Shape Memory Alloys in Textile Platform: Smart Textile-Composite Actuator and Its Application to Soft Grippers

Development of a magnified sunlight responsive shape memory bio-composite: effects of titanium nitride (TiN) nanoparticles on a bio-based benzoxazine/epoxy copolymer

This study uniquely explored the effects of loading titanium nitride (TiN) nanoparticles in a bio-based benzoxazine/epoxy copolymer on the shape memory performance of the resulting composite using normal and magnified sunlight irradiation stimuli scenarios. Additionally, the effects of loading the TiN nanoparticles in the copolymer on light absorbance capacity, thermal stability, visco-elastic properties, and tensile properties of the composites were analysed. Results reveal that the different loading amounts (1 to 7 wt%) of TiN dispersed well within the copolymer matrix and produced excellent composite samples (TiN-1(wt%), TiN-3(wt%), TiN-5(wt%), and TiN-7(wt%)). Interestingly, the obtained samples were found to exhibit improved light absorbance in the wavelength range of 200-900 nm, giving the samples greater sunlight absorbing capacity. Moreover, the thermal stability of the composites increases with an increase in the loading amount; for instance, the initial degradation temperature increased from 316 °C to 324 °C. Meanwhile, visco-elastic and tensile properties increased and reached the optimum for TiN-5(wt%), where 3.1 GPa and 10.4 MPa were recorded as storage modulus and tensile stress, respectively. Consequent to these improvements in the properties of the composites, the shape memory performance of the composites was positively impacted. For instance, average shape fixity ratio, shape recovery ratio, and recovery time of 95%, 96%, and 38 seconds, respectively, were achieved with TiN-7(wt%), which represents 19%, 17%, and 38% improvements, respectively, compared to when the neat copolymer (TiN-0(wt%)) was used using magnified sunlight irradiation stimulus. Overall, this finding provides the basis for the utilization of magnified sunlight irradiation stimulus to achieve excellent shape memory performance with TiN-filled polymer composites.

Resistance Feedback of a Ni-Ti Alloy Actuator at Room Temperature in Still Air

This paper illustrates an experimental activity for the closed-loop position control of an actuator made using shape memory alloy (SMA) wire. A solution with the self-sensing effect was implemented to miniaturize the systems, i.e., without external sensors. A proportional control algorithm was initially used, demonstrating the idea's feasibility; the wire can behave simultaneously as an actuator and sensor. An experimental investigation was subsequently conducted for the optimization of the developed actuator. As for the material, a Flexinol wire, Ni-Ti alloy, with a diameter of 0.150 mm and a length of 200 mm, was used. Preliminarily, characterization of the SMA wire at constant and variable loads was carried out; the characteristics detected were elongation vs. electric current and elongation vs. electrical resistance. The control system is PC based with a data acquisition card (DAQ). A drive board was designed and built to read the wire's electrical resistance and power it by pulse width modulation (PWM). A notable result is that the actuator works with good precision and in dynamic conditions, even when it is called to support a load up to 65% different from that for which the electrical resistance-length correlation has previously been experimentally obtained, on which the control is based. This opens up the possibility of using the actuator in a counteracting configuration with a spring, which makes hardware implementation and control management simple.

Advancements in Soft Robotics: A Comprehensive Review on Actuation Methods, Materials, and Applications

The flexibility and adaptability of soft robots enable them to perform various tasks in changing environments, such as flower picking, fruit harvesting, in vivo targeted treatment, and information feedback. However, these fulfilled functions are discrepant, based on the varied working environments, driving methods, and materials. To further understand the working principle and research emphasis of soft robots, this paper summarized the current research status of soft robots from the aspects of actuating methods (e.g., humidity, temperature, PH, electricity, pressure, magnetic field, light, biological, and hybrid drive), materials (like hydrogels, shape-memory materials, and other flexible materials) and application areas (camouflage, medical devices, electrical equipment, and grippers, etc.). Finally, we provided some opinions on the technical difficulties and challenges of soft robots to comprehensively comprehend soft robots, lucubrate their applications, and improve the quality of our lives.

Design and Evaluation of Smart Textile Actuator with Chain Structure

Textiles composed of fibers can have their mechanical properties adjusted by changing the arrangement of the fibers, such as strength and flexibility. Particularly, in the case of smart textiles incorporating active materials, various deformations could be created based on fiber patterns that determine the directivity of active materials. In this study, we design a smart fiber-based textile actuator with a chain structure and evaluate its actuation characteristics. Smart fiber composed of shape memory alloy (SMA) generates deformation when the electric current is applied, causing the phase transformation of SMA. We fabricated the smart chain column and evaluated its actuating mechanism based on the size of the chain and the number of rows. In addition, a crochet textile actuator was designed using interlooping smart chains and developed into a soft gripper that can grab objects. With experimental verifications, this study provides an investigation of the relationship between the chain actuator's deformation, actuating force, actuator temperature, and strain. The results of this study are expected to be relevant to textile applications, wearable devices, and other technical fields that require coordination with the human body. Additionally, it is expected that it can be utilized to configure a system capable of flexible operation by combining rigid elements such as batteries and sensors with textiles.

A 3D Anisotropic Thermomechanical Model for Thermally Induced Woven-Fabric-Reinforced Shape Memory Polymer Composites

Soft robotic grippers offer great advantages over traditional rigid grippers with respect to grabbing objects with irregular or fragile shapes. Shape memory polymer composites are widely used as actuators and holding elements in soft robotic grippers owing to their finite strain, high specific strength, and high driving force. In this paper, a general 3D anisotropic thermomechanical model for woven fabric-reinforced shape memory polymer composites (SMPCs) is proposed based on Helmholtz free energy decomposition and the second law of thermodynamics. Furthermore, the rule of mixtures is modified to describe the stress distribution in the SMPCs, and stress concentration factors are introduced to account for the shearing interaction between the fabric and matrix and warp yarns and weft yarns. The developed model is implemented with a user material subroutine (UMAT) to simulate the shape memory behaivors of SMPCs. The good consistency between the simulation results and experimental validated the proposed model. Furthermore, a numerical investigation of the effects of yarn orientation on the shape memory behavior of the SMPC soft gripper was also performed.

A Shape Memory Alloy-Based Soft Actuator Mimicking an Elephant's Trunk

Soft actuators that execute diverse motions have recently been proposed to improve the usability of soft robots. Nature-inspired actuators, in particular, are emerging as a means of accomplishing efficient motions based on the flexibility of natural creatures. In this research, we present an actuator capable of executing multi-degree-of-freedom motions that mimics the movement of an elephant's trunk. Shape memory alloys (SMAs) that actively react to external stimuli were integrated into actuators constructed of soft polymers to imitate the flexible body and muscles of an elephant's trunk. The amount of electrical current provided to each SMA was adjusted for each channel to achieve the curving motion of the elephant's trunk, and the deformation characteristics were observed by varying the quantity of current supplied to each SMA. It was feasible to stably lift and lower a cup filled with water by using the operation of wrapping and lifting objects, as well as effectively performing the lifting task of surrounding household items of varying weights and forms. The designed actuator is a soft gripper that incorporates a flexible polymer and an SMA to imitate the flexible and efficient gripping action of an elephant trunk, and its fundamental technology is expected to be used as a safety-enhancing gripper that requires environmental adaptation.