María Teresa Cortés

Artificial muscles based on conducting polymers

Abstract Natural muscles have mechanical properties that conventional actuators do not possess. These natural machines show large strain, moderate stress, high efficiency and stability, fast response time, high power/weight ratio, long lifetime, etc. In the last years a great interest has arisen to develop materials that mimic natural mechanisms. Conducting polymers have an array of potential applications as artificial muscles since they are capable to produce a moderate displacement when submitted to an electrochemical reaction. This property has been used to fabricate actuator devices that imitate and even improve the performance of natural muscles. For example, conducting polymers show stresses 15 times higher than those generated by mammalian muscles, a high power/weight ratio and a high degree of compliance. However, there are also several responses that need improvement in the actuators based on conducting polymers. Strains are still c. 50% lower than in natural muscles. Most of this kind of actuators only work in liquid media. It is necessary to increase the response time and obtain more durable actuators with longer lifetime and higher stability. In spite of these disadvantages, the first actuators based on conducting polymers are being commercialized. This paper presents a brief summary of some of the actuators based on these polymers, focusing on their design, performance and actuation mechanism.

Electrooxidación de glifosato sobre electrodos de níquel y cobre

The electrochemical oxidation of glyphosate on an electrode of nickel and on one of copper was studied. With both electrodes electrochemical signals related to the glyphosate concentration were observed. However, the behaviour of the copper electrode was much better than that of the nickel electrode. A calibration curve was obtained of the electrical signal of this electrode as a function of the glyphosate concentration. The detection limit was 30 µM. In the case of nickel, an increase in the oxidation signal, which is related to the glyphosate concentration, was obtained. However, the results were less reproducible and additional information is necessary to propose an interaction mechanism between glyphosate and the electrode.

Design and Optimization of an Electrochemical Equipment for the Synthesis and Evaluation of Conducting Polymers

Abstract A potentiostat system, focused towards the synthesis and evaluation of conducting polymers, was developed. This equipment consists of two main modules: the acquisition and control module, activated by means of a microcontroller which is connected through serial port to a computer, and the potentiostatic module, specially designed for handling the signals from the synthesis and characterization processes of the polymers. The user environment was programmed with Visual Basic 6. The resolution of the system AD/DA is of 12 bits; this allows sensibilities of 1 nA in current measurements. The achieved potential sweep is between −2 and +2 V. By means of this equipment, ClO4 −doped polypyrrole (PPy) and biphthalate doped PPy films were synthesized. The conducting polymers were synthesized by potential square waves. The thicknesses of the polymeric films were determined throughout the polymerization charge. The error percentage in the polymerization charge recorded by the developed potentiostat, relative to a commercial potentiostat, was about 6%. The ability to store the charge of the biphthalate PPy (biphthalate) films in potassium biphthalate aqueous solution was determined by cyclic voltammetry at various scan rates.