Electrochemically-driven actuators

This imique behavior has been exploited for applications including controlled release (discussed above) and electrochemically driven actuators. 

Many electrochemically driven actuators are fabricated via supramolecular assembly. This is in contrast to the other sections in this chapter, where most of the actuator devices... 

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... 

Actuators Electrochemical impedance spectroscopy (EIS) Electrochemically driven actuators Voltage v. current control Electromechanical characterization Electrothermally driven actuators Ionic liquids (IL) Pulse-width-modulated (PWM) control signal... 

The introduction of carbonaceous electrode materials for the electrochemically driven actuators intersected two classes of electrochemical devices that were considered as being separate beforehand - the electromechanical actuators and the electric double-layer capacitors (also known as supercapacitors). Although the... 

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. 

In the selection of carbons for use as the electrode material in electrochemically driven actuators, the primary factor of choice is the specific siuface area of the carbons. Generally, an actuator that has higher capacitance also has higher actuation performance however, this principle is vahd in the extent of the same electrode material only (Palmre et al. 2009). 

Electric conductivity along the carbon filament in case of the electrothermally driven actuators, and along individual electrodes in case of the electrochemically driven actuators, is an important characteristic that has a large impact on the speed of the actuators, as it is explained in Sect. 2.2. Conductivity of an electrode can be measured using four-point measurement setup. Alternatively, voltage drop along an eleetrode during actuation can be used to estimate its conductivity (Kruusamae etal. 2012). 

A couple of additional aspects must be considered in characterization of electromechanical response. The electrochemically driven actuators can also heatup during the working cycle. In contrast to the eleetrothermally driven actuators, this effect is usually not desired in case of the electrochemically driven actuators, as die actuator s constituents can significantly change their mechanical and electrical properties. In an extreme case, the temperature of the separator polymer can increase over its melting point, causing the actuator to short-circuit in turn. 

As the electrochemically driven actuators have viscoelastic properties and contain liquid electrolyte, it can undergo back-relaxation in long run (Kruusamae et al. 2014 Vunder et al. 2012). 

The strain levels are usually quite moderate, in the order of several percent in case of electrochemically driven actuators. Moderate strain levels can be amplified into large dimensional change by constructing an actuator in the cantilever configuration. 

This imique behavior has been exploited for applications including controlled release (discussed above) and electrochemically driven actuators. EAP-based actuators have been explored for use in artificial muscle fibers (AMFs) (442-444) and microelectromechanical systems (MEMS) (437). Non-conductive polymeric gel systems have been used for several decades as actuator devices (445-447) but with low elastic modulus and low 3ueld strength, applications of gel-based actuators are very limited. Gel-based actuators offer one significant advantage over EAPs in that their volume changes can exceed a factor of a thousand (448). 

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