Electrochemically driving actuators

In summary, the electrothermally driving actuators exhibit large actuation under a relative low driving voltage. Compared with the electrochemically driving actuators, they show better actuation stability because it is free of electrolyte. Unfortunately, they exhibit a slow responsiveness due to the unsatisfactory heat conduction of the polymer. Therefore, some efforts should be made to improve the heat conduction by decreasing the thickness of the polymeric layer or introducing functional additives. 

The twisting nanotube yam actuators based on first principle mentioned above enable fully dry torsional actuation as the main driving mechanisms are based on electrothermal and/or photothermal effects. These actuators do not require electrolyte, counter electrode, or extra package as it is needed for electrochemically driven actuators (Chun et al. 2014). Indeed, the electroactivity of nanotube yams were firstly described in setup where bundled fibers were immersed in electrolyte the overall capability of twisting of actuators was demonstrated later without ion... 

The capacitive nature of the electrochemically driven actuators with carbonaceous electrodes is of particular importance to consider when starting experimentation with this type of actuators - the capacitive properties of the actuators determine the most suitable driving waveform and characterization methods. 

Electrochemical supercapacitors (ESs) present important advantages that qualify them for many applications. In this chapter, several important ES use areas are briefly reviewed. Examples are power electronics, memory protection, battery enhancements, portable energy sources, power quality improvement, adjustable speed drives (ASDs), high power actuators, hybrid electric vehicles, renewable and off-peak energy storage, and military and aerospace applications. 

For any actuator based on electrochemical reactions, the electrical energy U) consumed by the driving reaction is... 

Letheby H (1862) XXEX. On the production of a blue substance by the electrolysis of sulphate of aniline. J Chem Soc 15 161-163. doi 10.1039/JS8621500161 Lu W, Fadeev A, Qi B et al (2002) Use of ionic liquids for pi-conjugated polymer electrochemical devices. Science 297 983-987. doi 10.1126/science.1072651 Martinez JG, Otero TF (2012) Biomimetic dual sensing-actuators theoretical description. Sensing electrolyte concentration and driving current. J Phys Chem B 116 9223-9230. doi 10.1021/ jp302931k... 

By the electrochemical point of view, another criterion should be taken account when comparing fasf and slow processes. While keeping driving voltage lower than 2 V, the electrochemical reactions will not occur in carbon-based actuators using nonaqueous solvents or ionic liquids (Janes et al. 2004 Torop et al. 2009). However, in aqueous media toe electrochemical oxidation of carbon-based electrodes appear already at +0.6 V (vs. Ag/AgCl reference) and may lead to intense gas evolution (Xi et al. 2009). 

The selection of an appropriate waveform for driving electrochemically and electrothermally driven actuators is essential to achieve their full actuation capability and to prevent them from degradation. To date, boffi types of actuators under consideration in this chapter lack practice of use in industrial appUcations, even at fire prototype level. Consequently, standard control methods have not yet been established for these types of actuators. The control signals that have been used in the scientific works on the smart electroactive actuators to date are selected primarily with the purpose to facilitate convenient comparison of the newly prepared actuators with the previously available ones. 

The equivalent electrical circuit is the primary concern in the selection of an appropriate waveform to drive any type of actuator. This chapter is to give an overview of the electrical control methods for electrochemically and electrothermally driven actuators, in consideration of their equivalent electrical circuits. 

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