Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. DSC research groups have been established around the worl ...

/pdf/dye-sensitized-solar-cells-50b0w2bhsr.pdf

Dye-Sensitized Solar Cells

Photoinduced reactivity of titanium dioxide

When considering new sensory technologies one should look to nature for guidance. Indeed, living organisms have developed the ultimate chemical sensors. Many insects can detect chemical signals with perfect specificity and incredible sensitivity. Mammalian olfaction is based on an array of less discriminating sensors and a memorized response pattern to identify a unique odor. It is important to recognize that the extraordinary sensory performance of biological systems does not originate from a single element. In actuality, their performance is derived from a completely interactive system wherein the receptor is served by analyte delivery and removal mechanisms, selectivity is derived from receptors, and sensitivity is the result of analyte-triggered biochemical cascades. Clearly, optimal artificial sensory sys-

Conjugated polymer-based chemical sensors.

Electromechanical actuators based on sheets of single-walled carbon nanotubes were shown to generate higher stresses than natural muscle and higher strains than high-modulus ferroelectrics. Like natural muscles, the macroscopic actuators are assemblies of billions of individual nanoscale actuators. The actuation mechanism (quantum chemical-based expansion due to electrochemical double-layer charging) does not require ion intercalation, which limits the life and rate of faradaic conducting polymer actuators. Unlike conventional ferroelectric actuators, low operating voltages of a few volts generate large actuator strains. Predictions based on measurements suggest that actuators using optimized nanotube sheets may eventually provide substantially higher work densities per cycle than any previously known technology.

/pdf/carbon-nanotube-actuators-1chbcyw6t7.pdf

Carbon Nanotube Actuators

Organic–inorganic hybrid materials do not represent only a creative alternative to design new materials and compounds for academic research, but their improved or unusual features allow the development of innovative industrial applications. Nowadays, most of the hybrid materials that have already entered the market are synthesised and processed by using conventional soft chemistry based routes developed in the eighties. These processes are based on: a) the copolymerisation of functional organosilanes, macromonomers, and metal alkoxides, b) the encapsulation of organic components within sol–gel derived silica or metallic oxides, c) the organic functionalisation of nanofillers, nanoclays or other compounds with lamellar structures, etc. The chemical strategies (self-assembly, nanobuilding block approaches, hybrid MOF (Metal Organic Frameworks), integrative synthesis, coupled processes, bio-inspired strategies, etc.) offered nowadays by academic research allow, through an intelligent tuned coding, the development of a new vectorial chemistry, able to direct the assembling of a large variety of structurally well defined nano-objects into complex hybrid architectures hierarchically organised in terms of structure and functions. Looking to the future, there is no doubt that these new generations of hybrid materials, born from the very fruitful activities in this research field, will open a land of promising applications in many areas: optics, electronics, ionics, mechanics, energy, environment, biology, medicine for example as membranes and separation devices, functional smart coatings, fuel and solar cells, catalysts, sensors, etc.

Applications of hybrid organic–inorganic nanocomposites

Polyaniline films are found to expand and contract by electrochemical oxidation and reduction, respectively. Two polyaniline films are used as cathode and anode muscles. In this system, the proton transfer between the films are essential chemical reaction. Two types of actuators, viz., “Backbone-type” and “Shell-type” actuators have been fabricated. The “Backbone-type” actuator responded to the frequency of more than 44Hz. The “Shell-type” actuator can be operated in free space.

Artificial muscle: electromechanical actuators using polyaniline films

Physical properties of multiwalled carbon nanotubes

Polypyrrole nanotube array sensor for enhanced adsorption of glucose oxidase in glucose biosensors.

An amperometric urea biosensor based on covalent immobilization of urease onto an electrochemically prepared copolymer poly (N-3-aminopropyl pyrrole-co-pyrrole) film.

Conducting polymer actuators have been attracting researchers and engineers who need powerful and light actuators because of their electrically induced stress (3–5 MPa), 10 times larger than that (0.35 MPa) of vertebrate muscle fibres. The moderate electrically generated strain (1–3 %) has however been restricting their applications to robots, for instance, and therefore relatively huge and heavy electric motors have been inevitably used in the robotic industry. A polypyrrole (PPy) film, which was prepared electrochemically from methyl benzoate solution of tetra-n-butylammonium tetrafluoroborate (TBABF4) on Ti electrode, exhibited 12.4 % strain and 22 MPa stress generated electrochemically in NaPF6 aqueous solution. The large electrochemical strain and stress of BF4−-doped PPy should meet applications of artificial muscles particularly where strong force is required. These novel conducting polymer actuators could dramatically alter any technologies concerning movements. Besides fundamental properties of the PPy actuators, some newly-devised configurations of the actuators for practical use are important. In order to fabricate actuator devices particularly where multiple layers of PPy films were required to increase force, flexible and tough CF3SO3−-doped PPy films were more suitable than BF4−-doped PPy.

Keiichi Kaneto

Papers

Artificial muscle: electromechanical actuators using polyaniline films

Physical properties of multiwalled carbon nanotubes

Polypyrrole nanotube array sensor for enhanced adsorption of glucose oxidase in glucose biosensors.

An amperometric urea biosensor based on covalent immobilization of urease onto an electrochemically prepared copolymer poly (N-3-aminopropyl pyrrole-co-pyrrole) film.

Artificial Muscles Based on Polypyrrole Actuators with Large Strain and Stress Induced Electrically