Remotely and Sequentially Controlled Actuation of Electroactivated Carbon Nanotube/Shape Memory Polymer Composites

Abstract

A shape memory material, when deformed to a temporary shape, can recover to its original shape under an external stimulus. [1] Owing to its low cost, ease in manufacturing, and high shape recovery ratio, shape memory polymer (SMP) has attracted more attention than metal and ceramic based shape memory materials. [1a,2] For SMPs, most of the research effort so far has focused on thermally activated shape recovery process using direct heating with an external heater. [3] In order to eliminate the external heaters and realize remote control, some research efforts have devoted to the study of filler/SMP composites activated by stimuli including electricity, [4] light, [5] and magnetic field. [6] Comparing to light-and magnetic fieldactivated filler/SMP composites, one of the significant advantages of electroactivated filler/SMP composites is the broad range of available conductive fillers, such as carbon black, [7] carbon nanotube (CNT), [8] carbon nanofiber (CNF), [9] short carbon fiber, [10] graphite oxide, [11] and metal particles. [12] In most of the above studies, the conductive filler/polymer matrix composites were processed using melt-blending and molding method. Furthermore, there are other facile methods for the fabrication of conductive filler/SMP composites. For example, Leng et al. [12b] fabricated conductive Ni chains with a magnetic field for the improvement of electrical conductivity of the SMP composite. Lu et al. [13] prepared CNF nanopaper/SMP composite with resin transfer molding process. Wang et al. [14] utilized a digitally controlled spraying-evaporation process to deposit CNT layers on SMP films for tunable electroactivated SMPs. Also, in recent years, the evolution of 3D printing technology attracted considerable interest due to its low cost and flexibility in the fabrication of complex structures. [15] The combination of 3D printing and stimulus-responsive materials, also known as 4D printing, has been extensively applied in the fabrication of intricate smart devices. [16] It is particularly noteworthy that some researchers have successfully fabricated conductive SMP actuators using 4D printing and demonstrated the electroactivated shape memory behavior. [17] However, the above limited researches have not provided a systematical investigation of the relations among printing parameters, electrical property, 4D printing technology is known as the combination of 3D printing techno logy and stimulusresponsive materials. 4D printed conductive filler/shape memory polymer composites have tremendous potential in the development of remotely and sequentially controlled smart devices. This work focuses on the temperature dependent volume resistivity, Jouleheating induced temperature distribution, and electroactivated shape memory behavior of 4D printed carbon nanotube (CNT) reinforced polylactic acid (PLA) under an applied DC voltage. The variation of volume resistivity of CNT/PLA composites with temperature can be attributed to matrix shrinkage and CNT contact resistance change. Enhanced elect...

3D printing of shape memory polymers

“…The conductive carbon filaments allowed for electrical actuation by resistive heating, leading to recovery above 95% in approx. 75 s. 58 Carbon nanotubes (CNTs) were introduced in PLA instead by Liu et al 61 They found a dependency of the volume resistivity on the raster angle as well as the temperature, especially above approx. 70 C. Resistive heating thus resulted in different time-dependencies of the temperatures reached in the samples.…”

Applications of Carbon Nanotubes in the Internet of Things Era

“…Besides, the human–machine interaction provides the approaches of obtaining human gesture and motion signals [ 100 ]. In addition, CNT devices guarantee the remotely controlled actuation [ 101 ], and wireless energy transfer [ 102 ]. The upcoming efforts should be put into the self-powered sensing system by energy harvesting from the environment and motion energy.…”

Electroactive Polymers Obtained by Conventional and Non-Conventional Technologies

“…Most of the SMPs already processed by AM do not present electroactive properties and, therefore, it is common to incorporate responsive particles into polymeric blends, forming polymer-based electroactive composites. In this context, PLA, a thermosensitive polymer commonly used in AM due to its extrudability and shape memory properties, was blended with carbon nanotubes (CNT) to prepare electroactive composites [ 75 ]. The PLA-based composite was acquired in a filament shape and then processed by FFF.…”