of pH on the binding interaction of d-glucose and d-fructose to phenylboronic acid was investigated. The best interaction was obtained at pH 12.0. Reusability of the sensor was tested and it was observed that there was no response change up to 10 usages. These results indicate that polypyrrole based type sensors can be developed for designing new reusable biosensors.     

Polypyrrole thin film fiber optic chemical sensor for detection of VOCs

A fiber optic reflectance sensor (FORS) using Polypyrrole (PPy) conducting polymer to detect volatile organic compounds (VOCs) is demonstrated. The conventional interfacial polymerization method is used to synthesize a sensitive polypyrrole membrane, which shows relatively low roughness and high reflectivity. In general the changes in electrical properties of conductive polymers are explored in sensing applications, however their optical properties have been less explored. In the present study, we evaluate the optical properties of PPy and transfer on the end face of polymer optical fiber (POF) for the detection of VOCs. The change in the reflected optical signal from PPy upon interaction with the VOCs is systematically evaluated. The fabricated PPy FORS shows the excellent sensitivity to the VOCs under test with the detection limit up to 1 ppm.     

Selective NH3 gas sensor based on Langmuir-Blodgett polypyrrole film

Polypyrrole thin films have been deposited onto a glass substrate by the Langmuir-Blodgett technique to fabricate a selective ammonia (NH₃) gas sensor. The d.c. electrical resistance of the sensing elements is found to exhibit a specific increase upon exposure to different gases such as NH₃, CO, CH₄, H₂ in N₂ and pure O₂. The polypyrrole thin-film detector shows a considerable increase of resistance when exposed to NH₃ in N₂, and negligible response when exposed to comparable concentrations of interfering gases such as CO, CH₄, H₂ in N₂ and pure O₂. The calibration curve for NH₃ in N₂ at room temperature is measured in the concentration range from 0.01 to 1%. The relative change of the electrical resistance is about 10% for the lower detectable limit of 100 ppm of NH₃ in N₂. The sensitivity of the Langmuir-Blodgett polypyrrole towards ammonia is considerably higher than that of the electrochemical polypyrrole. The fast rise time and the high sensitivity of the detector are reported as a function of number of the polypyrrole layers. Long-term aging tests of the selective NH₃ gas sensor are performed.     

Micron-scale polymer-metal cantilever actuators fabricated by focused ion beam

Polymer-metal microcantilever actuators have been fabricated using an innovative approach based on focused ion beam micromachining technology. The fabrication involves depositing a thin metal film onto the surface of the polymer and machining using the ion beam. The microcantilever created is then extracted and transferred to a desirable support using a micromanipulator. This approach demonstrates the potential for maskless and resistless prototyping of cantilevers that can be evaluated for use as MEMS/NEMS actuators. Nanometer-scale displacement of the resulting polystyrene-platinum bimorph microactuator with respect to temperature change is demonstrated via visual monitoring in a scanning electron microscope with a heating stage. The performance of the bimorph cantilever microactuators is verified using both analytical and finite element modeling.     

On the influence of local and global stress constraint and filtering radius on the design of hinge-free compliant mechanisms

Distributed compliant mechanisms are components that use elastic strain to obtain a desired kinematic behavior. Compliant mechanisms obtained via topology optimization using the standard approach of minimizing/maximizing the output displacement with a spring at the output port, representing the stiffness of the external medium, usually contain one-node connected hinges. Those hinges are undesired since an ideal compliant mechanism should be a continuous part. This work compares the use of two strategies for stress constrained problems: local and global stress constraints, and analyses their influence in eliminating the one-node connected hinges. Also, the influence of spatial filtering in eliminating the hinges is studied. An Augmented Lagrangian formulation is used to couple the objective function and constraints, and the resulting optimization problem is solved by using an algorithm based on the classical optimality criteria approach. Two compliant mechanisms problems are studied by varying the stress limit and filtering radius. It is observed that a proper combination of filtering radius and stress limit can eliminate one-node connected hinges.     

Ionic liquid as electrolyte in a self-powered controlled release system

Initial studies into the development of a self-powered controlled release system using ionic liquid electrolyte were performed via galvanic coupling of a conducting polymer doped with dye and a zinc anode. The conducting polymer employed was polypyrrole (PPy) doped with phenol red (PR) dye. The electrochemical properties of the polymer as well as the dye release process initiated by a Zn electrode were investigated. A bilayer conducting polymer structure wherein polypyrrole–polystyrene sulfonate (PPy-PSS) coated on top of PPy-PR ensured no leakage of dye, yet allowed efficient release of PR on galvanic coupling in a temperature sensitive electrolyte.     

Pre-programmable polymer transformers as on-chip microfluidic vacuum generators

This paper develops novel polymer transformers using thermally actuated shape memory polymer (SMP) materials. This paper applies SMPs with thermally induced shape memory effect to the proposed novel polymer transformers as on-chip microfluidic vacuum generators. In this type of SMPs, the morphology of the materials changes when the temperature of materials reaches its glass transition temperature (T _g). The structure of the polymer transformer can be pre-programmed to define its functions, which the structure is reset to the temporary shape, using shape memory effects. When subjected to heat, the polymer transformer returns to its pre-memory morphology. The morphological change can produce a vacuum generation function in microfluidic channels. Vacuum pressure is generated to suck liquids into the microfluidic chip from fluidic inlets and drive liquids in the microchannel due to the morphological change of the polymer transformer. This study adopts a new smart polymer with high shape memory effects to achieve fluid movement using an on-chip vacuum generation source. Experimental measurements show that the polymer transformer, which uses SMP with a T _g of 40°C, can deform 310 μm (recover to the permanent shape from the temporary shape) within 40 s at 65°C. The polymer transformer with an effective cavity volume of 155 μl achieved negative pressures of −0.98 psi. The maximum negative up to −1.8 psi can be achieved with an effective cavity volume of 268 μl. A maximum flow rate of 24 μl/min was produced in the microfluidic chip with a 180 mm long channel using this technique. The response times of the polymer transformers presented here are within 36 s for driving liquids to the end of the detection chamber. The proposed design has the advantages of compact size, ease of fabrication and integration, ease of actuation, and on-demand negative pressure generation. Thus, this design is suitable for disposable biochips that need two liquid samples control. The polymer transformer presented in this study is applicable to numerous disposable microfluidic biochips.     

Feedback control of tri-layer polymer actuators to improve their positioning ability and speed of response

Improving positioning ability of electroactive polymer actuators typified by polypyrrole (PPy) through feedback control of their position has been considered. The actuators operate in air, as opposed to their predecessors. One of the problems associated with the actuators is the forward relaxation/creep or drift, which occurs after the full reduction and oxidation processes are completed. A high-resolution laser displacement sensor was used to detect the position of the cantilever-type polymer actuators and the classical, yet effective, Proportional, Integral and Derivative (PID) control method has been employed to generate the appropriate control input in order to make sure that no drift occurs in the user-specified position of the actuators. A set of experimental results with and without feedbacking the position data are presented to demonstrate the efficacy of the control method for improving the positioning ability and the speed of response. The rise time is reduced by more than 500 times and the position tracking error is less than 10% for a time-varying user-specified position command.     

Multistep sequential batch assembly of three-dimensional ferromagnetic microstructures with elastic hinges

In this paper, we have developed a process for multistep sequential batch assembly of complex three-dimensional (3-D) ferromagnetic microstructures. The process uses the magnetic torque generated by an external magnetic field perpendicular to the substrate to lift hinged structures. We found that a dimensionless factor that depends on the volume of the magnetic material and the stiffness of the hinges determines the sensitivity of the hinged microstructures to a magnetic field. This factor was used as a criterion in designing a process for sequential batch assembly, i.e., for setting appropriate differences in sensitivity. Using a dimensionless factor in the design of the sequential assembly simplified the assembly process, which requires only placing the structures on a permanent magnet, and which can be used to carry out multistep sequential batch assembly. We fabricated hinged microstructures, which consist of 4.5-/spl mu/m-thick electroplated Permalloy plates and 200-nm-thick nickel elastic hinges of various sizes. In an experiment, four plates (600 /spl mu/m/spl times/800 /spl mu/m) were lifted sequentially and out-of-plane microstructures were assembled in a four-step process. Assembly of more complex out-of-plane microstructures (e.g., regular tetrahedrons, 800 /spl mu/m long on one side) was also shown to be feasible using this method of sequential batch assembly. [1351].     

High strain electromechanical actuators based on electrodeposited polypyrrole doped with di-(2-ethylhexyl)sulfosuccinate

The low-voltage electromechanical actuation of polypyrrole (PPy) doped with di-(2-ethylhexyl)sulfosuccinate (DEHS) has been investigated. The PPy-DEHS has been prepared both chemically (cast as films from solution) and by more conventional electrochemical polymerization. Very large strains of ∼30% were obtained during slow-scan redox cycling of the electrochemically prepared PPy-DEHS films. In constrast, PPy-DEHS films cast from solutions of the chemically polymerized polymer gave actuation strains of ∼2.5%. The polymerization method was also found to have a significant effect on the structure, conductivity and mechanical properties of the PPy-DEHS materials. The conductivity of the electrochemically polymerized PPy-DEHS was 75 S cm⁻¹, considerably higher than that found for the chemically derived polymer (7 S cm⁻¹). The structure of the PPy-DEHS was further elucidated from UV-vis, Raman and FT-IR spectral studies which indicated that the conjugation length of the PPy could be increased significantly by varying the polymerization method. Films obtained by casting chemically prepared PPy-DEHS showed higher modulus (2.3 GPa) than electropolymerized PPy-DEHS (0.6 GPa), but were more brittle. Both materials were electroactive in acetonitrile/water electrolyte. The higher actuation strain observed in the electrochemically prepared films was attributed to a more open molecular structure (as indicated by the lower modulus) allowing for easier ion diffusion and a higher conductivity allowing easier charge transfer.     

基于聚吡咯修饰的碳泡沫可压缩电极材料

在该研究中,通过高温碳化和原位聚合法制备了基于市售三聚氰胺泡沫和吡咯单体的聚吡咯/ 碳化三聚氰胺泡沫(Polypyrrole/Carbonized Melamine Foam,PPy/CMF)的可压缩超级电容器电极材料。 通过三电极体系在 1 mol/L 高氯酸钠电解液中研究了可压缩 PPy/CMF 电极材料的电化学性质。结果显 示,可压缩电极材料的体积电容在 2 mA/cm3 时可达到 3 168 mF/cm3,1 000 次充放电循环后可保持原 始电容的 86.88％。此外,该材料的循环伏安曲线和恒流充放电曲线在不同压缩下无显著变化,表明 PPy/CMF 是具有高压缩稳定性的可压缩电极,适合于超级电容器。以上结果表明,PPy/CMF 可作为可 压缩超级电容器的潜在电极材料。     

Flexible humidity and temperature sensor based on cellulose–polypyrrole nanocomposite

Recently, cellulose has been re-discovered as a smart material that can be used as sensor and actuator materials, which is termed as electro-active paper. In this work we demonstrate the application of cellulose as a flexible humidity and temperature sensor. Nanoscaled polypyrrole (PPy) as a humidity and temperature sensitive layer was introduced onto cellulose surface via in situ polymerization technique without disrupting cellulose structure. Atomic force microscopy, UV–visible spectroscopy, transmission electron microscopy and secondary ion mass spectroscopic analysis revealed the successful deposition of polypyrrole nanolayer onto cellulose surface, which is referred as a cellulose–PPy nanocomposite. Effect of polymerization time on sensing behavior of cellulose–PPy nanocomposite was investigated, experimental results revealed that cellulose–PPy nanocomposite with 16 h polymerization time suitable for suitable for humidity and temperature sensor.     

Comparative analysis of sensor responses of thin conducting polymer films to organic solvent vapors

A comparative analysis of responses of thin films of various conducting polymers (polyaniline, polypyrrole and poly-3-methylthiophene) to the vapors of polar as well as low- and nonpolar organic solvents was performed. Conductivity measurements, infra-red and electron paramagnetic resonance spectroscopy were used to characterize responses of the polymer films doped with different dopants. Main physical and chemical factors which define the magnitude of the response to the studied analytes were determined. It was shown that the differences in response of conducting polymer films are conditioned by the influence of chemical structure of the polymer and its dopant, and also by different nature of their doping.