Development and investigations on multiple carbon nanotube actuator systems for magnified performance and minimization of performance losses
Carbon nanotubes (CNT), as active materials have shown a great potential for industrial applications especially in medical technology due to their high strain, low driving voltage, light weight and flexibility. The driving principle of CNT actuator operation is electrochemical double layer charging, which necessities the presence of electrolyte. This represents a major set back with respect to possible applications. This has been overcome by the development of so called "dry" actuators. These are based on CNT -polymer composites, where the electrolyte is encapsulated within the polymer matrix. Such composites have been build up and used as three layer actuators, where two outer layers containing CNTs are considered as active layers and are separated by the middle layer, separator, which serves as electrical isolator as weH as an ion reservoir. CNT-polymer actuators, although appropriate from the performance point of view, have not yet reached the medical market due to the unknown interactions between CNTs and living organisms. However, the achievements obtained in the development of CNT actuators highlight the potential for applications in other market sectors. CNT actuators could be used as positioning systems, valves and pumps, switches and brakes. In order to have the possibility to offer CNT actuators to a broader spectrum of industries, further developments must be carried out. Within this work multiple actuator systems were developed with a target of multiplication of actuator performance by combining several of them together. Such developments demonstrated the possibility of symbiotic cooperation between integrated CNT actuators and mechanical systems to work as one. Multiple actuator systems were tested in respect to their displacement and force generation as the primary characteristic features of any actuator. Those systems were experimentally measured in an out-of-plane mode of operation at low frequency ranges « 1 Hz) and under Iow driving voltages (2 Volt). The first results indicated that there is no direct proportionality between the multiple actuator system performance and the number of actuators involved. For this reason experimental investigations were undertaken in order to define the performance of actuator systems and minimize the losses, which may occur due to the unsuitable amount of actuators used in a stack. Furthermore, in order to minimize the losses in the performance of actuator system extensive development work was carried out on the optimum design and implementation of electrodes within the system. In parallel various materials where tested in a search for best electrode, as it was observed that they can greatly influence the operating characteristics. The investigations carried out within this research are targeted in finding the optimum design for multiple actuator systems with improved displacement and exertion of force.